JP3424374B2 - Lightning arrester leakage current sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning arrester leakage current sensor for detecting a leakage current of a lightning arrester for monitoring the state of the lightning arrester.

[0002]

2. Description of the Related Art FIG. 9 shows a circuit of a conventional arrester leakage current sensor. In FIG. 9, LAa, LAb, and LAc are 3
It is a phase arrester, and one leakage current transformer CT is inserted in the ground-side zero-phase circuit. The secondary current of the leakage current transformer CT is converted into an optical signal by the light emitting diode 1, and the optical signal is transmitted to the opto-electric converter 4 of the monitoring unit 3 by the optical fiber 5.

A direct current bias current is supplied from the battery 2 to the light emitting diode 1 through the resistor R in order to reduce the impedance value and facilitate the flow of the measurement current.
Further, a direct current cut capacitor C is connected between the leakage current transformer CT and the light emitting diode 1. In the monitoring unit 3, the optical signal is converted into an electric signal by the optical-electrical converter 4, and an output proportional to the zero-phase leakage current is obtained.

In the leakage current sensor configured as described above, when an abnormality occurs in the arrester, each arrester LA
The balance of the currents flowing through a, LAb, and LAc is lost, and the zero-phase current increases. Therefore, when the zero-phase leakage current value detected by the sensor exceeds a predetermined value, it can be determined that an abnormality has occurred in the lightning arrester.

[0005]

In the above-mentioned conventional arrester leakage current sensor, it is necessary to form a zero-phase circuit on the side of the arrester. Therefore, when each phase of the arrester is grounded separately,
A zero-phase circuit could not be formed on the surge arrester side, and a leak current sensor could not be provided. Moreover, since only the zero-phase current can be measured, the leakage current for each phase cannot be measured. For this reason, when the abnormality of the arrester is detected, it is not possible to determine which phase of the arrester the abnormality has occurred.

The present invention is an arrester capable of measuring a zero-phase current even when a zero-phase circuit cannot be formed on the side of the arrester circuit .
It is an object of the present invention to allow a leakage current to be measured for each phase in a leakage current sensor and to identify a lightning arrester in which an abnormality has occurred.

[0007]

To achieve the above object, the present invention provides a multi-phase lightning arrester, a current transformer provided for each lightning arrester of each phase, a semiconductor light emitting element, and a current transformer. The lightning arrester leakage current sensor is composed of means for connecting the secondary side in parallel and supplying a secondary current of the current transformer to the semiconductor light emitting element and means for supplying a DC bias current to the semiconductor light emitting element.

According to the present invention, in the lightning arrester leakage current sensor configured as described above, the switch means for turning on / off the secondary current of the multiphase current transformer for each phase is provided. Alternatively, the present invention is provided with a switching means for turning on and off at the same time secondary currents of all the other phases except the one phase of the current transformer of a polyphase
It

[0009]

A zero-phase circuit is formed on the secondary side of the current transformer by connecting in parallel the secondary side of the current transformer provided for each arrester of each phase. Therefore, even if the arrester of each phase is grounded separately and the zero-phase circuit cannot be formed on the side of the arrester, the leakage current for the zero-phase of the arrester can be obtained from the secondary side of the current transformer.

The zero-phase leakage current is a minute current, and the semiconductor light emitting element exhibits a high impedance with respect to the minute current. On the other hand, by applying a DC bias current to the semiconductor light emitting element, its impedance is reduced. Therefore, the zero-phase leakage current easily flows through the semiconductor light emitting device. The semiconductor light emitting element converts an electric signal in which a zero-phase leakage current and a DC bias current are superimposed into an optical signal. This optical signal is transmitted to the monitoring unit by an optical fiber.

The monitoring section extracts the zero-phase leakage current from the transmitted optical signal and monitors this value to determine whether or not an abnormality has occurred in the lightning arrester. Further, by providing the switch means for turning on / off the secondary current of the multiphase current transformer for each phase, the monitoring unit can measure the leakage current for each phase. Leakage current of the arrester in the phase in which the switch means is turned on flows into the semiconductor light emitting element, and the optical signal is transmitted to the monitoring section. The monitoring unit extracts the leakage current equivalent from the transmitted optical signal and monitors this value to determine whether or not an abnormality has occurred in the arrester for each phase. As a result, it becomes possible for the monitoring unit to identify the arrester in which an abnormality has occurred.

Switch means for turning on / off the secondary current of the current transformer is provided in the remaining phases except for one phase, and each switch is turned off at the same time, thereby transmitting the number of switch means and an optical signal. The number of optical fibers can be reduced. When the switch means is turned off, the leak current for one phase of the phase to which the switch means is not connected can be measured. When the switch means is turned on, the total value of the multiphase currents flows in the semiconductor light emitting element, so that the zero phase leakage current can be measured.

[0013]

EXAMPLES Examples of the present invention will be described below. In addition, in each drawing of the following description, those having the same function are denoted by the same reference numerals, and overlapping description will be omitted.

[0014] The underlying technique of [base technology The present invention will be described with reference to FIG. Figure 1
, LAa, LAb, LAc are three-phase arresters,
CTa, CTb, and CTc are current transformers inserted in the arrester of each phase. The secondary sides of the current transformers CTa, CTb and CTc are connected in parallel, and are connected to the light emitting diode 1 via a DC cut capacitor C. A battery 2 is further connected to the light emitting diode 1 via a resistor R.

The output light of the light emitting diode 1 is transmitted to the optoelectric converter 4 of the monitor 3 by the optical fiber 5.
Next, the operation of the circuit of FIG. 1 will be described. As shown in the equivalent circuit of FIG. 2, the total leakage current Il of the lightning arrester is divided into a current Ir corresponding to the resistance R and a current Ic corresponding to the capacitor C. Of these, the current Ic for the capacitor C hardly changes with time, and the change over time is noticeable in the current Ir for the resistance R. Further, the current Ic for the capacitor C is much larger than the current Ir for the resistor R (Ic >> I).
r). Therefore, the total leakage current Il of the lightning arrester becomes almost constant even if there is a change over the years.

When an abnormality occurs in the arrester, the leakage current Ir corresponding to the resistance R increases. This abnormality does not usually occur in all the lightning arresters LAa, LAb, LAc at the same time.
It occurs in two lightning arresters. Therefore, when an abnormality occurs, the leak currents of the respective phases are unbalanced, and the zero-phase leak current increases. Further, since the resistance value of the lightning arrester shows a non-linear characteristic, when an abnormality occurs and the leakage current value increases, the current waveform is distorted and can be detected as a zero-phase current. Therefore, the abnormality of the arrester can be detected as an increase in the zero-phase current.

In the circuit of FIG. 1, three current transformers CT
A zero-phase circuit is formed on the secondary side of a, CTb, and CTc, the fundamental wave component of the leakage current of each phase is canceled, and a zero-phase current flows through the light emitting diode 1. The current value for this zero phase is minute. The light emitting diode 1 has a high impedance with respect to such a minute current. On the other hand, by causing a DC bias current to flow from the battery 2 through the resistor R, the impedance of the light emitting diode 1 is lowered and the measurement current easily flows. The capacitor C
Prevents the direct current from flowing from the battery 2 into the current transformers CTa, CTb, CTc.

A current in which a zero-phase current and a DC bias current are superposed flows through the light emitting diode 1, and this current is converted into an optical signal. This optical signal is sent to the monitoring unit 3 by the optical fiber 5.
Is transmitted to the optical-electrical converter 4. By thus connecting the sensor unit and the monitoring unit 3 with the optical fiber 5, electrical insulation between the two can be easily performed. In the monitoring unit 3, the optical-electrical converter 4 converts the optical signal into a voltage signal. As shown in FIG. 3, this voltage signal is a superposition of the voltage signal Vo corresponding to the zero-phase leakage current and the voltage signal Vb corresponding to the DC bias current. The monitoring unit 3 obtains the voltage signal Vo corresponding to the zero-phase leakage current by extracting only the AC component from this voltage signal, and when the value becomes larger than the predetermined value, it is determined that the lightning arrester has an abnormality. To do.

According to the surge arrester leakage current sensor described above, a zero-phase circuit can be formed on the secondary side of the current transformers CTa, CTb and CTc. Therefore, even if the arrester of each phase is grounded separately and the zero-phase circuit cannot be formed by the arrester circuit, the leakage current of the arrester can be measured.

[ Embodiment 1 ] In the above-described base technology , three-phase lightning arresters LAa, LAb, LA
It is not possible to determine which lightning arrester in c has an abnormality. In contrast, an example in which to be able to identify the abnormality occurs arrester will be described with reference to FIG. 5 as the first embodiment of the present invention.

The circuit of FIG. 5 differs from the circuit of FIG. 1 described above in the following points. In FIG. 5, the current transformer CTa,
On the secondary side of CTb and CTc, capacitors Ca, Cb and Cc and diodes Da, Db and Dc are connected in series between the light emitting diode 1 and each phase. A phototransistor P is provided between each of the connection points of the capacitors Ca, Cb, Cc and the diodes Da, Db, Dc and the battery 2.
Ta, PTb, PTc and resistors Ra, Rb, Rc are connected in series.

The monitoring unit 3 includes each phototransistor PT.
A controller 6 for controlling on / off of a, PTb, and PTc is provided. From the controller 6 to the optical fiber 7,
On / off control of each phototransistor PTa, PTb, PTc is performed for each phase by an optical signal transmitted through 8 and 9. Next, the operation of the circuit of FIG. 5 will be described.

All phototransistors PTa, PTb, P
When Tc is off, current transformers CTa, CTb, and CTc are 2
The secondary current is very small. The diodes Da, Db, Dc exhibit high impedance with respect to such a minute current.
Therefore, the light emitting diode 1 has current transformers CTa and CT.
b, CTc secondary current does not flow. Now, when an optical signal is supplied from the controller 6 of the monitoring unit 3 to the phototransistor PTa of one phase through the optical fiber 7, the phototransistor PTa is turned on, and a DC bias current flows from the battery 2 to the diode Da through the resistor Ra. . As a result, the impedance of the diode Da decreases, and the secondary current of the current transformer CTa of that phase flows in the light emitting diode 1.

In the monitoring section 3, the controller 6 turns on the phototransistors of the phases to be sequentially detected,
The optical signal transmitted by the optical fiber 11 is converted into a voltage signal by the optical-electrical converter 4. This electrical signal is shown in FIG.
As shown in, the electric signal Va corresponding to the total leakage current,
The electric signal Vb corresponding to the DC bias current is superposed. The monitoring unit 3 can obtain the electric signal Va corresponding to the total leakage current by extracting only the AC component from this voltage signal, and determine whether or not there is an abnormality in the arrester for each phase.

Here, the current observed for each phase is the total leakage current, and includes the current Ic for the capacitor and the current Ir for the resistor in FIG. As described above, since the current Ic for the capacitor C has little variation due to the change over the years, abnormality of the lightning arrester is determined by the leakage current Ir for the resistance. In order to extract the leakage current Ir of the resistance component, the resistance component is extracted by utilizing the phase difference between the two currents, or the resistance component is extracted by utilizing the waveform distortion due to the nonlinear characteristic of the resistance. Since this method is a known method, detailed description thereof is omitted here.

The monitoring unit 3 determines whether or not an abnormality has occurred in the arrester based on the extracted leakage current of the resistance component.

[ Second Embodiment ] A second embodiment of the present invention will be described with reference to FIG.
The circuit of FIG. 6 differs from the circuit of FIG. 5 described above in the following points. In the circuit of FIG. 6, a three-phase current transformer CT
Among a, CTb, and CTc, for one a phase, a switch circuit including a diode and a phototransistor is not provided on the secondary side, and a diode D is provided on the other two phases on the secondary side.
b and Dc are connected to the phototransistors PTb and PTc.

Two phototransistors PTb,
The PTc is simultaneously on / off controlled by the controller 12 of the monitoring unit 3 via one optical fiber 11. The operation of the circuit of FIG. 6 will be described. When the phototransistors PTb and PTc are off, the diodes Db and Dc exhibit high impedance, so that the light emitting diode 1 has
The total leakage current of one phase detected by the current transformer CTa flows. When the phototransistors PTb and PTc are on,
The diodes Db and Dc have low impedance, and the zero-phase current, which is the sum of all leakage currents of the three phases, flows through the light emitting diode 1.

Therefore, the monitoring unit 3 can measure the zero-phase leakage current when the phototransistor is turned on and the one-phase total leakage current when the phototransistor is turned off. The determination method using the zero-phase leakage current and the determination method using the one-phase total leakage current in the monitoring unit 3 can be performed by the method of the first or second embodiment described above. A duplicate description will be omitted.

In the circuit of FIG. 6 described above, the total leakage current can be monitored for only one of the three phases, but the number of switch circuits and the number of optical fibers can be reduced. Further, in this embodiment, the zero-phase current value of the arrester can be estimated by calculation by using the total leakage current for one phase as the reference value. When the voltage signal value due to the total leakage current of one phase is Va, the voltage signal value due to the zero phase output is Vo, and the total leakage current for one phase initially measured is Ia, the zero phase current value Io is [Equation 1] Io = Ia · (Vo / Va).

Here, Vo / Va is the ratio of the total leakage current and the zero-phase leakage current in the measured value. This ratio is Io / I
It is the same as the ratio of a, and since Ia does not change with age as described above, the zero-phase current value can be estimated by calculation according to the above [Equation 1].

[ Third Embodiment] In the above-described example, since the phase of the measurement is selected by the controller of the monitoring unit, an optical fiber is required to insulate the sensor unit from the controller. On the contrary,
By providing the controller in the sensor section, the optical fiber for controlling the switch circuit can be omitted.

An example thereof will be described with reference to FIG. The circuit of FIG. 7 differs from the circuit of FIG. 5 described above in the following points. A controller 13 for selecting each phase is provided on the sensor side. Further, instead of the phototransistor, ordinary transistors Ta, Tb, Tc are used. The battery 2 of the sensor unit is shared as the power source of the controller 13.
As described above, when the controller 13 is provided on the sensor side, it is not necessary to insulate the controller 13 from the sensor section. Therefore, the signal from the controller 13 can use the normal metal cable and the transistor as the switch, so that the cost can be reduced.

The operation of the circuit of FIG. 7 will be described. The controller 13 supplies a signal for selecting a phase to the transistors Ta, Tb, Tc in a predetermined order as shown in FIG. FIG. 8A shows that the transistors Ta, Tb, and Tc are sequentially turned on in one cycle, and then all the transistors Ta, Tb, and Tc are simultaneously turned on. Therefore, the optical signal of the light emitting diode is
As shown in (b), the total leakage current of the a phase, the total leakage current of the b phase, the total leakage current of the c phase, and the leakage current of zero phase are output in this order.

In the monitoring unit 3, from the optical signal transmitted from the optical fiber 5, the total leakage current of the a-phase, the total leakage current of the b-phase, c
The total leakage current of the phase and the leakage current of zero phase are identified, and the abnormality of the arrester is monitored using each current value. Further, the activation of the one cycle operation of the controller 13 may be performed by an optical fiber signal from the outside.

[0036]

According to the present invention, it is possible to obtain a lightning arrester leakage current sensor capable of measuring a zero-phase current even when a zero-phase circuit cannot be formed on the side of the arrester circuit. Further, according to the present invention, in the arrester leakage current sensor, the leakage current can be measured for each phase, and the arrester in which an abnormality has occurred can be specified.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a prerequisite technique of a lightning arrester leakage current sensor of the present invention.

FIG. 2 is an equivalent circuit diagram of a lightning arrester.

FIG. 3 is a diagram showing an output waveform of an optical signal of a light emitting diode when measuring a leakage current for zero phase.

FIG. 4 is a diagram showing an output waveform of an optical signal of a light emitting diode when measuring a total leakage current.

FIG. 5 is a circuit diagram of a lightning arrester leakage current sensor according to a first embodiment of the present invention.

FIG. 6 is a circuit diagram of a lightning arrester leakage current sensor according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a lightning arrester leakage current sensor according to a third embodiment of the present invention.

8 is a timing chart for explaining the operation of FIG.

FIG. 9 is a circuit diagram of a conventional surge arrester leakage current sensor.

[Explanation of symbols]

1 ... Light emitting diode 2 ... battery 3 ... Monitoring unit 4 ... Optical-electrical converter 5, 7, 8, 9, 11 ... Optical fiber 6, 12, 13 ... Controller LA ... Lightning arrester CT ... Current transformer T ... transistor C ... Capacitor D ... Diode R ... resistance PT ... photodiode

Continuation of the front page (56) Reference JP-A-1-112169 (JP, A) JP-A-2-73165 (JP, A) JP-A-6-302408 (JP, A) JP-A-7-244111 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01R 31/02 G01R 31/12

Claims (2)

(57) [Claims] 1. A multi-phase lightning arrester, a current transformer provided for each phase of the lightning arrester, a semiconductor light emitting element, and a secondary side of the current transformer are connected in parallel to generate a current transformer secondary current. A means for supplying a DC bias current to the semiconductor light emitting element, and a switch means for turning on / off the secondary current of the multiphase current transformer for each phase. avoid lightning device leakage current sensor shall be the. 2. A multi-phase lightning arrester, a current transformer provided for each phase of the lightning arrester, a semiconductor light emitting element, and a secondary side of the current transformer are connected in parallel to generate a current transformer secondary current. Means for flowing to the semiconductor light emitting element, means for supplying a DC bias current to the semiconductor light emitting element, and a switch for simultaneously turning on and off the secondary currents of all the phases other than one phase of the multiphase current transformer avoid lightning device leakage current sensor can comprise means, it characterized.