JPS59105540A - Measuring method for position of partial discharge in power cable system - Google Patents

Abstract

PURPOSE:To detect a region of partial discharge without fail by a method wherein a gas having the same quality as the one in a power cable is sent into the cable in which air or a gas of N2, SF6 or the like is filled up in a sheath, from one end thereof, and is collected from the other end thereof, and a time required untill the detection of a gas produced due to the partial discharge is measured. CONSTITUTION:A gas having the same quality as the one in a power cable 11 is sent from a cylinder 13 containing the gas into a power cable 11 having air or a gas of N2, SF2 or the like filled up in a gap 9 thereof, and is collected at the other end thereof. By using a continuous gas analyzer 14, a time required from the start of sending the gas to the detection of a cracked gas produced due to partial discharge in the power cable is measured. When said partial discharge occurs inside a crosslinked-polyethylene insulating layer 3 or on an interface between internal and external semi-conductive layers 2 and 4, CO and CO2 are produced by the reaction of H2 and hydrocarbon such as C2H4, C2H6, etc. produced by the decomposition of polyethylene with residual O2 and water in a cable core 7. Accordingly, a region of discharge is detected without fail by analyzing H2, hydrocarbon, CO and CO2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring partial discharge positions in power cable systems.

A destructive accident in an electric power cable system immediately leads to a power outage, and therefore, once this accident occurs, it can cause great social damage. Therefore, it is extremely important to discover the above-mentioned accidents in advance and take countermeasures to prevent them from occurring. However, although many proposals have been made to detect the occurrence of destructive accidents in power cable systems or to measure their positions, there have been few proposals to detect such accidents in advance.

By the way, in normal electric cables, partial discharge initially occurs starting from the electrical weak points inside the cable core, and this partial discharge causes the cable insulation layer to erode, eventually leading to dielectric breakdown. That's what I know.

Therefore, the inventors of the present invention have endeavored to conduct extensive research on bonding and parts of electric power cables, in view of the fact that if the fact that partial discharge occurs in electric power cables can be detected early, it is possible to discover electric power cable destruction accidents in advance. It was discovered that a specific gas is generated during discharge. That is, for example, air, nitrogen gas (N2), sulfur hexafluoride gas (SFs)
When a partial discharge occurs in a cross-linked polyethylene insulated cable cable with a corrugated aluminum sheath (rCAZV cable) filled with
This gas reacts with oxygen or moisture contained in the insulating layer or the air, N2, SFs, etc. to form hydrogen gas (H2), -carbon oxide gas (CO ), carbon dioxide gas (CO2) is generated.

The present invention has been made based on the above findings.

An object of the present invention is to provide a method that can accurately detect the presence or absence of partial discharge in a power cable, as well as its position.

That is, the gist of the present invention is that air, N2, SFs
A gas of the same quality as the above-mentioned gas is sent into the cable from one end of an electric cable filled with a gas such as, and collected from the other end, and the decomposition gas generated by partial discharge is detected. A method for detecting the presence and location of partial discharge in a power cable system based on the time between.

In order to analyze the decomposed gas from the gas body collected above, gas chromatography or mass spectroscopy is used, for example.

The present invention will now be described in detail with reference to the accompanying drawings.

First, the CA7V cable used in carrying out the present invention will be explained with reference to FIG. 1. 1 is a cable conductor, 2 is an inner semiconducting layer, 3 is a crosslinked polyethylene insulating layer, 4 is an outer semiconducting layer, and 5 is a cushion layer. , 6 are special copper wire woven cloth tape winding layers, which are collectively referred to as the cable core 7. 8 is a corrugated aluminum sheath installed on the cable core through a predetermined gap 9;
0 is a vinyl anticorrosion layer.

Further, the cable is used by vacuum drying the cable core 7 and then filling the aluminum sheath 8 with N2 gas.

On the other hand, in the above cable, if a partial discharge occurs inside the insulating layer 3 or at the interface between the insulating layer 3 and the inner/outer semiconducting layer 2.4, hydrocarbon gases such as H2, CH4, C2He, etc. The gas reacts with the residual oxygen or moisture inside the cable core to generate Co1C02W gas, and these gases also permeate through the cable core 7 itself and diffuse into the gap 9 filled with N2. However, since the outside is covered with an aluminum sheath 8, it is not released into the atmosphere and is accumulated in the void 9.

Therefore, the present inventors installed N2 through a gas flow meter 12 at one end of the cable system 11 laid as shown in FIG.
A gas cylinder 13 is connected to the other end, and a continuous gas analyzer 171 employing gas chromatography is connected to the other end.
J: Sea urchin can be checked at the same time. That is, now, from the other end of the cable system 11, I! It is assumed that partial discharge occurs at - of X (Cm) and the generated gas remains in the void 9 at that location.

In this state, a constant flow f enters the cylinder 13 and passes through the flowmeter 12.
f1V (an3/sea) gas to cable system 1
If the cross-sectional area of the gas passage in the cable system 11 to be measured is S(c#F> and the gas compression due to gas inflow within the cable system 11 can be ignored, then Tx =
After (SXfx)/V (sec), gas generated by decomposition due to partial discharge comes out at the other end.

4- Then, if this gas is detected by the gas analyzer 14, it will be found that decomposition gas has been generated at a position Jx-(V/5)XTX (cm) from the other end, and at the same time, a partial discharge has occurred at that position. I can see what's happening.

In this embodiment, the gas to be measured, that is, the gas produced by decomposition, was collected continuously, but it can also be collected intermittently. The same applies to the gas sent out from the cylinder 13.

As described above, the present invention allows a gas having the same quality as the above gas to be sent into the cable from one end of an electric cable whose sheath is filled with a gas, and to collect the gas from the other end. By utilizing the time it takes for the decomposition gas generated by discharge to be detected, it has become possible to confirm not only the presence or absence of partial discharge in an electric power cable system, but also its location, and its industrial value is extremely high. I can say it's a big deal.

[Brief explanation of drawings]

FIG. 1 is a CAZV-pull used in carrying out an example of the present invention, and FIG. 2 is a detailed explanatory diagram of the present invention. 1: Cable body, 2: Internal semiconductive layer, 3: Cross-linked polyethylene insulation layer, 4: External conductive layer, 5: Cushion layer, 6: Special copper wire woven cloth tape wrapping layer, 7: Cable core,
8: Corrugated aluminum sheath, 9: Gap, 10: Vinyl anticorrosion layer, 11: Cable system, 12: Gas flow meter,
13: N2 cylinder, 14: Continuous gas analysis equipment. 7- Non-1 Kokushu 2 Koku-20:

Claims (1)

[Claims] A lightning cable whose sheath is filled with a gas such as air, nitrogen gas, or sulfur hexafluoride gas is fed into the cable from one end and is collected from the other end. , a method for measuring the position of partial discharge in an electric power cable system based on the time taken until decomposition gas generated by partial discharge is detected.