JP2515353B2 - Voltage detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a power detection device capable of detecting a ground fault and a short circuit fault in an electric line and monitoring a load current.

(Prior Art) Conventionally, as a device of this type, for example, as shown in Japanese Patent Application Laid-Open No. 62-34065 (published on February 14, 1985) by the present applicant, each phase of a three-phase electric line An electro-optical element that modulates the optical power according to the electrical change in is connected in series in the middle of an optical transmission line having a light emitting portion at one end and a light receiving portion at the other end, and the optical power modulated by the electro optical element is There is known a means for detecting a zero-phase current or a zero-phase voltage by converting it into an electric signal and detecting the presence or absence of a line fault based on the fluctuation.

(Problems to be Solved by the Invention) However, in the above-described conventional device, since only the presence or absence of a line fault is detected based on the fluctuations of the zero-phase current and the zero-phase voltage, it is necessary to detect an inter-phase short-circuit fault. Had to add a dedicated current sensor separately.

The present invention can detect the line current of each phase without adding a dedicated current sensor, can detect the zero-phase current, and can reliably detect the inter-phase short circuit and the ground fault. It is to provide a voltage detection device.

Configuration of the Invention (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is a main unit in which a light emitting portion for optical power is connected to one end and a first light receiving portion for optical power is connected to the other end. A plurality of optical transmission lines and a plurality of units provided in each phase of the three-phase electric line, connected in series in the middle of the main optical transmission line, and modulating the optical power according to an electrical change caused by a ground fault and an interphase short circuit. Sensor, a first optical / electrical conversion circuit that is connected to the first light receiving unit, and that converts the optical power modulated by each sensor into an electrical signal, and between the sensors with respect to the main optical transmission line. First connected via first and second optical branching devices connected to each other
And a second optical branch transmission line, which is connected to the first optical branch transmission line via a second light receiving portion of optical power, and which is capable of outputting an electric signal proportional to the line current of the first phase. -Electrical signal that is connected to the electrical conversion circuit and the second optical branch transmission line via the third light receiving unit of optical power and that can output an electrical signal proportional to the combined line current of the first phase and the second phase A third optical-electrical conversion circuit and an electric signal connected to the second and third optical-electrical conversion circuits and proportional to the combined line currents of the first phase and the second phase to a line current of the first phase. A second-phase line current calculation circuit for calculating an electric signal proportional to the line current of the second phase alone by subtracting an electric signal proportional to
Connected to the optical-electrical conversion circuit, and subtracts the electric signal proportional to the combined line currents of the first and second phases from the electric signal proportional to the combined line currents of the first to third phases. And a third-phase line current calculation circuit for calculating an electric signal proportional to the line current of each of the three phases.

(Operation) Therefore, according to the present invention, the optical power passing through the main optical transmission line is modulated by the sensor corresponding to each phase according to the electrical change of each phase of the three-phase electric line, and the first light An electric signal is converted by the electric conversion circuit, and a zero-phase current obtained by combining the line currents of the respective phases is output.

Further, the second optical-electrical conversion circuit outputs an electric signal proportional to the line current of the first phase, and the second phase line current calculation circuit outputs an electric signal proportional to the line current of the second phase. . Further, an electric signal proportional to the line current of the third phase is output from the third phase line current calculation circuit. As a result, the ground fault current and the inter-phase short circuit current can be detected separately and the load current can be monitored.

(Embodiment) An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 2, the three-phase electric line is provided with a large number of electric poles 1 (only one is shown) erected at a predetermined distance, and the electric wires 2A, 2B, 2C of each phase are on each electric pole 1 The insulators 4 are insulated and supported by the insulators 4 provided on the one support arm 3. Voltage detector
5A, 5B, 5C are provided for each phase electric wire 2A, 2B, 2C, and are provided with an insulator body 7 standing on the other supporting arm 6 on the electric pole 1. A current transformer CTa, CTb, CT having an iron core and a winding wound around the iron core is provided in the voltage detecting portion 8 provided on the top of each insulator body 7.
c is built in, and in the state where each phase electric wire 2A, 2B, 2C penetrates through those iron cores, the penetrating portion is insulated and coated.

As shown in FIG. 1, an optical fiber for detecting the secondary burden resistances Ra, Rb, Rc, the ground fault current and the interphase short-circuit current is provided between the detection terminals of the current transformers CTa, CTb, CTc. Voltage sensor Sa, S
b and Sc are connected respectively. And each phase wire 2A, 2
Based on the commercial frequency current flowing in B and 2C, each current transformer CTa, CT
A secondary current flows through b, CTc, and a voltage based on the secondary current is applied to each sensor Sa, Sb, Sc.

On the other hand, as shown in FIG. 2, a light emitting circuit 11 and a light receiving circuit 12 are built in the control box 9 mounted on the telephone pole 1. The light emitting circuit 11 comprises a light emitting diode LED and a drive circuit 13 for causing the light emitting diode LED to emit light.
The light receiving circuit 12 is a first photodiode serving as a first light receiving section.
It is composed of PD1 and a first optical / electrical conversion circuit 14 for converting the optical power received by the photodiode PD1 into an electric signal. Further, the light emitting circuit 11 and the light receiving circuit 12
Is the main optical transmission line composed of multimode optical fiber 15
The sensors Sa, Sb, Sc are connected in series in the middle of the main optical transmission line 15.

As shown in FIG. 3, each of the sensors Sa, Sb, Sc has a Pockels element 17 for modulating the optical power passing through them.
And so on. That is, the light transmitted through the incident side lens 18 of each sensor is linearly polarized by the polarizer 19 and is phase-modulated in response to the voltage applied to the Pockels element 17. Then, it receives circularly polarized light by the quarter-wave plate 20, is intensity-modulated by the analyzer 21, and then passes through the transmission-side lens 22.
Therefore, the light power output from the light emitting circuit 11 is sequentially intensity-modulated in proportion to each phase current by passing through each of the sensors Sa, Sb, Sc, so that each phase current is vectorally three-phase synthesized. The received light intensity is modulated, and the light is received by the light receiving circuit 12.

The electric signal output from the first optical-electrical conversion circuit 14 of the light receiving circuit 12 is input to the correction circuit 23, and each sensor
The zero-phase current signal is output from the output terminal 23a of the correction circuit 23 in a state where the residual noise generated by the temperature change of Sa, Sb, Sc is removed by the correction circuit 23. The correction circuit 23 obtains the difference between the sensors Sa, Sb, and Sc by comparing the residual noise that changes gently with time like the change in the optical modulation due to the temperature change with the sensor output before a fixed time period. ,
The detection error is compensated for the zero phase component due to the residual noise.

First and second optical branching devices 24, 25 are connected to the main optical transmission line 15 so as to be located between the sensors Sa, Sb, Sc. A second photodiode PD2 as a second light receiver is connected to the first optical branching device 24 via a first optical branching transmission line 15a composed of a multimode optical fiber. Then, in the photodiode PD2, the second optical-electrical conversion circuit 26 for converting the optical power proportional to the first line current received by the diode into an electric signal and outputting the electric signal from the first phase terminal 26a. Are connected.

A third photodiode PD3 as a third light receiver is connected to the second optical branching device 25 via a second optical branching transmission line 15b composed of a multimode optical fiber. The photodiode PD3 is connected to a third optical / electrical conversion circuit 27 for converting the optical power proportional to the first and second combined line currents received by the diode into an electric signal. The first and second optical branching devices 24 and 25 are practically designed to branch about 10% of the optical power in the main optical transmission line 15, respectively.

The second and third optical-electrical conversion circuits 26 and 27 subtract the electric signal proportional to the line current of the first phase from the electric signal proportional to the combined line current of the first phase and the second phase. The first operational amplifier OP1 is connected as a second phase line current calculation circuit for calculating an electric signal proportional to the line current of the second phase alone,
An electric signal proportional to the line current of the second phase can be output from the output terminal 28.

Further, the first and third opto-electric conversion circuits 14 and 27 are provided to the combined line currents of the first phase and the second phase from an electric signal proportional to the combined line currents of the first to third phases. Is connected to a second operational amplifier OP2 as a third-phase line current calculation circuit for calculating an electric signal proportional to the line current of the third phase alone by subtracting the electric signal proportional to An electric signal proportional to the line current can be output.

Next, the operation of the electric power detection device configured as described above will be described.

Now, when a current (primary current) flows in each of the phase electric wires 2A, 2B, 2C, a secondary current is induced in each of the current transformers CTa, CTb, CTc,
The secondary current flows through the secondary burden resistors Ra, Rb, Rc, so that the voltage across each resistor is applied to each sensor Sa, Sb, Sc. At this time, when the light emitting diode LED is caused to emit light by the drive circuit 13 of the light emitting circuit 11, its optical power is changed to the main optical transmission line 1.
It passes through 5 and is transmitted to the sensor Sa.

Then, the optical power passing through the main optical transmission line 15 is sequentially intensity-modulated according to the current change of each phase wire 2A, 2B, 2C by the three sensors Sa, Sb, Sc, and in the three-phase combined state. Light receiving circuit
The 12 first photodiodes PD1 are irradiated. The first optical / electrical conversion circuit 14 of the light receiving circuit 12 converts the optical power applied to the photodiode PD1 into an electric signal, and the correction circuit 23 generates noise due to temperature fluctuations of the sensors Sa, Sb, Sc. In the removed state, it is output as an electric signal from the output terminal 23a. This electric signal shows a predetermined value corresponding to the zero-phase current during normal power transmission, but when a two-phase short-circuit accident or a ground fault accident occurs in the electric line, the zero-phase current becomes a value other than the predetermined value. . That is, the occurrence of a short circuit accident or a ground fault can be detected based on the output signal.

On the other hand, the optical powers branched from the first and second optical branching devices 24 and 25 respectively are the first and second optical transmission lines 15a and 15a.
The second and third photodiodes PD2 and P2 via b
Illuminated to D3, and second and third opto-electric conversion circuits
Converted into electric signals by 26 and 27, respectively. And
An electric signal proportional to the line current of the first phase output from the second optical / electrical conversion circuit 26 is output from the output terminal 26a.

Further, the electric signal proportional to the line current of the first phase and the electric signal proportional to the combined line current of the first phase and the second phase output from the second and third optical / electrical conversion circuits 26, 27 are , Is input to the second-phase current calculation circuit OP1, where an electric signal proportional to the line current of the second phase alone is output from the output terminal 28.

Further, it is proportional to the electric signals output from the first and third opto-electric conversion circuits 14 and 27, which are proportional to the combined line currents of the first and second phases, and to the combined line currents of the first to third phases. The electrical signal is input to the third phase line current calculation circuit OP2,
Here, an electric signal proportional to the line current of the third phase alone is output from the output terminal 29.

Therefore, from the above three output terminals 26a, 28, 29, an electric signal proportional to the line current of each of the three phases is input to, for example, a relay circuit (not shown), and it is determined which line of the three phases has caused a short circuit. It Then, a trip signal is output from the relay circuit to the circuit breaker.

In addition, in the embodiment of the present invention, since the independent line currents of three phases can be detected respectively, it is possible to judge the distinction between the two-phase short circuit and the three-phase short circuit and to monitor the load current.

By the way, in this embodiment, the light emitting diode is provided in the light emitting portion.
Since LEDs were provided and each sensor Sa, Sb, Sc was connected by the main optical transmission line 15 consisting of a multimode optical fiber, a laser diode was provided in the light emitting part and each sensor was connected by a single mode optical fiber. Compared with the case, the reliability of the light source can be improved and the light source can be manufactured at low cost.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and for example, an optical fiber magnetic sensor is used as a sensor, or a laser diode is used for a light emitting unit and each sensor is connected by a single mode optical fiber. It is also possible to arbitrarily change the configuration of each part without departing from the spirit of the present invention.

As described above in detail, according to the present invention, it is possible to detect the line current of each phase individually and to reliably detect the inter-phase short circuit and the ground fault without separately providing a current sensor. It has an excellent effect that the current can be monitored.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a power detection device embodying the present invention, FIG. 2 is an external view showing a usage state of the power detection device, and FIG. 3 is an explanatory view showing a configuration of a sensor. 11 …… Light emitting circuit, 12 …… Light receiving circuit, 13 …… Drive circuit, 14
...... First optical / electrical conversion circuit, 15 ...... Main optical transmission line, 24 ......
First optical branching device, 25 ... Second optical branching device, 26 ... Second optical / electrical converting circuit, 27 ... Third optical / electrical converting circuit, 28, 29 ...
… Output terminal, OP1 …… First operational amplifier as second phase line current calculation circuit, OP2 …… Second operational amplifier as third phase line current calculation circuit, LED …… Light emitting diode as light emitting part, PD1 to PD3… --- Photodiodes as first to third light-receiving units, Sa, Sb, Sc ... Optical fiber voltage sensors.

Claims (2)

(57) [Claims] 1. A main optical transmission line (15) having a light emitting portion (LED) of optical power connected to one end and a first light receiving portion (PD1) of optical power connected to the other end, and a three-phase electric line. A plurality of sensors (Sa, Sb, which are provided in each phase, are connected in series in the middle of the main optical transmission line (15), and modulate the optical power according to an electrical change caused by a ground fault and a short circuit between phases (Sa, Sb, Sc) and the first light receiving unit (PD1), and each sensor (Sa,
Sb, Sc) first optical-electrical conversion circuit (14) for converting the optical power modulated by Sb, Sc) into an electric signal, and the main optical transmission line (15) with respect to each sensor (Sa, Sb, S).
the first and second optical branch transmission lines (15a, 15b) connected via the first and second optical branching devices (24, 25) connected so as to be located between c), and A second optical / electrical conversion circuit which is connected to the first optical branch transmission line (15a) through the second light receiving section (PD2) of optical power and can output an electrical signal proportional to the line current of the first phase ( 2
6) and an electric signal which is connected to the second optical branch transmission line (15b) through a third light receiving part (PD3) of optical power and is proportional to the combined line current of the first phase and the second phase. Which can output
An optical / electrical conversion circuit (27) and an electric signal connected to the second and third optical / electrical conversion circuits (26, 27) and proportional to the combined line current of the first phase and the second phase A second-phase line current calculation circuit (OP1) for calculating an electric signal proportional to the line current of the second phase by subtracting the electric signal proportional to the line current of the first phase; Connected to the optical / electrical conversion circuit (14, 27), the electrical signal proportional to the combined line currents of the first to third phases, and the electrical signal proportional to the combined line currents of the first and second phases. The third phase line current calculation circuit (OP) for calculating an electric signal proportional to the line current of the third phase alone by subtracting
2) A voltage detector equipped with and. 2. The electric power detection device according to claim 1, wherein each of the sensors (Sa, Sb, Sc) modulates intensity of optical power.