JPH02167484A - Measuring method for partial discharge - Google Patents

Abstract

PURPOSE:To measure partial discharge with specific sensitivity by providing electrodes of specific area on the metallic conduit of an insulation connection part across an anticorrosive vinyl layer. CONSTITUTION:An anticorrosive vinyl layer 1 on a metallic sheath and an anticorrosive vinyl layer 2 on the metallic conduit 12 of the insulation connection part are connected and the conduit 12 is insulated by an insulation layer 3. Then when the conductor of a power cable is connected by a connection sleeve 11, capacitors with electrostatic capacity values C1 and C2 are formed between the conductor 10 and conduit 12. Further, couples of detection electrodes 4 and calibration electrodes 5 are provided on the external surface of the vinyl layer 2, and detection impedance 6, a measuring instrument 7, and a calibration signal generator 8 are connected to the electrodes 4 and 5 to form capacitors with electrostatic capacity values Cd1 and Cd2 by the electrodes 4 and capacitors with electrostatic capacity values Cp1 and Cp2 by the electrodes 5. Assuming that C1=C2, detection impedance Z>>Zc1=1/2pifC1, and C1>>C0 in this equivalent circuit, the terminal voltage across the impedance 6 is V2=V0.2C0/C1 and high frequency pulses can be detected at high level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring partial discharge in an insulated connection part of a power cable line.

[Conventional technology]

FIG. 4(a) shows a conventional partial discharge measuring method. A power cable 21 is connected via an insulated connection part 20,
Terminal connection portions 22 are provided at both ends. Termination connection part 2
2 is provided with a high voltage charging terminal 23, and the metal sheath near the insulated connection portion 20 is grounded via a detection impedance 6. A measuring device 7 is connected to detect the potential difference between both ends of the detection impedance 6 . Note that CK is a coupling capacitor.

In the above configuration, a high voltage is applied to the high voltage charging terminal 23. In this state, when a partial discharge occurs in the insulator, a high-frequency pulse is induced in the conductor and the metal sheath, and the high-frequency pulse in the metal sheath flows to the detection impedance 6, creating a potential difference at both ends proportional to the magnitude of the high-frequency pulse. Sign. The partial discharge is measured by detecting the potential difference with the measuring device 7.

When calibrating the measurement sensitivity of the measuring device 7, the high voltage terminal 23
The high voltage application is stopped, the calibration signal generator 8 is connected near the terminal connection part 11, and a high frequency pulse for calibration is applied between the conductor of the power cable 21 and the metal sheath. The equivalent circuit is shown in FIG. 4(b). As shown in FIG. 4, the calibration signal generator 8 sends a high frequency pulse of v0 volts to the capacitance
It is applied between the conductor 10 and the metal sheath 12 of the power cable 21 via a capacitor 8. Conductor 10 and metal sheath 1
A capacitance C is formed between the capacitance C and the high frequency pulse flowing through the capacitor having the capacitance C is shunted to the detection impedance 6. In this way, the sensitivity calibration of the measuring device 7 is performed. Here, if the apparent discharge charge by a capacitor with capacitance C is Q and the potential is V, then Q=VO・Co
=V+ ・c −−−−−−−−−−−(1)(1
) From the formula, O v, = VQ −−−−−(2)
is obtained. Substantially the same effect can be obtained by connecting a detection impedance between the metal sheaths on both sides of the insulating cylinder of the insulating connection part 20.

[Problem to be solved by the invention]

However, according to the conventional partial discharge measurement method, when the power cable line becomes long, such as several kilometers long, until the high-frequency pulse for calibration is transmitted to the partial discharge measurement position,
That level ■. is attenuated, and usually C>C,
Therefore, there is an inconvenience that the value of VI in equation (2) becomes small and a predetermined calibration operation cannot be performed. Furthermore, since the position of the terminal connection part to which the calibration signal generator is connected is far from the position of the measurement point where the calibration operation is performed, there is a problem that workability is poor.

Therefore, it is an object of the present invention to provide a partial discharge measuring method that allows obtaining a calibration signal of a predetermined level.

Another object of the present invention is to provide a partial discharge measuring method that improves the workability of the calibration operation.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides a pair of detection electrodes via an anti-corrosion vinyl layer on a separated metal sheath of an insulated connection part through which high-frequency pulses induced by partial discharge flow, and a detection impedance is provided between them. A partial discharge measuring method is provided in which a calibration signal generator is connected in parallel with a detection impedance.

The calibration signal may be injected directly to both ends of the detection impedance, but it can also be injected to the pair of detection electrodes described above. Alternatively, a pair of calibration electrodes may be provided on both sides of the outer surface of the anticorrosive vinyl layer of the insulating connection part via an insulating cylinder, and a calibration signal generator may be connected to the pair of calibration electrodes.

〔Example〕

Hereinafter, the partial discharge measuring method of the present invention will be explained in detail.

FIG. 1 shows an embodiment of the present invention, in which an anticorrosion vinyl layer 11 on a metal sheath and an anticorrosion vinyl layer 2 on a metal trunk tube at an insulating connection part are shown.
is continuous, and the metal trunk tube is insulated by an insulating tube 3. A pair of detection electrodes 4 and a pair of calibration electrodes 5 are provided on the outer surface of the anticorrosive vinyl layer 2 on the metal trunk tube, and a detection impedance 6 and a calibration signal generator 8 are connected in parallel to these electrodes 4.5. connected so that A measuring device 7 is connected to the detection impedance 6 to detect the potential difference between both ends thereof.

FIG. 2 is a circuit diagram of the embodiment shown in FIG.
The conductor 10 of the power cable is connected by a connection sleeve 11, and there is a capacitance CI between the conductor 10 and the metal trunk tube 12.
A capacitor C2 is formed, and the metal body tube 12 is connected to the insulating tube 3.
insulated by. A detection electrode 4 and a calibration electrode 5 are provided on the outer surface of the anticorrosive vinyl layer 2 on the metal trunk tube 12. The detection impedance 6, measuring device 7, and calibration signal generator 5 are as shown in FIG.

FIG. 3(a) is an equivalent circuit of FIG. 2, and the same parts are indicated by the same reference numerals, so redundant explanation will be omitted.
The detection electrode 4 forms a capacitor with capacitances C□ and Cd2, and the calibration electrode 5 forms a capacitor with capacitances CPI and CPZ. Here・CPI・CP2>
Co.

vinegar).

Therefore, the equivalent circuit shown in FIG. 3(b) is obtained. In this equivalent circuit, C,=C,.

Assuming that C, > C, the voltage V2 applied across the detection impedance 6 is: where C0, C1, C2, and Vo are known or can be measured. Comparing the equation (2) described in the related art and the equation (3) of the present invention, V 2 = 2 V l -----(4) is obtained.

However, C=C. As is clear from equation (4), the high frequency pulse is detected at twice the level compared to the conventional method, and there is no need to take into account the attenuation caused by propagation through a long electric cable.

In the above embodiment, CPI and CPU>CG were set, but Co is about 10 to 50PF, and to satisfy this, the area of the calibration electrode 5 is set to a predetermined value.
It is possible to set it to about 0 to 100 OPF.

ZcdI, Zcd2 (the same applies to Z).

Furthermore, if the calibration electrode 5 is omitted and the calibration signal is injected into the detection electrode 4, cP, CP□ will be omitted in the equivalent circuit of FIG. (
This is the same as the equivalent circuit of b). However, in order to improve the calibration accuracy, it is better to provide the calibration electrode 5.

Further, the explanation has been made under the conditions that C,=C2, Z>Z, but even if this condition is not satisfied, calibration is possible by finding a correction term based on the basic equation.

〔Effect of the invention〕

As explained above, according to the partial discharge measuring method of the present invention, an electrode of a predetermined area is provided on the metal trunk tube of the insulated connection part through the anticorrosion vinyl layer, and a detection impedance and a calibration signal generator are connected in parallel between them. Since they are connected and inserted, the following effects can be achieved.

(1) Partial discharge can be measured with a predetermined sensitivity at an insulated connection part of a long cable line. Moreover, it can be applied to existing railway lines as is.

(2) No distortion or attenuation of the waveform of the high-frequency pulse for calibration occurs.

(3) Workability is good because the calibration signal generator and measuring device are located at the same location.

(4) High safety because there is no need to inject high-frequency pulses for calibration into the high-voltage conductor.

(5) Sensitivity calibration can be performed even in live line conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing one embodiment of the present invention. Figure 2 is the first
A circuit explanatory diagram of the figure. 3(a) and 3(b) are equivalent circuit diagrams of FIG. 2, and FIGS. 4(a) and 4(b) are explanatory diagrams and equivalent circuit diagrams of a conventional partial discharge measuring method. Explanation of symbols 1 --- Corrosion-proof vinyl layer on metal sheath 2 ---
--------1 Corrosion-proof vinyl layer 3 on the metal trunk tube 4--Insulating cylinder 4-------1 Detection electrode 5--
--------- One calibration electrode 6 --------- Detection impedance 7 ---
-------1 Measuring device 810 Cable conductor 11/-12--1 Metal barrel calibration signal generator termination sleeve

Claims (2)

[Claims] (1) In a method for measuring partial discharge in an insulated connection part of an underground power cable line, a pair of detection electrodes are provided on both sides of the anticorrosive vinyl layer of the insulated connection part via an insulating tube, and the pair of detection electrodes is A method for measuring partial discharge, characterized in that a detection impedance connected to a measuring device is connected between the electrodes, and a signal for sensitivity calibration of the measuring device is injected into both ends of the detection impedance. (2) Providing a pair of calibration electrodes adjacent to the pair of detection electrodes on both sides of the outer surface via the insulating tube, and injecting the sensitivity calibration signal into the pair of calibration electrodes. The partial discharge measuring method according to claim 1, characterized in that: