JPH05256896A - Method for calibrating resonance type partial discharge detector - Google Patents

Abstract

PURPOSE:To obtain a calibrating method by which a resonance type discharge detector provided with a sensor composed of an electrode put on the peripheral surface of a power cable and inductance element connected to the electrode can be calibrated with high accuracy. CONSTITUTION:At the time of connecting, for example, power cables 11 and 12 to each other, the internal conductors 11a and 12a of the cables 11 and 12 are connected to each other and, at the same time, a sensor 3 composed of an electrode 1 and coil 2 is attached to one of the cables 11 and 12 near the connecting section. Then a pulse calibrator 14 is connected between the conductor connecting section 13 and earth and a calibration pulse is supplied to the power cable from the calibrator 14. Then a resonance type discharge detector is calibrated based on the output of the sensor 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge (Partia) generated inside an insulator of a power cable and at an insulator-conductor interface.
The invention relates to a method of calibrating a resonance type partial discharge detection device that detects PD.

[0002]

2. Description of the Related Art Conventionally, as a partial discharge detection device for detecting a partial discharge generated in a power cable, there have been proposed, for example, a method using a tuned detection method and a method using an AE (acoustic emission) sensor.

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.
A coupling content 23 and a detection impedance 24 are connected in series between the inner conductor of a or 22b and the metal shield layer, and the potential difference generated at both ends of the detection impedance 24 is adjusted by a 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 a directivity and has a drawback that the detection sensitivity is extremely lowered depending on the detection position.

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

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

Therefore, the inventors of the present invention have proposed a resonance type partial discharge detection device having a sensor composed of an electrode arranged on an insulating coating layer of a power cable and an inductance connected to this electrode ( 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 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 resonance type partial discharge detection device configured 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 end portions 44a and 44b, and the connection 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 resonance type partial discharge detection device constructed as described above, the coupling capacitance formed by the electrode 31 and the metal shielding layer 39 of the power cable 21 and the high frequency resonance circuit formed by the coil 32 are used. , A signal in a predetermined band of a traveling wave of a wide band generated by partial discharge is detected.

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

[0019]

However, the above-mentioned resonance type partial discharge detection device has a problem in that a method for calibrating the charge amount has not been established. That is, it is known that most of the cable accidents are accidents occurring at the connecting portion or the terminating portion. For this reason, the sensor of the partial discharge detection device is usually disposed near the connection portion of the power cable. In this case, as shown in FIG. 7, in order to calibrate the device main body portion 46 of the resonance type partial discharge detection device in the actual line, for example, in the terminal end portion 44a of the power cable 21, a pulse is applied between the high voltage portion and the ground. Calibrator 47
When the calibration pulse is supplied from the calibrator 47 to the power cable 21, the calibration pulse (especially high frequency component) is attenuated because the distance from the cable end portion 44a to the sensor 30 is long. In general, the distance from the cable end to the sensor installation position is several hundred meters to several kilometers, and the effective detection distance of the resonance type partial discharge sensor is within ten and several meters when the measurement frequency is 30 MHz, for example. Therefore, it is almost impossible to detect the calibration pulse by the above method.

The present invention has been made in view of the above problems, and provides a method of calibrating a resonance type partial discharge detection device capable of calibrating the device under the condition substantially equal to the state in which partial discharge actually occurs. The purpose is to do.

[0021]

A method of calibrating a resonance type partial discharge detection apparatus according to the present invention includes a sensor constituted by an electrode arranged on the peripheral surface of a power cable and an inductance element connected to the electrode. In the method of calibrating a resonance type partial discharge detection device, the sensor is attached at a position within an effective detection distance of the sensor from a connection portion of the power cable, and a calibration pulse is supplied to the power cable from the connection portion, The calibration is performed based on the output of the sensor.

[0022]

In the present invention, the sensor is arranged at a position within the effective detection distance of the sensor from the connection portion of the power cable, and the calibration pulse is supplied from the connection portion to the power cable. That is, in the present invention, the calibration of the partial discharge detection device is not performed by supplying the calibration pulse to the terminal end of the power cable in the state where the connection of the power cable is completed, but, for example, when the power cable is connected, A calibration pulse is supplied between the inner conductor connection portion of the cable and the shield layer or the ground while the inner conductor connection portion is not covered with the insulating material, and the device is calibrated by the output of the sensor at this time. Therefore, since the distance between the calibration pulse injection point and the sensor is short, the attenuation of the calibration pulse is small, and the resonance type partial discharge detection device can be calibrated under the condition substantially equal to the actual partial discharge.

[0023]

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

FIG. 1 is a plan view showing a method of calibrating a resonance type partial discharge detection device according to an embodiment of the present invention.

For example, at the time of connecting the power cables, after electrically connecting the internal conductors 11a and 12a of the power cables 11 and 12 to each other, the sensor 3 is placed near the conductor connecting portion 13 of one power cable 12 ( It is arranged within the effective detection distance of the sensor 3.

The sensor 3 is composed of an electrode 1 attached to the peripheral surface of the power cable 12 and a coil 2 connected to the electrode 1 (see FIG. 4). The electrode 1 constitutes a coupling capacitance with the metal shielding layer of the power cable 12,
The coupling capacitor and the coil 2 form a high frequency resonance circuit. The resonance frequency of this high-frequency resonance circuit is the coil 2
It is set to, for example, 30 MHz by adjusting the inductance or the width of the electrode 1. When a signal with a frequency of 30 MHz is transmitted through the power cable, it is said that there is about 30% attenuation at a position 5 m away from the signal generation source. For this reason, the sensor 3 is preferably installed at a position within 5 m (more preferably 1 to 2 m) from the cable connection portion. After that, the signal output end of the sensor 3 is connected to an apparatus main body (not shown) including an amplifier and the like.

After connecting the sensor 3 and the apparatus main body in this way, a pulse calibrator 14 is connected between the conductor connecting portion 13 and the ground, and a calibration pulse is supplied from the pulse calibrator 14 to the power cable 12. Supply. Alternatively, as shown in FIG. 2, a pulse calibrator 14 may be connected between the conductor connecting portion 13 and the metal shielding layer of the cable 12, and the calibration pulse may be supplied from the pulse calibrator 14 to the power cable 12. ..

The output of the sensor 3 at this time adjusts the amplification factor of the amplifier so that, for example, the charge amount of the calibration pulse and the instruction value of the apparatus main body correspond, and the resonance type partial discharge detection apparatus is calibrated.

In the present embodiment, since the distance between the calibration pulse injection point and the sensor is short, it is possible to calibrate the partial discharge detection device in a state where the high frequency component of the calibration pulse is less attenuated. Also, the attenuation of the high frequency component of the calibration pulse is the same condition as when partial discharge occurs at the cable connection part, so the calibration of the partial discharge detection device should be performed under the condition that it is approximately the same as the actual partial discharge condition. Can be implemented. Therefore, according to the method of this embodiment, the resonance type partial discharge detection device can be calibrated with high accuracy. Furthermore, in the method of this embodiment, it is not necessary to change the work of connecting the power cable, and the time required for the work of connecting the cable is hardly affected.

[0030]

As described above, according to the present invention, the calibration pulse is supplied to the power cable from the connection portion of the power cable, and the device is calibrated based on the output of the sensor at this time. The device can be calibrated under the condition that is substantially the same as the state in which the partial discharge has occurred, and the resonant partial discharge detection device can be calibrated with high accuracy.

[Brief description of drawings]

FIG. 1 is a plan view showing a calibration method for a resonance type partial discharge detection device according to an embodiment of the present invention.

FIG. 2 is a plan view showing an example of a method for supplying a calibration pulse to the power cable.

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

FIG. 4 is a cross-sectional view showing a sensor section of a resonance type partial discharge detection device.

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

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

FIG. 7 is a schematic diagram showing a calibration method of a resonance type partial discharge detection device in an actual line.

[Explanation of symbols]

 1, 31; Electrodes 2, 32; Coil 3, 30; Sensors 11, 12, 21; Power cable 13; Conductor connection part 14, 47; Pulse calibrator 35; Coaxial connector 38; Cable insulator 39; Metal shielding layer 40 ; Plastic sheath

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasuhiro Takahashi 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Masayuki Tan Tan 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd.

Claims (1)

[Claims] 1. A method of calibrating a resonance type partial discharge detection apparatus comprising a sensor, which comprises an electrode arranged on a peripheral surface of a power cable and an inductance element connected to the electrode, in a calibration method of a power cable connecting portion. Resonance type characterized in that the sensor is attached at a position within an effective detection distance of the sensor, a calibration pulse is supplied from the connection portion to the power cable, and calibration is performed based on the output of the sensor at this time. Calibration method for partial discharge detection device.