JPH07333291A - Existing cable withstand voltage testing method - Google Patents

Abstract

PURPOSE:To safely apply a high voltage to a cable to be detected and to conduct a safe withstand voltage test by applying a voltage from a high-voltage power source on the ground to the cable to be detected via a connecting unit for protecting a connecting part. CONSTITUTION:A method for testing the withstand voltage of a cable safely and effectively tests an existing cable at the site. The exposed end of the cable 10 to be detected and disposed to be exposed at its one end with a manhole 12a is inserted into one end of a connecting unit 20 having a cylindrical insulator. The end of a high-voltage lead cable 18 extended from a high-voltage power source 14 on the ground is inserted to the other end of the unit 20. Both the cables 10 and 18 are safely and effectively connected via the unit 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable withstand voltage test method, and more particularly to an existing cable withstand voltage test method suitable for a withstand voltage test of a cable laid underground.

[0002]

2. Description of the Related Art In an underground power line, there is a method of measuring the insulation resistance of a cable using a megger as a simple inspection method when the cable which has been temporarily stopped is restarted.
FIG. 2 is a schematic diagram showing this megger test method. According to this, the insulation resistance of the cable 2 can be measured by connecting the simple insulation resistance meter 3 to the existing cable 2 which is arranged with the end exposed in the manhole 1. Usually, if the cable is stored well, such a simple test will cause no problem. However, stricter inspection is desirable as the operating voltage becomes higher, and a withstand voltage test in which a high voltage is actually applied is desirable in order to secure more reliable safety.
However, general test equipment cannot be brought into the narrow manhole 1.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an existing cable withstand voltage test method capable of safely and reliably testing an existing cable on site.

[0004]

SUMMARY OF THE INVENTION The present invention accepts an exposed end of a cable to be inspected, which has one end exposed in a manhole, and which extends from a high voltage power source on the ground to the other end. It is characterized in that the test cable is charged from a high-voltage power source on the ground through a connection unit having a tubular insulator received from.

[0005]

According to the present invention, the high voltage lead cable extending from the high voltage power source on the ground is connected to the cable under test through the connection unit in the manhole, and the connection of both cables is made safely and surely by the connection unit. .

[0006]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a vertical sectional view schematically showing an existing cable withstand voltage test method according to the present invention. The cable 10 to be tested by the test method according to the present invention is an existing cable that is laid between, for example, a pair of manholes 12a and 12b in the underground electric line and is temporarily suspended from use. Prior to reuse of the existing cable 10, the cable 10 is subjected to a pressure resistance test in order to confirm its safety and the like.

A vehicle 16 having a power supply 14 for applying a DC high voltage to the cable 10 to be tested is installed on the ground. The high voltage lead cable 18 extending from the power supply 14 of the vehicle 16 is connected to the end 1 of the cable 10 to be tested safely and securely.
0a to connect to the first connection unit 20
Used in the manhole 12a. Further, in order to electrically insulate and protect the other end 10b of the cable 10 to be tested,
The second connection unit 22 is used in the second manhole 12b.

FIG. 3 is a vertical sectional view of the first connection unit 20. As shown in FIG. 3, the first connection unit 20 is made of an epoxy resin mold and has an open-ended insulator disposed inside a cylindrical metal case 26 provided with a handle 24 for transportation. 28 is provided. At the central portion of this insulator 28, a connection conductor 30 that constitutes a connection portion is arranged. At both ends of the insulator 28, taper-shaped cable insertion holes 32a, 32 are formed which gradually increase in diameter toward the outside.
b are formed respectively.

The cable 10 to be inspected is arranged in one of the insertion holes 32a so that its end is exposed in the one manhole 12a.
One end 10a is inserted. One end of the cable to be tested
In 0a, the shielding layer 34, the external semiconductor layer 36, the insulating layer 38, and the conductor 40 are sequentially exposed. A wedge-shaped male plug 46 that fits into a cylindrical female plug 44 having a cap member 42 is fixed to the tip of the conductor 40. Although not shown, a well-known contactor is provided between the plugs 44 and 46 and between the female plug 44 and the connecting conductor 30. As a result, a good conductive state is maintained. One end 10a of the inspection cable 10 has a connection conductor 30
Electrically connected to.

A stress cone 48 surrounding the end of the cable 10 is inserted into one insertion hole 32a of the insulator 28. A protective cap 50 that covers the end of the cable 10 is attached to one end of the metal case 26. The protective cap 50 is fixed with a screw member 54 to a flange 52 fixed to one end of the metal case 26.

A step portion 50a for receiving an annular washer 56 is formed on the inner surface of the protective cap 50, and a cylindrical pressing metal fitting 58 is in contact with the stress cone 48 inside the cap 50. Due to the pressing force of the spring assembly including the guide pin 60 extending from the pressing metal fitting 58 through the annular washer 56 and the coil spring 62 guided by the guide pin 60, the insulating portion 48 a of the stress cone 48 causes the stress cone 48 to move. The stopper 49 and the tapered surface of the insertion hole 32a, which are arranged at the front end of the, respectively, are appropriately pressed. Also, cable 1
The shield layer 34 of 0 is a washer 56 to which the lead wire 34a is connected.
Also, it is electrically connected to the semiconducting portion 48b of the stress cone 48 via the spring assemblies 60 and 62, so that a uniform potential is maintained at the connecting end 10a.

The other insertion hole 3 of the first connection unit 20.
The tip 18a of the high voltage lead cable 18 extending from the power supply 14 of the vehicle 16 is inserted into 2b. The tip portion of the lead cable 18 has a shield layer 64, an external semiconductor layer 66,
The insulating layer 68 and the conductor 70 are sequentially exposed.
A semiconductive tape 67 is wrapped around the surface of the shielding layer 64. Further, the insulating layer 68 is subjected to penciling, and a metal plug 72 is inserted into a conductor 70 exposed from the tip of the insulating layer 68. The metal plug 72 is the connection conductor 3
It is inserted in the metal sleeve 74 provided at 0, whereby the conductor 70 of the high voltage lead cable 18 is securely connected to the connection conductor 30.

A fixed flange 76 is provided at the other end of the metal case 26, and the screw member 7 is provided on the fixed flange 76.
A shield ring 80 is fixed via 8. The shield ring 80 includes a base 8 of a protective cap 82.
2a is fixed by a screw member 84, and a body portion 82b of a protective cap is screwed onto the base 82a. A pressing member 88 for appropriately pressing the insulating portion 86a of the stress cone 86 against the tapered surface of the insertion hole 32b is disposed inside the body portion 82b. The semi-conductive portion 86b of the stress cone 86 is the body portion 8 of the protective cap.
They are connected to the shield ring 80 and the shield layer 64 via the 2b and the semiconductive tape layer 67, respectively, so that the uniform potential is maintained at the connection end 18a.

Therefore, the conductors 40 and 70 of the high-voltage lead cable 18 and the cable 10 to be tested are securely connected inside the insulator 28, and the potential of this connection is also kept stable. From this, both cables 18
And 10 are safely and reliably connected via the first connection unit 20, and the safety of the worker in the first manhole 12a can be ensured. In addition, at the time of transportation,
An insulating plug as shown in the circle is attached instead of the cable 18. This insulating plug is made of insulating rubber 101, lid 102
And the protective electrode 103 are integrated. This insulating plug is fixed by using a base 82a having no through hole. This makes it easy to transport.

FIG. 4 is a vertical sectional view of the second connection unit. In FIG. 4, among the components of the second connection unit 22, the components having the same operation as the first connection unit 20 are designated by the same reference numerals as those in FIG. The second connection unit 22 shown in FIG. 4 does not have the metal case used for the first connection unit, and the fixing flanges 52 abutting against the respective end faces are provided at both ends of the insulator 28 made of epoxy resin. Bolt 90 through
Further, each fixing flange 52 is fixed by a nut 92 screwed to this.

The other end 10b of the cable 10 to be tested is treated in the same manner as that of the one end 10a, and is inserted into the insulator 28 through the tapered cable insertion hole 32a. The conductor 4 at the other end 10b of the cable 10 to be tested
A conductive plug 44 is compression-connected to 0. The conductive plug 44 is detachably locked by a positioning device 93 provided on the connection conductor 30.

The pressing metal fitting 58 of the stress cone 48 is provided with an inner washer 56a corresponding to the annular washer 56, and an inner guide pin 60a and an outer guide pin 60b are provided between the washers 56 and 56a, respectively. A guided coil spring 62 is arranged. The outer guide pin 60b penetrates the inner washer 56a and is fixed to the fixing flange 52. Also, the outer guide pin 6
A stopper 94 that abuts the outer surface of the washer 56 is fixed to 0b. The inner guide pin 60a is fixed to the washer 56a, and a stopper 94 that abuts the outer surface of the washer 56 is fixed to the inner guide pin 60a.
Therefore, due to the pressing force of the coil spring 62, the insulating portion 48a of the stress cone 48 is moved to the stress cone 48a.
The stopper 49 and the tapered surface of the insertion hole 32a, which are arranged at the front end of the, respectively, are appropriately pressed.

In the insertion hole 32b of the second connection unit 22, instead of the cable, an insulating portion 96a and a semiconductive portion 9 are provided.
A blind plug 96 with 6b has been inserted. A connecting portion 96c formed at the tip of the blind plug 96 is connected to the plug 44 via a connecting fitting 98. The stress cone 48 arranged around the blind plug 96 receives the pressing force of the coil spring 62 similar to that described above from the pressing metal fitting 58, thereby suppressing the generation of the uneven electric potential.

From the above, the tip portion, that is, the other end 10b of the cable 10 to be tested is reliably insulated and terminated by the second connecting unit 22. As a result, it is possible to ensure the safety of the worker in the second manhole 12b, as in the first manhole. Therefore, it is possible to apply high-voltage power from the power supply 14 to the cable 10 to be inspected without fear of damaging the worker in each manhole.
As a result, the pressure resistance test can be safely performed on site.

The connection unit according to the present invention is not limited to the example shown in the figure, and connection units having various structures such that the connection high-voltage portion is not exposed can be used.
The configuration of the connection unit shown in FIG. 4 can be freely replaced and used. Although a power supply device installed on the ground can be used as the power supply, it is preferable to mount the power supply on the vehicle as shown in the figure in order to efficiently visit the test site.

[0021]

As described above, according to the present invention,
A high-voltage lead cable extending from a high-voltage power source on the ground is connected to a cable under test via a connection unit in a manhole, and both cables are connected safely and securely by the connection unit. Therefore, a high voltage can be safely applied to the cable to be tested without bringing a large and heavy power supply device into the manhole, which enables a safe withstand voltage test.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view schematically showing an existing cable withstand voltage test method according to the present invention.

FIG. 2 is a schematic diagram showing a conventional test method.

FIG. 3 is a vertical cross-sectional view of the connection unit according to the present invention shown in FIG.

FIG. 4 is a vertical sectional view of another connection unit according to the present invention shown in FIG.

[Explanation of symbols]

 10 Test Cable 12a, 12b Manhole 14 High Voltage Power Supply 18 High Voltage Lead Cable 20 Connection Unit 28 Cylindrical Insulator

Claims (2)

[Claims] 1. A tubular insulator that receives the exposed end of a cable to be tested, which is arranged with one end exposed in a manhole, from one end, and receives the end of a high voltage lead cable extending from a ground high voltage power source from the other end. An existing cable withstand voltage test method, characterized in that the both cables are electrically connected via a connection unit provided, and the high-voltage power source applies a voltage to the test cable. 2. A cylindrical insulator, the other end of which is disposed so as to be exposed to another manhole and which receives the exposed end from one end and receives a blind plug made of an insulating material from the other end. The connection unit terminates the other end of the cable to be tested.
The existing cable withstand voltage test method described in.