JPH0556089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for heating insulation at the joints of rubber-plastic power cables.

[Prior Art] Methods for forming reinforcing insulators at the connection portions of power cables can be roughly divided into two methods: extrusion molding;
There are two methods: applying a pre-molded reinforcing insulator and wrapping insulation tape. In any of these cases, a heating step is necessary. For example, methods using extrusion molding or pre-molded reinforcing insulators require heating during vulcanization and crosslinking, while methods involving winding an insulating tape require heating during softening and vulcanization/crosslinking of the insulating tape. This heating is carried out from the outside of the mold using heating wires or high frequency/electromagnetic waves, but in reality it is necessary to bring the inside of the reinforcing insulator to a specified temperature, but it is not possible to do so accurately. Currently, there is no internal temperature control.

[Object of the Invention] An object of the present invention is to accurately estimate the internal temperature of the reinforcing insulator based on the surface temperature of the reinforcing insulator at the connection part, and to control the energy applied from the outside, thereby achieving good performance. An object of the present invention is to provide a method for heating an insulator at a cable connection part, which efficiently forms a reinforcing insulator.

[Summary of the invention] The gist of the present invention for achieving the above object is as follows:
A plurality of temperature sensors are attached to the surface of the reinforcing insulator of the cable connection part, and the average value is determined, and the reinforcing insulator is A method for heating an insulator of a cable connection part, characterized in that the reinforcing insulator is heated for a predetermined period of time by supplying energy from the outside to bring the internal temperature of the reinforcing insulator to a predetermined temperature.

[Embodiments of the Invention] A method according to the present invention will be described in detail based on illustrated embodiments.

Here, FIG. 1 and FIG. 2 are a longitudinal cross-sectional view and a cross-sectional view of the cable connection section, respectively, and the two to be connected.
The insulating layers 2a, 2b of the two cables 1a, 1b are formed in the shape of a pencil sharpener, and the core wires 3a, 3b are connected by a conductor sleeve 4. A reinforcing insulator 5 made of, for example, a polyethylene insulating tape containing a cross-linking agent is wound around the conductor sleeve 4, and a reinforcing insulator 5 made of a heat-resistant split rubber cylinder that also serves as a restraint layer is wrapped around the reinforcing insulator 5. An outer protective layer 6 is provided. This outer protective layer 6 is made of EP rubber, silicone rubber, fluorine rubber, etc., and its inner circumference 4
Temperature sensors 7 for control consisting of small-diameter thermocouples are embedded in several equally divided locations, and a temperature sensor 8 for monitoring is embedded in the other location. A cut 6a along the longitudinal direction of the outer protective layer 6
is secured with heat-resistant tape.

Here, it is necessary to melt the reinforcing insulators 5 by heating and bring them into close contact with each other, and around the reinforcing insulators 5 and the outer protective layer 6, a high-frequency coil 10 is mounted on a cylindrical coil support member 9. Arrange the wound heating part. Then, the temperature of the outer protective layer 6 is displayed on an indicator recorder based on the output of the inspection temperature sensor 8 and monitored. On the other hand, the average value of the outputs of the plurality of temperature sensors 7 is connected to, for example, an arithmetic circuit (not shown) that performs a control operation, and the current flowing through the high-frequency coil 10 is controlled by the output of this arithmetic circuit.

The high frequency waves emitted from the high frequency coil 10 enter the reinforcing insulator 5 and generate eddy currents due to the magnetic flux, thereby heating the reinforcing insulator 5. At this time, the high frequency output is controlled based on the average value of the output of the temperature sensor 7, that is, the surface temperature of the outer protective layer 6.

However, since the actual temperature to be controlled is the internal temperature of the reinforcing insulator 5, temperature sensors were placed inside the reinforcing insulator 5 and in the external protective layer 6 in advance in an experiment. It is necessary to determine the relationship between the outputs of the two temperature sensors while heating the temperature sensor 5 with high frequency.

As shown in FIG. 2, this relationship shows that the temperature increases with time, but the internal temperature T1 of the reinforcing insulator 5 is lower than the external temperature T2. This temperature difference T2-T1 is obtained as a function of time, and the arithmetic circuit estimates the internal temperature based on the output of the temperature sensor 7, and the high-frequency coil 10
The energy applied to the reinforcing insulator 5 is controlled. Therefore, it is desirable to program the set values of the arithmetic circuit, and for example, it is possible to use a programmed temperature controller.

Furthermore, the method according to the present invention is fully applicable to heating energy not limited to high frequency, but also heating by radiant heat from an electric heater or heating by electromagnetic waves.

Note that the temperature sensors 7 and 8 may be embedded not only in the outer shielding layer 6 but also in an external shielding layer made of, for example, copper tape or semiconductive EP rubber tape.

[Effects of the Invention] As explained above, the method for heating an insulator of a cable connection part according to the present invention accurately measures the surface temperature by providing a plurality of temperature sensors on the surface of a reinforcing insulator. The energy applied from the outside is adjusted while estimating the internal temperature of the reinforcing insulator, taking into account the heating time, making it possible to accurately control the temperature of the reinforcing insulator, improving the performance of the reinforcing insulator, Work efficiency can be improved.

[Brief explanation of the drawing]

The drawings show an embodiment for realizing the insulator heating method for a cable connection part according to the present invention, in which FIG. 1 is a longitudinal sectional view of the connection part, FIG. FIG. 3 is a diagram showing the output relationship between temperature sensors provided outside and inside. Codes 1a and 1b are cables, 5 is a reinforcing insulator,
6 is an outer protective layer, 7 and 8 are temperature sensors, 9 is a coil support material, and 10 is a high frequency coil.

Claims (1)

[Claims] 1. Attach a plurality of temperature sensors to the surface of the reinforcing insulator of the cable connection part, calculate the average value, and measure the reinforcing insulation based on the relationship between the obtained surface temperature, the heating time obtained in advance, and the internal temperature. 1. A method of heating an insulator for a cable connection part, comprising heating the reinforcing insulator for a predetermined period of time by supplying energy from outside the body to bring the internal temperature of the reinforcing insulator to a predetermined temperature.