JPH0360056B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of Application When connecting power cables with bare wire insulation, the insulation coating must be removed.

The present invention relates to a method for inspecting whether the insulating film has been successfully removed in the above case.

Prior Art FIG. 5 shows a state in which the insulating film has been removed.

10 is the entire cable, 12 is its conductor, 14
is a strand of wire, and the insulation film at the 16th part has been removed, and the insulation film remains at the 18th part.

In the conventional case, the distance between the strands 14 was pried open one by one using a jig such as a screwdriver, and the degree of removal of the insulating film was visually determined.

However, with this method, (1) the work is troublesome and time-consuming; (2) the strands are spread out, so it is necessary to restore the strands after inspection; and (3) the underside of the tip of the cable conductor 12 is If you see
There were also some complications, such as the lack of space to look into the room, requiring tools such as a hand mirror.

Therefore, there has been a proposal to attach electrodes between both ends of the portion 16 from which the film has been removed and measure the electrical resistance therebetween to inspect the degree of removal of the insulating film. However, there were many variations in the measured values, and good results could not be obtained.

Purpose of the Invention In the above method of measuring electrical resistance, there are many variations due to (1) variations in the contact status between the measurement electrode and the surface of the cable conductor, and (2) variations in the contact status between the strands. It was found that this is because the contact resistance between each strand varies greatly due to the variation.

Therefore, in consideration of the above points, in order to check the degree of removal of the film on the conductor's internal strands after the inspection, an electrical method that does not require opening the internal strands of the conductor is used, and at the same time, it is possible to avoid variations in the measured values. The purpose of this invention is to provide an inspection method that requires only a small amount of insulation film removal.

Structure of the Invention Electrodes are attached to both ends of the portion 16 from which the film has been removed as described above, and the electrical resistance therebetween is measured. 20: A ring-shaped thing surrounding the cable conductor is divided into upper and lower halves, and a bolt 24 with a spring 26 inserted is passed through the collar 22 protruding from the halves to be assembled in a ring-shape, (2) When measuring electrical resistance, an insulating pipe 28 is placed over the cable conductor between the electrodes 20, and the pipe 28 is used to measure the electrical resistance.
The conductor is characterized by being able to compress the conductor with a constant pressure from the entire surrounding area.

Example (Fig. 1, Fig. 2) 20 is an electrode.

It is made of a non-magnetic material with high electrical conductivity, such as copper or brass.

Its shape is a ring surrounding the cable conductor 12, and the inner surface is smooth.

Further, the structure is divided into upper and lower halves, and a bolt 24 with a spring 26 inserted is passed through a collar 22 protruding from the halves, and assembled into a ring shape.

When assembled into a ring shape, the inner diameter is made to be slightly smaller than the outer diameter of the cable conductor 12 (the reason for this will be explained later).

28 is an insulated pipe.

This is made from an insulator such as Bakelite or Teflon.

The length a is approximately equal to the length between the electrodes 20 attached to both ends of the portion 16 from which the film has been removed,
Smooth its inner surface.

Also, in the same way as the electrode 20, the structure is divided into upper and lower halves, and the bolt 32 with the spring 34 inserted is passed through the collar 30 protruding from the halves to form a ring shape (the structure of this part is the same as the electrode 20). Therefore, the illustration is omitted).

In addition, when combined, the inner diameter is made to be slightly smaller than the outer diameter of the cable conductor 12 (the reason for this will be described later).

36 is an electrical resistance measuring device.

Inspection method Portion 16 of cable conductor 12 from which the film has been removed
Electrodes 20 are attached to both ends. Then, the bolt 24 is tightened so that the length b of the spring 26 becomes a preset length.

Then, the outer diameter of the cable conductor 12 and the electrode 2
Since the inner diameter of the electrode 20 is constant, the inner diameter of the electrode 20 is slightly smaller, and the inner surface of the electrode 20 is smooth, the contact pressure between the electrode 20 and the cable conductor 12 is always constant. become.

Next, an insulating pipe 28 is attached between the electrodes 20.

At that time, as in the case of the electrode 20, the spring 3
Set the length of 4 to the preset length.

In this case, since the cable conductor 12 is always compressed with a constant force from the entire circumference, the contact surface pressure between the strands 14 is always constant.

In the above manner, the electrical resistance between the electrodes 20 is measured.

Then, a constant measurement value will always be shown for a constant degree of removal of the insulating film.

Figure 3 shows the relationship between the degree of film removal, current distribution, and electrical resistance. A is a case where the film is not removed, the current 38 is small and the resistance is large. b is film removal 50%
In the case of , the current increases and the resistance is moderate. c is for 100% film removal, the current is maximum,
Resistance is minimal.

Therefore, based on the measured values, it is possible to know the degree of removal of the insulating film, and quantitative evaluation is also possible.

In addition, attach the insulated pipe 28 first,
Thereby, the cable conductor 12 may be tightened before the electrode 20 is attached.

In addition, as in the single-core OF cable shown in FIG. 4, a hollow part (oil passage 1
If 3) is present, an insulating pipe or rod 40 with high mechanical strength is inserted therein before the above inspection is performed. The length of the pipe to be inserted is equal to or longer than the length between the electrodes 20, and its outer diameter is equal to the inner diameter of the hollow portion, so that there is no gap between the two.

Effects of the invention (1) As an electrode: A ring-shaped material surrounding the cable conductor is divided into upper and lower halves, and a spring-loaded bolt is inserted through the brim protruding from the two halves, so that the electrodes are combined into a ring-like shape. As mentioned above, a constant contact pressure can always be maintained between the inner surface and the surface of the cable conductor, and when measuring electrical resistance,
An insulating pipe is placed over the cable conductor between the electrodes, and the pipe compresses the conductor from the front with a constant pressure, so the measurement conditions are always constant. .

Therefore, there is less variation in the measured values.

(2) It is possible to quantitatively evaluate the degree of insulation film removal.

(3) No expensive equipment is required, and jigs can be used semi-permanently.

(4) Can be measured in a short time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the implementation status of the present invention, and the second
2 and 4 are enlarged side views of the same as seen from the left, FIG. 2 shows the case where there is no hollow part in the conductor, and FIG. 4 shows the case where there is a hollow part in the conductor. FIG. 3 is an explanatory diagram showing the relationship between the degree of film removal, current distribution, and electrical resistance, and FIG. 5 is an explanatory diagram of the cable conductor from which the insulating film has been removed. 12: cable conductor, 14: bare wire, 16: part from which film was removed, 20: electrode, 24: bolt, 2
6: Spring, 28: Insulated pipe, 32: Bolt, 3
4: Spring.

Claims (1)

[Scope of Claims] 1. Electrodes are attached to both ends of the portion of the power cable conductor with bare wire insulation from which the insulation film has been removed,
In a method for inspecting the degree of removal of an insulating film that measures the electrical resistance between these electrodes, the electrode is a ring-shaped thing surrounding the cable conductor that is divided into upper and lower halves, and a spring is attached to the brim that protrudes from the halves. When measuring the electrical resistance, an insulating pipe is placed over the cable conductor between the electrodes, and an insulating pipe is placed over the cable conductor between the electrodes. Therefore, the conductor
A method for inspecting the extent of removal of an insulating film, which is characterized by compressing the surrounding area with a constant pressure from the front.