JPH08178997A - Partial discharge measurement method for power cables - Google Patents

Abstract

(57) [Abstract] [Purpose] To measure the partial discharge occurrence position of a power cable wound on a cable drum with high sensitivity and efficiency. [Structure] The power cables 1 and 1'wound on the cable drums 2 and 2'are connected by an insulating connection portion 5, and cable end portions 4a and 4b are formed at the ends of the power cables at both ends. Further, the sheath edge cutting portions 8a and 8b in the vicinity of the cable terminating portions 4a and 4b and the partial discharge detectors 6a and 6 at the insulating connection portion 5 are also provided.
b and 6c are connected. Then, a high voltage is applied from the terminal end 4a by the AC transformer 3, and the partial discharges generated in the power cable are connected to the partial discharge detectors 6a, 6b, 6c, and the high frequency partial discharge measuring instruments 7a, 7b, 7c are connected. (Measurement frequency band is 1 MHz to 50 HHz). In addition, the position locator 10 allows the partial discharge detectors 6a, 6a to
The location of the partial discharge occurrence is detected based on the time difference between the partial discharge pulses reaching b and 6c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring a partial discharge of a power cable, and more particularly to a method of measuring a partial discharge of a power cable wound on a drum with high sensitivity and efficiency. .

[0002]

Prior to shipping a power cable, a partial discharge measurement is carried out by applying a high voltage to the power cable while being wound on a drum. FIG. 3 is a diagram showing a conventional test method for the above-described power cable. In the figure, 1 is a power cable to be measured, 1a is a cable conductor, 1b is a sheath, and the sheath 1b is grounded as shown in the figure.
2 is a cable drum in which a power cable is wound into a coil,
3 is an AC for applying a high voltage to the conductor 1a of the power cable 1.
The transformers 4a and 4b are cable terminating portions composed of bushings.

Reference numeral 21 is a coupling capacitor,
One end of the coupling capacitor 21 is the cable conductor 1
It is connected to a and the other end is connected to the partial discharge detector 22 formed of a detection impedance. The other end of the partial discharge detector 22 is grounded, and both ends thereof are connected to the partial discharge measuring device 23. In the figure, in order to test the power cable, a high voltage is applied from the AC transformer 3 to the cable conductor 1a. When a partial discharge occurs in the power cable 1, a partial discharge pulse is generated across the partial discharge detector via the coupling capacitor 21 and measured by the partial discharge measuring device 23.

As the partial discharge measuring instrument 23,
A tunable partial discharge meter is used to measure partial discharge pulses in a single low frequency band of 400 kHz.

[0005]

The above-described conventional partial discharge measurement has the following problems. (1) For each drum-wound power cable, it is necessary to connect a bushing to both ends of the power cable to form a cable end portion to configure a test facility, which results in poor test efficiency. (2) Since the partial discharge is measured in a single low frequency band of 400 kHz, the waveforms may overlap due to the round-trip reflection at the cable end, and the sensitivity in the longitudinal direction may be significantly reduced.

For example, assuming that the center frequency of the tunable partial discharge measuring instrument is 400 kHz, the cable propagation speed is 200
m / μs, the resonance point is about 125 m, the anti-resonance point is about 250 m, and the cable length is usually 300 m to 1.
Since it is about 5 km, the detection sensitivity is significantly lowered depending on the place where the partial discharge occurs. (3) Since the partial discharge is measured at one place, even if the partial discharge is detected, the generation position is unknown. (4) Since the measurement frequency band is a low frequency band of 400 kHz, the S / N ratio is poor and the measurement sensitivity is lowered due to the influence of noise. Therefore, it is necessary to remove the influence of external noise, for example, by installing the test equipment in a shield room.

The present invention has been made in consideration of the above-mentioned problems of the prior art, and an object of the present invention is to enable efficient partial discharge measurement of a power cable wound on a cable drum. Another object of the present invention is to provide a partial discharge measuring method capable of measuring a partial discharge occurrence position with high sensitivity without being affected by noise.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is to connect several power cables wound on a drum with an insulating connection portion, and to connect the end portions of the power cables at both ends. A cable termination is formed on the cable, the sheath near the cable termination is cut off to connect the partial discharge detector, and the insulation connection is connected to the partial discharge detector, and a high voltage is applied from one of the terminations. Is applied to measure the partial discharges that occur in the above-mentioned power cables with a high-frequency partial discharge measuring instrument connected to the partial discharge detectors, and the partial discharge pulse detected by each partial discharge detector arrives. The partial discharge occurrence position is detected based on the time difference.

According to a second aspect of the present invention, in the first aspect of the invention, the measurement frequency band of the high frequency partial discharge measuring instrument is selected within the range of 1 MHz to 50 MHz.

[0010]

[Function] Since a plurality of drum-wound power cables are connected to each other by the insulation connection and the cable end portions are formed at the ends of the power cables at both ends, it is possible to simultaneously test several power cables. Therefore, an efficient test can be performed. In addition, the sheath near the cable end is cut off to connect the partial discharge detector, and the partial discharge detector is connected to the insulation connection part, and a high voltage is applied from one of the end parts, and Since the partial discharge generated in the electric power cable of Article is measured by the high frequency partial discharge measuring instrument connected to the partial discharge detector, it is possible to detect the partial discharge occurrence position based on the arrival time difference of the partial discharge pulse. .

Further, the measurement frequency band is 1 MHz to 50.
By measuring the partial discharge using the high frequency partial discharge measuring instrument selected for MHz, the waveforms are overlapped by the reciprocal reflection as in the conventional example and the sensitivity in the longitudinal direction is significantly reduced, and the influence of external noise Can be eliminated and the sensitivity can be improved.

[0012]

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, 1 and 1'are power cables to be tested,
1a is a cable conductor, 1b is a sheath, 2 and 2'are cable drums, 4a and 4b are cable terminal portions, and 5 is a gas insulated connection portion. In this embodiment, two cable drums 2 and 2'are provided. One end of each of the two wound power cables 1 and 1'is connected to the gas insulation connection portion 5, and terminal portions 4a and 4b are formed at the other ends of the power cables 1 and 1 '.

Reference numeral 3 is A for applying a high voltage to the power cable 1.
The AC transformer 3 is a C transformer and is connected to the cable conductor 1a at the terminal end 4a of the power cable 1. 6
Reference numerals a, 6b and 6c denote partial discharge detectors, the partial discharge detector 6a is connected between the sheath edging portions 8a formed near the terminal end 4a, and the partial discharge detector 6c is formed near the terminal end 4b. The partial discharge detectors 6b are connected between the insulated cylinders of the gas insulating connection portion 5.

Reference numerals 7a, 7b and 7c are partial discharge measuring instruments composed of a spectrum analyzer and the like, and the measuring frequency band of the partial discharge measuring instruments 7a, 7b and 7c of the present embodiment is 1.
It is selected in the high frequency band of MHz to 50 MHz. By selecting the measurement frequency band in the high frequency range as described above, it is possible to prevent a decrease in sensitivity due to the partial discharge pulse being reflected back and forth at the cable end portion to cause anti-resonance. Further, since the frequency band of external noise can be removed, it is possible to prevent the sensitivity from decreasing due to external noise without providing a shield room as described above.

The measurement frequency band is not limited to the above-mentioned band, and can be appropriately selected as an optimum high frequency band excluding the frequency band of external noise. Reference numeral 10 is a position locating device, and the position locating device locates the partial discharge generation position from the arrival time difference of the partial discharge pulses measured by the partial discharge measuring devices 7a, 7b and 7c.

FIG. 2 is a diagram showing an example of the structure of the gas-insulated connecting portion 5, 11 is a casing, 12 is an insulating cylinder made of epoxy resin or the like, and the casing 11 is connected via the insulating cylinder 12. The casing 11 is filled with an inert gas 16 such as SF6. Also,
1, 1'is a power cable, 13 is an insulator tube, 14 is a shield, and 15 is a shielded connector. The insulator tube 13 is attached to the end of the power cable 1, 1 ', and the cable conductor of the power cable 1, 1'is Shielded connector 15
Are connected to each other.

Although the cable conductors are connected by the shielded connector 15 in FIG. 2, the cable conductors may be connected via a matching impedance.
Next, partial discharge measurement in this embodiment will be described with reference to FIGS. A bushing is connected to one end of each of the power cables 1 and 1 ′ to be measured that are wound on two drums to form cable end portions 4 a and 4 b, and sheaths near the cable end portions 4 a and 4 b are formed. A part is removed to form the edge cut portions 8a and 8b.

The other end of each of the power cables 1 and 1'is connected to the gas insulation connecting portion 5 shown in FIG.
That is, the porcelain insulator 13 is attached to the ends of the power cables 1, 1 ′, the cable conductors are connected to each other by the shielded connector 15, and SF 6 gas is sealed in the gas insulation connection portion 5. At this time, as described above, the cable conductor may be connected via the matching impedance.

Next, one end portion, for example, the end portion 4a.
The AC transformer 3 is connected to the cable conductor of the above, and sheath edging portions 8a and 8b are provided near the end portions 4a and 4b at both ends.
The partial discharge detectors 6a and 6c are connected across the line. Further, the partial discharge detector 6b is connected across the insulating cylinder 11 of the gas insulation connecting portion 5. Then, an AC high voltage is applied from the AC transformer to the cable conductor, and the partial discharge measuring instruments 7a, 7
The occurrence of partial discharge is detected in the measurement frequency band of 1 MHz to 50 MHz by b and 7c.

The power cable 1 has defects such as voids,
For example, when a partial discharge occurs in the power cable 1, the partial discharge pulse propagates in the power cable 1 to reach the gas-insulated connection portion 5 and the terminal portion 4a, and the partial discharge pulse is detected by the partial discharge detectors 6a and 6b. It Further, the partial discharge pulse generated in the power cable 1 is partially reflected when reaching the gas-insulated connection portion 5 and partly passes therethrough and propagates in the power cable 1 ′ to the partial discharge detector 6 c. Reach

The partial discharge measuring devices 7a, 7b, 7c analyze the detected partial discharge pulse in the measurement frequency band of 1 MHz to 50 MHz to detect the occurrence of partial discharge. Further, the detected partial discharge pulse is sent to the position locator 10,
The position locating device 10 locates the position where the partial discharge occurs from the arrival time difference of the partial discharge pulses transmitted from each detection point and the propagation speed of the partial discharge pulse.

As described above, in this embodiment, the two cables wound around the cable drum are connected by the gas insulation connector, and the partial discharge detector is attached to the terminal end and the gas insulation connection of both cables. Since the partial discharge is measured, the position where the partial discharge occurs can be detected, and the test of two cables can be performed at the same time, so that the test efficiency can be improved. Further, since it is sufficient to provide one pair of cable end portions to which the bushings are attached for the two cables, the test equipment can be simplified.

In the above embodiment, an example in which two cables are connected with one gas-insulated connection and partial discharge is measured is shown. However, several cables are connected with a plurality of gas-insulated connectors. Even if a partial discharge detector is attached to each gas insulated connection, the partial discharge measurement can be performed similarly. Further, in the above-mentioned embodiment, since the cable can be easily connected / disconnected, the example in which the two cables are connected by using the gas insulated connector is shown, but the present invention is not limited to the above-mentioned embodiment. Alternatively, other known cable connecting means can be used.

[0024]

As described above, according to the present invention, a plurality of drum-shaped power cables are connected to each other by an insulating connection portion, and cable end portions are formed at the ends of the power cables at both ends. Part of the electric power cable by connecting a partial discharge detector to the insulation connection part by cutting the sheath in the vicinity of the part and applying a high voltage from one of the terminal parts. Since the partial discharge generated therein is measured by the high frequency partial discharge measuring instrument connected to the partial discharge detector, the following effects can be obtained. (1) It is possible to test several electric power cables at the same time and perform efficient tests. (2) The partial discharge occurrence position can be detected based on the arrival time difference of the partial discharge pulses. (3) By selecting the measurement frequency band as a high frequency band of 1 MHz to 50 MHz, for example, the waveforms do not overlap due to reciprocal reflection and the sensitivity in the longitudinal direction is not significantly reduced, and the influence of external noise is eliminated. It is possible,
The measurement sensitivity can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a gas insulation connecting portion used in this embodiment.

FIG. 3 is a diagram showing a conventional example.

[Explanation of symbols]

 1, 1'Power cable 1a Cable conductor 1b Sheath 2, 2'Cable drum 3 AC transformer 4a, 4b Cable end portion 5 Gas insulation connection portion 6a, 6b, 6c Partial discharge detector 7a, 7b, 7c Partial discharge measuring instrument 8a , 8b Sheath edging portion 10 Position locator 11 Casing 12 Insulation cylinder 13 Insulator pipe 14 Shield 15 Shielded connector

Claims (2)

[Claims] 1. A plurality of drum-wound power cables are connected at an insulating connection, cable ends are formed at the ends of the power cables at both ends, and a sheath near the cable ends is trimmed to form a portion. The discharge detector is connected, the partial discharge detector is connected to the insulation connection, and a high voltage is applied from one of the terminal ends to generate the partial discharge generated in the power cables of the above-mentioned several lines. Partial discharge of power cable characterized by detecting the position of partial discharge occurrence based on the arrival time difference of the partial discharge pulse detected by each high frequency partial discharge measuring device connected to the detector and detected by each partial discharge detector Measuring method. 2. The method for measuring partial discharge of a power cable according to claim 1, wherein a measurement frequency band of the high frequency partial discharge measuring instrument is selected within a range of 1 MHz to 50 MHz.