CA1258095A - Apparatus for measuring and calculating fourier components of a power line parameter - Google Patents

Abstract

ABSTRACT

Self contained radio transmitting state estimator mod-ules are mounted on power conductors on both sides of power transformers in electrical substations and on power conduc-tors at various places along electrical transmission lines.
They are electrically isolated from ground and all other conductors. These modules are capable of measuring current, voltage, frequency and power factor (or the fourier compo-nents thereof) the temperature of the conductor, and the temperature of the ambient air. The modules transmit these parameters to local receivers. The receivers are connected by an appropriate data transmission link, to a power control center which allows determination of the state of the power system. Appropriate control signals are transmitted back to the electrical switchgear of the system to bring it to the appropriate optimum state. Direct local control may also be effected, for example, the prevention of overloading a transformer. A "donut" state estimator module comprises a novel hot stick operated hinge clamp and a novel voltage sensor which measures the current between an isolated capa-citor plate and ground. The donut measures the fourier components of voltage and current over a number of cycles and transmits the components to the local receiver. The local receiver derives the desired electrical measurements such as voltage, current, power factor, power, and reactive power and transmits them to local or remote control stations. Up to 15 donut modules may transmit on a single channel to a single local receiver. Each transmits at intervals which are an integral number. The intervals between transmissions of all donuts do not have a common factor and the average interval is the desired transmission rate. Each donut uses the zero crossover of current of its conductor to establish its transmission interval. The system is self-calibrating using known reference signals within the donut module.

Description

3~i APPARATUS FOR MEASURING AND CALCULATING
FOURIER COMPONENTS OF A POWER LINE PARAMETER
RELATED ~ N ~ ~ ~
This application is related to United States Patent No. 4,384,289 of Howard R. Stillwel and Roosevelt A.
Fernandes entitled TRANSPONDER UNIT FOR MEASURING T~MPERA-TURE AND CURRENT ON LIVE TRANSMISSION LINES, issued ~ay 17, 1983.

3~; 196-0o7 - TECHNICAL FIELD

This invention relates to a system and apparatus for monitoring and control of a bulk electric power delivery system. More particularly it relates to such systems em-ploying transmission line mounted radio transmitting elec-trically isolated modules, preferably mounted on all power conductors connected to both the primary and secondary sides of each power transformer to be monitored, on the highest temperature portions of transmission lines, and at int~rvals through the power delivery system. When so attached the modules form the basis for a dynamic state estimation for real-time computer control of an electric power delivery system.
Each module takes the form of a two piece donut tha~
may be hot stick mounted on a live conductor utilizing a novel hinge clamp and novel hot stick tool.
Novel voltage measuring and fourier component measuring apparatus and a novel common channel unsynchronized trans-mission system are disclosed.

-3~ 5~ 196-007 - BACKGROUND ART
-Various power line monitored sensors have been dis-closed in the prior art~ For example, see United States Patent Nos. 3,428,896, 3,633,191, 4,158,810 and 4,268,818.
It has been proposed to use sensors of this type and of the greatly improved form disclose,d in the above-identified Stillwel and Fernandes ~ for dynamic line rating of elec-trical power transmission lines. See for example, papers numbered 82 SM 377-0 and 82 SM 378-8 entitled D~NAMIC
THERMAL LINE RATINGS; PART I, DYNAMIC AMPACITY RATING-ALGO-RITHM; and, DYNAMIC THERMAL LINE RATINGS, PART II~ CONDUCTOR
TEMPERATURE SENSOR AND LABORATORY FIELD TEST EVALUATION;
papers presented at the International Association of Elec-trical and Electronic Engineers P.E.S. 1982 summer meeting.
However, the full potential of this new technology has not been realized.

Today, for control and protection, power supply to and from an electrical substation over various transmission lines is monitored by separate devices (current transform-ers, potential transformers and reactive power transducers) for measuring electrical potential, power factor and current in the conductors of the transmission line and the conduc-tors connected to substation power transformers. These measurements are transmitted in analog fashion by various -4~ 196-007 wires to a central console at the substation where their values may or may not be digitized and sent to a central station for control of the entire power system~ The wirins of these devices is difficult and expensive, and every ex-cess wire in a substation presents an additional electrical shock hazard or an induction point for electromagnetic interference on protection/telemetry circuits. Furthermore, when a failure occurs, these sensor lines may be abruptly raised to higher voltages, thus increasing the possibility of shock and failure in the measurement system.

. . _ The high cost of capital, uncertain power utility load growth trends, coupled with increasing constraints in ac-quiring and licensing new facilities including right of-way for transmission lines make greater use of existing power delivery facilities (remote generating stations, the EHV
bulk power network, subtransmission and distribution facili-ties) a paramount consideration. With deferrals that have occurred in new generation and power ~ransmission facili-ties, all elements of the power system will be strained to a greater degree than in the past. In order to maintain cur-rent reliability levels under these conditions, additional real-time monitoring will be required to assist the dispatch operator and other bulk network functions conducted through a modern Power Control Center.
Some of the functions in a hierarchical modern Power Control Center, operating through Regional Control Centers down to the distribution level, that require a real-time _5~ 196-007 Supervisory Control and Data Acquisition System are as follows:
1. State Estimation

2. On-Line Load Flow Detection

3. Optimum Power Flow Control for Real and ~eactive Power Dispatch

4, Security (i.e. Stability) Constrained Economic Dispatch

5. Contingency Analysis

6. Automatic Generation Control and Minimum- Area Control Error

7. Dynamic System Security Analysis

8. Eneryy Interchange Billing

9. System Restoration After an Emergency

10. Load Shedding and Generation Redispatch

11. Determination of Effects of Voltage Reduction and Real and Reactive Power

12. Synchronization of System Load Profiles to validate various computer models and to provide snap shots of maximum, minimum loads, peak day real and reactive powers on lines and equipment

13. Maintain Power Delivery Quality Including Harmonic Content for Critical Loads and Power Factor

14. Limit checking of voltage, line thermal loadings and rate of change under contingency conditions

15. Protective Relaying.

5~
--~-- 19~-00~

_ The key parameters that require measurement for a modern Power Control Center State Estimator and On-Line Loac Flow that provide the input data base for the various functions listed above are~
Line and Transformer Bank or Bus Power (MW) Flows Line and Transformer Bank or Bus Reactive Power (MVAR) Flow ~ranch Currents (I), Bus Voltage and Phase Angles Bus MW and MVAR Injections Energy (MWh) and Reactive Energy (MVAR-h~ ~ _ Circuit Breaker Status Manual Switch Positions l`ap Changer Positions Frequency (f) Protective Relaying (Differential Currents, etc.) Operation Power Line Dynamic Ratings Based on Conductor Thermal (Temperature) Limits or Sag Ambient Temperature/Wind Speed Line and Equipment Power Factors Sequence-of-Events Monitoring One of the major problems in implementing a modern Power Control System is to add instrumentation throughout the bul~
transmission network at Extra High Voltage (up to 765 kV) line voltages and at distribution substations and feeders.
This must be done without disrupting existing operations of equ~pment and facilities that are largely in place. Another requirement is to avoid adding too many transducers that might alter the burden on existing current transformers and degrade accuracy of existing metering or relaying instrumentation.
The toroidal conductor State Estimator Module and ground station processor, receiver/transmitter of the present invention eliminates the necessity for multiple wiring of transducers required with conventional current and potential transformers and collects all-the data required from lines and station buses with a compact systern._ The invention results in significant investment, insta~llation labor and tlme savings. It completely eliminates the need for multiple transducers, hard-wiring to current transformers and potential transformers and any degrading effects on existing relaying or metering links. The system can be retrofitted on existing lines or stations or new installations with equal ease and measures:
Line Voltage Power Factor or Phase Angle Power Per Phase Line Current Reactive Power Per Phase Conductor Temperature Ambient Temperature Wind Speed -8~ 196-007 _ Harmonic Currents Frequency MW~h and MVAR-h (processed quantities) Profiles of above quantities from stored values The state-estimator data collection system described in this application enables power utilities to implement moderr.
power control systems more rapidly, at lower cost and with considerable flexibility, since the devices can be movec around using hot-sticks without having to interrupt power flow. The devices can be calibrated and checked throu~h the radio link and the digital output can be multiplexed with other station data to a central processor via remote communication link.
Many problems had to be overcome to provide an electrically isolated state estimator module that can be hot stick mounted to energized conductors including the highes~
used in electrical transmission.
Among these were: The design of a positive actinc mechanism for hinging the two parts of the module anc securely clamping and unclamping them about a live conductor while they were supported by a hot stick. Measurement of the voltage of the conductor in a self-contained electrically isolated module. The desire to make many electrical measurements with a necessarily small and light module and common utilization of a single radio channel by the up to 15 modules which might be required at a single substation~

-9~ 196-007 _ Such hot stick activated hinge and clamp mechanisms do not exist in the prior art. The voltage transformers and capacitive dividers of the prior art are not electrically isolated. Separate measurements of all electrical quantities desired would require too much apparatus in the module. Synchronization of module transmi~sions would require a radio receiver in each module.

c~s BRIEF DESCRIPTION OF THE DRA~INGS

For a fuller understanding of the nature and objects of the invention refer~nce should be had to the following de-tailed description taken in connection with the accompanying drawings, in which:
Figure 1 is a perspective view of the state estimator module of the invention installed on an electrical trans-mission line;
Figure 2 is a perspective view showing how a~ state estimator module according to the invention may be hot stick mounted to a live conductor;
Figure 3 is a perspective view of a state estimator module according to the invention mounted to a conductor;
Figure 4 is a diagrammatic view of a substation totally monitored by means of the system of the invention;
Figure 5 is a diagrammatic schematic view of a power deliver system monitored and controlled according to the system of the invention;
Figure 6 is a top view of a state estimator according to the invention with the covers thereof removed;
Figure 7 is a bottom view of the covers of a state estimator module according to the invention;
Figure 8 is a top ~iew of one of the covers;
Figure 9 is a side view of one of the covers, partly in cross section;
Figure 10 is an enlarged cross sectional view taken along the line 10-10 of Figure 6 with the cover in place;

Figure 11 is an enlarged cross sectional view taken along the line 11-11 of Figure 6 with the cover in place;
Figure 12 is an enlarged fragmentary view of the hub portion of the state estimator module of Figure 6;
Figure 13 is a cross sectional view taken along the line 13-13 of Figure 12;
Figure 14 is an enlarged view of the conductor clampino jaws shown in Figure 12;
Figure 15 is a cross section taken along the line 15-lS
of Figure 14;
Figure 16 is a side view showing the inside of-one of the jaws shown in Figure 14;
Fi.gure 17 is a enlarged perspective view oE one of the jaws of Figure 14;
Figure 18 is a view of one of the pins of the hinge clamp mechanism of the invention;
Figure 19 is a cross sectional view thereof taken along the line 19-19 of Figure 18;
Figure 20 is a fragmented partially diagrammatic top view of the hinge clamp of the invention and the tool uti lized to open it if it jams;
Figure 21 is a top view similar to Figure 20 showing the hinge clamp mechanism of the invention when the state estimator module of the invention is clamped about a con--ductor;
Figure 22 is a view similar to Fiyure 21 showing the hinge clamp mechanism when the state estimator module of the invention is opened for engagement or removal from a conduc-tor;

g c ~ 2 ~
~ 19~-007 Figure 23 is a fragmentary side view, partially in cross section taken from the top of Figure 22;
Figure 24 is an exploded cross sectional view of the working mechanism of the hinge clamp o the invention;
Figure 25 is a diagrammatic front view of the hot sti.ck hinge clamp operating tool of the invention;
Figure 26 is a back view thereof;
Figure 27 is a side view thereof;
Figure 28 is a schematic block diagram of the electronics of the state estimator of the invention; ~
Figure 29 is a detailed schematic electrical circuit diagram of the power supply of the state estimator of the invention;
Figure 30 is a detailed electrical schematic block diagram of a portion of the electronics illustrated in Figure 28;
Figure 31, comprising Figures 31A through 31D which may be put together as shown in Figure 31E, is a detailed sche-matic electrical circuit diagram of the electronics shown in Figure 30;
Figures 32 and 33 are schematic electrical circuit dia-grams illustrating the voltage measurement system according to the invention;
Figure 34 is a timing diagram o the electronics illus-trated in Figure 30;
Figure 35 shows a sub-routine call as utilized in the flow charts of Figures 4~ through 61;

Figure 36 is a memory map of the program;

9 D ~L~2 5 19 6 - O O /

Figure 37 is a diagram of PIA port assignments of the program;
Figure 38 is a diagram of the message transmitted by the donuts 20;
Figure 39 is a diagram of task management of the pro-gram;
Figures 40 through 61 are flow charts of the sub-routines of a program that may be utilize~ in the donuts 20;
Figure 62 is an overall block diagram of a ground station receiver xemote termin~l interface according -to the invention;
Figure 63 is a diagram of a type of substation ~hat may be monitored by the electronics shown in Figure 62;
Figure 64 is a state diagram of a program that may be utilized in the receiver 24; and Figures 65, 66, 67, and 68 are diagrams of tables and buffers utilized in the program of Figure 64.
The same reference characters refer to the same elements throughout the several views of the drawings.

~2~a~

SUMMARY OF THE INVENTION

Various aspects of the invention are as follows:

Apparatus for measuring at least one characteristic of a power line conductor comprising:
a housing removably attachable to said conductor;
means for measuring the amplitude o~ at least one cyclic characteristic of power transmitted on said conductor;
said means for measuring including means for timing amplitude measurements such that said measurements occur at a plurality of different intervals within the period of a cycle of ~aid cyclic characteristic;
said timing means including means for delaying said measurements by a fixed time interval such that each of said measurements is taken in a different cycle for a plurality of cycles; and wherein said measurements are taXen over a period of n cycles with the time duration of each cycle equaling t and said fixed time interval between measurements equaling t~l/n~t;
means for calculating Fourier components of said cyclic characteristic from said measurements;
means for transmitting said Fourier components to a remote receiver; and said means ~or measuring, means for calculating and means for transmitting each being contained in said housing.

9F 125~C~5;

Apparatus for measuring at lPast one characteristic of a power line conductor comprising:
means for measuring the amplitude of at least one cyclic characteristic of power tran~;mitted on said conductox;
means for controlling said means for measuring such tha-t said measurements occur at a plura:Lity of different intervals within the period of a cycle of said cyclic characteristic;
said means ~or controlling including means for delaying said measurements by a ~ixed time interval such that each of said measurements is taken in a different cycle for a plurality of cycles;
means for calculating Fourier components of said cyclic characteristic from said measurements; and wherein said measurements are taken over a period of n cycles with the time duration of each cycle equaling t and aid fixed time interval between measurements equaling t+(1/n)t.

-lo- ~ 095 196-007 - DISCLOSURE OF THE INVENTION

Referring to Figure 1, toroidal shaped sensor and transmitter modules 20 are mounted on live power conductors 22 by use of ~ special, detachable hot-stick tool 108 (see Figure 2) which opens and closes a positively actuated hinging and clamping mechanism Each module contains means for sensing one or more of a plurality of parameters associated with the power conductor 22 and its surrounding environmentO These parameters include the temperat~re of the power conductor 22, the ambient air temperature near the conductor, the current flowing in the conductor, ~nd the conductor's voltage, frequency, power factor and harmonic currents. Other parameters such as wind velocity and direction and solar thermal load could be sensed, if desired. In addition, each module 20 contains means for transmitting the sensed information to a local receiver 24.
Referring to Figure 3, each toroidal module 20 is configured with an open, spoked area 26 surrounding the mounting hub 28 to permit free air circulation around the conductor 22 so that the conductor temperature is not disturbed. The power required to operate the module is collected from the power conductor by coupling its magnetlc field to a transformer core encircling the line within the toroid. The signals produced by the various sensors are converted to their digital equivalents by the unit electronics and are transmitted to the ground xeceiver in periodic buxsts of transmission, thus minimizing the averase power required.
One or more of these toroidal sensor units, or modules, may be mounted to transmission lines within the capture range of the receiver and operated simultaneously on the same frequency channel~ By slightly varying the intervals between transmissions on each module, keeping them integral numbers without a common factor and limiting the maximum number of modules in relation to these intervals, th~ sta-tistical probability of interference between transmissions is controlled to an acceptable degree. Thus, one re~eiver, ground station 24, can collect data from a p:Lurality of modules 20.
The ground station 24, containing a receiver and its antenna 30, which processes the data received, stores the data until time to send or deliver it to another location, and provides the communication port indicated at 32 linking the system to such location. The processing of the data at the ground station 24 includes provisions for scaling factorsj offsets, curve correction, waveform analysis and correlative and computational conversion of the data to the forms and parameters desired for transmission to the host location. The ground station processor is programmed to contain the specific calibration corrections required for each sensor in each module in its own system.

-12~ 3.~ 196-007 - Referring to Figure 5, the ground stations 24 are con-nected to the Power Control Center 54 by appropriate data transmission links 32 (radio, land lines or satellite chan-nels) where the measured data is processed by a Dynamic State Estimator which then issues appropriate control sig-nals over other transmission links 33 to the switchgear 58 at electri~al substations 44. Thus the power supply to transmission lines may be varied in accordance with their measured temperatures and measured electrical parameters.
Similarly, when sensors are located in both the prima~y and secondary circuits of power transformers, transformer faults may be detected and the power supplied to the transformer controlled by the Dynamic State Estimator through switch-gear.
In one aspect of the invention a Dynamic State Estima-tor may be located at one or more substations to control the supply of electrical power to the transformers located there or to perform other local control functions.
Thus, as shown in Figure 4, an electrical substation 34 may be totally monitored by the electrically isolated mod-ules 20 of the invention. Up to 15 of these modules may be connected as shown transmitting to a single receiver 24.
The receiver may have associated therewith local control apparatus 36 for controlling the illus~rative transformer bank 38 and the electrical switchgear indicated by the small squares 40. The modules 20 may be mounted to live conduc-tors without the expense and inconvenience of disconnecting any circuit~ and require no wiring at the substation 34.

The receiver 24 also transmits via its transmission link 32 -the information received, from the modules 20 tfor determin-ing the total state of the electrical substation) to the Central Control Station 54 of the electrical delivery system The system of the invention is adapted for total moni-toring and control of a bulk electrical power delivery sys-tem as illustrated in Figure 5. Here, modules 20 are lo-cated throughout the delivery system monitoring transformer banks 40 and 42, substations 44 and 46, trans~ission lines generally indicated at 48 and 50, and feeder sections gener-ally indicated at 52.
A number of modules are preferably located along~trans-mission lines such as lines 48 and 50, one per phase at each monitoring position. By monitoring the temperature of the conductors they indicate the instantaneous dynamic capacity of the transmission line. Since the~ are located at inter-vals along the transmission line they can be utilized to determine the nature and location of faults and thus facili-tate more rapid and effective repair.
The ground stations 24 collect the data from their local modules 20 and transmit it to the Power Control Center 54 on transmission links 33. The Power Control Center, in turn, controls automatic switching devices 56, 58 and 60 to control the system.
As illustrated in Figure 5, ground station 24 located at transformer bank 42 may be utilized to control the power supplied to transformer bank 42 via a motori~ed tap system generally indicated at 62.

~25~

- As shown in Figure Ç, the module 20 according to the i.nvention comprises two halves of a magnetic core 64 and 66, and a power takeoff coil 68, and two spring loaded tempera-ture probes 70 and 72 which contact t:he conductor and an ambient temperature probe 74.
In order to insure that the case 76 is precisely at ~he potential of the conductor 22 when the conductors are con-tacted by the probes 70 and 72, a spring 78 is provided, which engages the conductor 22 and remains engaged with the conductor and connects it to the case 76 before ~and ~uring contact of the probes 70 and 72 with the conductor.
Alternatively, or simultaneously, contact may be ma~ntained through conductive inputs in the hub 28.
The electrical current in the conductor is measured by a Rogowski coil 80 shown in Figure 7.
The voltage of the conductor is measured by a pair of arcuate capacitor plates 82 in the cover portions of the donut, only one of which is shown in Figures 8 and 9. The electronics is contained in sealed boxes 84 within the donut 20 as shown in Figure 10.
Block diagrams of the electronics of the donut 20 are shown in Figures 28 and 30.
Referring to Figure 30, the voltage sensing plates 82 are connected to one of a plurality of input amplifiers generally indicated a~ 86. The input amplifier 86 connected to the voltage sensing plates 82 measures the current be-tween them and local ground indicated at 88, which is the electrical potential of the conductor 22 on which the donut 0~5 20 is mounted. Thus the amplifier 86 provides a measure of the current flowing between the plates 82 and the earth through a capacitance Cl (see Figures 32 and 33). That i5, it measures the current collected by the plates 86 which would otherwise flow to local sround. This is a direct measure of the voltage of the conductor with respect to earth.
As also shown in Figure 30, the temperature transducers 70, 72, and 74, and Rogowski coil 80 are each connected to one of the input amplifiers 86. An additional tempe~ature transducer may be connected to one of the spare ampl~fiers 86 to measure the temperature of the electronics ~in the donut. The outputs of the amplifiers are multiplexed by multiplexer 90 and supplied to a digital-to-analog converter and computer generally indicated at 92, coded by encoder 94, and transmitted by transmitter 96 via antenna 98, which may be a patch antenna on the surface of the donut as illustrated in Figure 3.
As illustrated in the timing diagram of Figure 34, the current and voltage are sampled by the computer 92 nine times at one-ninth intervals of the current wave form; each measurement being taken in a successive cycle. The computer initially goes through nine cycles to ad~ust the one-ninth interval timing period to match the exact frequency of the current at that time, and then makes the nine measurements.
These measurements are transmitted to the ground station 24 and another computer 334 at the ground station (Figure 62) calculates the current, voltage, power~ reactive power,

-16- ~ 196-007 pow~ factor r and harmonics as desired; provides these to a communications board 106; and thus to a communications lin~
32.
For a maximum of fifteen donuts for which it is desired to transmit information each second or two, the relative transmission intervals can be chosen to be between 37/60ths and 79/60ths of a second; each transmission interval being an integral number of 6Oths of a second which do not have a common factor. This form of semi-random transmission according to the invention will insure 76% succ~ssful transmlssion with less than two seconds between successful transmissions from the same donut in the worst case. ,~
The hot stick mounting tool of the invention generally indicated at 108 in Figure 3 is shown in detail in Figures 25, 26, and 27. It comprises a Allen wrench portion 110 and a threaded portion 112, mounted to a universal generally indicated at 114. Universal 114 is mounted within a shell 116 which in turn is mounted to a conventional hot stick mounting coupling generally indicated at 118; and thus the hot stick ]76.
When the hot stick tool 108~ as shown in Figure 3, is inserted into the opening 122 in the donut 20~ the Allen wrench portion engages barrel 124 (Figure 24) which is op-positely threaded on each of its ends 126 and 128. Threaded portion 126 is engaged with a mating threaded portion of a cable clamp 130 and threaded portion 128 engages a mating threaded portion 144 of a nut 132. The nut 132 is fixed by means of bos5es 134 in plates 136 and 138, mounted to hinge

-17- ~5~ 196-007 pin~ 140 and 142 (Figure 23). Thus, when the hot stick tool 108 is inserted, and barrel 124 rotated in one direction, cable clamp 130 is brought towards nut 132, while when barrel 124 is rotated in the other direction, cable clamp 130 moves away from nut 132. Threaded portion 144 of nut 132 engages the threaded portion 112 of the hot stick tool 108, such that when cable clamp 130 and nut 132 are spread apart the threaded portion 112 of the hot stick tool is threaded into nut 132 so that the donut module 20 may be supported on the tool 108. *
Since hinge pins 140 and 142 are located near the outer edge of the donut 20 and fixed pins 146 and 148 are ~affixed to the donut more inwardly, if the pins 146 and 148 are spread apart, the donut will open to the position shown in Figure 6 and if the pins 146 and 148 are brought together, the donut will close. The pins 142 and 146 and 140 and 148 are joined by respective ramp arms 150 and 152. When cable clamp 130 is separated from nut 132, the ramp arms, and thus pins 146 and 148, are spread apart by the wedge portions 154 and 156 of cable clamp 130. At the same time the threaded portion 112 of the hot stick tool 108 engages the threaded portion 144 of nut 132 so that the donut 20 is securely mounted to the tool 108. A cable 158 passes around pins 146 and 148 and is held in cable clamp 130 by cable terminating caps 160 and 162. Thus when cable clamp 130 and nut 132 are brough~ together, the cable 153 pulls fixed pins 146 and 148 together to securely close the donut 20 and clamp it about the conductor 22. Shortly after it is drawn tight/ the

-18- ~ 196-007 thr~aded portion of the hot stick tool 108 disengages the threaded portion 144 of nut 132 by continued turning in the same direction.
If for any reason the donut 20 cannot be removed from a conductor 22 by using the hot stick tool 108, another hot stick tool generally indicated at 164 in Figure 20 may be used to cut the cable 158~ Tool 164 has a file 166 mounted thereon for this purpose~ It may also be provided with a threaded portion 168 to engage the threaded portion 144 of nut 132 after the cable 158 has been severed. -~

19 OBJE~TS OF ~SP~CTS OF THE INVfNTION

It is therefore an object o~ an aspect of the invention to provide a system and apparatus for monitoring and control o~ an electric power delivery system.
An obj~ct o~ an a~pect of the invention is to provide such a system predominantly employing radio transmitting modules mounted to power conductors.
An object of an aspect of the invention is to providQ such a system greatly reducing, if not eliminating, the use of wiring to transmit measurements at an electrical substation.
An object of an aspect of the invention is to provide such a system for determining the state o~ a substation dynamically.
An ob-Ject of an aspect of the invention is to provide such a system for determining the state o~ an electrical power delivery system dynamically.
An object of an aspect of the invention is to provide such a system for deteY~ining dynamic thermal line rating~.
An object of an aspect of the invention is to provide such a system for monitoring and controlling the status of electrical power ~tation equipment.
An object of an aspect of the invention is to provide such a system wherein the sensors are capable of measuring, as desired, current, voltage, frequency, phase angle, the fourier components of current and voltage from which other quantities may be calculated, the temperature of the conductor to which they are attached, or the temperature of the ambient air surrounding the conductor to which they are attached.

c)~

An object of an aspect o~ the invention is to provide a s~ate estimator ~odule to sense various power qu~ntities including those necessary for dynamic line ratings that can be rapidly, safely and reliably installed and removed from an energized high voltage transmission facility, up to 345KV line to line.
An object of an aspect of the invsntion is to provide a state estimator module that can be installed and removed with standard utility "hot stick" tools with an adaptor tailored for the module and for operation by a single lineman or robot.
An object of an aspect of the invention is to provide a "hot stick" mountable unit that is light weight, compact in 8ize, can be remotely calibrated, is toroidal in shape with a metallic housing consisting of a central hub suitable for various conductor sizes with the "hot stick" tool capable of opening and closing the toroidal housing around the conductor; and hub being provided with ventilating apertures and thermally 2a insulated inserts which grip the transmission line.
An object of an aspect of the invention is to provide a module of the above character that is brought to conductor potential before delicate electric equipment contacts the conductor.

An object o~ an aspect of the invention is to provide a stat~ estimator module that maintains positive engagement with a hot stick mountable tool except whe~
it is "snap shutl' around the conductor.
An object of an aspect of the invention i5 to provide a hinge clamp ~or a module of the above character.
An object of an aspect of the invention is to provide a hinge clamp of the above character that may be opened by an alt~rnative hot stick mounted tool in case of failure of the hinge clamp.
An object of an aspect of the invention is to provide an electrically isolated voltage sensor for a state estimator module of the above character.
An object of an aspect of the invention is to provide an unsynchronized single channel radio transmission system for a plurality of modules oP the above character.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the functions and relationship thereo~ and the features of construction, organization and arrangement of parts, which will be exemplified in the system and apparatus hereinafter set forth. The scope of the invention is indicated in the claims.

-26- l~S~9.~ 196-00~

-- sEST MODE FOR CARRYING OUT THE INVENTION

The State Estimator Module General The state estimator modules 20 ('7Donuts") clamp to a high-tension power conductor 22 and telemeter power parameters to a ground station 24 (Fiyure 1). Each module obtains its operating power from the magnetic _field generated by the current flowing in the high-tension conductor 22. Each module is relatively small ancl~shaped like a donut, with a 12 5/8" major diameter and a maximum thickness of 4 3/4". It weighs approximately 16 pounds and may be mounted in the field in a matter of minutes using a "hot stick" (Figure 2).
Typically, three donuts 20 are used on a circuit; one for each phase. Each donut is equipped to measure line current, line to neutral voltage, frequency, phase angle, conductor temperature and ambient temperature. Digital data is transmitted by means of a 950 MHz FM radio link in a 5-10 millisecond burst. A microcomputer at the ground station 24 processes data from the 3 phase set and calculates any de-sired power parameter such as total circuit kilowatts, kilo-vars, and volt~amps. Individual conductor current and vol-tage is also available. This data may then be passed on to a central monitoring host computer (typically once a second) over a data link 320 -27- ~2S~ 196-007 - One ground station 24 may receive data from as many as 15,donuts 20, all on the same RF frequel-cy (Figure 4). Each donut transmits with a different interval between its successive transmission bursts, ranging from approximately 0.3 seconds to 0.7 seconds. Thus, there will be occasional collisions, but on the average, greater than 70% of all transmissions will get through.
Environmental operating conditions include an ambient air temperature range of -40F to +100F; driving rain, sleet, snow, and ice buildup; falling ice from conductor-overhead; sun loading; and vibrations of conductors 22~
Current measurements over a range of 80-3000 ~amperes must be accurate to within 0.5%. Voltage measurements over a range of 2.4-345KV (line-line) must be accurate to within 0.5%. Conductor diameters range from 0.5 to 2 inches.
All exterior surfaces are rounded and free from sharp edges so as to prevent corona. The module weighs approximately 16 pounds. It is provided with clamping inserts for different conductor diameters which are easily removeable and replaceable. The conductor clamping does not damage the conductor, even after prolonged conductor vibration due to the use of neoprene conductor facings 170 in the inserts 186 (Figure 13).

09~i _ The sp~cial hot stick tool 108 is inserted into the donut 20. Turning of the hot stick causes the donut to split so that it may be placed over a conductor. Turning the hot stick in the opposite direction causes the donut to close over a conductor and clamp onto it tightly. The tool 108 may then be removed by simply pulling it away. Reinser-tion and turning will open the donut and allow it to be removed from the line.
Conductor temperature probes 70 and 72 (Figure 6~ are spring loaded against the conductor when the donut is in-stalled. The contacting tip 174 (Figure 10) is beryllia and inhibits corrosion and yet conducts heat efficiently~to the temperature transducer within. It is also a non-conductor of electricity so as not to create a low resistance path from the conductor to the electronics.
The hub and spoke area in the center of the donut 20 and the temperature probe placement are designed with as much free space as possible so as not to affect the tem-perature of the conductor.
All electronics within the donut are sealed in water-tight compartments 84 (Figure 10).
The xadio frequency transmitter power of the donut 20 is typically 100 milliwatts. However, it may be as high as 4 watts~ The donut 20 is protected against lightning surges by MOV devices and proper grounding and shielding practice.
All analog and digital cixcuitry is CMOS to minimize power consumption.

-29- 1~5BO~.~ 196-007 No potentiometers or other variable de~ices are used for calibration in donut 20. All c~libration is done by the ground station 24 by scaling factors recorded in computer memory.
Each donut is jumper programmable for current ranges of 80-3000 amperes or 80--1500 amperes, Current is measured by using a Rogowski coil 80 (Figure 7)~ Voltage is measured by two electrically insulated strips of metal 82 (Figure 8) imbedded flush on the exterior of one face of the donut. These strips act as one pl~te of a capacitor at the potential of the conductor. The~other plate is the rest of the universe and is essenti~lly at calibrated ground (neutral~ potential with respect to the donut. The amount of current collected by the donut plate from ground is thus proportional to the potential of the donut and the conductor on which it is mounted.
Power to operate donut electronics is derived from a winding 68 on a laminated iron core 64-66 which surrounds the line conductor. This core is split to accommodate the opening of the donut when it clamps around the conductor.
The top and bottom portions of the aluminum outer casing of the donut are partially insulated from each other so as not to form a short circuited turn. The insulation is shunted at high frequency by capacitors 176 (Figure 10) to insure that the top and bottom portions 76 and 81 are at the same radio frequency potential.

-30~ 196-007 - The data is transmitted in Manchester code. Each message comprises the latest measured Fourier components of voltage and current and another measured condition called the auxiliary parameter, as well as an auxiliary parameter number to identify each of the five possible auxiliary parametersO Thus, each message format is as follows:
Donut Identification Number 4 bits Auxiliary Parameter Number 4 bits Voltage Sine Component (Fourier Fundamental) 12 bits Voltage Cosine Component (Fourier Fundamental) 1-~ bits Current Sine Component (Fourier Fundamental) 12 bits Current Cosine Component (Fourier Fundamental) ~12 bits Auxiliary Parameter 12 bits Cyclic Redundancy Check 12 bits The auxiliary parameter rotates among 5 items on each successive transmission as follows:
Auxiliary Parameter No. Parameter 0 Conductor Temperature 1 Ambient Exterior Temperature 2 Check Ground (0 volts nominal) 3 Check Voltage (1.25 volts nominal) 4 Interior Temperature -31- ~ 3~ 196-007 _ More specifically, and referring to Figure 2, the hot stick tool 108 may be mounted on a conventio~al hot stick 176 so that the module 20 may be mounted on an energized conductor 22 by a man 178.
In Figure 3 it can be seen how the hot stick tool 108 provided with an Allen wrench portion 110 and a threaded portion 112 fits within a hole 122 provided in the donut 20 mounted on conductor 22. The donut comprises two bottom portions 76 and two covers, or top portions 81, held together by six bolts 180. Each bottom portion ~6 is provided with a top hub 182 and a bottom hub 184 (see also Figure 13), supported on three relatively open spokes 185.
Conductor temperature probes 70 and 72 (see also Figure 6) are aligned wikhin opposed spokes 185.
Identical clamping inserts 186 are held within opposed hubs 182 and 184 (see Figure 13) and clamp conductor 22 with hard rubber facings 170 provided therein. The tops 81 (Figure 3) are each provided with an arcuate flat flush con-ductor 82 insulated from the housing for measuring voltage and one of the bottom portions 76 is provided with a patch antenna 98 for transmitting data to the ground station.
Although the top portions 81 are each provided with a non-conductive rubber seal 188 (Figure 7) and the area around the hinge is closed by cover plates 193, water escape vents are provided in and around the access opening 122, which due to the hot stick mounting is always at the lower portion of the donut 20 when installed on a conduc~or 22.

~5~5 196-007 - Now referring to Figure 6, a hinge mechanism is provid-ed, generally indicated at 192. It comprises hinge pins 140 and 142, mounted in a top plate 136 and a bottom plate 138 (see Figure 23). When opening or closing, the bottom por-tions 76 along with their covers 81 rotate about pins 1~0 and 142. The two halves of the donut 76-76 are drawn to-gether to clamp the conductor by bringing fixed pins 146 and 148 together by means of cable 158. They are separated by pushing a wedge against wedge arms 150 and 152 to separate pins 146 and 148 which are affixed to the bottom p-ortion 76-76.
To make certain that the bottom portions 76-76~of the donut 20 are at the potential of the conductor, a spring 78 is provided which continuously contacts the conductor during use and contacts it before it comes in contact with the tem-perature probes 70 and 72, protecting them against arcing.
To insure that the unit comes together precisely, a locating pin 194 and locating opening 196 are provided. The multi-layer power transformer cores 64 and 66 come together with their faces in abutting relationship when the unit is closed. They are spring loaded against each other and mounted for slight relative rotations so that the flat faces, such as the upper faces 198 shown in Figure 6 will fit together with a minimum air gap when the unit is closed.
The temperature probes 70 and 72 are spring loaded so that they press against the conductor when the unit is closed.
The ambient probe 74 is provided with a shield 200 covering the hub are~ so that it looks at the temperature of the shield 200 rather than the temperature of the conductor.

_33~ 95 196-007 _ The temperature probes 70 and 72 are located in align-ment with opposed spokes 185 so as to provide the least amount of wind resistance so that the conductor at the probes 70 and 72 will be cooled by the ambient air in sub-stantially the same way as the conductor a distance away from the module 20.
The ten radio frequency shunting capacitors 176 can also be seen in Figure 6, as well as the patch antenna 98.
Now referring to Figure 7, a Rogowski coil 80 is af-fixed to the covers 81 by eight brackets 202 and i5 connect-ed by lead 203 to the electronics~in the bottom portions 76 (Figure 10). The non-conductive rubber seal 188 may be seen in F.igure 7, as well as recesses 206 for stainless steel fiber contacting pads 202 which contact the RF shunting capacitors 176 (Figure 10).
Now referring to Figures 8 and 9, the capacitor plate 82 can b seen mounted flush with the surface of one of the covers 81. It may also be seen in Figure 9 how the openings 206-208 for the Rogowski coil are provided with slots Z10 to prevent the formation of a short circuiting path around it.
Now referring to Figure ].0, the arcuate capacitor plates 82 are insulated from the case 81 by teflon or other non-conducting material 212. The surface gap between the capacitor plate 82 and the surface of the case 81 is .005 inches. The plates 82 are mounted to the tops 81 by means of screws 214 passing through insulated bushings 216 and ~5~3g)~

nuts 218, or by other comparable insulated mounting means.
Connection bctween the capacitor plates 82 and the elec-tronics may be made by means of the screws 214. A stainless steel wool pad 202 may be seen in Figure 10 connecting to the shunt capacitor 176 which may be in the form of a feed through capacitor. The insulating seal 188 is shown next to the shunt capacitor 176.
The temperature probe 70 comprises an Analog Device AD-590 sensor Z20 mounted against a beryllia insert 174 which contacts the conductor 22. The three cond~ctors generally indicated at 222 connect the electronics to the sensor 220 through an MOV 224.
The sensor 220 and beryllia insert 174 are mounted in a probe head 226 which in turn is mounted to a generally cy-lindrical carriage 227 pushed out by spring 228 to force the beryllia insert 174 against the conductor. A rubber boot 229 protects the interior of the probe 70. The probe head 226 is formed of an electrical and heat insulating material.
The probe 72 is mounted in a cylindrical post 230 which pre-ferably is adjustable in and out of the lower casing 76 for adjustment to engage conductors of differing diameters. The other conductor temperature probe 72 is identical.
An electronics box B4 is mounted within each of the two bottom portions 76 and top portion 81. The boxes 84 are hermetically sealed. The power pickup transformer core 66 and its mating transformer core 64 (Figure 6) in the other half of the module is pressed by leaf spring 232 against the _35_ 196-007 mating core 64 and is pushed against post 234 by means of spring 236 so that the flat faces 198 of the two cores 64 and 66, shown in Figure 6, will come together in a flat face to face alignment when the module is closed.
Referring now to Figure 11, it can be seen how the end face 238 of the core 66 passes through the end plate 240 of lower portion 76. Opening 242 is provided for electrical wirlng connecting the sealed circuit containers 84 in both halves of the device. It should be noted how opening 242 is open, again to prevent encircling the wiring.
The opening 244 for the ambient sensor 74 and the open-ing 246 for the conductor sensor 70 may be seen in,Figure 11. The hubs 182 and 184 and spokes 185 may be seen in Figures 10 and 11 although the openings 248 in the spoke 185 of Figure 10 are not shown in order that the temperature probe 70 may be shown in detail.
Now referring to Figure 12 and 13, it can be seen how the clamping inserts 186 fit within the hubs 182 and 184 and how the facings 170 fit within the inserts 186. The inserts 186 are made in sets having differing inner diameters to accommodate conductors 22 of differing diameters.
As shown in Figures 15 through 17, the clamping inserts 186 are provided with alignment t~bs 250 which fit into the hubs 182 and 184. Each of the inserts 186 is identical, one being upside down with respect to the other when installed as shown in Figure 14. Each is provided with a screw hole 252 for screw mounting them within hubs 182 and 184 and are pxovided with a raceway 254 for insertion of and to hold the -36- ~5~ 196-007 har~ conducting neoprene rubber facings 170, which may be of material, having a hardness of 70 durometer on the Shore A
scale. The facings 170 are preferably filled with a con-ducting powder, such as graphite, to establish electrical contact with the conductor 22.
One of the pins 142 of the hinge is shown in Figure 180 All of the pins are provided with a non-conducting ceramic coating 256 which may be plasma sprayed thereon, so that the pins do not provide, together with the plates 136 and 138 of the hinge ~Figure 23), a shorted turn.
Now referring to Figure 20, an emergency hot :stick mo~ntable tool 164 can be used to open the donut 20~if for any reason the hinge clamp jams. This tool comprises an elongated file 166 used to cut the cable 158. After the cable 158 has been cut, a threaded portion 168 of the emergency tool may be threaded into the thread portion 144 of nut 132 (see Figure 24) to remove the opened donut 20.
Also, in Figure 20, it can be seen how the cable clamp 130 is provided with a raised key portion 258 which guides the cable clampls motion in a guideway opening 260 in the top plate 136. Also, the circular opening 262 in the top plate 136 may be seen, in which the boss 134 of nut 132 fits to keep it from moving. A similar boss on the bottom of the nut 132 fits into a circular opening in bottom plate 138, as does a similar key 264 on the bottom of cable clamp 130 fit into a guiding opening in bottom plate 138. The pla~es 136 and 138 are secured together by bolts 266 and 268 and are _37_ ~2`5~ 5 196-007 hel~ apart by spacers 270 and 272 (Figures 21 and 23) about the bolts 266 and 268. Cover plate 136 is machined with openings 274 and ribs 276 to make it as strong and light as possible.
Figure 21 shows the hinge clamp mechanism with the top plate 136 removed and the donut 20 closed, the cable 158 pulling pins 146 and 148 tightly together.
In Figure 22 the hinge clamp mechanism is shown with top plate 136 removed and the cable clamp 130 spread apart from the nut 132 by the barrel 124. The wedges 154 a~d 156 have pushed ramp arms 150 and 154 to spread apart fixed pins 146 and 148, to open the donut.
In Figure 23 it can he seen how hinge pins 140 and 142 fit into receiving portions 278 and 280 of each bottom portion 76 of the donut 20. Similarly, fixed pins 146 and 148 fit into portions 282 which are shown partly cut away in Figure 23. Portions 282 are located closer to the central axis of the donut 20 than hinge pins 142.
Also seen in Figure 23 are the nuts 284 and 286 on the bolts 266 and 268.
As previously described the hot stick tool 108 (Figures 25, 26 and 27) for mounting to a conventional hot stick 176 comprises a conventional hot stick mounting coupling 118, a barrel portion 116, a universal joint 114 which accommodates misali~nment of the line of the stick 120 and the receiving opening 122 (see Figure 3) in the donut 20. Also seen in _3~ 196-007 Figures 25, 26, and 27 ar~ the donut engaging Allen wrench portion 110 and threaded portion 112 of the hot stick tool 108, and the sleeve 116 which holds the base 288 of the universal 114 rigidly to -the mounting 290 for the hot stick tool mounted portion of the coupling 118.

State Estimator Module Electronics The state estimator module electronics are shown in their overall configuration in Fiyure 28. They comprise a power supply 292, digitizing and transmitting electronics 294, sensors indicated by the box 296, and antenna 98.
The center tap 9 of the power pickoff coil 68 ~s COII-nected to the aluminum shell of the module 20, which in turn is connected directly to the power conductor 22 by spring 78 and by the conducting facings 170 (Figures 12 and 13).
Thus, the power conductor 22 becomes the local ground as shown at 88 for the electronics 294. The power supply sup-plies regulated +S and -8 volts to the electronics 294 and an additional switched 5.75 volts for the transmitter as indicated at 300. The electronics 294 provides a trans-mitter control signal on line 302 to control the power supply to the transmitter. The sensors 296 provide analog siynals as indicated at 304 to the electronics 294. The de~ailed schema~ic electrical circuit diagram of the power supply 292 is shown in Figure 29.

9~
_39_ 196-007 - Figure 30 is a schematic block diagram of the electron-iC5 2g4. As shown therein, the Rogowski coil 80 is connect-ed to one of a plurality of input amplifiers 86 through current range select resistors 306. The voltage sensing plates 82 are connected to the uppermost ~nplifier which is provided with a capacitor 308 in the feedback circuit which sets gain and provides an amplifier output voltage in phase with line to neutral high tension voltage. It also provides integrator action for the measurement of current the same way as the amplifier connected to the Rogowski coil. ~ Thus amplifier 86 connected to the voltage sensing plate 82 is a low impedance current measuring means connected betw~en the power conductor 22 (i.e., ground 88) and the plates 82.
Each of the temperature transducers 72 and 74 is con-nected to a separate one of the amplifiers 86 as shown.
Spare amplifiers are provided for measurement of additional characteristics such as the interior temperature of the donut 20. Each of the amplifiers 86 is connected for com-parison with the output of digital analog converter means 310, 2.5 volt reference source 312 at comparator 314 by the multiplexer 90 under control of the digital computer 316.
The digital computer may be a Motorola CMOS 6805 micro-processor having I/O, RAM, and timer components. A program-mable read only memory 318 is connected thereto for storing the program. A zero crossing detector 320 detects the zero crossings of the current in the Rogowski coil 80 and provide basic synchronization. The donut ID number is selected by jumpers generally indicated at 322. The digitized data -40- ~5~S 196-007 ass4mbled into appropriate messages is encoded in Manchester code by the encoder 94 and supplied to a 950 megahertz transmitter 96 which then supplies it to the antenna 98.
The schematic electrical circuit diagram of the elec-tronics 294 is shown in Figure 31, comprising Figures 31 through 31D which may be put together to form Figure 31 as shown in Figure 31Eo The grounds therein are shown as tri-angles~ A inside the tria~gle indicates an analog ground and D a digital ground. Both are connected to the common terminal as indicated in Figures 28 and 31C.

The Voltage Sensor The operation of the voltage sensor may be understood with reference to Figure 32. We wish to measure the alter-nating current voltage VL between the conductor 22 and the ground 324~ The metal plates 82 form one plate of a capaci-tive divider between conductor 22 and ground, comprising the equivalent capacitor Cl between ground and plate 82 and equivalent C2 between conductor 22 and the plate 82.
The voltage VL between ground and the conductor 22 is thus divided across the equivalent capacitor Cl and C2.
Prior art methods have attempted to measure the poten-tial developed across capacitance C2. However this capaci-tance can change value and affect the accuracy of the measurement. It may also develop a spurious voltage across it due to the high electric field in the vicinity of the high voltage conductor 22. The low impedance integrating operational amplifier of the invention, generally indicated -41- ~`5~ 196-007 at ~26, shunts capacitance C2 and effectively eliminates it from the circuit. The potential of plates 82 is therefore made to be the same as that of concluctor 22 through the operational amplifier 326. Now the potential between the plates 82 and ground 324 is the potential VL between the line 22 and the ground 324. Therefore, the current in the capacitance Cl is now directly proportional to the voltage VL. Therefore, the low impedance integrater connected operational amplifier 326 will provide an AC output voltage exactly proportional to the current in the capacitance Cl and thus directly proportional to the high voltag~ V~ on the conductor 22.
Now referring to Figure 33, all of the circuitr~
including the integrater connected operational amplifier 326 is housed within a metal housing 81, which is connected to the conductor 22 via the spring 78. The plates 82 are on the outside of the housing ~1 and must be electrically insulated from it. The plates 82 cannot protrude from the housing 81 since this would invite corona on very high voltage lines. It therefore must either be flush with the surface of the housing 81 or recessed slightly in it.
Unfortunately rain water or snow collecting on the surface will provide a path of high dielectric constant shunting the high electric field about the conductor 22 so that the current I2 to the operational amplifier 326 will not be equal to the current Il in the capacitance Cl. Thus the measurement will be in error.

~L2~ 5 - In o.rder to minimize this effect the width and length of the sensing plates must be made very large in comparison with the width of the gap separating them from the housing and if any protective coating is used over the sensing plate it must have no appreciable thickness. Furthermore, the outer surface of the sensing plate must conform, as closely as possible, with the outer surface of the housing 81.
Thus the sensing plates 82 shown in Figures 8, 9~ and 10, are made very long and have gaps to the housing at their ends of only .020 inches and gaps 212 along them of .005 inches in width. The plates 82 are approximately 3/8ths of an inch in width, which is of course very much greater than the gaps of .05 inches and .020 inches.
When constructed in this manner, water droplets covering the metallic sensing plate and bridging the adjacent housing do not materially affect the measurement of VL. This is true because:
1. the sensing plates 82 are directly exposed and water overlying them which has a high dielectric constant, simply conducts the capacitive current 11 directly to the plate;
2~ the amount of current shunted by water at the gap between the plates 82 and the housing 81 is very small in proportion to the amount collected by the much larger area sensing plates themselves;

3~
-~3- 196-007 - 3O the alternating current lost through the shun~
path across the gap between the plates 82 and housing 81 is very small because of the low input impedance of the integrater connected operational amplifier 326.

Deriving the Fourier Components of Current and Voltage . _ . . . _ . _ Since the state estimator module 20 is mounted in isolation on a high-tension transmission line it is desirable to derive as much information as possible frbm the sensors contained within it with a minimum of complexity and to transmit this raw data to the ground station 24~,(Figure 1~. Calculation of various desired quantities may then be made on the ground.
It is therefore convenient to sample and hold both the current and voltage simultaneously and to send these quantities to the ground sequentially by pulse code modulation.
When it is desired to derive phase and harmonic data rather than merely transmitting the root mean square of the voltage and current to the ground, the shape of the waveforms and their relative phase must be transmitted.
We do this by transmitting Fourier components. We sample the waveform of both current and voltage at intervals of l~9th of a cycle. ~owever, rather than doing this during one cycle, we do this making one measuremen~ at each cycle, changing the interval over nine cycles.

4~ ~5~95 196-0~7 - The ground station can then easily compute the quan-tities of interest, for example, RMS amplitude of voltace and current, their relative phase and harmonic content.
Since current and voltage are sampled simultaneously, their relative phases are the same as the relative phases of the sample sequence. The harmonic structures are also the same, so that, except ror brief phenomena, any desired analysis may be made by the ground station.
The data transmissions take place in a ive to ten second millisecond interval, which is synchronized with the zero crossing of the donut 20. With thi.s information, the relati.ve phase of three phases of a transmission line as shown in Figure 1 may be derived.
In the embodiment disclosed herein we only compute the fundamental Fourier components of VA and VB and IA and I~
which are:

V~ = 5 ~VS .COS (S . - S ) ST
B 5 ,~ S ( S T S ) S=l A S ~ IS . COS (s~ . S ) S=l B ~ . ~IS . SIN ~S . S ) -45- ~ O~S 196-007 w~re ST equals the total nurnber of samples in the apparatus disclosed 9 9 S equals the sample, and Vs and IS are the value of the measured voltage and current at ea~h sample S.
From these the RMS voltage V and current I may be derived by the formulas:
V = ~Va~2 + (V )2~1/2 L(IA) + (IB) real power is:

(VB x IB) + (VA x IA) and reactive power is:

(VA x IB) ~ (~B x IA) If it is desired to have information about the~shape of the waveform (that is harmonic data) more samples may he taken and the desired Fourier harmonic components calculated and transmitted.

"Random" Transmissions on a Single Radio Channel _ As shown in Figure 4, a single substation 34 may have as many as fifteen donuts 20 transmitting data to a single receiver 24. Since radio receivers are expensive and radio frequency channel allocations are hard to obtain, it is de-sirable to have all units share a single channel. For weight and economy it is desirable to minimize the equipment in the donuts 20 at the expense of complicating the receiver 24.

Idealy, all donuts 20 transmitting on a single channel would transmit, in turn, in assigned time slots. Unfortu-nately, the only way to synchronize them according to the -46~ 6-0~7 pr~or art would be to provide them each with a radio receiver.
Our donuts 20 are programmed to send out short burst transmissions at "random" with respect to each other, and to do so often enough that occaslonal interference between t~o or more transmissions does not destroy a significant portion of the data. This is accomplised by assigning to each donut

20 transmitting to a single receiver 24 a fixed transmission repetition interval so that no synchronization is required.
The interval between transmissions of each of the donuts is an integral number and these numbers are chosen so that no two have a common factor.
For example, for fifteen donuts, we choose the inter-vals W measured in sixtieths of a second according to the following table:
Donut Number W

1~ 79 _ It is desirable that the messa~e length be reduced to a bare minimum in order to minimize simultaneous message transmission. One way we accomplish this is to transmit "auxiliary" information in repeating cycles of five transmissions.

Timing of the Measurements and_Transmissions A timing diagram is shown in Figure 4, where the sine wave is the current as measured by the Rogowski coil. At zero crossing labeled 0 timing is started. During t~e next cycle ]abled 1 and succeeding cycles through the eighth, the nine successive Fourier rneasurements IS and Vs a~e made.
During the ninth cycle the period of the previous eight cycles is utilized to define the sampling interval and the Fourier samples of the current and voltage are again taken during the next eight cycles. These measurements are uti-lized to compute VA, VB, IA and IB. At the end of the next cycle labeled 9 at the 0 crossings, twenty-one cycles have occurred. During the followup period of time, up to a total of W - 1 cycles, the program loads shift registers with the identification number of the donut, the auxiliary number, the Fourier components VA~ VB~ IA, IB, the digiti~ed auxiliary parameters and the CRC (a check sum). At W - 1 the transmission 328 begins and takes place over a short interval of 5 to 10 milliseconds, (approximately 5 milli-seconds in the apparatus disclosed). Then at the ~ crossing at the end of the cycle beginning a~ W - 1, that is af~er W cycles, the program is reset to ~ going back to the left hand side of the timing diagram of Figure 34.
In the program discussed below there is a timer labeled Z which is set to 0 at the far left, beginning ~ cross over.
It is reset to ~ = 21 at the end of t:he twenty first cycle, the second nine to the right in Figure 34.

_4g~ t~ 196-007 The Donut Software -Copyright ~ 1983, Produc~ Development Services, Incorporated (PDS) Scope The state estimator module 20 ~sometimes called herein the substation monitor) is a MC146805E2 microprocessor device.

Introduction The "Donut" software specification is divi~.ed into three major sections, reflecting the three tasks perEormed by the software. They are:
Data structures, The background processing that performs the bulk of the "Donut" operations. Included are transmitter control, sample rate timing, analog value conversion, and general "housekeeping", Common utility sub-routines, The interrupt processing that handles A.C. power zero-crossing interrupts and maintains the on-board clock which is used for cycle timing, and The restart processing that occurs whenever the microprocessor is restarted.

The program listings are found in Appendix ~.

-50- ~5~95 196-007 No~tion Conventions a) Logic Statements Program modules are described via flowcharts and an accompanying narrative. The flowcharts use standard symbols, and within each symbol is noted the function being performed, and often ~ detailed logic statement.
Detailed statements conform to the following conventions:
IX Index Register SP Stack Pointer PC Program Counter A,B Register A or B
CC Condition Codes Y Contents of register or contents of memory location Y.
(y) Contents of memory location addressed by the contents of register or contents of memory location y.
A,X Contents of location whose address is A - IX.
y(m-n) Bits m-n of the contents of register y or the contents oE memory location y.
a-~b a replaces b. The length of the move (one or two bytes) is determined by the longer of a or b.
For instance:
ABC-~XYZ Move the contents of memory location ABC to memory location XYZ.
IX-~XYZ Save the Index Register in location XYZ .
(IX~-~XYZ Store the contents of the address pointed to by the Index Register in location XYZ.
0,X-~XYZ Same as above.
XYZ~2,X-~SP Move the bytes in location XYZ~2~(IX) and XYZ+3~(IX) to the Stack Pointer.
IX--~(XYZ) Store the Index Register in the mem-ory location pointed to by location XYZ .
(IX)-~(XYZ) Store the contents of the m~mory lo-cation pointed to by the Index Register in the memory location pointed ~o by location XYZ.
ABC (2-3) Bits 2-3 of memory location ABC.

- b) Subroutine Calls Subroutine calls contain the name of the subroutine, a statement of the sub-outline, a statement of its function, and the flowchart section which describes it as shown in Figure 35.

Data Structures . ~ . .
The memory map is shown in Figure 36, the PIA

Definitions in Figure 37, and the Data Transmission Format in Figure 38.

Background Processing `~

The Background Processing Hierarchy is shown in Figure 39.

~5~

Substa~ion Monitor Mainline (MAIN) FlG. 40 PURPOSE: MAIN is the monitor background prQeess-ing loop.
ENTRY POINT: MAIN
CALLING SEQUENCE: IMP MAIN (from RE~SET) REGISTER STA7 US: A, X not preserved.
TA13LES USED: None.
CALLED BY: RESET
CALLS: SYNC, HKEEP, GETVAL, COMP~3T, CRC12, SHIFI', XMIT
E~YCEPTION CONDmONS: None.
DESCRIPIJON: Main ealls SYNC to time ~hc AC
frequency and compute the sampling rate, HKEEP
~ perform general initializaiion, and GETVAL to sample the analog values. COMPUT is ealled to fin-ish the Fouricr calculations, the watehdog timer is kicked, and CRCI~ is ealled to ealculate the CRC
value for the data lo bc transmitted. SHlFT is eallcd to lo~d thc shift register, XMIT is ealled to transmit the data to thc ground station, the watehdog is kicked, and the entire cyele is repeated.

53 125B09.S

Synchronize ~iming (SYNC~ FIG. 41 PURPOSE: SYNC timcs the AC frequency and calcu-lates the sampling interval.
ENTRY POINT: SYNC
CALLING SEQUENC:E:
ISR SYNC
Return REC;ISTER STATUS: A, X no press:rved.
TABLES USED: None.
CALLED BY: MAIN
CALLS: DIV3X9 EXCEPTION COMDITIONS: None.
DESCRIPrION: SYNC initialka the zero crossing count and scts the 3ync modc n~g. The 3um buf~r is clearecl for use a~ a timc accumulator, the zero cross-ing occurrcd flag is raet, ar~d the cycle counter is sa to 10. The zero crossing occurred nag i5 mOnitQred Lmtil 10 zero cros3in~ interrupts havc occurred, at which point thc time value is moved ~o the surn buf~er. DIV3X2 ~s called to divid~ the 10 cycle time by 9, the quoticnt is saved as thc sampling ~ime, the start flag is set, and a return is e~ecutcd.

5~ ~ ~5~0~.5 Perform Housckeeping (HKEEP) FIG. 42 PURPOSE: H~CEEP performs cycle initiali~ation.
ENTRY POINT: HKEEP
CALLING SEQUENCE:
ISR H[KEEP
Return RECISTER STATUS: A, X nor preserved.
TABLES USED: TIMTBL-Timing Intcrval Table CALLED ElY: MAIN
CALLS: None.
EXCEPTION CONDITIONS: None.
DESCRIErrlON: HKEEP rdeases the DAC tracking register, clcsrs the sum buffe}s, and resets the timing value remainder. The Donut 1. D. number is read and stored in the data buffer, the cycle interval sime is retrievcd fro~ the TIMTBL based on the 1. D. num-b~r, and the ~uxilliary data I. D. number is bumpal. A
retllrn is then e~cecuted.

~ . .

~5~95 Collect All Data (GETVAL) FIG. 43 PURPOSE: GETVAL reads the nine data samples.
ENTRY POI~T: GETVAL
CALLING SEQUENCE:
JSR GEI VAL
Return REGISTER STATUS: A, X not preserved.
TABLES USED: None.
CAI,LED BY: MAIN
CALLS: SAMPLE
EXCEPrION CONDITIONS: Nonc.
DESCRIPTION: GETVAL monitors thc time to-s~
pte flag. When set, the flat i.s rcset, SAMPLE is called to sample the analog values, and the watchdog timer is Icicked. When ~he cycle has been repeated nine time~, a retum is e~lecllted.

Read Analog Values (SAMPLE) FIG. 44 PURPOSE: SAMPLE reads and saves ~he analog val-ues.
ENTRY POINT: SAMPLE
CALLING SEQUENCE:
JSR SAMPLE
Return REGISTER STATUS: A, X not preserved.
TA~LES USED: Nonc.
CALLED BY: GETVAL
CALLS: READAC, SUMS
EXCEPTION CONDITIONS: Mone.
DF,SCRIPTION: SAMPLE calls READAC to read the currcnt and voltage values ~nd SUMS to update the Fourier su ns. A rcturn is e~tecuted unless all nine samples have bcen taken, in which case READAC is eallcd to read the au~illiary data value. The analog value tracking register is released. Dnd a return is e~ecu~ed.

57 ~ 8~

R~d DAC/Comparator Circuit (READAC~ FIG. 45 PURPOSE: READAC converts the analog;s to digital val~
ENTRY POINT: READAC
CALLING SEQUE~ICE:
ISR READAC
Return A, X= 12 bit vaJue REGISTER STATUS: A, P, X not preserved.
TABLES USED: None CALLED 13Y: SAMPLE
CALLS: Nonc EXCEPTION CONDITIONS: None DESCRlPlrlON:
E~EA!DAC initiali~es tbe trial and incremental values.
The trial valuc is writtcn to thc DAC as threc four-bit values, and the DAC conversion is initi-ated. A short register-decrement delay loop allows the l)AC time to convert, the incremental value is divided by two, and tbe comparator input is checked. The incremental value is subtractcd/ad-ded to the test value if the test value was higher/-lower ~han the actual analog value.
When the incremcntal value reach~s zero, thc vahle is converted to true two's complement and a return is e~ecuted with the value in A, X.

Maintain E~ouriet Sums (SUMS) FIG. 46 PUR~SE: SUMS multiplies the analog values by the trigonometric values of the phase angles and sums the tesults.
ENTRY POINT: SUMS
CALLING SEQUENCE:
JSR SUMS
Return REGISrER STATUS: A, X not preserved.
TABLES USED:
COSINE--Table of cosine values SINES--Table of sine values CALLED BY: GETVAL
CALLS:
~ULT
Local 3ubrou~ines: ABSVAL, ADDCOS/ADD-SIN--FIGS. 47 & 48 EXCEI~ION CONDITIONS: None.
DESCRIPTION: SVMS calls ABSVAL to move the absolute value of the analog value to the multiply buf~er, moves the trig value to the buf~er, and calls MULT to perforrn the multiplication. ADDCOS or ADDSIN is called to add the produc~ to the sine and cosine valucs for both voltage and current.

59 ~ 5 Perfonn Daea Manipula~ions (COMP~I ) FIG. 49 PURPOSE: COMPIJT perfor ns nccessary scaling functiol~s.
ENTRY PO[NT: COMPUT
CALLING SE~UENCE~:
ISR COMPUI
Retum REGISlER STATUS: A, X not prescrved.
TA13LES USED: NOQC
CALLED 8Y: MAlN
CALLS: DIVA13S, DIV4X2, DIVCNV
EXCEPTION CONDITIONS: None.
DESCRIPTION: COMPUT mov the scale factor to the dividc buffer, call~ DIVABS to move the absolute value of thc fourier sum to the buff~r, and calls DIV4X2 to perfor n the division. DlVCNV is callcd to apply the proper sign to thç quotient, and the Yalue is movcd to thc data buffcr. This cycle is rcpested for each of the four fouficr sums, and a return is c~e-cuted.

ompute Cyclic Redundancy Check Yalue (CRC12) FIG. Sû
PURPOSE: C~aC12 computes the CRC value.
ENTRY POINT: CRC12 CALLING SEQUENCE: JSR CRC1t Return REGISTER STA~US: A, X not preserved.
TABLES USD: None.
CALLED BY: MAIN
CALLS: Local Subroutine: CPOLY--FIG. 51 EXCEPI'ION CONDITIONS: None.
DESCRIPTION:
CRC12 sets a counter to the number of bytes in the data buffer, initializes the CRC value, and gets the data buffer start address. Each 6 bit group of data is e7~clusively "or"ed into the CRC value, ;md CPOLY is callcd to "or" the resulting value with the polynomial value. When all bits have been processed, a return is e~ecuted.
CPOLY sets a shift counter ~or 6 bits. The CRC value is shifted left one bit. If the bit shifted out is a one, the CRC value is e~clusively "or"ed with the poly-nc~mial value. When 6 bits have been shifted, a returtl is e~ecuted.

6 ~

Load Shift Register (SHIFT~ FIG. 52 PURPOSE: SHIFr loads the shift register with the da~ to bc transmitted.
ENTRY POINT: SHIFT
CALl,ING SEQUENCE:
JSR SHIFI
ReturTI
REGISTER STATUS: A, X not preser~ed.
TABLES USED: None.
CALLED BY: MAIN
CALLS: Local Subroutine: SHIFT4/SHFAG-N--FIG. 53 EXCEPTION CONI:)ITIONS: None.
DESCRI~ION:
SHIFT calls SHIFt4 successively to shift four bits of data at a time into the shift register, starting with the most significant bit.. When all twelve-bit values have bcen shifted in, SHI~T4 and SHFAGN are called to fill the shift register with trailhlg ~eroes and a return is executed.
SHIFI4 shiits the four data bits in A(~3) into the hardwa~e shift register by setting/resetting the data bit and toggling the register clock bit. When four bits have been shifted, a return is executed.
SHFAC"N is a special entry to SHIFI 4 which allows the desired bit count (1~) to be passed in X.

Transmit Dala ~XMIT) FIG. 54 PURPOSE: XMIT transmits the contents of Ihc shift register to thc ground st~tion.
ENTRY POINT: XMIT
(::ALLING SEQUENCE:
JSR XMIT
Return REGISTEIR STATUS: A, X not preserved.
TABLES USED: None.
CALLED BY: MAIN
CALLS: None.
EX(::EPI`ION CONDITIONS: None.
DESCRI~ION: XMIT monitors tbe zero-crossing count. When the count reach the time-to-transmit count, the transmitter is enabled, and a one millisec--63- ~5~

Double Precision Multiply (MULT~ Figure 55 -PURPOSE: MULT performs a double precision multiply.

ENTRY POINT: MULT

CALLING SEQUENCE: MLTBUF+1,2 = Multiplier MLTBUF+3,4 = Multiplicand Return MLTBUF~5,6,1,2 = Procluct REGISTER STATUS: A, X not preserved.

TABLES USED: None CALLED BY: COMPUT, SUM5 CALLS: None EXCEPTION COMDITIONS: None DESCRIPTION: MULT performs a double precision multiplication by shifting a bit out of the multiplier 7 successively adding the multiplicand to the product, and shifting the product. When finished, the watchdog timer is kicked, and a return is executed.

~;~5~

Gct Absolute Value (DIVABS) FIC;. 56 PURPOSE: DIVABS gets the absolute value of the value at X and sets the sign flag.
E~RY POlNr: DIVABS
CALLING SE(~UEN(:E:
X=Value Add~ess Return ABSIGN=Sign flag ($F~=Negative) REGISTER STATUS: X is preserved.
TA~LES USED: None.
CALLED E~Y: COMPUT
CALLS: COMP2 EXCEPI ION COI`JDITIONS: None.
DFSCRIPI'ION: DIVA~lS resets the sign nag and tests the most si8nificant bit of the value at X. If set, COMP2 is called to find thc two's complement of the four byte value, ~nd the sign flag is set to SFF. A
rcturn is then e.~ecuted.

~ 35 C:onvert Scaled Value ~DIVCNV) FIG. 57 PURPOSE: DIVCNV applies the sign and divides the value by si~tecn.
EN~RY POINT: DIVCNV
CALLING SEQIJENCE:
X = Value Address lSR DIVCN~
Retu~n REGISTEIR STATUS: A, X l~ot preserved.
TABLES USED: None.
CALLED EIY: COMPUT
CALLS: COMP2 EXCEPTION CONI~ITIONS: None.
DESCRlErrION: DlVCNV tats th~ :iign nag, AB
SIGN. If non-zcro, COMP2 is called to find the two's complement of the four bytc valuc at X. The vnlu~ is then shifted nght four bits, ~nd a return is executcd.

Find Two's Complement Value ~COMP2) FIG S8 PURPOSE: COMP~ finds the two's complement value of the value at X.
ENTRY POINT: COMP2 CALLING SEQUENCE:
X = Valuc Address Return REGISTER STAl US: X is Prescrved.
TABLES USED: None.
CALLED PY: DIVABS, DIVCNV
CALLS: None.
EXCEPTION CONDITIONS: None.
DESCRIPTION: COMP2 complcments each byte of the four byte value at X, adds one to Ihe least signifi-cant bytc, and propagates lhe carry through the re maining bytes.

67 1~58~S

Process Zero Crossing Inte~rup~s (ZCIN 1~ FIG. 59 PU~POâE: ZCINT processes zero crossing in~errupts.
ENTRY POINT: ZCINI-CALLING SEQUENCE:
From IRQ Vector Return (RTI) ~EGISI ER STATUS: A, X ase preser~ed.
TA8L.ES USED: None.
CALLED BY: Hardware IRQ V~tor CALLS: None.
EXCEPI ION CONDITIONS: None.
DESCRlPl ION:
ZCINT tests the cyclc start nag. If set, thc analog tracking registcl is frozcn, the cycle st~rt flag is reset, ~he time-to-sample flag is set, and the clocik is set to the t-l/9 cycle time.
If the start synchronize na~s is set, the clock p~cscaler is r~et, /he clock is reset tQ ma;dmum value, and the start.synchronize nag is reseL
The elapsed clock time is saved as the last cycle time the zero-crossing~ccurred flag is set, the zero crossin~ count is bumped, and a return is exccuted.

I i 6 8 3L.

Process Clock Interrupt (CLINT) FIG. 60 PURPOSE: CLINT processes clock interrupts.
ENTRY POINT: CLINT
CALLING SEQUENCE:
I:rom IRQ Vcctor Relurn (RTI) REGISTER STATUS: A, X are preserved.
TABLES USED: None.
CALLED BY: Hardware Clock IRQ Vectot CALLS: None.
EXCE~ION CONDITIONS: None.
DESCRIPIION: CLINT free~es the analog tracking rcgister, rcscts the clock IRQ flag, and sets the time-to-sample flag. The cycle time remainder value is added into thc time accumulator. If a oarry results, the 1-1/9 cyclc time is increased by one. The clock is re~et to th~ cycle time, and a retum is e~cecuted.

69 ~ 7~5 Perfonn Powcr-On Resct (RESET) FICi. 61 PURPOSE: RESET perfonns power-on initializa~ion.
ENTRY POINT: RESET
CALLING SEQUENCE:
From Hardware Reset Vector JMP MAIN
REGISTER STATUS: A, X not presenfed.
TABLES USED: None.
CALLED BY: Hardwarc Rcsct Vector CALLS: I~L4IN
EXCEPI ION CONDmONS: None DESC~IPI`ION: RESET inhibit~s intermpts, clears R AM to zeroes, and initialkes thc intannl clock and PlA's. 'rhe initial time values arc initiali~cd, and the l~ancbester er~coder nnd transmitter nre dis~bled.
Interrupts are reallowed, and a jurnp to thc bacl~- ¦
ground processing loop is e~ecuted.

- The Receiver The receiver 24 at a substation 34 as shown in Figure 4 receives data from fifteen donuts.
In Figure 62 there is shown an overall circuit block diagram for such a receiver 24.
In addition to receiving transmissions from up to fif-teen donuts 20, via its antenna 30 and radio receiver 330, the receiver 24 can also receive analog data from up to 48 current transformers and potential transformers generally indicated at 332. The receiver 24 is operated by a type 68000 Central Processing Uni.t 334. The Manchester ~oded transmissions from the donuts 20 received by the rèceiver 330 are transmitted via line 336 to a communication board 106 and thence on data bus 338 to the 68000 CPU 334. The transformer inputs 332 are conditioned in analog board 340 comprising conditioning amplifiers, sample and hold, multi-plexing and analog-to-digital conversion circuits under control of analog control board 342. The digitized data is supplied on data bus 338 to -the CPU 334 The CPU 334 is provided with a random access memory 346, a programmable read only memory 348 for storing its program, and an elec-trically erasable read only memory 349 for storing the scaling factors and personality tables.
The central processing unit 334 may be provided with a keyboard 350 and a 16 character single line display 352. It is also provided with an RS232 port 354 for loading and unloading so called personality tables comprising scaling factors and the like for the donuts 20 and the trans~ormer -71- ~ 8~ 196-0~7 inputs 332. The receiver 24 which is sometimes called here-in a remote terrninal unit interface, supplies data to a remote terminal unit via current loop 356 from an RS232 comrnunications port on communications board 106.

~ 72- ~2~ 196-007 _ The Receiver Software Copyright ~ 1983, Product Development Services, Incorporated (PDS) Functional Specification of the Receiver The remote terminal unit may be a Moore MPS-9000-S
manufactured by Moore Systems, Inc., 1730 Technology Drive, San Jose, California 95110, modified to receive and store a table ~f digital data each second sent on line ~5~7. U~modi-fied, the MPS-900-S receives inputs from potential and cur-rent transformers, temperature sensors and the lihe at a substation, and converts these measurements to a digital table for transmission to a power control center 54 (Figure 5) or for use in.local substation control.
Simultaneous transmissions from two or more donuts 20 are ignored since the garbled message received will not produce a check sum (CRC) that matches the check sum as received. The CRC check portion of the circuit is shown at 337.

-73- ~ ~ ~ 196-007 Ove~view:
An integral part of commercial power generation is monitoring the amount of power delivered to customers and, if necessary, purchase of power from other companies durins peak demand periods~ It is advantageous to the power com-pany to be able to make measurements at remote substations, and be able to relay all the measurements to a central point for monitoring. Because of the large voltages and currents involved in commercial power distribution, direct measure-ment is not feasible. Instead, these values are scale~ down to easily measured values through the use of Potential Transformers (PT's) for voltage, and Current Tran~formers (CT's) for current. Recently, we have developed another means for monitoring power line voltage and current. This is the Remote Line Monitor, a donut shaped (h~nce the nick name "donut") device which clamps around the power line itself, and transmits the measured values to a radio re-ceiver on the ground.
The Remote Terminal Interface (RTI) monitors power line voltage, current, and temperature by means of Potential Transformers (PT's), Current Transformers (CT's), and tem-perature transducers respectively. These parameters may also be obtained from Remote Line Monitors, or "donuts"
which are attached to the power lines themselves. It is the job of the RTI to receive this data, and in the case of PT's, CT's and temperature transducers, digitize and analyze the data. This data is then used to calculate desired out-put parameters which include voltage, current, temperature, -73.1- ~2~ 95 196-007 fr~quency, kilowatt hours, watts, va, and vars, (the last three being measures of power). These values are then sent to the Remote Terminal Unit (RTU), and are updated once per second.
Data obtained from PT's, CT's, and temperature trans-ducers must be digitized by the RTI before it can be used.
Data obtained in this way is termed "analog" data. Donuts, on the other hand, send their data to the RTI in digital form. For this reason, input received from donuts is said to be "digital" input. Each donut supplies three parame-ters, (voltage, current, and temperature) thus it is equi-valent to three analog inputs.
Virtually all commercial power systems in the United States today are three phase systems. There are two con-figurations used: the 3 conductor or delta configuration, and the 4 conductor or wye configuration. To calculate power (va, vars) it is necessary to measure the voltage and current in all but one of the conductors. That one con-ductor is used as a reference point for all voltages measured. For a delta configuration, voltage and current in two of the three conductors must be measured (only two phases). This is referred to as the two wattmeter method.
It is desirable to use the two wattmeter method whenever possible because only ~ PT's and CT's are required. For a wy2 configuration however, voltage and current must be measured in all 3 phases. (The fourth conductor is an ex-plicit reference point. No such reference is provided in -73.2- ~5~0~ 196-007 the delta configuration, so one of the phases must be usec instead.) This latter method is known as the three wattmeter methodO
The program listings for the receiver rernote terminal interface are found in Appendix B. They comprise a number of subroutines on separately numbered sets of pages. The subroutines are in alphabetical order in Appendix B. At the top of page l of each subroutine the name of the subroutine is given, ~e.g., ACIA at the top of the first pa~e of Appendix B). The routine INIT initializes the computer and begins all tasks.
Appendix C compxlses e~uates and macro definitions used in the system. Those headed STCEQU are for the system timing controller (an AM9513 chip). Those headed XECEQU are for the Executive program EXEC in Appendix B. Those headed RTIEQU are unique to the remote terminal interface and used throughout the programs of Appendix Bo Accuracy: Ali calcula~ions will be performed to 5 sig-nificant digits, rcpresenting an accuracy of O.01% offull scale.
Input ranses:
Analog voltages and currents will be digitized to a 12 bit bipolar value ranging from--2048 to 2047.
Analog temp~rature will also be digitized to a 12 bit value which may or may no~ be bipolar.
All incoming digital data will be 12 bit values ranging from--2048 to 2047.
Number of inputs/outputs: There shall be no more than 48 analog inputs and IS digital inputs, and no more than 64 outputs. Tbe analog inputs may monitor no more tb; n 5 separate groups. (A group is defined as a circuit who~: voltage is used for the frequency refer ence and power calculations) The donuts may be used to monitor a ma~imum of 5 additional groups.
Digital inputs: Digital inputs, if used, will be supplied by 'donuts'. (see donut documentation) Scaling Ranges:
1. R~nge of donut scaling factors will be from 0.~ to 2. In addition, the temperature value may also havc an offset from--1024 to + 1023 added to it.
2. Each PI- has a scaling factor associated with it~
This factor may range from 0.5 to 2.Q
3. Each CT has four scaling factors associated with it.
These factors may each range from 0.5 to 2Ø

8~
Data Acquisition:
Analog dah input:
Analog data can come from three sources: Poten~ial Transformers, (Pl~s~; Curren~ Transfonners (Crg~, or temperatute transducers. The order of sampling will be de~ermined by the outputs de-sired. ~see Data Output) For voltage and current, 9 egually spaced sasnples must be taken over the space of a power line voltage cycle for the pur-poses of data analysis. (see Data Processing). For each voltage group (ma~imum of 5), a timer mus~
be mainained to provide proper sarnpling intervals.
This timer will be checked e~ch sampling period and adjusted if neccssary. The first phase of the voltage sampled wi~l be used as the reference for checking the ~npling period timer.
The input task Icnows it may begin sampling for a given group of inputs ~cluster) whcn all of thc input buffe~ connected ~vith it are ready for input. Thc necessa y data is collected from the A/D con-verter, and stored in the appropriate input buffer.
When this sampling is complete, the buffer is marked as unavailable for further input, and madc availabe for Fourier analysis. The sarnpling timer is then adjusted if necessary, anrl the input task then proceeds to the next group of buffers in the Input Sequence Table.
13. Digital Input:
Input from the 'donuts' (if used) is already digitized and analyzed. It is orly necessary to apply a scalins factor (unique for each paramc~er from each donul) to the data, and convert it to 2's complement form.
After this has been done, the data is in a suitable form to calculatc output data Donut input is not solicited, but rather is transmitted in a continuous stream to the RTI. When data is received from a donut, the processor is interrupted.
The incoming data is then collected in a local buf,~er until a full m~ssage frorn a donul is received and validatcd. If the data is not valid, the transmis-sion is ignorcd, and norrnal processing continues. If the buffer hJs already received valid input data for this sampling period, the transmission is ignored.
Otherwise, the new data is moved frorn the receive buffer into thc appropriate data buffer. the age count is cleared, is marked as waiting to be pro-cessed, and is made available for effective value calculations.
C. Analog Input Error Detection/Action: None.
D. Digital Input Error Detection/Action: A Cyclical Redundancy Check (CRC) word will be provided at the end of each donut transmission. If the CRC fails, the last good data transmitted by that particular donut will be reused. lf the output task references the buS~r before new data comes in, the old data will be reused. If a donut should fail more than N (to be defined) conseculive times, that donut will be consid-ered to be bad, and its data will be reset to ~ero.

, ~.

76 ~L~r~

Data Processing Analog data nnust be subjecled to Fourier transforrna-tion to e~tract the sine and cosine components of the voltage and current prior to calculating output values. Also, if the input was a voltage, the sine and cosine components must be scaled by a factor be-tween 0.5 and 2Ø Illis scaling fac!or is found in ~he Input Personality Table, and is unique to each input. If the input was a current, the effective value and the Fourier components must be scaled by one of four factors ranging between 0.5 and 2Ø The scale factor used is dependent on the raw value of the effective current (leff). Each current input has a unique set of four factors. These may also be found in the Input Personality Table.
The purpose of Fourier transformation is to e~tract the peak sine and cosine components of an input waveforrn. These components are then used to calculate the amplitude (effective value) of the waveform. For this application, ve are only con-cerned with the components of the fundamen~al (60 Hz) line frequency.
If the buffer is an analog input buffer, then the 9 samples are analy~ed, yielding the sine and cosine components of the fundamental. The effective value of the waveform is then computed and stored in the buffer. The buffer is then marked as being ready for more raw data.
If the buffer is a digital (donut~ buffer, then only the effective voltage and current are computed and stored in the buffer. When these calculations are complete, the buffer is marked as being ready for more raw data.
After the data has bcen appropriately pracessed. then the output valu may be calculated. Parameters that may be calculated are: voltage, current, kilo-watt hours, wat~s, va, and vars. Also, tempcrature, and frequency may be ousput. (ll-hese are mea-sured, not calculated pararneters.) Error Detecsion/Action: None.

Vata Output Oulput data will be transmitted to the host in serial fashion, Data to be tran~mitted to the host ~vill be stored in a circular FIFO buffet to be emptied by the transmission routine which will be interrupt driven. All data must be converted lo o~fset binary and formatted before transmission. A new set of output dat~ wiJI be transmitted to the host once per seeond.
When a buff~r is ready to be output, the wattage must be calculated ~If it hasn't been already) and stored in the bufler corresponding to the phase I of the current involved in the calculation. When the watt-age is calculated, the kilowatt hour value is up-dated also. After ealculating powet and updating KWH, the output task will ealeulate the requested output parametet and output it (if the appropriate buffers to perforrn the calculation are ready). The output t~sk will then proceed to the ne~t entry in the Output Personality Table. When the end of the table is reachcd, all buffer~, both analog and digital, are marked as ready for analysis. In addition, the output task will enable the transtnission of the bloek of data just calculated, and wait until the start of the ne~ct one seeond interval befote statting at the top of the table again.
If the second current input speeifier in the output table entry is not--1, the parameter will be calcu-lated using the Breaket-and-a-half method. (see glossa~y) ~5~

Error Detection/Action:
If the requested psramater cannot be calculated be-cause the requisitc bufl~ers are not yet ready, and the output buffer is empty, we have a fata~ e~Tor in that we haven't been able to caiculate the requisite data in ti ne for transmission. For now we'll just wait un~il the data does come along.

79 ~5~

RTI Monitoring/Programming The RTI will ~e supplied with an integral 16 key keypad, and single line (16 column) display. From this keyboard the user may:
con.inuously ;nonitor any particular output value (the display being updated once per second).
display all diagnositc error counts.
transmit an upload request to the host thru the au~iliary port.
In addition, the RTl will have the capability to upload/download any EEPROM based table through the au~tiliary port upon request from the host. All programming of the RTI (confi6uration and scaling factor entry) will be perforrned through this link. Communications protocols will be defined in the d~sign spec.
Error Detection/Action:
When each table is up/down lo~ded, a 16 bit CRC
word is transmitted with it. Should this CRC check fail on down load, the RTI will rcquest a retrans-mission and the table in EEPROM will not be updated. On upload, it is the responsibility of the host to request a retransmission.

;,.
,. ..

~5~95 Initialization A. Various hardware must be initialized ptior to start of opcration. Presently defined hardwsre is:
STC (System Timing Controller). The S~C consists of S indepcndent timcrs, any one of which may be se-lected to generate an intemlpt up<~n timing out. This i5 used to insure that the analog samples are t Iken at the proper time. ~he STC is made by Advanced Micro Devices, and its part number is 9513.
PI/T: Set timer to provide interrupts at one second intervals to signal the start of data transmission to the host.
ACIA 1: Host interface 4800 baud Odd parity I stop bit 8 data bits Host interface monitor (RCV half of ACIG 1) ACIA 2: Auxiliary link To be defincd.
Error Detection/Action: None.
B. Software initialization:
Thc analog and digital buffers must be initialized at startup time. Also at this time, thc Input Sequence Table and Cluster S~atus Masks are built. Finally, the various tasks must be initialized and started.

Equations:
Fourier analysis (voltage and current):

Va (Cosin~ Compon~rn) = ~ Vs X cos(~ X 40-)/4.5 -(sin~ compon~nt) = 5 Vs X sin(s X ~ 4 5 -Where s is the sarrlple number.
Note: sin (sX40-)/4.5 and cos (sX40)/4.5 are con-stants, and may be stored in a table.
Effective voltage (currcnt):

r~ ra2 + Vb2 Temperature: no calcula~ion--the input value is just passed on.
Power:
Wa~ts:
per phnse: Watts=(Vbxlb)+(Vaxla) Total power: (this applies to Watts, VARS, md VA) Three phase (wattmeter) method: pwtY(Phnse I
pwt+Phase 2 pwr+Phase 3 pwr)/6144 Two phase (wattmeter) method: pwr=(Phnse I
pwr ~ Phase 2 pwr) 4096 where pwr may be WAl~S, VARS, or VA.
Note: The constants 6144 and 4096 above are included so that full scale voltage and full scale current will yield full scale power. Proper scaling to actual watts, vars, va. or watt-hours will be performcd by thc host.
VARS:
VARS = (Ve X rb)--(Vb X la~ (per phase) Tota~ VARS calculated as per total watts above.
VA:
VA = VeffX le~f Total VA calculated as per ~otal watts above.

82 ~5~
Tables Input Personality Table- This tablc is EEPROM based, nnd binds a specific inpul number to an input type (voltage, current, tcmpcrature), group 1, phase 1, and seI of correction factors. lllis table is of a fi~ed size and may have no more than 48 entries. Unus~ entries will have a value of 0. Thc values in this tabk will be determined at installation time.
Output Personality Tablc:
The Output Personality Table is an EEPROM based table which defines each of the parameters to be output, and which parameters are necessary to calculate them. The numbcr of entries (up to 64) in the tablc is unique to thc site. and is determincd at installation ~ime. llle en~ries are arranged in the order in which thcy are able to be output. There may be no more than 64 entries in this table.
When donuts are used, both voltage and current read-ings from the selected donut(s) will be used for power (volt-amp) calculations. (ie. using voltage from a donut and current from a CT will not be permitted) Donuts shall have ID's ranging from I to 15. Each installation using donuts must start the donut ID's from 1.
Donuts must be used in groups of three. (Their output is suitable only for use in the 3 wattmeter method.) The ID's of the donuts must be consecutivc, the lowest numbered one being assumed to be phase one, and the hi~hest numbcre~ one will be assumed to be phase 3.
Zero entries in the table will be ignored.
Input Sequence Table: The Input Sequence Table is RAM based, and built at RTU startup time, based on thc Outpu~ and Input Personality tables. For each group, this table specifies which inputs must be sarn-pled simultaneously to calculate the desired outputs.
The groups are ensered inlo Ihe table in order of their first reference in the Output Personality Table. The Input Personality Table is then referenced to find the input numbcrs of all phases of a given input typc (ie.
curren~) for any group. &ch group is terrninated by a zero word. l['he table is terminated by a word set to all ones.
Donut Scale Factor Table: This table is EEPROM
based and contains the donut's group number and scaling facîors to be applied to donut inputs. Scale factors are unique to each parameter input from each donut. In addition, the temperature input may also have an offset from--1024 to 1023 added to it. ll~is offset is added after the scalirlg fac~or has been ap-plied. The entries are arranged in order of donut ID's.

83 ~IL2~ 5 D~La FOrm~LS:
A Inconn~Donu~ Data Fortntlt:
word biu funclion 11-8 don't car~
7-4 donut id 1{) U1. id 2 1 1~ VD (co~inc componcnt of VOIL;g~) 3 11~ Vb (~inc component of vol~-ge~
I 1{~ 1~ (co~in~ connpon~nt of curr~nt) 11~ lù (sin~ componcnt of curr~nt) 6 11~ Aua 7 N -0 CR.C vvord a Host Tran miss~on Formr~
For dal3 typcs 0-6:
word hts func~ion 7-6 Iw-y~ zero ~ value ~Y
2 7-6 ~IWIy~ one 5~) MS 6 biu of v-lue 3 7-6 ~.lw~y~ one 5-0 LS 6 bits of value For da~t ~vPe ? ~ICWH)._ word bits function 7 alw~ys on~
6 Iw-ys ~-o 5 0 value A!
2 7-6 alw~ty~ one 5~) MS 6 bils of v~lu~
3 7-6 always onc 5-1) LS 6 bh~ of V31U~
C. Uplo~d/Download formll:
byt~ biu funcdon _ _ _ _ 0-4 0-7 sync charac~cr SYN (~Y16) ~7 t-bk I.D. - ASCII digit ~3 wherc:
0- I.D. Lable I Input l'crsonality Tabl~
2 - Output Pessonality T~blc ~ - Donut Scak F~ctor T~blc 6-7 0-7 byt~ CoUnl - ~ of bytes of tabl~ tnnsmin~-l 8-N 0-7 table d;lta - N = by~c count + 8 N+ 1-~J+2 0-7 CRC word. CRC includes bv~es 5 ~hru N

~, 3.

84 ~5~30~3~

Fourier constant lable: In the Fourier analysis, the val-ues sin (sX40)/4.5 and cos (sX40)~4.5 (where s ranges from I to 9) are constants, and thus may be stored in a tablc. This avoids needless computation.
Each entry will be a 32 bit floating point number.
There will be 9 ent~ics for each table. (sine and co-sine) Analog Input Buffer: There are 48 of these buffers, one per A/~ channel. The number of buffers actuallv used is inst~llation dependcnt. These buffers accept ra-v input from the A/D, and hold the results of intermediate calculations until output time. ~e inter-mediate values are the cosine and sine components oo the Fourier analysis of the 9 input samples, the effec-tive value (col7~puted from these components), total wattage, watt seconds, and kilowatt hours. The last three parameters are only defined for Analog Input buffers corresponding to phase I C1~5.
Digital Input Buf~er: There are 16 digital input buffers in the system. The number of buffers actually used is installation dependent. These buffers are similar in function to the analog input buffers, but their formaE
is different due to the fact that data from donuts has already been analy~ed, and voltage, current and tem-perature data are sent from each donut, being equiva-lent to three analog inputs. The data containcd in these tables are the cosine and sine components of voltage, cosine and sine components of current, tem-perature, effective voltage and current, total watts.
watt seconds, and kilowatt hours. The last three pa-ra~neters are used only in buffers corresponding to donuts connect~d to phase one of a group.

GLOSSARY
13reaker-and-a-half method: Method used to calculatc parameters when the substation bus is configured as shown in FZG. 63 Such a configuration is called a Ring 8us. In this conf~guration, any given circuit is fed from t~vo sources. As a result, two crS are used to calculate thc current in the circui~, one CT on each source. As a result. any parameter requiring current must bc calculatcd in a special way. The currents from each sourcc must be sumraed and then used in the calculation. This is true whether the effective value (leff) is used, or the compon~nts (la, Ib) are used. l['o calculatc power, ~hen, the rcsults of 3 inputs are now necessary rather thao two a~ before. Cir~uit brcakers are identified as 358.
Circuit: Three (or four) wircs whose purpose is to trans-mit power from the power company. Al.so called a bus.
Clustcr: A collection Or inputs which must bc sampled at the same timc due to phase considerations. (ic A
given voltagc group and all the currents related to it through the output personality table constitute a clus-ter. Also, an 'cntry' in thc input scquence table) Current Group: A three phase circuit (3 or 4 conductor) whose current is rncasured. There may be a ma~irnum of 23 current groups.
Donut: Remote power line monitoring device-linked to RTI via radio link.
~: Current (abbr.) [a: Cosine component of current waveform.
~b: Sine component of current waveform.
Phase:
1. A power carTying wire in a circuit or bus.
2. Time relationship between two signals. (often, voltage and current) usuaJly el~pressed in degre~s or radians. (i.e. The phase relationship betwcen any two phases of a three phase circuit is 120 degrees) V: Vol1age (abbr.) Va: Cosine component of voltage waveform.
Vb: Sine component of voltage wavefonn.
VA: Volt Amps~ e vector sum of resistive (watts) and reactive power (VARS).
Voltage Group: A three phase circuit (3 or 4 conductor) whose voltage is used both as a frequ~ncy reference and as a vol!agc refereuce for subsequent calcula-tions. Therc may be 8 ma~imum of five of these volt-age graups (I per cluster).

~25~

ReGeiver Operation A state diagram for the program of the central proces-sing unit 334 of Figure 62 of the receiver 24 is shown in Figure 64. Processing tasks are indicated by the six-side~
blocks. Tables stored in the electrically erasable read only memory 349 are indicated by the elongated oval boxes.
Data paths are shown by dotted lines and peripheral inter-faces are indicated by zig-zag lines. The transformer in-puts 332 and donut input 336 are shown in the upper_left.
The RS232 port 354 is shown in the lower right and the out-put RS23~ port 32 is indicated in the middle of the d~iagram.
The donut scale factor table is shown in ~igure 65.
Since donuts are normally operated in groups of three for three-phased power measurement, word 0 comprises the group number of the donut (GP), followed by the phase number of the donut (PH). The following words are the voltage scale factor, current scale factor, temperature scale factors, and temperature offset respectively. Temperature offset is an 11 bit value, sign extended to 16 bits. All two word values are a floating point. There is, of course, a separate scale factor table for each of the fifteen donuts provided for.
The donut scale factor tables are stored in the electrically erasable read only memory 349.
Figure 66 is a table of the digital input buffers.
There are sixteen required, one to store the received value of each of the fifteen donuts and one to act as a receiver bufer for the serial port of the communication board 106.

- Word 0 comprises, in addition to the donut ID and z number called buffer age, indicating how long since the in-formation in the buffer has been updated; the followina flags:
DI(Data In) - Set when all data has been received and is ready for analysis. Clear when ready for new data.

AC(Analysis Complete) - Set when effective value and temperature scaling calculations are complete.

VP(Valid Power) - Set if total watts has already been calculated.

IT(Input Type) - Always 3. Identifies this buffer as donut input.
All single word values are 12 bits, sign extended to 16 bits. All double word values are floating point. Buffer age is the number of times this data has been used. The first buffer (buffer ~) is used to assemble incoming donut data. Words 14-16 are defined for 0 1 donuts only. Word in the buffer number 0 is used for the donut status map.
The digital input buffers are stored in the read only memory 346.
Figure 67 is the input personality table of which there are 48 corresponding to the 48 potential transformer and current transformer inputs. IT identifies the input type which may be voltage~ current~ or temperature. Link is the input number of the next phase of this group o~ donuts. It is -1 if there are no other donuts in the group. Correction -88~ 196-007 factor number 1 is used for correcting ~oltage values. Each of the four correction factors corresponds to a range of input values from the current transformers. Again, as with the donuts, the group number identifies groups of trans-~ormers associated with a single power line and PH identi-fies the phase number of the particu:Lar transformer. VG
identifies the voltage group that the current is to be associated (that is, sampled) with. It is used, of course, only when the table is used to store values from a current transformer. The input personality tables are stored ~n the electrically erasable read only memory 349.
48 analog input buffers are provided to store measure-ments received from the 48 current potential transformers.
The form of each of these buffers is shown in Figure 68.
The follow flags are provided:
DI~Data In) - Set when all raw data has been received and sign extended. Clear when buffer is ready for more data.

AC(Analysis Complete) - Set when Fourier analysis and effective value computations are complete.

VP(Valid Power) - Set if total watts value has already been calculated.

IT(Input Type) - ~ = voltage, 1 = current, 2 = tempera-ture.

-8~- ~96-007 ~ Words 1-9 and 10-18 are 12 bit val~es, sign extended to 16 bits. All 2 word values are floating point. Words 16-18 are defined for ~ 1 of current inputs only. Words 10-18 are undefined for temperature inputs. VP only applies to buf-fers associated with 0 1 current inputs. If IT = 2 (temper-ature), the first sample will be converted to floating point and stored at offset 10.
In operation, transmissions are received randomly from the donuts 20, transmitted in Manchester code to the serial port to the communications board 106. The checked sum (CRC) is calculated and if it agrees with the check sum (CRC) received, an interrupt is provided to the central pro~essing unit 334, which then transfers the data ~o data bus 338 The central processing unit 68000 applies the scale factors and temperature offset to the received values, and calcu-lates the Temperature, effective Voltage (VEFF), effective Current (I~FF), Scaled Temperature, Total Watts, Watt Seconds and Kilowatt hours from the received data and stores the data in the appropriate Digital Input Buffer in random access memory 346.
In the analog board 340, each of the 48 transformer inputs is sampled in turn. After its condition has been converted to digital form, an interrupt is generated, and the data is supplied to data bus 338. It should be noted that the analog board 340 causes the inputs from the poten-tial and current transformers 332 to be Fourier sampled nine times just as current and voltage are sampled in the donuts (see Figure 343. Thus, the data supplied to the data bus -go- 196-007 ~5~9~

33~ from the analog board 340 comprises 3 successive values over nine alternating current cycles. After all nine have been stor~d in the random access memory 346, and the appro-priate correction factors ~Figure 67) applied, the funda-mental sine and cosine Fourier components are calculated just as in the donuts 20.
Then the effective value of current or voltage is cal-culated and~ if appropriate, the Total Watts, Watt Seconds, and Kilowatt hours, and the entire table (Figure 68) stored in the random access memory 346.
When the receiv4r 24 is initially set up, the appro-priate donut scale factors (Figure 65) are loaded through R5232 port 354 into the electrical erasable read only memory 349, and these are used to modify the values received from the donuts 20 before they are recorded in the digital input buffers of the random acces~ memory 346. Similarly, an input personality table (Figure 67) is stored in the elec-trical erasable read only memory 349 corresponding to each of the current and potential transformers and this is uti-lized to apply the appropriate corrections to the data re-ceived by the analog board 340 before it is recorded in the analog input buffers of the random access memory 346. The scaled data stored in the digital input buffers and the corrected data stored in the analog input buffers is then assembled into a frame or message containing all of the defined data from all of the donuts 20 and all of the trans-formers 332 and transmitted via transmission link 32 ~o a receiver which may be the remote terminal interface of the prior art as previously described.

~ The form of the analog-to-digita, multiplexed input sample and hold circuitry and program in the receiver 24 may be essentially the same as that in the donut. The same is true for the Fourier component calculation program and the calculation of the check sum ~CRC). The programs are appro-priately modified to run in the 68000 central processing unit with its associated memories.
If harmonic data is desired, then higher Fourier har-monics are calculated in the donuts 20 and transmitted to the receiver 24. The receiver then uses the higher ha~monic values to calculate the amplitude of each harmonic it is desired to measure.
The frequency at any donut 20 may be determined, if desired, by measuring the time between transmissions re-ceived from the donut as these are an integral multiple (W, see Figure 34) of the line frequency at the donut. Alter-natively, the donut may employ an accurate quartz clock to measure the time between zero crossings (Figure 34) and transmit this frequency measurement to the receiver.
If desired, power factor may be calculated from the Fourier components and stored in the input buffers (Fiyures 66 and 68). Reactive power (Vars) may be calculated from the Fourier components rather than real power (Watts) as selected by an additional flag in each of the Donut Scale Factor Tables (Figure 65) and the Input Personality Table (Figure 67). ~lternatively, all of these calculations and others, as well as other information such as frequency, may be stored in expanded Input Buffers (Figures 66 and 68).

-92- ~5~5 196-007 - The electrical erasable read only memory 349 may be unloaded through the RS232 port 354 when desired to check the values stored therein. They may also be displayed in the display 352 and entered or changed by means of the keyboard 350.
The output from the receiver 24 is a frame of 64 (for example) data values from the Input Buffers (Figures 66 and 68) chosen by an output Personality Table (not shown) stored in the electrically erasable read only memory 349. This frame of values is transmitted to the Moore remote terminal unit once each second. The output personality table may be displayed on display 352 and entered by keyboard ~350 or entered on read out through RS232 port 354.

~5~35 Pr~ctical Application It will thus be seen that a number of separate novel concepts have been applied to develop a practical state estimator module which may be applied t:o live power lines; a module which is capable of measuring the temperature of the power line, the ambient temperature, the voltage and current of the line; the frequency and harmonic content of the line;
and transmits this information to a receiver where power information such as real and reactive power and power factor may be calculated.
Thus, we have provided a state estimator module-which may be installed to all of the live power lines lea`~ing to and from a substantion and to both sides of power transfor-mers in the substation, and thus provide the totality of information required for complete remote control of the power station from a power control center, and also provide for local control. Our state estimator modules may be in-stalled on live monitored circuits in an existing substation having current and voltage transformers and our receiver used to collect this totality of information and transmit it to a remote terminal unit and thence to a power system con-trol center.
Some of the important concepts which make this novel system possible are the metallic toroidal housing for the module (which is a high frequency but not a low frequency shunt about its contents); the supporting hub and spoke means; spring loaded temperature sensors; novel voltage -94~ 9~ 196-007 measuring means; transmission of Fourier components; random burst transmission on a single radio channel with the timing between bursts being artfully chosen to minimize simultane-ous transmissions from two or more donuts; novel hinge clamp which may be operated by a novel hot stick mounted tool facilitating the mounting of the module to a energized power conductor; and the concept that such hot stick mounted modules when distributed throughout a power delivery system, can provide for total automatic dynamic state estimator control.
I~ will thus be seen that the objects set forth above, among those made apparent Erom the preceding desc.tiption, are efficiently attained and, since certain changes may be made in the above circuits, constructions and systems, without departing from the scope of the invention, it is intended that all matter contained in the above description, or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all state-ments of the scope of the invention which as a matter of language might be said to fall therebetween.
Having described our invention, what we claim as new and desire to secure by Letters Patent is:

Claims (22)

Claims:

1. Apparatus for measuring at least one characteristic of a power line conductor comprising:
a housing removably attachable to said conductor;
means for measuring the amplitude of at least one cyclic characteristic of power transmitted on said conductor;
said means for measuring including means for timing amplitude measurements such that said measurements occur at a plurality of different intervals within the period of a cycle of said cyclic characteristic;
said timing means including means for delaying said measurements by a fixed time interval such that each of said measurements is taken in a different cycle for a plurality of cycles; and wherein said measurements are taken over a period of n cycles with the time duration of each cycle equaling t and said fixed time interval between measurements equaling t+(1/n)t;
means for calculating Fourier components of said cyclic characteristic from said measurements;

means for transmitting said Fourier components to a remote receiver; and said means for measuring, means for calculating and means for transmitting each being contained in said housing.

2. Apparatus as defined in Claim 1 further including means for measuring conductor temperature, conductor voltage, and conductor current.

3. Apparatus as defined in Claim 2 wherein said measurements are analog values and including processing means for converting said analog values into digital values.

4. Apparatus as defined in Claim 3 wherein said processing means includes means for forming said digital values into a digital message to be transmitted to said remote receiver.

5. Apparatus as defined in Claim 4 wherein said data message includes an apparatus identification number, a voltage value, a current value, and an auxiliary value.

6. Apparatus as defined in Claim 5 wherein said auxiliary value is one of a number of selectable characteristics including conductor temperature.

7. Apparatus as defined in Claim 6 wherein said one of a number of selectable characteristics represented by said auxiliary value is identified by an auxiliary parameter number included in said data message.

8. Apparatus as defined in Claim 7 wherein an auxiliary value corresponding to a different selectable characteristic is transmitted on each successive transmission and the auxiliary parameter number rotates among the numbers identifying said selectable characteristics.

9. Apparatus as defined in Claim 3 further including central timing means and wherein said means for processing and said means for transmitting are controlled by said central timing means and said central timing means is synchronized to the zero-crossings of alternating current carried on said conductor.

10. Apparatus as defined in Claim 4 wherein said processing means includes means for calculating an error check value and said error check value is transmitted as part of said digital message.

11. Apparatus as defined in Claim 1 wherein said means for measuring includes means for converting said measurements from analog values to digital values.

12. Apparatus as defined in Claim 11 wherein said means for calculating Fourier components includes means for computing a check value and said means for transmitting includes means for transmitting said check value with said Fourier components.

13. Apparatus as defined in Claim 12 wherein said receiver includes means for calculating a check value, means for comparing said calculated check value to said check value transmitted with said Fourier components, and means for disregarding said transmitted Fourier components if said compared check values are not the same.

14. Apparatus as defined in Claim 1 wherein said means for measuring measures the amplitude of voltage and current simultaneously.

15. Apparatus as defined in Claim 14 wherein said receiver receives the Fourier components of voltage and current and includes means for calculating real and reactive power values from said received components.

16. Apparatus as defined in Claim 1 wherein said cyclic characteristic of power is voltage.

17. Apparatus as defined in Claim 1 wherein said cyclic characteristic of power is current.

18. Apparatus for measuring at least one characteristic of a power line conductor comprising:
means for measuring the amplitude of at least one cyclic characteristic of power transmitted on said conductor;
means for controlling said means for measuring such that said measurements occur at a plurality of different intervals within the period of a cycle of said cyclic characteristic;
said means for controlling including means for delaying said measurements by a fixed time interval such that each of said measurements is taken in a different cycle for a plurality of cycles;
means for calculating Fourier components of said cyclic characteristic from said measurements; and wherein said measurements are taken over a period of n cycles with the time duration of each cycle equaling t and said fixed time interval between measurements equaling t+(1/n)t.

19. Apparatus as defined in Claim 18 wherein said means for measuring measures the amplitude of voltage and current simultaneously.

20. Apparatus as defined in Claim 19 further including means for transmitting said Fourier components of voltage and current to a remote receiver.

21. Apparatus as defined in Claim 20 wherein said receiver includes means for calculating real and reactive power from said received Fourier components.

22. Apparatus as defined in Claim 21 further including a housing removably attachable to said conductor, said means for measuring, means for controlling, means for calculating Fourier components and means for transmitting each being contained in said housing.