JPH02154170A - Measuring method for partial discharge - Google Patents

Abstract

PURPOSE:To allow a measurement in a live-line state by mounting iron cores having high inductance to a lead wire for grounding line, etc., from the outside as it is and connecting a partial discharge measuring instrument in parallel with the cores. CONSTITUTION:A power cable 1 is connected with a connection part 2, and the grounding line 5 is connected to a ground terminal 11 of the connection part 2 and mounted with three iron cores 12. The iron cores 12 can be mounted without removing the grounding line 5 from the terminal 11 as they are made in half-slit. The cable 1, to which the partial discharge measuring instrument 8 is connected parallel to the grounding line 5, is in a working condition, and the rated voltage with a commercial frequency is impressed to an insulated body. When the partial discharge is generated on the insulated body, high frequency pulses are induced on a metal sheath then appeared on the terminal 11. As a high frequency impedance of the grounding line 5 is large, almost all of the high frequency pulses flow into the measuring instrument 8 and are measured therein. The measurement can be thus performed in the live-line state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a partial discharge measuring method for diagnosing insulation deterioration of electric cables and the like.

[Conventional technology]

FIG. 3 shows a conventional partial discharge measuring method. The cable under test 1 is connected by an intermediate connection part 2 and is connected to a high voltage charging part 4 via a terminal connection part 3. The sheaths of the intermediate connection 2 and the end connection 3 are grounded via a ground conductor 5.6.

Here, when measuring the partial discharge of the insulator of the test cable 1, the grounding wire 6 is removed, a detection impedance 7 is inserted therein, and a partial discharge measuring device 8 is connected to the detection impedance 7. At this time, the operation of the power cable I is stopped, and a test voltage is applied from the high voltage charging section 4 to measure partial discharge. Since the partial discharge of the insulator is a high frequency pulse, the detection impedance 7 is determined based on the high frequency pulse.
A potential difference occurs between both ends of the . This is detected by the partial discharge measuring device 8. The detected data is subjected to predetermined data processing, thereby diagnosing the deterioration of the insulation of the test cable 1.

[Problem to be solved by the invention]

However, according to the conventional partial discharge measurement method, the grounding wire 6 must be removed, the detection impedance 7 must be inserted, and the system must be returned to its original state after the measurement is completed, which reduces the reliability of the power cable line as a system. In addition, since measurement cannot be performed while the line is live, system operation must be stopped.

Therefore, an object of the present invention is to provide a partial discharge measuring method that allows partial discharge to be measured without removing the grounding wire or the like.

Another object of the present invention is to provide a partial discharge measuring method that allows measurement even when the system is in operation.

[Means for Solving the Problems] In order to achieve the above object, the present invention attaches a high inductance element to a lead wire such as a ground wire through which a partial discharge signal flows, thereby increasing the high frequency impedance of the lead wire.
A partial discharge measuring method is provided in which a partial discharge measuring device is connected in parallel to a lead wire and a partial discharge signal is measured.

A high inductance element is made of, for example, a silicon steel material or other high-permittivity iron core, and has a mounting hole inside that corresponds to the outer shape of the lead wire, and is cut into two parts or the like to allow it to be mounted from the outside of the lead wire. Easy to install. There is no need for the wire to be removed for this purpose. The attached iron core is preferably fixed by a retaining means such as a hook, but may also be fixed by an adhesive tape or the like.

This iron core is adapted to the characteristics of the partial discharge meter. That is, the dimensions of the iron core are determined based on the frequency characteristics of the inductance and the saturation magnetic flux density, and the commercial frequency zero-sequence current flowing through the lead wires are also taken into consideration. When a predetermined high frequency impedance cannot be obtained even with one iron core, a plurality of iron cores are attached in series. In this way, the high frequency impedance of the lead wire is set to a predetermined value. Connect a partial discharge measuring device in parallel to this lead wire. Since the partial discharge is a high frequency pulse, it is prevented from flowing through the lead wire by the high frequency impedance of the lead wire. Therefore, it flows through the partial discharge meter and is measured there.

Deterioration diagnosis of the insulator is performed based on the number and level of partial discharge pulses.

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

FIG. 1 shows a first embodiment of the present invention, in which an electric cable 1
are connected by the connecting part 2. A grounding wire 5 is connected to the grounding terminal 11 of the connection part 2, and the grounding wire 5 has a
Three iron cores 12 are attached. Since the iron core 12 is divided into two parts, the grounding wire 5 can be attached to the grounding terminal 11 without being removed. The power cable 1, in which the partial discharge measuring device 8 is connected in parallel to the grounding wire 5, is in operation, and the rated voltage of the commercial frequency is applied to the insulator. When a partial discharge occurs in the insulator, a high frequency pulse is induced in the metal sheath and appears at the ground terminal 11.

Since the high frequency impedance of the grounding wire 5 is large, almost all of this high frequency pulse flows into the partial discharge measuring device 8 and is measured there. A measurement lead wire may be connected in parallel to the ground wire 5, and a detection impedance may be inserted therein to measure the voltage across the lead wire.

FIG. 2 shows a second embodiment of the present invention, in which R phase, S phase, T
A phase power cable 1 is connected by an insulated connection part 2,
The metal sheaths of each connection part 2 are connected by cross bond wires 20. Note that 13 is an arrester that protects the insulated portion of the insulated connection portion 2 from surge voltage.

When measuring partial discharge, a halved iron core 20 is attached to the cross bond wire 20. When measuring T-phase partial discharge, a partial discharge measuring device 8 is connected to both ends of the insulated connection part 2. The R phase and S phase can also be measured in the same manner.

In the first and second embodiments, the iron core is attached to the ground wire and the cross bond wire, but it may be attached to a jumper wire or the like.

Moreover, it can be attached not only to power transmission lines but also to grounding wires of motors, transformers, switches, etc.

Furthermore, the present invention can also be applied to a carrier wave communication system using a metal sheath as an information communication medium.

In this case, the signal can be received by inserting the receiving device into the partial discharge measuring device.

〔Effect of the invention〕

As explained above, according to the partial discharge measuring method of the present invention, a high inductance iron core is attached from the outside to the lead wire such as a grounding wire, and a partial discharge measuring device is connected in parallel with the lead wire. This prevents the reliability of the system from decreasing, and enables measurement under live conditions. Naturally, the workability of measurement work can be improved.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams showing first and second embodiments of the present invention. FIG. 3 is an explanatory diagram showing a conventional partial discharge measuring method. Explanation of symbols 1-・-1--Power cable 2-・・-・
Connection part 3---Terminal part 4--
・Charging part 5.6--・Grounding wire 7--・--Detection impedance 8--・-m----・Partial discharge measuring device 11--・・-- Grounding terminal 12--
・-Iron core 13--1--Arrester

Claims (3)

[Claims] (1) In a partial discharge measurement method for diagnosing deterioration of an insulator by detecting partial discharge in an insulator to which a high voltage is applied, a predetermined inductance is installed in a lead wire through which a high-frequency pulse induced based on the partial discharge flows. A partial discharge characterized in that: an iron core having an iron core is attached from the outside of the lead wire, a measurement lead wire that bypasses the high frequency pulse is connected to the lead wire in parallel, and the high frequency pulse flowing through the measurement lead wire is measured. Measuring method. (2) The partial discharge measuring method according to claim 1, wherein a partial discharge measuring device is inserted into the measurement lead wire. (3) The partial discharge measuring method according to claim 1, wherein a detection impedance is inserted into the measurement lead wire.