JPH0766025B2 - Cable partial discharge measurement method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring a partial discharge of a cable, and more particularly, to an improvement in a method for measuring a pinhole caused by a manufacturing defect in a high voltage cable. It is a thing.

[Prior Art] Generally, there are various types of partial discharge detection devices for a cable of this type, and a device for detecting partial discharge in a test cable having an extruded inner semiconductive layer and an outer insulating layer. As an example, in the case of a two-layer type cable having only an extruded inner semiconductive layer and an insulating layer, there is one as shown in FIG.

That is, the center conductor at the starting end of the drum 2 around which the cable 1 having the extruded inner semiconductive layer and the insulating layer is wound is grounded using the ground wire 3 via a slip ring electrode mechanism (not shown), The cable 1 drawn out from the drum 2 passes through a partial discharge detection device section 20 which will be described later in detail, and then is wound around a winding drum 4.

The partial discharge detection device section 20 has an insulating tube 5 formed in the middle part thereof with an insulating material such as a cylindrical acrylic pipe material filled with distilled water 7 inside, and a conductive material at both ends thereof. The containers 6, 6 formed in 1 above are arranged in communication with each other via a watertight packing (not shown). The containers 6 and 6 are grounded via grounding wires 9 and 9 so that the distilled water 7 is at ground potential.
Further, such distilled water 7 is circulated by a circulation device (not shown).

The cable 1 is provided at the center of the inside of the insulating cylinder 5.
A measuring electrode 8 having a shape that covers the outer periphery of the measuring electrode 8 is arranged. One end of the output of a high voltage source 10 for generating a predetermined test voltage is connected to the measuring electrode 8 and the other end is grounded. Furthermore, this measuring electrode 8 is connected to a partial discharge detector 12 via a coupling capacitor 11.

Therefore, the output of the high voltage source 10 is applied between the measuring electrode 8 and the ground, and as a result, the output of the high voltage source 10 is applied between the center conductor of the cable 1 and the measuring electrode 8 via the distilled water 7. . At the same time, when the cable 1 wound around the drum 2 is pulled out and wound around the drum 4 side, the cable 1 runs inside the measurement electrode 8.

If the cable 1 has a defect such as a pinhole in this state, a partial discharge occurs at the defective portion, so the pulse at this time is the coupling capacitor 11
It is supplied to the partial discharge detector 12 via the, and the partial discharge detector 12 detects the partial discharge of the cable 1. Therefore, it is determined that the portion corresponding to the position of the measurement electrode 8 has a defect.

The reason why the distilled water 7 (pure water) is used is that the output voltage of the high voltage generation source 10 is divided by the impedance (resistance component) of the distilled water 7 in the insulating cylinder 5 and detected by the partial discharge detector 12. The purpose is to facilitate the above and to absorb the Joule heat generated in the distilled water 7, and the distilled water having a high electric resistance is used.

On the other hand, an example of an apparatus for measuring partial discharge in a three-layer type power cable having an external semiconductive layer formed by extrusion is shown in FIG.

That is, the drum 32 around which the cable 31 is wound is collectively grounded, the output of the high voltage source 10 is supplied to the central conductor of the cable 31, and the partial discharge at that time is detected through the coupling capacitor 11. It is detected by device 12. Reference numeral 10 'is an output impedance of the high voltage source 10, and reference numeral 12' is an input impedance of the partial discharge detector 12.

Therefore, if the cable 31 wound around the drum 32 has a defect such as a pinhole, a partial discharge occurs at the defective portion, and the pulse at this time is the coupling capacitor.
It is supplied to the partial discharge detector 12 via 11, and the partial discharge detector 12 detects that partial discharge has occurred inside the cable 31, and the cable 31 wound around the drum 32.
You can judge that there is a cable defect on the way.

[Problems to be Solved by the Invention] However, in the above-described cable partial discharge detection apparatus shown in FIG. 3, a defect of the cable 1 located at the position of the detection electrode 8 is detected, so that the defect position can be specified. However, the resistance value of the distilled water 7 is much larger than that of the outer semiconductive layer. Therefore, heat generated by the impedance of the distilled water 7 and power consumption are high. Becomes so large that it becomes impractical. For this reason, the partial discharge detection device for such a type of cable is limited to the application to a two-layer type cable having no external semiconductive layer.

On the other hand, in the cable partial discharge detection apparatus shown in FIG. 4, since the capacitance of the cable 31 is all connected in parallel to the partial discharge detection circuit system, the detection sensitivity of the partial discharge pulse is lowered. However, there is a problem that it is difficult to detect the weak partial discharge.

Therefore, an object of the present invention is to provide a method for measuring a partial discharge of a power cable in which electrical contact with a test cable is surely made and a detection sensitivity of partial discharge can be kept good.

[Means for Solving Problems] A cable partial discharge measuring method according to the present invention is a method for continuously or intermittently measuring a partial discharge of a power cable having an external semiconductive layer formed by extrusion. In, a semi-conductive material formed of a semi-conductive material having flexibility and lubricity is formed on a cylindrical body through which the power cable is inserted, and has curved portions that open radially at both ends of the opening of the cylindrical body. Conductive electrode, a conductive electrode formed of a flexible metal conductive material disposed so as to cover the outer peripheral portion of the semiconductive electrode, and an annular shape made of an insulating material so as to cover the outer peripheral portion of the conductive electrode. And an electrode composed of an electrode pressing member which expands when the inside thereof is filled with a fluid, and the inside of the electrode pressing member when the power cable is inserted into the opening of the semiconductive electrode. Fill and flow By applying body pressure and expanding the electrode pressing member, the semiconductive electrode is brought into close electrical contact with the outer semiconductive layer of the power cable through the conductive electrode.

[Operation] Therefore, when the power cable is inserted into the opening member of the semi-conductive electrode and fluid is applied to the inside of the electrode pressing member to apply a fluid pressure, the expansion of the electrode pressing member causes the conductive electrode to pass through the conductive electrode. The semiconducting electrode is in close contact with the outer semiconducting layer of the cable to ensure electrical contact.

[Embodiment] Hereinafter, the method of the present invention will be described in detail with reference to FIGS. 1 and 2.

FIG. 1 is a vertical sectional view of a partial discharge measuring apparatus for a power cable applied to the measuring method of the present invention in actual use, and FIG. 2 is a transverse sectional view showing a state before actual use. In the figure, the test cable has an insulating layer 14 formed by extrusion on the outer periphery of a center conductor 13, and an outer semiconductive layer 15 is formed on the outer periphery of this insulating layer 14.

The outer circumference of such a test cable is formed in a tubular body through which the cable is inserted, and has curved portions that open radially at both ends of the opening of the tubular body, and has a semi-flexible and lubricious structure. A semiconductive electrode 16 made of a conductive material is formed.
The semiconductive electrode 16 is formed of a stretchable plastic thin film in which, for example, a fluororesin is used as a base resin and highly conductive powder or fibers such as carbon and metal are blended.

Then, on the outer peripheral portion of the semiconductive electrode 16, a conductive electrode formed of a metal conductive material having flexibility so as to cover it.
17 are formed. The conductive electrode 17 is formed of, for example, a metal braided wire. On the outer peripheral portion of such a conductive electrode 17, an electrode pressing member 18 which is annularly arranged so as to cover the conductive electrode 17 and expands when filled with a fluid (for example, air) is formed. There is.

A cylindrical pressing jig 19 is arranged on the outer peripheral portion of the electrode pressing member 18 so as to restrict the expansion of the electrode pressing member 18.

Further, the center conductor 13 of the cable is connected to a high voltage source (not shown) so that a predetermined output voltage is supplied.

Further, although not shown, a partial discharge detector for detecting a partial discharge pulse is connected to the conductive electrode 17.

Therefore, when the above-mentioned cable is inserted into the opening of the semiconductive electrode 16 and the inside of the electrode pressing member 18 is filled with a fluid and pressurized, the electrode pressing member 18 expands and the expansion is suppressed. Since the surface pressure is applied to the semiconductive electrode 16 via the conductive electrode 17 in a state where the outer peripheral position of the cable is regulated by the tool 19, the outer semiconductive layer 15 of the cable is closely contacted and surely electrically contacted.

When the cable is run in such a state, partial discharge occurs between the semiconductive electrode 16 and the central conductor 13 at the position where the cable defect occurs, and this state is detected by a partial discharge detector (not shown).

At this time, the cable and the semi-conductive electrode 16 are kept in lubricity and are brought into close contact with each other with a predetermined pressing force, so that electrical contact becomes extremely reliable and measurement can be performed with high sensitivity. Here, if the pressure of the fluid (for example, air) in the electrode pressing member 18 is adjusted, the outer semiconductive layer 15 of the power cable is adjusted.
The degree of electrical contact with the measurement electrodes such as the conductive electrode 17 and the semiconductive electrode 16 can be arbitrarily and easily changed.

Further, since the measuring electrode follows a slight fluctuation of the traveling power cable, the outer semiconductive layer of the power cable is not damaged at all.

The present invention is not limited to the above method,
Various modifications can be made without departing from the spirit of the invention.

For example, by applying a lubricant such as silicone oil or water between the semiconductive electrode 16 and the outer semiconductive layer 15 to the extent that electrical contact does not cause a problem, the lubrication state of both can be made more reliable.

In addition, the semiconductive electrode 16 and the like may be configured by a split mold such as divided into two in order to make the work of inserting the cable efficient.

Further, it is possible to provide a plurality of sets of measurement electrode systems in the length direction of the cable and use them as a guard electrode or a differential detection electrode.

Further, in one measurement electrode system, only the conductive electrode or the conductive electrode and the semiconductive electrode are collectively set, and a plurality of sets are provided, and these are used for the measurement electrode, the guard electrode, the differential detection, and the like. Can also be used as

Further, the electrode system according to the present invention and the conventional type electrode system may be used in combination.

[Effect of the Invention] As described above, the cable partial discharge measuring method according to the present invention eliminates the problem of heat generation since it is not measured in distilled water unlike the conventional method.

Further, since the electrostatic capacity of the cable is not connected to the partial discharge detection circuit system, weak partial discharge can be easily detected.

Further, the electric contact with the cable is ensured by using the electrode pressing member for the semi-conductive electrode having flexibility and lubricity, so that extremely stable electric contact can be maintained.

In addition, even if the outer diameter or shape of the cable changes for some reason, the semi-conductive electrode is brought into close contact with the cable and the electric contact is surely made by following the change.

As described above, in short, the cable partial discharge measuring method according to the present invention ensures reliable electrical contact with the running test cable and maintains good partial discharge detection sensitivity.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a partial discharge measuring apparatus for a cable applied to the method of the present invention in actual use, FIG. 2 is a cross-sectional view showing a state before actual use, and FIG. FIG. 4 is a schematic configuration diagram showing an example of a cable partial discharge detection device applied to a conventional method, and FIG. 4 is a schematic configuration diagram of a cable partial discharge detection device similarly applied to another method. 13 …… Center conductor 14 …… Insulating layer 15 …… Outer semiconductive layer 16 …… Semiconductive electrode 17 …… Conductive electrode 18 …… Electrode pressing member 19 …… Holding jig

Claims (1)

[Claims] 1. A method for continuously or intermittently measuring a partial discharge of a power cable having an extruded outer semiconductive layer over the entire length of the cable, wherein the power cable is formed on a tubular body, and the tubular body is formed. A semi-conductive electrode formed of a semi-conductive material having flexibility and lubricity, which has curved portions that open radially at both ends of the body opening, and a semi-conductive electrode that covers the outer peripheral portion of the semi-conductive electrode. A conductive electrode formed of a flexible metal conductive material and a ring-shaped insulating material that covers the outer peripheral portion of the conductive electrode, and expands when the inside is filled with a fluid. When the power cable is inserted into the opening of the semi-conductive electrode, the inside of the electrode pressing member is filled with a fluid to apply a fluid pressure to expand the electrode pressing member. Through the conductive electrode Then, the semi-conductive electrode is brought into close electrical contact with the outer semi-conductive layer of the power cable.