JPH03107778A - Detection of deterioration of crosslinked polyolefin insulated cable - Google Patents

Abstract

PURPOSE:To accurately and surely detect the degree of deterioration by sampling the gas generated from an insulator and analyzing and measuring the components and quantity of the gas. CONSTITUTION:An annular cap 11 provided with an insertion hole at the end face is put on the end part of an aluminum covering 7 in the juncture of the CV (crosslinked polyethylene insulated) cable 1 and one end of a flexible tube 12 is fitted into the insertion hole. This tube 12 passes the inside of a waterproof intimate mixture 9 of liquid and the other end is connected to a connector 14 for sampling with a cock 23 mounted to a connecting copper tube 6. The cock 13 is periodically removed and a sampling tube or the like is connected to the connector 14 to sample the gas generated from the cable insulator 4 and accumulated in the covering 7; thereafter, the components in the gas are analyzed and the amt. of a combustible gas, such as hydrogen, is measured. The deterioration of the insulator is early detected in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for accurately and reliably detecting the degree of deterioration of an insulator of a crosslinked polyolefin insulated cable.

(Prior art) The conventional method for investigating the degree of insulation deterioration in OF cables is to collect insulating oil used in cables from connections, etc., and analyze the gas components contained therein. A method has been used to detect abnormalities such as local discharge by determining the amount of flammable gas such as acetylene gas generated as a result of deterioration.

This method has very reliable detection and high precision, and greatly contributes to the maintenance of OF cables, but CV cables (
In a crosslinked polyolefin insulated cable such as a crosslinked polyethylene insulated cable (crosslinked polyethylene insulated cable), the insulator is solid, and such a method cannot be used as is.

For this reason, the deterioration of the insulator of the Cv cable has been determined by electrical methods such as leakage current, dielectric loss tangent, presence or absence of partial discharge, or direct current component.

(Problem to be Solved by the Invention) However, with these electrical measurement methods, it is impossible to detect unless the deterioration of the insulator has progressed to a considerable extent, and there is no reliable means for detecting and determining the deterioration of the insulator. I couldn't say that.

The present invention has been made to address these conventional difficulties, and an object of the present invention is to provide a deterioration detection method that can accurately and reliably detect the degree of deterioration of the insulator of a crosslinked polyolefin insulated cable. do.

[Structure of the Invention] (Means for Solving the Problems) The method for detecting deterioration of a crosslinked polyolefin insulated cable of the present invention includes extracting gas generated from an insulator of a crosslinked polyolefin insulated cable to the outside of the cable, and collecting the gas. The method is characterized in that the degree of deterioration of the insulator is determined by analyzing and determining the components contained in this gas.

In the present invention, in order to collect gas generated from the insulator of the crosslinked polyolefin insulated cable, the following method can be adopted, for example.

In other words, for cross-linked polyolefin insulated cables that have a metal sheath such as an aluminum jacket, there is a method in which the gas in the metal sheath is guided out of the cable through a tube or the like from the metal sheathed end at the connection or terminal end, or the gas is collected from the cable. Methods such as directly drilling holes in the metal coating of the metal coating can be used. At this time, a connector with an airtight stopper is attached to the outer opening of the tube end, and a sampling tube or the like is connected to this connector to periodically sample gas.

In addition, in crosslinked polyolefin insulated cables that have a wire shield around the outer periphery of the insulator, multiple through holes are continuously provided in the wall along the length of one or more wires, along with ordinary copper wire. It is also possible to use perforated copper pipe lines and to extract gas from the ends of these steel vibrating lines at cable connections or terminations.

(Function) In the method for detecting deterioration of a crosslinked polyolefin insulated cable of the present invention, gas generated from the insulator is guided to the outside of the cable and collected, and the type and amount of components contained in this gas are analyzed using a known method. By measuring this, it is possible to reliably detect the presence or absence of deterioration of the insulator.

That is, crosslinked polyolefin insulators such as crosslinked polyethylene undergo deterioration due to electrical discharges within the microvoids within them, which are almost undetectable by conventional electrical measurement methods; By collecting flammable gases such as carbon oxide, oxygen, and hydrogen, and analyzing and determining all the components therein, it is possible to accurately detect the presence or absence of electrical discharge and insulation deterioration caused by it.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a longitudinal cross-sectional view for explaining a method for detecting deterioration of an insulator at a connection portion of an aluminum CV cable according to an embodiment of the present invention.

At this connection, the ends of the pair of CV cables 1 are stripped off in stages, and the exposed conductors 2 are transferred to the conductor connection tube 3.
connected by. On this conductor connection part, an insulating reinforcing body 5 is formed by winding a rubber or plastic insulating tape in a spindle shape, spanning over insulators 4 made of crosslinked polyethylene on both sides. A connecting copper tube 6 is fitted on the outside of the insulation reinforcing bodies, and the end of the connecting copper tube 6 is covered with a winding layer 8 of waterproof tape on the aluminum sheath 7 to prevent the corrugation of the cable. Fixed. Furthermore, a liquid waterproofing mixture 9 is injected and filled into the connecting steel pipe 6.

Note that the reference numeral 10 in the figure indicates a wound layer of insulating paper inserted between the cable insulator 4 and the aluminum coating 7.

In the connection part of the aluminum sheathed CV cable having such a structure, the end of the aluminum sheath 7 is airtightly covered with an annular cap 11 having an insertion hole in the end surface. One end of a flexible tube 12 is fitted.

Further, this tube 12 passes through a liquid waterproof mixture 9'11, and the other end is connected to a sample collection connector 14 with a seal plug 13 attached to the connecting steel pipe 6.

By periodically removing the seal plug 13 and connecting a collection tube etc. to the connector 14, the cross-linked polyethylene insulator 4
After collecting the gas generated from the aluminum Mi7 and collecting it inside the aluminum Mi7, we analyze the components in the collected gas and determine the amount of combustible gas such as hydrogen by 11 pl, which quickly detects the deterioration of the insulator. can do.

Furthermore, the degree of deterioration of the insulator can be accurately determined from changes in the amount of gas components over time.

Next, another embodiment of the deterioration detection method of the present invention will be described.

In this embodiment, as shown in FIG. 2, in a CV cable in which a cross-linked polyethylene insulator 16 is provided on a conductor 15 and a wire shield 17 is provided around the outer periphery, a length of One or more perforated copper vibe wires 19 are used in which a plurality of through holes are continuously provided in the wall surface along the direction. In addition, the code|symbol 20 in the figure shows a corrosion protection layer.

The gas generated from the insulator 16 is collected into the vibrator through the holes of the perforated copper vibrator wires 19, and collected from the open end of the connecting portion or the like.

Also in this embodiment, the presence or absence of deterioration of the insulator can be reliably detected by analyzing the components in the gas thus collected and measuring the amount of combustible gas such as hydrogen.

[Effects of the Invention] As explained above, in the method for detecting deterioration of a crosslinked polyolefin insulated cable of the present invention, gas generated from an insulator is sampled, and the components and amounts of the gas are analyzed and measured. It is possible to quickly and reliably detect insulator deterioration caused by an abnormality such as discharge in the insulator, which is almost difficult to detect using the electrical δ11 determination method.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view for explaining a method for detecting deterioration of an insulator at the connection part of an aluminum cable, which is an embodiment of the present invention, and FIG. FIG. 2 is a cross-sectional view for explaining a method for detecting deterioration of an insulator in a shielded CV cable. 1...CV cable 4...Cable insulator 6...Connecting steel pipe 7...Aluminum coating 9・・・・・・
...Waterproof mixture 11...Cap 12...Tube 14...Connector

Claims (1)

[Claims] (1) The degree of deterioration of the insulator is determined by extracting the gas generated from the insulator of a cross-linked polyolefin insulated cable outside the cable and analyzing and measuring the components contained in this gas. A method for detecting deterioration of a crosslinked polyolefin insulated cable.