JP2628715B2 - Power cable test equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test apparatus that can be used for both a withstand voltage test and an internal partial discharge test, which are important as power cable performance evaluations.

(Prior art)

2. Description of the Related Art Hitherto, a withstand voltage test and an internal partial discharge test have been performed in a development test or a shipping test of a power cable. In particular, in the case of a solid insulated cable such as a cross-linked polyethylene insulated cable, defects (voids or foreign substances) inside the insulator, the insulator-
The internal partial discharge test is important for inspecting the interface of the semiconductive layer for defects (projections, peeling, etc.). Of course, oil-immersed insulation (OF)
This test is important for inspecting not only the main insulating portion such as SF ₆ gas but also the composite insulating portion such as the connecting portion and the insulating support for the presence or absence of defects.

Conventionally, when an internal partial discharge test is performed, an inductance called a blocking coil is inserted between a voltage application terminal of a cable and a test transformer. This is for the following reasons. In other words, the amount of partial discharge charge that is discharged due to a defect inside the cable is usually extremely small, and the amount of discharge charge generated on the air side of an external connection part or a test transformer is generally larger. This is because it is necessary to reduce the noise due to the LC filter effect composed of the blocking coil and the cable to make it easier to detect the partial discharge from inside the power cable.

This blocking coil may be provided as a part of a gas insulation test terminal installed between the voltage application end of the cable and the test transformer. Fig. 3 shows an example. The high voltage generated by the power supply voltage regulator 11, the test transformer 12, the insulating bus 13, the air terminal connection 15, the gas terminal connection 16, the blocking coil 18, the high voltage conductor 20, the gas terminal connection 22 The power is applied to the power cable 26 through the like. The shields 14, 17, 19, and 21 are for reducing a local concentrated electric field so as not to cause a partial discharge at each location. Reference numerals 23 and 25 indicate protective fittings, reference numeral 24 indicates an insulating cylindrical tube, reference numeral 27 indicates a gas insulation test container on the voltage application end side, and reference numeral 28 indicates a gas insulation test container on the opposite side. In test containers 27 and 28,
An insulating gas such as SF ₆ gas, N ₂ gas, or a mixed gas is sealed.

Usually, when a partial discharge test is performed, a capacitor called a coupling capacitor is often required in addition to the cable under test (this is regarded as a capacitance load during the test). This is used to compare whether the pulse generated from the cable is a noise or a signal (partial discharge pulse), or to take out the signal to the outside. When the blocking coil is connected to the high voltage bus, the coupling capacitor is usually connected to the high voltage bus between the blocking coil and the test terminal. It is often connected to a high voltage conductor inside the blocking coil and the cable under test. There are various types of coupling capacitors, for example, a method of using a plurality of test cables and using one of them, a method of dividing the ground side of the test cable and using one of them, etc. The most common method is to use a standard capacitor which has been tested from the beginning to prevent partial discharge.

In the test method using the gas insulation test terminal, when this standard capacitor is used, as shown in Fig. 3,
A cylindrical electrode 30 is provided on the outer periphery of the high-voltage conductor 20 via an insulating spacer 29.
It is most efficient and effective to form a coupling capacitor by supporting the above. Of course, variations such as branching the high voltage conductor 20 at the rear end of the blocking coil 18 and connecting a coupling capacitor to one of them and a test cable to the other are possible. The insulating spacer 29 may be omitted in some cases.

The cylindrical electrode 30 of the coupling capacitor is an insulating bush
It is connected to a detection impedance 32 outside the test container 27 through 31. The sheath of the test cable 26 is an insulated cylindrical tube 24.
Is insulated from the gas insulation test container 27 and connected to the detection impedance 33.

In such a configuration, the partial discharge signals emitted from the test cable 26 and the coupling capacitor are detected by the detection impedances 32 and 33, respectively, amplified by the partial discharge measuring device 34, subjected to waveform processing, and the like, and are then subjected to the oscilloscope 35. Observed at In this example, the detection impedance is constituted by a resistor and a capacitor, but another impedance may be used.

〔Task〕

However, when the blocking coil is installed in the gas insulation test terminal as described above, there are the following problems. In other words, the incorporation of a blocking coil in the gas insulation test terminal has a significant effect on the partial discharge test, but an AC withstanding voltage test is performed using this terminal near the insulation limit of the cable under test. If the cable breaks down, there is a high probability that the cable will break down.
Some of the insulated wires of the blocking coil are likely to be short-circuited. This is because the applied voltage and current suddenly change at the time of dielectric breakdown of the cable, so that the transient shared voltage at both ends of the blocking coil sharply increases, and a part of the insulating coating of the coil is easily broken down.

In this way, if a dielectric breakdown occurs in a part of the blocking coil, then when performing a partial discharge test, the effect of noise due to the discharge of the broken part is large, making the test impossible or erroneous judgment. Or will be.

For this reason, if dielectric breakdown occurs in a part of the blocking coil, the blocking coil needs to be repaired.However, since the coil is in a gas insulation test container, gas recovery, disassembly, repair, and vacuum treatment are required for repair. , A series of steps such as gas re-sealing are required, which requires a great deal of cost and cost.

Also, when a steep rising voltage such as an impulse voltage or switching surge voltage is applied to the test cable, a steep voltage can be applied because the insulation of the blocking coil is burned out by the same phenomenon as described above. Absent. For this reason, when performing an impulse voltage or switching surge voltage application test, the test must be performed after separately replacing the terminal with a dedicated terminal.
Procedures such as conducting a test after replacing the blocking coil with a normal conductor were required, resulting in poor efficiency.

[Means for solving the problem and its operation]

The present invention, in order to solve the problems of the prior art as described above, in a power cable test apparatus having a blocking coil for removing electrical noise in the gas insulation test container on the voltage application side from the test cable, In the gas-insulated test container, a short-circuiting / opening device at both ends of the blocking coil, which can be operated in a non-contact manner from the outside of the test container, is provided.

If such a short-circuit / opening device is provided, the withstand voltage test and destruction test by AC, impulse,
It is possible to short-circuit both ends of the blocking coil so that a high voltage is not applied to the blocking coil, and to release the blocking coil during a partial discharge test so that the blocking coil has its original function. Also, by making this short-circuit / opening device operable in a non-contact manner from the outside of the gas insulation test container, there is no need to open and close the gas insulation test container, and the work of switching between short-circuit and open can be performed simply and efficiently. It becomes possible.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 and 2 show a main part of a power cable test apparatus according to one embodiment of the present invention.

In the drawing, reference numeral 41 denotes a driving device installed in the shield 17 on one end side (voltage application side) of the blocking coil 18. The driving device 41 provides an insulating wire 42 and a conductive wire in an insulating cylinder 18 a of the blocking coil 18. 43 is extended (see Fig. 2). The insulated wire 42 is folded back by a guide roll 44 installed in the shield 19 at the other end of the blocking coil 18, and the tip is connected to the conductive wire 43. A movable contact 45 that is in conduction with the conductive wire 43 is attached to the connection between the insulating wire 42 and the conductive wire 43. The base ends of the insulated wire 42 and the conductive wire 43 are respectively wound around reels in the drive device 41, and when the motor in the drive device 41 rotates forward and backward,
The insulated wire 42 and the conductive wire 43 run in opposite directions, and the movable contact 45 reciprocates in the axial direction of the blocking coil 18.

On the other hand, one end of the blocking coil 18 is electrically connected to the driving device 41 and the shield 17 by a lead wire 46, and the other end of the blocking coil 18 is a fixed contact set inside the insulating cylinder 18 a by a lead wire 47. 48 and the shield 19 are electrically connected.

A control circuit 49 of the driving device 41 and a battery 50 are provided in the shield 17 (see FIG. 2). The control circuit 49 controls the normal rotation, the reverse rotation, and the stop of the motor in the drive device 41. This control circuit 49 includes a phototransistor 51
It operates by turning on and off. A light source 52 is provided at a position facing the phototransistor 51 outside the gas insulation test container 27, and a portion of the test container 27 through which light from the light source 52 passes is formed of a transparent glass plate 53. I have. A slit plate 54 is provided in front of the phototransistor 51.

 Next, the operation of this device will be described.

First, when light is applied from the light source 52 to the phototransistor 51, the control circuit 49 operates to rotate the motor in the driving device 41 forward, thereby moving the movable contact 45 in the direction of arrow A. The driving device 41 operates until the movable contact 45 contacts the fixed contact 48, and stops when the movable contact 45 contacts the fixed contact 48. In this state, both ends of the blocking coil 18 are connected to the lead wire 46 and the driving device 4.
1, conductive wire 43, movable contact 45, fixed contact 48, lead wire 4
7 is short-circuited.

Next, when light is applied from the light source 52 to the phototransistor 51, the control circuit 49 operates in the opposite direction, reverses the motor in the driving device 41, and moves the movable contact 45 in the direction of arrow B. The driving device 41 stops when the movable contact 45 has moved a predetermined distance. In this state, both ends of the blocking coil 18 are opened, and the blocking coil 18 is
It will be in the state inserted between 19.

Next, when light enters from the light source 52, the blocking coil
It returns to a state where both ends of 18 are short-circuited. In this way, both ends of the blocking coil 18 in the gas insulation test container 17 can be short-circuited and opened from the outside of the container 17 without contact. Cable withstanding voltage test is blocking coil
18 is performed with both ends short-circuited, and the partial discharge test is performed with both ends of the blocking coil 18 open.

If both ends of the blocking coil 18 are short-circuited, the blocking coil 18 and the conductive wire 43 will be connected in parallel to the high-voltage part. However, since the conductive wire 43 has an extremely small impedance, most of the current is Flow to 43.
Therefore, the shared voltage across the blocking coil 18 is
Even when the applied waveform is steep or when the cable causes dielectric breakdown, the voltage is extremely small and the blocking coil 18 does not cause dielectric breakdown. Further, since the blocking coil itself also functions as a shield for relaxing high voltage, it is possible to apply high voltage of various waveforms.

The above is one embodiment of the present invention, and the present invention is not limited to this. Short circuit at both ends of the blocking coil
The opening can be performed by various means.

〔The invention's effect〕

As described above, the power cable testing device according to the present invention uses the same gas insulation test terminal because both ends of the blocking coil can be short-circuited and opened from the outside of the gas insulation test container in a non-contact manner. Thus, a withstand voltage test and a destructive test by AC, impulse, switching surge and the like can be performed with both ends of the blocking coil short-circuited, and a partial discharge test can be performed with both ends of the blocking coil open. In addition, various tests can be repeatedly performed without the possibility of breaking the insulating coating of the blocking coil during the withstand voltage test and the breakdown test.

[Brief description of the drawings]

FIGS. 1 and 2 are cross-sectional views each showing a main part of a power cable test apparatus according to an embodiment of the present invention, and FIG. 3 is an overall configuration diagram of a conventional power cable test apparatus. 17: shield, 18: blocking coil, 19: shield, 2
6: Test cable, 27: Gas insulation test container, 41: Drive unit,
42: Insulated wire, 43: Conductive wire, 44: Guide roll, 45: Movable contact, 46/47: Lead wire, 48: Fixed contact, 49: Control circuit, 5
0: battery, 51: phototransistor, 52: light source, 53: transparent glass plate.

Claims (1)

(57) [Claims] 1. A power cable test apparatus having a blocking coil for removing electrical noise in a gas insulation test container on the voltage application side of a test cable, wherein the power insulation test container includes a blocking coil for removing electric noise. A power cable testing device comprising a short-circuiting / opening device at both ends of a blocking coil operable in a non-contact manner.