JPH0627763B2 - Orientation method of cable partial discharge generation position - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of locating a partial discharge occurrence position of a cable, and more particularly, for testing the insulation state of a high voltage CV cable with an external shielding layer. The present invention relates to a method of imposing a test pulse signal on a high-voltage conductor and locating the position of partial discharge generated at that time.

[Prior Art] A conventional method of locating a partial discharge occurrence position of a cable is carried out by using a test device configured as shown in FIG. 3, for example.

That is, a terminal bushing 4 for charging is provided at one end of the measured cable 3 having the outer conductive layer 2 on the outer periphery of the high voltage core wire 1, and a terminal bushing 5 for taking out a signal is provided at the other end of the measured cable 3. Is provided.

A high-voltage pulsed test voltage S is applied via the terminal bushing 4, and a signal generated at the terminal bushing 5 of the cable under test 30 at this time is
The DC component and the power supply frequency (for example, 50 HZ or 60 HZ) are supplied to the capacitor 6 for cutting.

Furthermore, the external conductive layer 2 is formed at the portion of the terminal bushing 5.
Is grounded, and a current / voltage conversion resistor 7 is connected between the grounded end and the end via the capacitor 6. The signal generated at both ends of the resistor 7 is supplied to the pulse waveform measuring device 8.

Therefore, if a high-voltage pulsed test voltage S is applied to the high-voltage core wire 1 of the measured cable 3 via the terminal bushing 4 and a partial discharge pulse is generated in the defective portion of the measured cable 3, this pulse is The high voltage core wire 1 of the cable 3 propagates from the terminal bushing 4 side to the terminal bushing 5 side and reaches the measurement end. The DC component and the power supply frequency component of this signal are cut by the capacitor 6, converted into a voltage value by the resistor 7, and then supplied to the pulse waveform measuring instrument 8.

The measurement pulse supplied to the pulse waveform measuring device 8 includes a direct wave component corresponding to the above-described high-voltage pulsed test voltage S and a partial discharge component corresponding to the partial discharge pulse generated by the test voltage S. It is divided into a component reflected at the end of the measured cable 3.

Therefore, the time difference between the direct wave and the indirect wave can be calculated using the measured cable 3
The position where the partial discharge pulse is generated can be obtained by performing calculation based on the propagation speed of the high voltage pulsed test voltage S in the high voltage core wire 1.

[Problems to be Solved by the Invention] In such a conventional method of locating a partial discharge occurrence position of a cable, a capacitor 6 is used when detecting a partial discharge pulse generated at the terminal portion of the high voltage core wire 1. Since the DC component and the power source frequency component are cut off, a high performance capacitor 6 is required for high precision measurement.

That is, since the high voltage is applied to the capacitor 6, the withstand voltage is improved by connecting the capacitor elements in series,
In order to compensate for the decrease in electrostatic capacitance due to such series connection, the series connected capacitor element groups are connected in parallel to obtain a predetermined capacity and withstand voltage.

Therefore, there is a problem that the shape of the capacitor 6 becomes large and the inductance component becomes large, and accordingly the detected waveform becomes dull, and an accurate partial discharge position cannot be obtained.

There is also a problem that a corona-free installation space for installing such a capacitor 6 is required, and the installation place is restricted.

Therefore, an object of the present invention is to provide a method of locating a partial discharge occurrence position of a cable, which can obtain an accurate partial discharge position without blunting the pulse component of the partial discharge pulse signal generated in the high voltage core wire. .

[Means for Solving the Problems] In order to achieve the above-mentioned object, a method for locating a partial discharge occurrence position of a cable according to the present invention is a method for allocating a high voltage pulse to a high voltage conductor of a long cable having an outer conductive layer. When the test voltage is applied, the partial discharge pulse signal generated in the high voltage conductor is supplied to the partial discharge voltage detection circuit through the part taken out by insulating a part of the outer conductive layer in the cable in the longitudinal direction. Then, the generation position of the partial discharge pulse generated in the high voltage conductor of the cable is determined based on the output of the partial discharge voltage detection circuit.

[Operation] A method of locating a partial discharge occurrence position of a cable according to the present invention forms a capacitor component in a portion where the number m of the external conductive layers at the end of the measured cable is insulated in the longitudinal direction of the cable and taken out. By supplying the partial discharge pulse signal generated in the high voltage core wire of the cable to be measured to the partial discharge voltage detection circuit through the capacitor component, an accurate partial discharge position can be obtained without blunting the pulse component.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2.

In FIG. 1, the outer conductive layer 12 is formed on the outer periphery of the high voltage core wire 11.
The measured voltage of the cable under test 3 is 22kV.
And the cross-sectional area is 1 x 100 mm ² and the total length is 237 m.
The CV cable is an extrusion compound type. At one end of such a measured cable 13,
The terminal bushing 14 is fixed, and the terminal bushing 15 is fixed to the other end. Further, an edge cut portion 16 is formed at a position 57 m from the end portion of the measured cable 13 near the terminal bushing 15, where the outer conductive layer 12 is cut and separated to separate the first outer conductive layer 12a and the second outer conductive layer. Layer 1
2b, and the first outer conductive layer 12a is grounded.

Further, the first outer conductive layer 12a closer to the terminal bushing 14 than the edge cut portion 16 of the outer conductive layer 12 and the edge cut portion 1 are formed.
6 to the second outer conductive layer 12 near the terminal bushing 15
A resistor 17 is connected to each of b. Both ends of the resistor 17 are connected to the pulse waveform measuring device 18.

Therefore, when the high-voltage pulse-shaped test voltage S is injected into the high-voltage core wire 11 through the terminal bushing 14, this test voltage S
Propagates through the high voltage core wire 11, is supplied to the resistor 17 via the capacitor component of the second outer conductive layer 12b, is converted into a voltage, and is then supplied to the pulse waveform measuring device 18.

Here, the polarity of the high voltage pulsed test voltage S is the high voltage core wire 1
If one side is the positive electrode and the outer conductive layer 12 side is the negative electrode, the resistance 1
When the signal waveforms generated at both ends of 7 were observed, the result shown in FIG. 2 (A) was obtained. This result is obtained by once recording the voltage generated across the resistor 17 in a digital memory (not shown) and observing the reproduced waveform with an ordinary oscilloscope.
The value of μsec / div is obtained in relation to reading / writing of the digital memory, and corresponds to 0.5 μsec / div in terms of real time. Then, in FIG. 2A, the pulse of the first wave is a near-end direct wave propagating through the high-voltage core wire 11, and the second wave is a wave in which the wave reflected at the far-end from the injection point returns to the near-end. And the third
The wave is a round-trip reflected wave of the first wave.

For reference, the signal generated at both ends of the resistor 7 was observed in the same manner as described above by the method of locating the partial discharge occurrence position of the cable using the conventional device (see FIG. 3). Came to show.

Here, as is clear from comparing the waveform shown in FIG. 2 (A) and the waveform shown in FIG. 2 (B), the waveform shown in FIG. 2 (B) is slightly dull. It is considered that this is because pulse detection is performed via the capacitor 6 having a large inductance component. On the other hand, the pulse waveform detected by the method for locating the partial discharge occurrence position of the cable according to the present invention has an extremely fast rise and fall as shown in FIG. 2 (A). This is because the external conductive layer 12 of the cable to be measured 13 is provided with a second external conductive layer 12b, which is insulated and separated, to provide a capacitor component to replace the conventional capacitor 6 (see FIG. 3). This is due to the fact that the inductance component in is very small.

Therefore, when the high voltage pulse test voltage S is applied to the high voltage core wire 11 of the cable 13 to be measured having the outer conductive layer 12 via the terminal bushing 14, the partial discharge pulse signal generated in the high voltage conductor 11 is The voltage is converted into a voltage by the resistor 17 via the capacitor component formed by the second outer conductive layer 12b, and this voltage is supplied to the pulse waveform measuring device 18 so that the position where the partial discharge pulse is generated can be accurately located.

Further, such accurate detection can be performed because the rise and fall of the signal waveform becomes very steep because the inductance component of the capacitor component formed by the second outer conductive layer 12b is very small. Is based.

The method for locating the partial discharge occurrence position of the cable according to the present invention can be applied not only to the three-layer extrusion type compound type CV cable but also to various cables such as an OF cable, a butyl rubber cable and the like.

[Effects of the Invention] As described above, in the method for locating the partial discharge occurrence position of the cable according to the present invention, it is not necessary to separately provide a capacitor for cutting the DC component and the power supply frequency, so that the configuration is simplified, and its installation No space is needed.

Further, since the residual inductance component is smaller than that of the conventional capacitor, the responsivity to the pulse is excellent, and as a result, it is possible to accurately locate the partial discharge occurrence position.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram showing an example of a measuring device used in the method of the present invention, and FIG. 2 is an example of a detection result of the measuring device shown in FIG. 1 and a detection result using a conventional device. FIG. 3 is a schematic circuit diagram showing an example of a measuring device used in a conventional method for locating a partial discharge occurrence position of a cable. 11 ... High-voltage core wire 12 ... External conductive layer 12a ... First external conductive layer 12b ... Second external conductive layer 13 ... Measured cable 14,15 ... Terminal bushing 16 ... Edge cut portion 18 ... Pulse waveform measuring instrument

Claims (1)

[Claims] 1. When a high-voltage pulse test voltage is applied to a high-voltage conductor of a long cable to be measured having an outer conductive layer, a partial discharge pulse signal generated in the high-voltage conductor is supplied to the high-voltage conductor of the long cable to be measured. Part of the external conductive layer is cut and separated, and one of the separated external conductive layers is connected to the partial discharge voltage detection circuit and supplied, and based on the output of this partial discharge voltage detection circuit, the high voltage conductor of the cable is connected. A method of evaluating the partial discharge occurrence position of a cable, characterized by evaluating the occurrence position of the generated partial discharge pulse.