JPH09311155A - Method of discharge detection of detecting sensor self-contained part of prefabricated connecting part for cv cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separate an epoxy unit low voltage electrode from a connecting part and a cable sheath electrode around it to form one detecting end, use a metal case for the cable sheath electrode and a connecting part as the other detecting end, and perform a highly sensitive detection between the detecting ends. SOLUTION: The low voltage electrode 7 of an epoxy unit 2 is electrically independent to form one detecting end of a detecting electrode. A copper pipe 10 forming an external metal case to which other connecting parts and a cable body part sheath electrode are connected is used as the other detecting end of the detecting electrode. Both the detecting ends are delivered to the outside by lead wires and connected to a detecting impedance 9, and the potential difference between both the ends is measured by a measuring instrument 14. From a pair of detecting electrodes having rubber mold stress cone conductive layers 4', 4' as detecting ends, and brought into contact and allowed to communicate each other by a pressing hardware 5, the detecting ends may be delivered to the outside by lead wires, and connected to the detecting impedance 9. According to these methods, a partial discharge detection can be performed to the prefabricated connecting part of a CV cable 1 with high sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a partial discharge of a prefabricated type connecting portion for a CV cable, and more particularly to a method for detecting a partial discharge of a prefabricated type connecting portion of this type having a detection sensor for detecting a partial discharge. .

[0002]

2. Description of the Related Art FIG. 3 shows a structure of a previously developed prefabricated type connecting portion for a CV cable. In this prefabricated type connecting portion, the conductors exposed at the stepped-off end portions of the CV cables 1 and 1 are connected by a conductor connecting pipe, and an epoxy insulating unit is inserted on the conductor connecting pipe. The epoxy insulation unit has a built-in electrode on the inner diameter side, and this electrode is electrically connected to the conductor connecting pipe. Tapered grooves are formed on both ends of the epoxy unit, and a premold insulator called a rubber mold stress cone is pushed into and inserted into the groove, and further compressed by a spring unit; premold insulator compressing device. The pre-molded insulation is pressed against the groove taper surface of the epoxy insulation unit and the CV cable insulation, thus ensuring electrical insulation performance.

The epoxy insulation unit has the above-mentioned high-voltage electrode and the earth side electrode on the outer diameter side, and the pre-molded insulator has a conductive layer on the outside to improve the electrical characteristics. Contributes.

Now, the prefabricated type connecting portion for the CV cable as described above is subjected to a completion test at the time of completion of the line to verify its soundness. The verification method up to now has been carried out by the DC withstand voltage, but it is being carried out by the AC withstand voltage which is excellent in the defect detection capability. At this time, partial discharge measurement is performed to improve the defect detection level.

The principle of measuring partial discharge will be briefly described. When a voltage is applied to a cable conductor and a partial discharge occurs in an insulator, a high frequency pulse is induced in the conductor and the metal sheath,
The high frequency pulse of the metal sheath flows into the impedance as the detection element, and a potential difference proportional to the magnitude of the high frequency pulse is generated at both ends of the impedance. The partial discharge is measured by detecting the potential difference with a measuring instrument through the detection impedance.

[0006]

As in the prior art described above, a partial discharge detection method, which is a type of non-destructive test, has been adopted as a method for verifying the soundness of the CV cable or its connection. In the conventional measurement of the prefabricated type connection portion, a coupling capacitor is connected to the line termination portion, and a detection impedance is connected to the ground to perform detection. At this time, the shield of the cable and the connection part was grounded and used for the measurement. However, in this conventional detection method,
Since the insulator including the connection portion is measured all at once, there is a drawback that the electrostatic capacitance is large and thus the pulse voltage due to partial discharge is low and the detection sensitivity is not good. For this reason, it was necessary to develop this type of partial discharge detection method capable of highly sensitive partial discharge detection at the connection portion.

Therefore, the problems to be solved by the present invention (objects)
Is to provide a partial discharge detection method with a built-in detection sensor for a prefabricated type connection part for a CV cable, which is capable of detecting a partial discharge with high sensitivity to a prefabricated type connection part of a CV cable. Another object (objective) is to establish this type of partial discharge detection method without significantly changing the structure of the CV cable prefabricated type connecting portion.

[0008]

As a first means provided by the present invention, a partial discharge detection method with a built-in detection sensor for a CV cable prefabricated type connecting portion is such that an epoxy unit low-voltage electrode is connected to a surrounding connecting portion and a cable sheath electrode. Separated and taken out as a detection electrode as one detection end, as the other detection end, the cable sheath electrode and the metal case of the connection part as a sheath electrode and the sheath electrode part as a detection end of the detection electrode, and these two In this method, a measuring instrument is connected between the detection electrodes and the partial discharge is detected by the measuring instrument.

According to the above-mentioned partial discharge detection method, since one detection electrode is only the low voltage electrode of the epoxy unit, the electrostatic capacitance of that part is small and the detection signal level of partial discharge is high. Further, since the other detection electrode is made of a metal case, its own detection electrode has a shielding effect against ambient external noise, and therefore the external noise level becomes low. Further, the external noise guided to the sheath of the CV cable main body is suppressed from being guided to the detection electrode because the metal case serving as the detection electrode is electrically separated. As described above, in the present detection method, since the detection signal level of the partial discharge is high and the induction of the external noise to the detection electrode is suppressed, the S / N which is the ratio of the signal of the partial discharge and the external noise becomes large. As a result, the detection sensitivity is improved.

As a second means, a partial discharge detection method with a built-in detection sensor for a prefabricated type CV cable connecting portion is used for the conductive layer of the rubber mold stress cone at one end of the rubber mold stress cone at both ends of the epoxy unit. Take out the pressing metal fitting as the detection electrode, similarly, take out the pressing metal fitting for the conductive layer of the rubber mold stress cone at the other end as the detection electrode, and connect the measuring instrument between these two detection electrodes, There is a method of detecting partial discharge by this measuring device. Also by this method, the same operation as the above-mentioned first means can be performed.

[0011]

1 is an embodiment of a partial discharge detection method with a built-in detection sensor of a prefabricated type connection portion for a CV cable embodying the first means of the present invention. In this prefabricated type connecting portion, the conductors are connected by a conductor connecting pipe at the terminal of the CV cables 1 and 1 that have been stripped, and the epoxy unit 2 is inserted on the conductor connecting pipe. The epoxy unit 2 has a built-in high-voltage electrode 3 so that the high-voltage electrode 3 electrically contacts and conducts with the conductor connecting pipe. Further, both ends of the epoxy unit 2 have tapered grooves, and the rubber mold stress cones 4 are pushed and inserted into these grooves.
The rubber mold stress cones 4, 4 have conductive layers 4 ',
4 ', and by pressing the metal fitting 5 of the spring unit 6 against the conductive layer 4', the rubber mold stress cones 4, 4 are pressed, and the rubber mold stress cones 4, 4 and the epoxy unit. The taper groove surface of 2 and the insulator surface of the CV cable 1 are brought into close contact with each other to ensure electrical insulation performance.

In the present embodiment, the low-voltage electrode 7 of the epoxy unit 2 is electrically independent from the prefabricated type connecting portion for the CV cable having the above-mentioned basic structure, and is used as the detection end of one of the detection electrodes. In addition, with the copper tube 10 serving as an external metal case and connected to the other connection portion cable body portion sheath electrode as a detection end of the other detection electrode, a lead wire is connected to each of the lead wires and led out to the outside to detect the detection impedance 9 Connect to. A measuring device 14 for detecting the potential difference between both ends is connected to the detection impedance 9. The measurement principle itself is the same as before. (If necessary, refer to the section of the prior art.) Reference numeral 8 is an external insulating cylinder for electrically isolating the copper tube 10 and the CV cable. Further, 11 is a compound to be filled in the copper pipe, 12 is an insulating cylinder, and has a hole for drawing out a lead wire.

FIG. 2 embodies the second means of the present invention,
It is an example of a partial discharge detection method with a built-in detection sensor of a prefabricated type connection portion for a CV cable. 1 are used for the same or substantially the same parts as in FIG.
Please also refer to the explanation of.

In this embodiment, the rubber mold stress cone conductive layers 4 ', 4'are used as the detection ends of the detection electrodes, and the detection electrodes 13, 13 which are brought into contact with each other by the pressing member 5 are taken out to the outside by a lead wire to detect the detection impedance. The method of connecting to 9 is adopted.

Although the conductive layer 4'has been used as the detection end of the detection electrode in the above, the pressing metal 5 and the rubber mold stress cone conductive layer 4'are electrically connected to each other. It can be said that the detection ends are the same as each other.

[0016]

According to the present invention as described above, C
(EN) It is possible to achieve an intended problem (objective) of providing a partial discharge detection method with a built-in detection sensor for a prefabricated type connection part for a CV cable, which can detect a partial discharge with high sensitivity to a prefabricated type connection part of a V cable. it can. Since partial discharge can be measured with high sensitivity in this way, early diagnosis of insulation deterioration is possible. Further, according to the first and second means of the present invention, the detection sensor can be incorporated without changing the structure so much that the cost does not increase. And so on.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a main part showing a partial discharge detection method (epoxy unit low-voltage side; a method of detecting from a metal case) in a prefabricated type connection portion for a CV cable according to an embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional explanatory view of a main part showing a partial discharge detection method (a method of detecting from a pressing fitting of a rubber mold stress cone on both sides) in a prefabricated type connection portion for a CV cable according to another embodiment of the present invention.

FIG. 3 is a half cross-sectional explanatory view showing a conventional prefabricated type connecting portion for a CV cable.

[Explanation of symbols]

 1 CV Cable 2 Epoxy Unit 3 High Voltage Electrode 4 Rubber Mold Stress Cone 4'Conductive Layer 5 Pushing Metal Fitting 6 Spring Unit 7 Epoxy Unit Low Voltage Electrode; Detection Electrode 8 External Insulation Cylinder 9 Detection Impedance 10 Copper Tube (Metal Case) 12 Insulation Cylinder 13 Detection electrode 14 Measuring instrument

Claims (2)

[Claims] 1. In a prefabricated type connecting portion for a CV cable, which is constructed by combining an epoxy unit and a rubber mold stress cone and compressing with a spring, the epoxy unit low voltage electrode is separated from the surrounding connecting portion and the cable sheath electrode. As a detection electrode, this is taken out as one detection end, as the other detection end, the cable sheath electrode and the metal case of the connection part are taken out as the sheath electrode, and the sheath electrode part is taken out as the detection end of the detection electrode. A partial discharge detection method with a built-in detection sensor for a prefabricated type connection for a CV cable, in which a measuring device is connected in between and a partial discharge is detected by this measuring device. 2. In a prefabricated type connecting portion for a CV cable, which is constituted by combining an epoxy unit and a rubber stress cone and compressing with a spring, a pressing metal fitting for a conductive layer of a rubber mold stress cone at one end is a detection electrode. In the same way, the metal fitting for the conductive layer of the rubber mold stress cone at the other end is taken out as a detection electrode, and a measuring instrument is connected between these two detecting electrodes. A partial discharge detection method with a built-in detection sensor for the prefabricated type connection for CV cables.