JP2657025B2 - A method for measuring the partial discharge of live lines in power cable lines. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing insulation of a power cable line.

[0002]

2. Description of the Related Art A conventional countermeasure against external noise in an insulation diagnosis method for a power cable line is described in, for example, Technical Report of the Institute of Electrical Engineers of Japan (11), No. 222, pp. 13-22 (April 1986). ing.

[0003] However, all of these methods are diagnostics at the time of stoppage, that is, a method in which the power cable line is stopped and disconnected from the system, and the measurement is performed using a high-voltage test power supply separate from the system. It was not intended for live line measurement as is.

[0004]

When the power cable line is laid in triple bales or triplex with three cables, the three cables are tightly electromagnetically coupled. Partial discharge or external noise generated from a certain cable is guided to each of the three cables with almost the same magnitude, and a comparison of the magnitude of the partial discharge pulse detected from each of the three cables shows that the partial discharge or external noise from the cable has a small value. It is difficult to determine whether an internal partial discharge pulse or an external discharge pulse is guided to the cable line by a hot-line partial discharge or measurement.

[0005] Further, when the sheath is cross-bonded at the insulated connecting portion, there is a method of inserting a high-frequency iron core into the cross-bond wire to reduce the coupling. Therefore, a method that does not attach an iron core is desired. Therefore, when an external partial discharge pulse irrelevant to the cable line is detected by the cable detection unit, it is difficult to determine that.

An object of the present invention is to distinguish between an internal partial discharge pulse and an external partial discharge pulse from the power cable line, and to improve the reliability of the partial discharge measurement as a high voltage insulation test method.

[0007]

SUMMARY OF THE INVENTION According to the present invention, when detecting a partial discharge from a connection portion or a cable portion in a long power cable line, another cable line or a metal conductor closely laid outside is detected. Acts as a source of noise and is guided by the cable line, thereby detecting external noise or external partial discharge at a position close to the external noise source of the other cable line or metal conductor. Then, by comparing the signal with the signal from the connection portion or the cable portion, the external partial discharge or the external noise is determined, and the partial discharge from the connection portion or the cable portion is detected. This is a line partial discharge measurement method.

[0008]

[Function] Detects noise at a high-level portion close to the noise source in a cable or metal conductor that is a specific external induction source, and compares it with the signal detected in the cable, and detects it at the same moment The determined signal is determined to be noise. In this case, the external noise is detected at a high level, and even if the signal from the cable is reversely guided to the external induction source, the magnitude relationship is reversed, so that the partial discharge from the cable is not possible. It is easy to determine whether the noise is external.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of a method for measuring a partial discharge of a live line of a power cable line according to an embodiment. The power cable line 2 connected by the insulating connection part 1 is laid in the underground cave 12. An external noise induction cable 3 is laid in parallel with the power cable line 2, and one end thereof is connected to a high voltage transmission line by an air transmission line 5 via an induction cable air termination 4. When an aerial corona (partial discharge) occurs at the aerial transmission line 5, the underground cave 12
The corona and external noise propagate to the induction cable 3 laid inside. Since the power cable line 2 laid in the same underground passageway 12 is laid in parallel with the induction cable 3, external noise from the induction cable 3 is induced.

At this time, the partial discharge detection electrode 6 provided on the insulating connection portion 1 causes the partial discharge detection impedance Zs
7, a partial discharge is detected. At this time, external noise induced from the external noise inducing cable 3 is also detected. Therefore, an external noise detection electrode 13 is provided at a position near the induction source (air transmission line 5) of the external noise induction cable 3, that is, near the cable end 4, and an external corona or an external corona through the external noise detection impedance Zn 8. Detect external noise. At this time, both of these signals are led to the external noise discriminating device 11 via the connection signal amplifier 9 and the external nozzle amplifier 10, respectively.
The signal S of the amplifier 9 and the signal N of the amplifier 10 are simultaneously detected. And the signal level is N
In the case of> S, it is determined that the noise is external noise. Also, when noise from the inductive source propagates through the inductive cable 3, the noise is reflected at the end and the noise amplitude level is not necessarily high at a certain position or at a detection frequency due to an interference phenomenon. Even in such cases, the method of the present invention can be applied.

FIG. 2 is a block diagram showing a modification of the present invention. To detect external noise with high sensitivity, a dedicated antenna 14 is provided near the induction cable 3. On the other hand, the coupling with the power cable line 2 is reduced, and the partial discharge generated in the power cable line 2 which is the target cable is installed at a position where the antenna 14 cannot easily receive the partial discharge.

When a tunable amplifier is used for the amplifiers 9 and 10 shown in FIGS. 1 and 2, the signal S of the amplifier 9 is detected at a higher frequency than the signal N of the amplifier 10 and the insulated connection 1 is detected.
In contrast to the method of detecting the partial discharge with high sensitivity, the signal N of the amplifier 10 is detected at a lower frequency, the attenuation due to the line propagation is reduced, and the external noise is detected at a high signal level with high sensitivity. It is valid.

In both of the above examples, the cable laid in the underground passageway 12 has been described. However, even if the cable is a directly buried cable line or a cable line laid in the air, an external noise source can be specified, and the detection unit detects the external noise source. If the relationship of the signal N of the amplifier 10> the signal S of the amplifier 9 is satisfied, the detection may be performed based on the relationship.
Although FIGS. 1 and 2 show the case where the detection of noise and partial discharge is performed by the partial discharge detection electrode 6 of the insulated connection part 1, it is needless to say that the present invention can be applied to other detection methods.

Although FIG. 1 shows an example of measuring a partial discharge from an aerial transmission line as an external noise source, the present invention can be widely applied to general external noise. Further, if the relationship of the signal N of the amplifier 10> the signal S of the amplifier 9 is maintained, there is no need to depend on physical dimensions. In this case, the cable is used as the inductive source. However, other good electrical conductors, for example, a metal structure, electric wires, or a tension member using metal may be used.

[0015]

As described above, according to the method for measuring a live line partial discharge of a power cable line according to the present invention, it is possible to reliably distinguish external noise and a partial discharge pulse from the cable line in the live line. Is possible, and the reliability of the partial discharge measurement is improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a method for measuring a live part partial discharge of a power cable according to the present invention;

FIG. 2 is a circuit diagram showing a modification in which external noise is received by a dedicated antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulated connection part 2 Cable line 3 External noise induction cable 4 Induction cable air termination 5 Air transmission line 6 Partial discharge detection electrode 7 Partial discharge detection impedance 8 External noise detection impedance 9 Connection part signal amplifier 10 External noise amplifier 11 External noise discriminator 12 Underground tunnel conduction 13 External noise detection electrode 14 Antenna

Continued on the front page (72) Inventor Hiroshi Suzuki 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture "Inside Power System Research Laboratories, Hitachi Cable Ltd." (72) Inventor Tomoaki Imai Hitachi City, Ibaraki Prefecture 5-1-1 Hidaka-cho, Power System Research Laboratories, Hitachi Cable, Ltd. (72) Inventor Mikio Hagiya 5-1-1, Hidaka-cho, Hitachi, Ibaraki, Japan (56) References JP-A-63-234173 (JP, A)

Claims (1)

(57) [Claims] When detecting partial discharge from a connection portion or a cable portion in a long power cable line,
If another closely laid cable line or metal conductor acts as a source of external noise, and is thereby guided and detected on the cable line, the above-mentioned other line is detected .
By detecting external noise or external partial discharge at a position close to an external noise source such as a cable line or a metal conductor, and comparing the detected external noise or external partial discharge with a signal from the connection portion or the cable portion , external partial discharge or external partial discharge is detected. Determine the noise and release the part from the connection or cable part.
A method for measuring a partial discharge of a live line of a power cable line, comprising detecting electricity .