JPS603751B2 - Method for heating and forming 3-core power cable connections - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for thermoforming a three-core power cable connection.

Connection of cables, especially polyethylene or cross-linked polyethylene insulated cables, is carried out by penciling each core of the cable ends to be connected, then following each conductor with a sleeve and wrapping a semiconductive polyethylene tape over the connecting conductor. After winding an uncrosslinked or semi-crosslinked polyethylene tape into a spindle shape to form an insulating reinforcing layer, a silicon release tape such as polyester is wound thereon, and then the three cores are wrapped together as shown in Figure 3. Alternatively, as described above, wrap a silica-repellent tape around each core of the connector, wrap three cores together, and wrap a tape heater over the tape heater. There is a method of heating and forming the connection part by applying electricity.

In the former method, a bulky and heavy heater must be brought to the connection work site, which is very inconvenient, and the connection work is difficult to perform in a narrow space such as a manhole.

Furthermore, in the latter conventional method, the area near the electric heating wire of the tape heater is strongly heated, but the area away from the heating wire is not sufficiently heated, resulting in uneven heating.

In particular, when heating and forming the connection part of a three-core power cable, the inner side where the three cores touch is the furthest away from the heater, as shown in Figure 4, and even when the tape heater is energized and sufficiently heated, the fourth
The leakage temperature point D shown in the figure is only 70% of A (6
．． (In the case of VCVIOO x 3 cores) It has been confirmed that this tendency increases as the size of each core increases.

The present invention was made in order to solve the above problems, and the insulation part of each core of a three-core power cable is stripped in stages, and the upper half of the conductor is coated with a conductive layer and an insulated conductor part. In the method of sequentially providing layers and then heating and forming the part, ■ winding a silica-releasing tape on each layer of insulating tape on each core; winding a steel tape around each core; ■ three cores. It is characterized by uniformly winding the tape heater all at once, and then uniformly winding a tape made of a heat insulating material on top of the tape heater.After that, the tape heater is energized to heat-form the subsequent part. be.

Next, the present invention will be explained with reference to examples and drawings.

6. Shoes Vloo box An internal semiconductive layer 3 is formed by winding the inner semiconductive layer 3, and an insulating layer 4 is formed by wrapping an uncrosslinked or semi-crosslinked polyethylene tape in a paper cone shape over the insulating layer of the core wire to be connected. A polyester tape (with a thickness of 0.5 mm) is used as the control layer tape 5, which allows gas generated from the uncrosslinked polyethylene tape winding layer to be easily discharged when the connection portion is heated, and which can withstand thermal expansion of the insulating layer. 025
1.5 to 2.3 times in 1/2 lap.

When winding the control layer tape, it is not necessary to wind it strongly from the beginning, but rather to wind it relatively loosely at the beginning or one round trip, and to gradually wind it more tightly toward the end. Next, in order to spread the heat from the tape heater heat source well to the entire insulating layer of the connection part to be heated, a steel tape 6 with a thickness of 0.1 willow and a width of 4 mm is used.
Wrap it once in 1/2 wrap.

If the winding is uneven at this time, heat propagation will be uneven, which will have a negative effect on the electrical and physical characteristics of the connection. Also, at this time, a thermocouple 7 (another side heating element may be used) is inserted between the control layer tape winding layer and the copper tape at an appropriate location, and a compensating conductor 8 is drawn out. After performing the above processing for each core, combine the three cores, and then
A tape heater 9 of two lengths is butt-wound on both sides, and an asbestos tape 10 is further wound thereon with a uniform thickness.
At this time, if the thickness is non-uniform, the heat insulation effect will vary, which will adversely affect the electrical and physical characteristics of the connection portion. Electricity is applied to the tape heater 9 of the cable connection part prepared as described above, and the temperature of the semiconductive layer and insulating layer near the conductor is increased to approximately 90°C.
It reached 120°C in 1 minute, maintained that temperature for 15 minutes, and then returned to room temperature in 6 minutes.

A comparison of the temperatures at the side temperature points shown in FIG. 4 between the heating method of the present invention and the conventional heating method is as shown in Table 1. In the conventional method, the lowest temperature is shown in Table 1. While this is less than 70% of the highest temperature, in the method of the present invention, it is 92%, indicating that heating unevenness is extremely small. Table 1 Note that in actual connection work, it is not possible to measure the temperature by inserting a multi-9 temperature element inside the semiconducting layer or insulating layer, so a thermocouple inserted between the control layer and the copper tape is used. The correlation between the detected temperature and the temperature inside the semiconducting layer and the insulating layer is determined experimentally in advance, and the temperature is controlled based on the experimental value.

Figure 2 shows each Enoki tree shown in Figure 4 obtained in the experiment. This is a temperature curve of a hot spot. The data shown in Figure 2 differs depending on the size and voltage class of the connection, so it is necessary to select a standard size and type and take experimental values in advance. In this embodiment, 6. The heating times for other voltage classes and sizes are approximately as shown in Table 2, although this is only for the Vlo0 x 3'D CV cable.

Table 2 Next, Table 3 shows a comparison of the method of heat forming a subordinate cable connection using the heater shown in FIG. 3 and the method of heat forming according to the present invention.

Table 3 (Note) The above is data for a straight connection section of a 6.6KV I0O tiger x 300V cable.

As is clear from Table 3, the method of heating and forming a three-core power cable connection of the present invention has no change in electrical properties compared to the conventional method using a heater, and the workability and power consumption and requirements for heating are the same. This method has achieved significant improvements in terms of time, etc., and is of great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a cable connection according to the method of the invention. FIG. 2 is a heating curve diagram by the method of the present invention, and FIG. 3 is a heating curve diagram according to the method of the present invention.
FIG. 4, which is a perspective view of a conventionally used heater, is a cross-sectional view of the connecting portion showing measurement points of temperature unevenness during heat forming of the connecting portion of a three-core cable, and the indicators in the figure are as follows. 1,1':
Cable, 16: Heater, 17: Leg. 1 figure, 2 figures, 3 figures, 4 figures

Claims (1)

[Claims] 1 In a method in which the insulated portion of each core of a three-core power cable is stripped in stages, each conductor is connected, a semiconductive layer and an insulating layer are sequentially provided on the conductor portion, and then the portion is heated and formed (1) Each core Wrap silicon-release tape on each layer of insulating tape (2) Wrap copper tape uniformly around each core (3)
A three-core tape heater is evenly wound (4). A tape made of a heat insulating material is evenly wound thereon (5). After that, the tape heater is energized to heat-form the connection part. A method for heating and forming a three-core power cable connection part, characterized by: