JPS603752B2 - Heat forming method for T-type and Y-type connections - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of thermoforming a T-type or Y-type connection, and more particularly to a method of heat-forming a connection using a tape heater.

To connect cables, especially polyethylene or cross-linked polyethylene insulated cables, after stripping off the sheath at the end of the cable to be connected and penciling the insulating layer, the conductors are connected to each other with a T-shaped sleeve or a Y-shaped sleeve, and then A semiconductive polyethylene tape, uncrosslinked or semi-crosslinked polyethylene tape is sequentially wound to form an insulating reinforcing layer.

A heating and pressurizing control layer is formed by winding polyester tape and cotton tape on the insulation reinforcing layer prepared as above,
After that, heat molding was carried out using a mold or a heater, but in this conventional method, (1) the heater was bulky, making it difficult to work in narrow work sites such as manholes; ■ Poor thermal efficiency and high power consumption.

(For example, a T-type connection requires power from circuit W to bulb W)■
There were problems such as the need for dedicated heaters with T-type and Y-type connections.

Additionally, as an alternative to the heat forming method using a mold or heater, there is a method using a tape heater, but the previously known heat forming method using a tape heater has uneven heating, resulting in electrical and physical There remains a problem with high-voltage power cables that have never been put into practical use.

The present invention was made in view of the above problems, and after sequentially stripping off the end sheath and insulator of a power cable that is connected in a T-type or a Y-type, and connecting each conductor, a semiconducting layer is placed on the connecting conductor. and insulation reinforcing layers are sequentially provided, and then the semiconducting layer and the insulation reinforcing layer are heated and molded.
Mild Steel Tape ■ Tape Heater ■ This tape is characterized by successively winding a heat-insulating tape as a heat-retaining layer, and heating and forming the surface of each branched insulation reinforcing layer while controlling the temperature.

Next, embodiments of the present invention will be described with reference to the drawings. Pencil ring 6, each insulation layer 1, 1', 1'' of the cable to be connected.
6', 6'' to expose the internal semiconductive layer, and expose the cable conductors 2, 2', 2'' according to the depths of the conductor insertion holes 7, 7', 7'' of the T-shaped compression sleeve 3. Conductor 2, 2', 2''
the conductor insertion holes 7, 7', 7'' of the T-shaped compression sleeve 3.
and compressed with a compression molding machine (not shown). * After that, a semiconductive polyethylene tape is uniformly wound over the conductor of the connection part over the internal semiconductive layer of each connection cable to form the conductor upper semiconductive layer 4, and an electron beam is irradiated onto the semiconductive layer 4. The insulating reinforcing layer 5 is formed by winding the half-crosslinked polyethylene loop under uniform tension until it reaches a desired thickness.

The T-shaped joint prepared as described above is subjected to the treatments shown in Table 1. Table 1: As the heating and pressurizing control layer 8, polyester tape having a width of 50 mm and a thickness of 0.025 mm is wound in 5 layers with 2/3 wraps.

When winding this polyester tape, so that the gas generated from the insulation reinforcing layer during heat molding can be easily discharged.
Further, in order to withstand the expansion of the insulation reinforcing layer due to heating, it is preferable that the winding is somewhat loose at the beginning, and the winding becomes stronger toward the upper layers. Next, wrap 4 layers of cotton tape with a width of 5 mm and a thickness of 0.05 in a 1/2 wrap while applying uniform tension.

Furthermore, if necessary, a heating and pressing control layer 8 is formed by winding two layers of 1/2 wrap of asbestos tape having a width of 7 mm and a thickness of 1 layer. Next, in order to uniformly transfer the heat from the tape heater to the insulating reinforcing layer to be heated, a European steel tape 9 having a width of 5 strands and a thickness of 0.1 strands is uniformly wrapped in a 1/2 wrap.

When winding the soft copper tape, thermocouples TC, TC2, and TC3 are inserted between the wrapped soft steel tapes in the middle of each branch, and compensating conductors are drawn out. Next, 200V, 400W (
A tape heater 10 with a width of 5 mm and a length of 2 mm is wound around each branch of the connecting cable, and a heat insulating layer 1 is placed on top of the tape heater 10.
Asbestos tape on 1/2 side with width 7 sides and thickness 1/2
Wrap in 4 layers of plastic wrap.

When winding the mild steel tape, tape heater, and asbestos tape, it is necessary to make the winding tension and wrapping as uniform as possible.

Non-uniformity causes deterioration of electrical and physical characteristics. For heating, a tape heater wound around each branch of the connection section is controlled using a known temperature control circuit and device.

At this time, if the tape heaters of each branch are controlled all at once, the heating of each branch will vary, which is not preferable. The heating conditions were such that the temperature at which the semi-crosslinked polyethylene tape constituting the reinforcing layer was thermally fused to the inside of the insulating reinforcing layer for about 60 minutes from the start of energization (
120° C.) and then maintained at a temperature of 120 qo to 150° C. for 6 to 90 minutes, and then slowly cooled.

Note that in actual construction, it is not possible to insert a thermocouple inside the insulation reinforcement layer, so we used a model in advance to understand the correlation between the temperature inside the insulation reinforcement layer in the heated state and the lap part of the mild steel tape. It is necessary to keep it.

Table 2 shows 6. Ship V cross-linked polyethylene cable 150
Using the above-mentioned model, the temperature inside the insulation reinforcing layer and the temperature of the lap part of the soft copper tape in the heated state were measured for the fence 250 and 325 Iso, and based on this, the side temperature control conditions of the lap part of the mild steel tape were determined. This figure shows the appearance and breakdown voltage of each type.

Table 2 Table 2 shows that rapid heating is not preferable because if the initial set temperature is too high, unevenness or voids may be formed on the surface of the insulation reinforcing layer.

As explained above, according to the method of the present invention, compared to the conventional method using a heater, the equipment is smaller, it is easier to work in a narrow space, the power required for hot molding is reduced by about 70%, and the work time is reduced. This can reduce the time by approximately 15%.

■ In addition, the conventional heating forming method using a tape heater, which does not involve placing a mild steel tape under the tape heater, cannot be used practically for high-pressure T-type or Y-type connections because the electrical and physical characteristics of the connection part are unstable. However, the present invention has many advantages such as stable characteristics and sufficient practical use.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of thermoforming of a T-type connection according to the present invention, and FIG. 2 is a temperature curve diagram of each part during heat-forming using a T-type connection model. 8: heating and pressure control layer, 9: mild steel tape, 10: tape heater, 11: heat insulation layer, 12: temperature curve directly above the connecting conductor,
13, 13', 13'': Detected temperature curves of TC・, TC2, TC3.

Claims (1)

[Claims] 1. After sequentially stripping off the end sheath and insulator of a power cable to which T-type and Y-type connections are made and connecting each conductor, a semiconducting layer and an insulating reinforcing layer are placed on the connecting conductor. In the method of sequentially forming the semiconductive layer and the insulation reinforcing layer, the insulation reinforcing layer is provided with (1) a silicon release tape and a cotton tape (2) and an annealed copper tape (3) as a heating and pressing control layer. ) Tape heater (4) A T-type, characterized in that a heat-insulating tape as a heat-retaining layer is sequentially wound, and the surface of each branched insulating layer is heated and formed with the tape heater while controlling the temperature measurement. , a method of heat forming a Y-shaped connection.