JPH0642945A - Internal inspection method of power cable using X-ray - Google Patents

Abstract

(57) [Summary] [Purpose] To be able to inspect a power cable while it is in a live state and to prevent the insulation layer from being adversely affected. [Structure] The X-ray irradiation range is narrowed to an arbitrary width, and the insulating layer 2 of the power cable 1 or the outer insulating layer 3 of the cable connecting portion
The inside of the power cable 1 is irradiated with the light from the outside and the inside of the power cable 1 is photographed by the X-ray image pickup tube 4 for inspection. [Effect] It is not necessary to stop the current supply to the cable 1 one by one at the time of inspection, or to interrupt the power supply area during that time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting the inside of a power cable or its connecting portion using X-rays, and more particularly, to a method for inspecting a power cable in a live state. Is.

[0002]

2. Description of the Related Art A core of an electric power cable such as an OF cable, a GF cable, and a CV cable may expand or contract after installation, due to inclination, vibration, temperature change, etc. of an installation site (underground). In this case, the outer conductor outside the insulating layer outside the core may be cracked or distorted. This situation applies not only to the cables themselves, but also to the connecting portions that connect the cables to each other, and the outer coating layer is cracked or distorted. If this happens, the insulation characteristics will deteriorate, so conventionally these conditions (internal structure) have been detected by regular inspection. Since it is not possible to open the inside of cables and connections during inspection, the internal structure of power cables is inspected from the outside.

As one of the inspection methods, there is an inspection method using a radiography technique as shown in FIG. This is to irradiate the power cable B with X-rays generated from the X-ray tube A, and set the internal structure of the cable B behind it.
The film C is photographed, and the film C is developed so that the internal structure of the power cable or the connecting portion can be inspected. In addition, in the radiography method, which is a step further than this, an X-ray image pickup tube such as an image intensifier or an X-ray vidicon is used instead of the X-ray film C so that the structure of the power cable can be directly displayed on the TV monitor in real time. There are also some.

[0004]

However, in the above-mentioned radiography method, since X-rays are applied to the entire power cable B (core D, insulating layer E, outer conductor F), a high-voltage current flows in the core D. If so, the insulating layer E causes an ionization action by X-rays to increase the leakage current, which adversely affects the insulating layer E. Therefore, it is difficult to inspect the power cable B during hot line. Therefore, at the time of inspection, the current supply to the cable B must be stopped one by one, and during that time, there is a problem that the power supply area is out of power.

The method for inspecting an electric power cable using X-rays according to the present invention can inspect the electric power cable in a live state.
Moreover, the purpose is to prevent the insulating layer from being adversely affected.

[0006]

An internal inspection method for a power cable using an X-ray according to the present invention is as follows, as shown in FIGS.
The X-ray irradiation area is narrowed down to an arbitrary width and is irradiated to the outside of the insulating layer 2 of the power cable 1 or the outer insulating layer 3 of the cable connection portion, and the inside of the power cable 1 is photographed by the X-ray image pickup tube 4. It is characterized in that the inspection is carried out.

[0007]

In the method for inspecting the inside of the power cable using the X-ray according to the present invention, even if a high-voltage current flows through the conductor 5 of the power cable 1, the insulating layer 2 surrounding the conductor 5 (outer insulation at the cable connection portion) is used. Since the layer 3) is not exposed to the X-rays, the insulating layer 2 (outer insulating layer 3) is not adversely affected by the increase of the leakage current due to the ionizing action of the X-rays. Internal inspection by X-ray can be performed.

[0008]

1 and 2 show an embodiment of an internal inspection method for a power cable using X-rays according to the present invention. In the figure, 1 is an electric power cable such as an OF cable, a GF cable, a CV cable, etc. For example, in a CV cable (crosslinked polyethylene insulation cable), as shown in FIG. Outer conductor 20, aluminum coating 21,
The resin coating 22 is covered in this order, and at the connecting portion, a sleeve 23 for connecting the two butted conductors 5 is provided with an inner semiconductive layer 24, an outer insulating layer 3 of cross-linked polyethylene, The protective tube 26 is covered with the shielding layer 25, and the protective tube 26 is covered with the aluminum 2 through the waterproof mixture 27.
It is covered over 1 and is connected by plumbing.

Reference numeral 7 in FIGS. 1 and 2 is an X-ray tube for generating X-rays.
Reference numeral 4 denotes an X-ray image pickup tube such as an image intensifier or an X-ray vidicon that receives an X-ray emitted from the same X-ray tube 7 and takes an image. The X-ray tube 7 and the X-ray image pickup tube 4 are substantially L-shaped. It is attached to the jig 10. A diaphragm 8 made of a metal (for example, lead) that blocks X-rays is attached to the X-ray tube 7 so that the X-ray irradiation range can be freely adjusted.

The jig 10 to which the X-ray tube 7 and the X-ray image pickup tube 4 are attached is set in a manhole having an object to be photographed (coaxial cable), and the X-ray tube 7 is adjusted to adjust the X-ray intensity. The X-ray TV monitor 13 that displays the image taken by the X-ray image pickup tube 4 is connected to the X-ray controller 12 respectively. The diaphragm 8 and the jig 10 are provided with a photographing jig controller 11
Connect. The controller 11 adjusts the irradiation range of the diaphragm 8 and the positions of the X-ray tube 7 and the image pickup tube 4.

As an inspection procedure, first, irradiation of X-rays is started from the outer periphery of the power cable 1, and the photographing jig controller 11 is operated while observing the image on the X-ray TV monitor 13 to gradually extend the X-ray irradiation range. Move to the center of 2 and observe the internal condition (Fig. 2). Then, when the outermost layer of the insulating layer 2 (the outer insulating layer 3 in the cable connecting portion) is reflected on the X-ray TV monitor 13, the movement to the inside is stopped and the X-ray tube 7 and the image pickup device 3 are shown in the figure. The electric power cable 1 is inspected by moving it in the direction of the arrow. Further, the X-ray tube 7 and the image pickup device 3 are moved in the longitudinal direction of the power cable 1 for inspection.

[0012]

According to the method of inspecting an electric power cable using X-rays of the present invention, the internal structure of the electric power cable 1 can be inspected in a live state. There is no need to shut down the power supply or interrupt the power supply area during that time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an internal inspection method for a power cable using X-rays according to the present invention.

FIG. 2 is a schematic view showing an inspection method using an internal inspection method of a power cable using the X-ray of FIG.

FIG. 3 is an enlarged cross-sectional view of a cable connecting portion in FIG.

FIG. 4 is a schematic diagram showing an example of a conventional internal inspection method for a power cable using X-rays.

[Explanation of symbols]

 1 power cable 2 insulating layer 3 outer insulating layer 4 X-ray image pickup tube

Claims (1)

[Claims] 1. An X-ray image of the inside of the power cable 1 is obtained by irradiating the X-ray to an arbitrary width and irradiating the power cable 1 outside the insulating layer 2 of the power cable 1 or the outer insulating layer 3 of the cable connecting portion. An internal inspection method for an electric power cable using X-rays, characterized in that an image is taken and inspected by a tube 4.