GB2096370A

GB2096370A - Electrical energy consumption meter

Info

Publication number: GB2096370A
Application number: GB8205917A
Authority: GB
Original assignee: South Eastern Electricity Board
Current assignee: South Eastern Electricity Board
Priority date: 1979-02-21
Filing date: 1979-02-21
Publication date: 1982-10-13
Also published as: GB2096370B

Abstract

An electrical energy consumption meter for use on a consumer's premises has data processing means 20 with input means 13 and 16 responsive to the sensed voltage and current respectively and having a memory 21 and clock input 22 providing data for computing and displaying, on a display 23, charges in monetary terms. A data link 26, 27 with the utility enables the utility to make use of this information and to add hire purchase commitments, etc. to the charges for energy consumption and also to enter credits for payments received. Coin, "electronic money" or token prepayment facilities 30 are provided, and the data processing means controls switching means in the load circuit (or in load sub-circuits) to limit the permissible demand when the level of remaining credit is low. <IMAGE>

Description

SPECIFICATION Improvements in or relating to meters for measuring electrical energy consumption This invention relates to meters for measuring electrical energy consumption, such as are used for example by consumers connected to an electrical power supply network.

It is the common practice at the present time to employ electromechanical kilowatt-hour meters which integrate the product of the magnitudes of the voltage and current and record, usually by means of pointers on dials, the energy consumption in kilowatt-hours. For some consumers, prepayment is required by means of a coin-operated mechanism or possibly a mechanism operated by tokens which have to be purchased in advance.

According to the present invention, a meter for measuring electrical power consumption by a load circuit of a consumer comprises sensing means for sensing the voltage applied to that circuit and the current flowing in the circuit, digital data processing means responsive to the sensed voltage and current from said sensing means and operative to compute therefrom, using data from a programmable store, the charges in monetary unit for energy consumed, and means for indicating or operable to indicate the accumulated credit or debit information in monetary terms and is characterised in that a prepayment device is associated with the data processing means, the prepayment device being arranged to accept coins or electronic money or tokens and to provide data in accordance with accepted prepayment to the data processing means for updating the credit information in a memory, and in that the data processing means is arranged to control switching means in said load circuit or in one or more of a plurality of load subcircuits energised from said load circuit to limit the permissible demand, when the credit is exhausted, to a low level.

With such a prepayment device, the indicator would display the total unused credit available.

The data processing means may include a clock.

Such a clock for example may control the tariff rate used for computing charges for kilowatthours so permitting the use of a single meter with time varying tariffs. Preferably the data processor is arranged to control switching means, conveniently solid state switches, in a load circuit or in one or more of a plurality of load subcircuits, as for example in the manner described and claimed in the specification of co-pending Application No. 7906213 (2043371). With such switching means, the data processing means can be arranged to give a warning to the consumer, e.g. by a momentary interruption of the supply to the load, shortly before the outstanding credit is used up; such an interruption will cause the lights to flicker thereby warning the consumer that further prepayment is required.Alternatively or additionally a display on the indicating means may be caused to flash or other warning means may be operated.

With a switching system, which can switch off one or more load circuits, it moreover is possible to program the data processing means so that, when the credit is exhausted, power may be disconnected or alternatively the power may be limited to a very low level, for example 250 watts.

A data link may be provided between the aforementioned data processing means and a remote central processor, e.g. in the utility so that data about payments by the customer to the utility can be applied to update the record of the credit or debit balance displayed on the consumer's premises.

Such a data link may make use of telephone lines or power transmission lines, for example using a carrier system, or a radio link or opticlal fibres.

Credit limits can be put in the program in the data processing means. When the limit is approached, warning may be given to the consumer by momentary interruption of supply, as described above, by making use of switching circuits controlled from the data processing means or by causing the display to flash. Such warnings may be followed subsequently by reduction of the current to a low level or by complete interruption of the supply. The frequency and duration of such warning at the current level settings can be set into the data processing means in accordance with the particular requirements of each consumer.

In Application No. 7906212, out of which the present application has been divided, there is described and claimed a meter for measuring electrical power consumption by a consumer 5 circuit which meter comprises means for sensing the voltage applied to that circuit and the current flowing in the circuit, digital data processing means responsive to the sensed voltage and current and operative to compute therefrom, using data from a programmable store, the charges in monetary units for energy consumed, means for periodically adding, to the computed charge, a time-dependent component, and means for indicating or operable to indicate the accumulated credit or debit information in monetary terms.

The following is a description of one embodiment of the invention, reference being made to the accompanying drawing which is a block diagram illustrating diagrammatically energy consumption metering apparatus for coin prepayment.

Referring to the drawing there is shown diagrammatically incoming live and neutral leads 10, 1 1 providing an alternating power supply from a utility. In the customer's premises, there is a unit 12 containing a voltage transformer 13 having an input winding 14 connected between the live and input leads and an output winding 15 to provide a voltage signal output. On the live lead there is a current transformer 16 having an output winding 17 giving a current output signal. The unit 12 also includes a switching device 18, conveniently a solid state switch formed of thyristor units, which can be switched to limit the magnitude of the current on the output lead 19 or to interrupt that current. The lead 19 is connected to the consumer's load.In the consumer's premises but possibly remote from the unit 12 is a data processing unit 20 containing a microprocessor which receives voltage information from the voltage winding 15 and current information from the current winding 17 and which determines therefrom the instantaneous power consumption and integrates this power consumption. Conveniently this is done by pulse sampling the voltage and current waveforms simultaneously at a plurallity of points in each cycle as is described in the specification of co-pending Application No.7901133 (2040051).

The microprocessor unit 20 includes or has associated therewith a programmable memory 21 for storage of data including tariff information.

This tariff information may be dependent on clock time and the microprocessor includes a clock 22 so that the determined energy consumption can be converted into a charge in monetary units. The memory also includes any necessary further information relating to charges, for example a time based charge to enter pro-rata amounts periodically for any fixed charge component in the consumer's tariff. The microprocessor can determine maximum demand and compute any charges based on maximum demands within predetermined counting periods. The total accumulated debit or credit charge can be displayed on a display unit 23. In the particular embodiment illustrated, the display unit 23 is part of a unit including a key pad 24, and a key, such as one of the keys 25, has to be operated to display in indicator 23 the amount in the appropriate register in the unit 20.

A coin prepayment mechanism 30 is associated with the microprocessor 20. The coin prepayment mechanism utilises the display 23 to display the outstanding balance of credit from coins inserted in the unit 30.

A data link 26 is provided leading to a central processor at the utility. This data link includes a modem or other isolator 27 and may make use of telephone lines or power transmission lines, e.g.

using a carrier frequency for data transmission in both directions between the central processor and the data processing unit 20. Any other suitable form of data link may be employed, e.g. a radio link or an optional pulse link.

The programmable memory 21 may include information about credit limits and provision may be made for comparing the accumulated charge with the credit limit. As credit limit is approached, a warning may be given. For example the display 23 may be made to flash or the switching circuit 1 8 may be operated momentarily to cause the consumer's lights to flicker and the picture on his television set to roll. This may be done periodically and, in accordance with the program set in the memory 21, the switching unit 18 may be operated either to disconnect power from the consumer's load circuit 19 or possibly to limit the power supplied to that credit to a predetermined low value, for example 250 watts.

The data link 26 enables the consumer effectively to insert credit into the meter by paying cash directly to the utility, who can then increase the meter credit remotely via the data link. The data link also permits of modification of the information in the microprocessor as may be necessary. For example the tariff may be modified to cover past debts as well as to cover current consumption. The prepayment mechanism conveniently is an add-on device which may be associated with a normal credit meter; the credit in this case is derived from the payments made by insertion of coins and possibly by prior payment to the utility as described above. When the prepayments are exhausted, the credit meter operates as described above to give warning of exhaustion of a credit limit. A mechanical flag signal may be provided to indicate the need for further payment to be made to obtain restoration of supply to the consumer.

Claims

1. A meter for measuring electrical power consumption by a load circuit of a consumer comprising sensing means for sensing the voltage applied to that circuit and the current flowing in the circuit, digital data processing means responsive to the sensed voltage and current from said sensing means and operative to compute therefrom, using data from a programmable store, the charges in monetary unit for energy consumed, and means for indicating or operable to indicate the accumulated credit or debit information in monetary terms and is characterised in that a prepayment device is associated with the data processing means, the prepayment device being arranged to accept coins or electronic money or tokens and to provide data in accordance with accepted prepayment to the data processing means for updating the credit information in a memory, and in that the data processing means is arranged to control switching means in said load circuit or in one or more of a plurality of load sub-circuits energised from said load circuit to limit the permissible demand, when the credit is exhausted, to a low level.

2. A meter as claimed in Claim 1 wherein the data processing means is arranged to give momentary interruptions of the supply to the load circuit or load sub-circuit shortly before the outstanding credit is used up.

3. A meter as claimed in either Claim 1 or Claim 2 wherein the data processing means has a visible display and is arranged to cause said display to flash shortly before the outstanding credit is used up.

4. A meter as claimed in any of the preceding claims wherein the data processing means includes a clock.

5. A meter as claimed in Claim 4 wherein said clock controls the means for periodically adding a time-dependent component to the computed charge.

6. A meter as claimed in any of the preceding claims wherein the data processing means is arranged to control switching means in said load circuit or in one or more of a plurality of load subcircuits energised from said load circuit.

7. A meter as claimed in any of the preceding claims wherein the data processing means is arranged, when the credit is exhausted, to operate said switching means either to disconnect the power or alternatively to limit the permissible demand to a low level.

8. A meter as claimed in any of the preceding claims and having a data link between the said data processing means and a remote central processor.

9. A meter as claimed in Claim 8 wherein the data link is arranged for two-way data transmission.