JPH058989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for measuring insulation of high voltage power cable connections.

[Prior Art] In high-voltage equipment, partial discharge at a specific location has been conventionally measured with the measurement electrode completely insulated from surrounding electrostatic shielding parts. As a result, the electrostatic shielding effect of the insulated part disappears, and the electric field concentrates at the end of the measurement electrode or the edge of the surrounding electrostatic shielding part, which may cause a defect in that part due to the insulation structure. However, it has not been possible to apply this measurement method to measurements of real high-voltage systems.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned points, and its object is to obtain a method for measuring the insulation of high voltage power cable connections that can be measured even in an actual system.

Therefore, in this invention, it has become possible to have an electrostatic shielding effect and to attach a partial discharge detection electrode only at the cable connection portion.

[Means and effects for solving the problem] In the present invention, a connecting part external semiconducting layer is coated around the insulating layer of a high voltage power cable connecting part, and a metal electrode for detecting a connecting part partial discharge is further provided on the outer periphery of the connecting part external semiconducting layer. The cable portion is provided at a constant distance from the outer shielding metal layer. By connecting this partial discharge detection electrode and the external shielding metal layer to a measuring device, a partial discharge signal at the cable connection portion is extracted and insulation measurement is performed.

Therefore, electrostatic shielding is completely performed by the external semiconductive layer from the connection part to the cable, and it becomes possible to measure partial discharge in the insulating layer part during operation at the connection part of a high-voltage power cable in an actual system.

[Example] Hereinafter, an example of a method for measuring insulation of a high voltage cable connection portion according to the present invention will be described based on the drawings. Both high-voltage cables 1 and 1' to be connected have the outer shielding metal layers 7 and 7', the outer semiconducting layers 8 and 8', and the insulating layers 2 and 2' stripped in sequence at their ends, and The tips of the layers 2, 2' are penciled into a conical shape. Then, the conductors 3 and 3' are connected to each other by a predetermined conductor connection pipe 4, and the connection part internal semiconducting layer 5 is placed on the circumference thereof, and both ends of the connection part are connected to the internal semiconducting layer of each cable 1 and 1'. 6 and 6'. The cable connection portion 20 thus formed is covered with an insulating material 9 so as to have a predetermined shape. This insulating material 9 is
For CV (cross-linked polyethylene power) cables, this is a wrapping layer of polyethylene tape and a molded layer of polyethylene, and for OF (oil-filled) cables, this is a wrapping layer of oil-impregnated paper. In this example, over the ends of the cables 1, 1' and the connection insulating layer, the connection outer semiconducting layer 15 connects both ends of itself to the cable outer semiconducting layers 8, 8'. coated. Furthermore, a metal electrode 10 for detecting a partial discharge at the connection part is coated on the cable part external shielding metal layer 7, 7' at a constant interval 11, 11' (with an edge cut part provided). .

The spacing between the edge cutting parts 11, 11' is determined by the specific resistance of the semiconducting layers 8, 8', the diameter of the cable of the edge cutting parts 11, 11', the detection impedance of the measuring device,
It is determined by measurement sensitivity, etc., but it is desirable that it be as narrow as possible.

Therefore, the metal electrode 1 of the cable connection part 20
0 is electrostatically connected to the external shielding metal layer 7, 7' of the cable by the semiconductive layer 8, 8', although the edge cut portion 11, 11' has a certain resistance value. This means that it has been done. Here, if the metal electrode 10 serving as the connection part partial discharge detection electrode at the location where partial discharge is to be detected and the cable part external shielding layer 7 are connected to the measuring device 12 and a high frequency partial discharge pulse is detected, the cable connection part 20 can be detected. It becomes possible to measure partial discharge with high sensitivity.

Next, FIG. 2 shows an application example of insulation measurement of a cable connection part. The same members as in FIG. 1 are given the same reference numerals, and their explanations will be omitted. That is, in the cable connection part 20' to be measured, a cutting part 10c is provided in the middle of the metal electrode 10, and the metal electrode 10 is divided into two left and right electrodes 10a and 10b. When the cable is in operation, the cross bond voltage of the sheath circuit is applied here. Therefore, partial discharge detection transformer 1 is installed to cut out the commercial frequency component.
High-frequency capacitors 14 and 14' are inserted and connected between the primary side of 3 and electrodes 10a and 10b. A measuring device 12 is connected to the secondary side of the partial discharge detection transformer 13 for measurement.

There are various methods for detecting partial discharge, and many methods have been used to date. All of these conventionally known detection methods and measurement methods can be applied to the present invention.

In addition, since there are many cable connections in an actual system, the partial discharge at each connection can be connected to one measuring device via the metal electrode of each connection, and each connection can be measured by switching between them. It can be configured to measure the insulation of each section, or it can be configured to measure the entire connection section at once.

[Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to measure with high sensitivity partial discharge due to insulation deterioration at the connection portion of a cable power transmission system. In addition, it can be used not only to check the initial insulation performance when the cable system is completed, but also as an insulation diagnosis to monitor the insulation state during actual operation by connecting these measuring instruments.

[Brief explanation of the drawing]

Fig. 1 is a partially cross-sectional side view of a cable connection part showing one embodiment of the insulation measurement method of a power cable connection part according to the present invention, and Fig. 2 shows another method for measuring insulation of a power cable connection part. FIG. 3 is a partially cross-sectional side view showing only the upper half of the cable connection part, illustrating an example. 7, 7'...Cable part external shielding metal layer, 8,
8'... Cable part outer semiconducting layer, 15... Connection part outer semiconducting layer, 10, 10a, 10b... Connection part metal electrode for partial discharge detection, 11, 11'... Edge cutting part, 12... Measurement 20, 20'... Power cable connection section.

Claims (1)

[Claims] 1. In a connecting portion of a high-voltage power cable line, a connecting portion outer semiconducting layer is coated around the connecting portion so that both ends of the connecting portion are connected to ends of the cable portion outer semiconducting layer. , Furthermore, a connection part partial discharge detection electrode is coated on the outer side of the cable part with a fixed interval to the external shielding metal layer, and the partial discharge detection electrode and the external shielding metal layer are connected to a measuring device. 1. A method for measuring insulation of a power cable connection section, characterized in that insulation measurement is performed by extracting a partial discharge signal at the section.