JPH06308191A - Testing method for resonance type partial discharge detector - Google Patents

Abstract

PURPOSE:To accurately execute the confirmation of an operation, calibration, etc., in a resonance type partial discharge detector having a high frequency partial discharge sensor which has a signal detecting electrode arranged on a periphery of a power cable and an inductance element connected to the electrode. CONSTITUTION:A signal injecting electrode 10 is provided on a periphery of a power cable near a high frequency partial discharge sensor 30, and a capacitor 11 is connected to the electrode 10. A reference pulse generated from a pulse calibration unit 50 is injected to a power cable 21 through the capacitor 11 and the electrode 10. The confirmation of an operation, the calibration, etc., of a resonance type partial discharge detector are executed based on the output of the sensor 30 at this time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention checks the operation of a resonance type partial discharge detection device having a high frequency partial discharge sensor composed of electrodes arranged on the peripheral surface of a power cable and an inductance element connected to the electrodes. And a method for testing a resonance type partial discharge detection device performed for calibration, etc., in particular, a pulse output from a pulse calibrator is injected into the power cable, and a signal output from the high frequency partial discharge sensor in response to this pulse. The present invention relates to a method for testing a resonance type partial discharge detection device for confirming the operation and calibration of the resonance type partial discharge detection device.

[0002]

2. Description of the Related Art Conventionally, as a partial discharge detecting device for detecting a partial discharge (PD) generated in a power cable, there is a partial discharge detecting device using, for example, a tuning type detection method and a method using an AE (acoustic emission) sensor. Proposed.

As shown in FIG. 3, a tunable detection device using the tuned detection method has a terminating portion 22 of a power cable 21, as shown in FIG.
The coupling capacitor 23 and the detection impedance 24 are connected in series between the inner conductor of a or 22b and the metal shielding layer, and the potential difference generated across the detection impedance 24 is adjusted by the tuning amplifier 25 having a tuning frequency of several hundred kHz. I took it out.

However, this tunable detection device has a problem that it is difficult to detect the signal under the hot line because it is necessary to take out a signal from the inner conductor of the power cable, and a dedicated coupling capacitor is also required. . Further, since the tuning frequency in this device is several hundred kHz, it is easily affected by ambient noise, and although good detection accuracy can be obtained in an experiment in a shielded room, it is difficult to apply it to a cable after installation.

On the other hand, the detection device using the AE sensor is
Although an AE sensor detects elastic waves propagating inside the insulator by partial discharge, this device is not affected by electrical noise, but it is strong because the ultrasonic waves have straightness. It has directivity, and there is a problem that the detection sensitivity is extremely lowered depending on the detection position.

As a method for detecting partial discharges that solves these drawbacks, a metal shield layer is insulated in a connection portion of a power cable, and a potential difference generated between the two metal shield layers sandwiching the insulating portion when a partial discharge occurs is determined by measuring the potential difference between both metal shield layers. A detection method has also been proposed in which detection is performed using a detection impedance connected between shield layers (“Partial discharge test results for the Minamiikegami 275kV CV cable line”; Katsuta et al., Institute of Electrical Engineers, Insulation Material Research Material EIM-90-20). .

However, this method is limited in its application only to the connection portion where the metal shield layer is insulated, and the metal shield layer is in a non-grounded state, resulting in a lack of safety when a short-circuit accident occurs. There is. In addition, there is a drawback that the device becomes large and requires skill in measurement.

Therefore, the inventors of the present application have proposed a resonance having a sensor (high frequency partial discharge sensor) composed of an electrode disposed on an insulating coating layer (sheath) of a power cable and an inductance connected to this electrode. A type partial discharge detection device was proposed (Japanese Patent Application No. 2-310197).

FIG. 4 is a sectional view showing a sensor portion of this resonance type partial discharge detection device.

On the outer circumference of the power cable 21, an electrode 31 formed of a conductive paint or a metal tape is provided over the entire circumference. The electrode 31 includes an insulating cylinder 33a attached to the power cable 21, a brass cylinder 33b arranged on the outer circumference of the insulating cylinder 33a, and a lead tape 34 covering the outer circumference.
It is housed in a shield container formed by.
A coaxial connector 35 such as a BNC connector is attached to the brass tube 33b.
A coil 32 as an inductance element is connected between the inner conductor of the electrode and the electrode 31. The shield container is connected to the ground wire to which the metal shield layer of the power cable 21 is connected.

The power cable 21 to be detected is, for example, a 275 kV CV cable, and the inner conductor 36, the inner semiconductive layer 37, and the cable insulator (XLPE:
cross-linked polyethylene) 3
8. A metal shielding layer 39 as an outer metal layer and a plastic sheath 40 as a coating layer are coaxially arranged.

FIG. 5 is a block diagram showing the structure of a partial discharge detecting device using this high frequency partial discharge sensor.
This apparatus includes a sensor 30 having the above-described structure, a wide band amplifier 41 that amplifies the output of the sensor 30, and a digitizing oscilloscope 42 that performs signal processing such as averaging on the output of the wide band amplifier 41. Has been done.

A plurality of power cables 21 are connected to each other via connecting portions 43a and 43b so as to have a predetermined length, and inner conductors 36 of terminal portions 44a and 44b thereof are connected to a high voltage power supply line 45. In addition, the metal shield layer 39 of the power cable 21 includes the end portions 44a and 44b and the connecting portion 43.
It is properly grounded at a, 43b and the like.

Next, the operation of the partial discharge detection device constructed as described above will be described.

The equivalent circuit of the power cable 21 is generally considered as a circuit as shown in FIG. That is, the ground lines of the inner conductor 36, the metal shielding layer 39, the terminal ends 44a and 44b, and the connecting portions 43a and 43b form an RL series circuit. The inner conductor 36 and the metal shielding layer 39 are capacitively coupled via a cable insulator 38 interposed therebetween. Further, the detection unit D is composed of the coupling capacitance determined by the electrode 31 of the sensor 30 and the plastic sheath 40 of the power cable 21, the inductance of the coil 32 provided in series with this capacitance, and the input impedance of the measuring instrument. Composed. The coupling capacity of the electrode 31 can be adjusted by, for example, the length of the electrode 31 in the cable longitudinal direction.

When a partial discharge occurs in the cable insulator 38, the pulsating current generated by the partial discharge is i2 in the figure.
, I2 ′, ... and the coaxial modes i1 and i1 in FIG.
.., i3, i3 ', ... Propagate separately in the earth return mode. As a result, the detection section D has i1 + i
Since the current indicated by 1'flows, the sensor 30 detects this current.

In the partial discharge detection device thus constructed, the metal shield layer 3 of the electrode 31 and the power cable 21 is used.
The coupling capacitance formed by 9 and the high frequency resonance circuit formed by the coil 32 detect a signal in a predetermined band of a traveling wave in a wide band generated by partial discharge.

This resonance type partial discharge detection device has the advantages that the sensor can be easily installed on the power cable, the safety is high, and the partial discharge can be detected in a live state.

FIG. 7 is a schematic view showing an example of a test method of the above-mentioned resonance type partial discharge detection device. Power cable 2
Partial discharge sensor 30 composed of electrode 31 formed on the peripheral surface of No. 1 and coil 32 connected to this electrode 31
Is output to the oscilloscope 52 via the amplifier 51. In the conventional method for testing a resonance type partial discharge detection device, a pulse calibrator 50 is connected between the inner conductor 36 and the ground (metal shield layer 39) at the end of the power cable 21, and the pulse calibrator 50 is connected to the pulse calibrator 50. A reference pulse is injected into the inner conductor 36. Then, based on the output of the partial discharge sensor 30 at this time, operation confirmation and calibration of the resonance type partial discharge detection device are performed.

[0020]

However, the above-described method of testing the resonance type partial discharge detection device has the following problems. FIG. 8 is a graph showing the relationship between the two, with the horizontal axis representing the charge amount of the input signal (reference pulse) and the vertical axis representing the sensor output. As can be seen from FIG. 8, the charge amount of the reference pulse is proportional to the sensor output. On the other hand, FIG.
Is the distance between the reference pulse injection point and the sensor on the horizontal axis,
The sensor output is plotted on the vertical axis, and the injected charge amount is constant (10 p
It is a graph figure which shows the relationship of both when it is set as C). As can be seen from FIG. 9, even if the charge amount of the reference signal is constant, the sensor output changes depending on the distance from the pulse injection point.

Therefore, in the case of a short cable, it is possible to check the operation and calibrate the sensor even if a reference pulse is injected from the end of the cable as shown in FIG.
However, for example, as is clear from FIG. 9, there is an attenuation of about 30% at a distance of 5 m from the pulse injection point, so in a real line where one span is about 300 to 500 m, the reference pulse is injected from the cable end. However, the output of the sensor corresponding to this reference pulse is extremely small, and it is difficult to confirm the operation and calibrate the partial discharge detection device.

The present invention has been made in view of the above problems, and even with a long cable, the resonance type partial discharge detecting apparatus can be highly accurately checked for operation and calibration. An object of the present invention is to provide a method for testing a partial discharge detection device.

[0023]

A method of testing a resonance type partial discharge detection device according to the present invention is directed to a signal detection electrode arranged on a peripheral surface of a power cable and an inductance element connected to the signal detection electrode. In the method of testing a resonance type partial discharge detection device including a high frequency partial discharge sensor configured by, a signal injection electrode is provided on the peripheral surface of the power cable, and a capacitor is connected to the signal injection electrode, and the capacitor and A reference signal is injected into the power cable through the signal injection electrode, and the resonance type partial discharge detection device is tested based on a signal output from the high frequency partial discharge sensor according to the reference signal. And

[0024]

In the present invention, the signal injection electrode is provided on the peripheral surface of the power cable, the capacitor is connected to the signal injection electrode, and the reference signal generated by the pulse calibrator, etc.
The power cable is injected through the capacitor and the signal injection electrode. That is, the signal injection electrode constitutes a coupling capacitance with the metal shield layer via the plastic sheath of the power cable. The reference signal provided to the capacitor is injected into the metal shield layer through this coupling capacitance,
The metal shield layer propagates along the length of the power cable.

By the way, the capacitor is provided for carrying out the test in the same state as when the reference pulse is directly injected into the inner conductor of the power cable. That is, in the conventional method shown in FIG. 7, the capacitance of the pulse calibrator 50 is C _Q , the coupling capacitance between the internal conductor and the shielding layer is C _C , the coupling capacitance between the shielding layer and the electrode is C _S , and the inductance of the coil 32 is Is L and the input impedance of the measuring instrument is Z _d , the equivalent circuit of this circuit is as shown in FIG. In the present invention, the capacitor corresponds to the coupling capacitance C _S , and the test can be performed under the same conditions as when the reference signal from the pulse calibrator was directly injected into the inner conductor.

The capacitor connected to the signal injection electrode is preferably a variable capacitor so that fine adjustment can be performed during the test.

According to the present invention, the reference signal can be injected into the power cable at any position in the length direction of the power cable, not limited to the end portion of the power cable. Therefore, for example, the distance between the signal injection electrode and the high-frequency partial discharge sensor is made close to a level where the attenuation of the reference signal is negligible, or the distance between the signal injection electrode and the high-frequency partial discharge sensor is made constant. As a result, the operation confirmation, calibration, and the like of the resonance type partial discharge detection device can always be performed with high accuracy.

[0028]

Embodiments of the present invention will now be described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a method of testing a resonance type partial discharge detection device according to an embodiment of the present invention.

The high frequency partial discharge sensor 30 includes electrodes (signal detection electrodes) 31 provided on the peripheral surface of the power cable 21.
And a coil 32 connected to this electrode 31. The output of the high frequency partial discharge sensor 30 is given to the oscilloscope 52 via the amplifier 51.

An electrode (signal injection electrode) 10 is provided on the peripheral surface of the cable near the high frequency partial discharge sensor 30, and a capacitor 11 is connected to the electrode 10. Like the electrode 31, the electrode 10 is formed of a conductive paint, a metal tape, or the like. The capacitance value of the capacitor 11 is set according to the capacitance value of the coupling capacitance C _S between the shield layer of the power cable and the electrode 31, for example.

A pulse calibrator 50 is connected between the capacitor 11 and ground. The reference pulse output from the pulse calibrator 50 is injected into the power cable 21 via the coupling capacitance formed by the electrode 10 and the metal shielding layer 39 of the power cable 21, and propagates in the length direction of the power cable 21. To do. The high frequency partial discharge sensor 30 detects this signal and outputs it as an output signal. For example, the reference pulse and the output signal from the sensor 30 are compared with each other to check the operation of the resonance type partial discharge detection device and calibrate it.

2A and 2B are equivalent circuit diagrams of the method of this embodiment. The capacitor C _Q is the capacity of the pulse calibrator 50, the capacitor 11 is the capacitor disposed between the pulse calibrator 50 and the electrode 10, and the capacitor C _Q
s ′ is the coupling capacitance between the electrode 10 and the shielding layer, Z _d is the input impedance of the measuring instrument, and this input impedance Z _d
A coil L and a capacitor C _S connected in series to the sensor are coupling capacitances between the coil and the electrode of the sensor and the shielding layer, and a capacitor C _C is a coupling capacitance between the inner conductor and the shielding layer. In this embodiment, a resonance type partial discharge detection device is tested by providing a capacitor 11 between the pulse calibrator and the signal injection electrode in the same manner as the conventional method of injecting a reference pulse from an internal conductor into a cable. can do.

In the present embodiment, since the signal injection electrode provided on the peripheral surface of the power cable and the reference pulse are injected into the power cable via the signal injection electrode, the reference signal is directly supplied to the inner conductor of the power cable. Then, by reducing the distance between the signal injecting electrode and the high frequency partial discharge sensor, it is possible to avoid a decrease in accuracy due to the attenuation of the reference signal. That is, according to the present embodiment, it is possible to accurately check and calibrate the resonance type partial discharge detection device regardless of the cable length of the power cable. Also, even in the test of the resonance type partial discharge detection device for a short cable, it is not necessary to expose the conductor of the power cable, and it suffices to dispose the signal injection electrode around the sheath, which shortens the work time. There is an effect that can be done.

In the above embodiment, the capacitor 11 may be a variable capacitor. As a result, the capacitance value can be finely adjusted after the cable is installed, and the accuracy of operation confirmation and calibration can be further improved.

[0036]

As described above, according to the present invention, the signal injection electrode is provided around the power cable, the capacitor is connected to the signal injection electrode, and the capacitor and the signal injection electrode are interposed. Since the reference signal is injected into the power cable, it is possible to test in the same state as when the reference signal is directly applied to the inner conductor of the power cable, and it is possible to avoid deterioration of accuracy due to attenuation of the reference signal, Regardless of the length of the power cable, it is possible to accurately check and calibrate the resonance type partial discharge detection device. Further, according to the present invention, it is not necessary to expose the conductor of the cable, so that there is an effect that the working time can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a test method for a resonance type partial discharge detection device according to an embodiment of the present invention.

2A and 2B are equivalent circuit diagrams of the method of the present embodiment.

FIG. 3 is a block diagram showing a conventional tunable partial discharge detection device.

FIG. 4 is a perspective view showing an example of a high frequency partial discharge sensor.

FIG. 5 is a block diagram showing a configuration of a partial discharge detection device using the same sensor.

FIG. 6 is an equivalent circuit diagram of a power cable and a detection system.

FIG. 7 is a schematic diagram showing an example of a test method for a conventional resonance type partial discharge detection device.

FIG. 8 is a graph showing the relationship between the input signal injected into the power cable and the output of the high frequency partial discharge sensor.

FIG. 9 is a graph showing the relationship between the distance from the reference pulse injection point and the output of the high frequency partial discharge sensor.

FIG. 10 is an equivalent circuit diagram of a conventional resonance type partial discharge detection device testing method.

[Explanation of symbols]

 10; Signal injection electrode 11; Capacitor 21; Power cable 30; High frequency partial discharge sensor 31; Signal detection electrode 32; Coil 36; Inner conductor 39; Metal shielding layer 40; Sheath 50; Pulse calibrator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Takahashi 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Watanabe 1-5-1 Kiba, Koto-ku, Tokyo Stockholders Inside Fujikura

Claims (1)

[Claims] 1. A test of a resonance type partial discharge detection device comprising a high frequency partial discharge sensor composed of a signal detection electrode arranged on the peripheral surface of a power cable and an inductance element connected to the signal detection electrode. In the method, a signal injection electrode is provided on a peripheral surface of the power cable, a capacitor is connected to the signal injection electrode, and a reference signal is injected into the power cable through the capacitor and the signal injection electrode. A method of testing a resonance type partial discharge detection device, characterized in that the resonance type partial discharge detection device is tested based on a signal output from the high frequency partial discharge sensor in accordance with a reference signal.