JPH04127820A - Method of judging the cause of the ground fault of high-voltage distribution line - Google Patents

Abstract

PURPOSE:To simplify and secure maintenance and inspection work by specifying the cause of a ground fault to a cable when the waveform of zero-phase voltage is a step form wave or in a rectangular wave and the pulse of 0.1-1mS in width appears in a zero-phase current. CONSTITUTION:If a ground fault occurs in one or two lines of nongrounded three-phase AC type high-voltage distribution lines 22, zero-phase voltage V0, through a GPT10, and zero-phase current I0, through the ZCT 18 of a corresponding feeder, are detected respectively. And the zero-phase voltage V0 and the zero-phase current I0 are inputted into a waveform recording and analyzing device 20, and there the waveform is recorded, and also the frequency is analyzed. Moreover, recorded each phase is displayed on the CRT screen of the waveform recording and analyzing device 20. Hereupon, making it a judgment condition that the waveform of the zero-phase voltage V0 is a step form wave or a rectangular wave, and that the pulse 0.1-1mS in width appears in the zero- phase current I0, the cause of the ground fault is specified to a feeder 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for determining the cause of a ground fault in an ungrounded three-phase AC high voltage distribution line.

[Prior art] Although the supply reliability of high-voltage distribution lines is already at a fairly high level, ground faults may occur due to failures in cables, high-voltage pin insulators, pole transformers, lightning arresters, and other equipment. There is. There are also ground faults caused by animals such as birds, animals, and snakes coming into contact with live parts of power distribution lines. Contact with trees such as bamboo or cedar may also be the cause.

When a ground fault occurs in one or two wires of a three-phase AC high-voltage distribution line, zero-sequence voltage and zero-sequence current are generated even in non-grounded distribution lines. 67G) and ground fault overvoltage relays (64G) were used to detect the occurrence of these failures. Based on this detection, the automatic switch of the corresponding distribution line is opened. The circuit will be reclosed after a certain period of time, and in the case of a permanent failure, the automatic switch will open again as a reclosing failure accident. If the failure is instantaneous and reclosing is successful,
Power continues to be supplied with the automatic switch closed.

[Problems to be Solved by the Invention] When a failure occurs, regardless of whether the reopening is successful or not, it is necessary to search for the cause of the failure and reliably remove it.

However, in the past, the presence or absence of a ground fault was only detected based on the magnitude and phase of the zero-sequence voltage and zero-sequence current, and it was not possible to identify the cause of the fault. Therefore, even if a ground fault actually occurs due to poor insulation of the high-voltage pin insulator, it is necessary to carry out a thorough inspection of all equipment, including other equipment, in order to determine the cause of the failure. In other words, all cables, not just high voltage pin insulators,
This meant that all pole transformers, all lightning arresters, etc. had to be thoroughly investigated for abnormalities.

Furthermore, in the case of a ground fault caused by an animal coming into contact with a live part of a power distribution line, the faulty object may be carried away by another animal after the fault occurs, and patrol inspection work often ends up being a waste of effort.

In addition, because the search range was too wide, it was not possible to find the item that caused the ground fault, and the item was left unattended, resulting in a serious permanent failure due to the same item causing the failure. This may later occur.

The present invention has been made in view of the above points, and provides a method for determining the cause of a ground fault failure, with the aim of simplifying and ensuring maintenance and inspection work for high-voltage distribution lines. be.

[Means for Solving the Problem] In the method for determining the cause of a ground fault in a high-voltage distribution line according to the present invention,
When identifying the cause of a ground fault failure in a cable, the conditions for determining this are that the waveform of the zero-sequence voltage becomes a staircase waveform or a rectangular waveform, and that a pulse with a pulse width of 0.1 to 1mS appears in the zero-sequence current. . When using the frequency analysis method, the discrimination conditions are that the zero-sequence voltage contains large odd harmonics and that the 5th, 7th, and 9th harmonics of the harmonic components of the zero-sequence current are large. shall be.

When identifying the cause of a ground fault failure as a high-voltage pin insulator, the condition for determination is that a peak appears at the wavefront of the zero-sequence current.

When using the frequency analysis method, the discrimination condition is that the third harmonic among the harmonic components of the zero-sequence current is large and the fifth and seventh harmonics are small. Furthermore, when the waveform of the zero-sequence voltage is used to identify the cause of a failure, an additional AND condition for these discrimination conditions is that the harmonic component of the zero-sequence voltage is small.

When identifying the cause of a ground fault failure as dielectric breakdown of the insulating oil in a distribution line equipment that uses insulating oil, such as a pole transformer, the condition for determining this is that the wave crest of the zero-sequence current appears rounded.

When identifying the cause of a ground fault failure as a lightning arrester, the condition for determining is that intermittent high-frequency vibration appears in the zero-sequence current. When using the frequency analysis method, the determination condition is that the seventh and ninth harmonics among the harmonic components of the zero-sequence current become intermittently large.

When identifying the cause of a ground fault failure as contact of an animal with a live part of a distribution line, the condition for determination is that a dent appears in the wave crest of the zero-sequence current. When using the frequency analysis method, the third harmonic among the harmonic components of the zero-sequence current is large, and the harmonic components of the zero-sequence current become smaller in the order of the third, fifth, and seventh harmonics. This is the determination condition. Furthermore, when the waveform of the zero-sequence voltage is used to identify the cause of a failure, an additional AND condition for these discrimination conditions is that the harmonic component of the zero-sequence voltage is small.

When identifying the cause of a ground fault as the contact of a tree with the light/form part of the distribution line, the discrimination condition is that the harmonic components of both the zero-sequence voltage and zero-sequence current are small.

[Function] The inventors of the present application used waveform data of zero-sequence voltage and zero-sequence current obtained through collecting actual ground fault waveforms at distribution substations and conducting failure reproduction experiments on simulated high-voltage distribution lines. As a result of frequency analysis and cluster analysis, it was found that both waveforms have unique characteristics based on the differences in the causes of ground faults.

In the method for determining the cause of ground fault failure in high-voltage distribution lines according to the present invention,
Based on this characteristic, when a ground fault is caused by a fault in each component such as a cable, high-voltage bottle insulator, pole transformer, or lightning arrester, it is not only possible to identify the cause of the fault to each component, but also to identify the cause of the fault in each component. The cause of the failure can be identified even if it is caused by contact of an animal or tree with a live part of the distribution line.

[Example] FIG. 1 is a single line diagram showing an example of an ungrounded three-phase AC high voltage distribution line to which a method for determining the cause of a ground fault failure in a high voltage distribution line according to an example of the present invention is applied.

A 66 kV three-phase power transmission line 2 is introduced into a distribution substation 4 and connected to the primary side of a main transformer 6.

The main transformer 6 has delta-connected windings on both the primary and secondary sides, and has a transformation ratio of 66 kV/6.6 kV. A bus 8 in the substation is connected to the secondary side of the main transformer 6, and a zero-phase voltage V is connected to the secondary side of the main transformer 6.

The primary side of GPTIO for detection of is connected.

The GPTIO winding has a star connection with a neutral point grounded on the primary side, and a broken delta connection on the secondary side. This 2
The next broken delta winding is closed with a resistor 12. A plurality of feeders 14 are drawn out from the bus bar 8 via automatic switches 16, respectively. Each feeder 1
4 is provided with a ZC718 for detecting the zero-phase current Io.

The output of the zero-sequence current Io of this ZCTIII is GPTlO
The zero-sequence voltage V of the resistor 12 connected to the secondary winding of. It is input to the waveform recording analysis device 20 along with the output of. Each feeder 4 is drawn out from the substation 4 as a high voltage distribution line 22. The high-voltage distribution line 22 uses cables, high-voltage pin insulators, pole transformers, lightning arresters, and other unillustrated equipment.

A ground fault occurs in one or two wires of this ungrounded three-phase AC high-voltage distribution line 22 (the ground fault point is indicated by reference numeral 24).
Then, the zero-sequence voltage Vo is passed through the GPT 10, and the zero-sequence current is passed through the ZCT 18 of the corresponding feeder 4. are detected respectively. These zero-sequence voltage V and zero-sequence current I.

is not only input to the ground fault direction relay and ground fault overvoltage relay (not shown), but also its waveform is recorded and frequency analyzed by the waveform recording and analysis device 20. Further, each recorded waveform is displayed on the CRT screen of the waveform recording and analysis device 20.

FIGS. 2(a) and 2(b) show the zero-sequence voltage ■ in the case of a cable ground fault in the high-voltage distribution line 22. and a zero-sequence current Io.

As shown in (a) and (b) of the same figure, the zero-sequence voltage V. The waveform becomes a staircase waveform or a rectangular waveform, and the zero-sequence current ■o
The cause of the ground fault is identified in the cable, with the condition that a pulse with a pulse width of 0.1 to 1 mS appears in the cable. When using the frequency analysis method, the zero-sequence voltage■. The determination conditions are that the current 1o contains large odd-numbered harmonics, and that the fifth, seventh, and ninth harmonics among the harmonic components of the zero-sequence current 1o are large.

Figures 3(a) and 3(b) show the zero-sequence voltage V and zero-sequence current in the case of a ground fault in the high-voltage pin insulator. FIG.

As shown in the figure (b), the zero-sequence current I. The cause of the ground fault failure is identified in the high-voltage pin insulator, using the presence of a peak at the top of the wave as a discrimination condition. When using frequency analysis techniques,
Zero sequence current! . The determination condition is that the third harmonic among the harmonic components of is large and the fifth and seventh harmonics are small.

Furthermore, the zero-sequence voltage■. When using the waveform for identifying the cause of a failure, an additional AND condition for these discrimination conditions is that the harmonic component of the zero-phase voltage Vo is small.

FIGS. 4(a) and 4(b) show the zero-sequence voltage V in the case of a ground fault caused by dielectric breakdown of the insulating oil in the pole transformer. and zero-sequence current■.

FIG. Moreover, FIGS. 5(a) and 5(b) are respectively enlarged time-axis views of FIGS. 4(a) and 4(b).

6.6k by the following method using a simulated high-voltage distribution line.
A ground fault caused by dielectric breakdown of the insulating oil in a V-pole transformer was reproduced. In other words, 600 cC of the deteriorated insulating oil from the pole transformer was collected inside the container, a small amount of water was added to this to lower the insulation resistance, and two electrodes were placed in the container with one end grounded. A ground voltage of 3.8 kV was applied between these electrodes from a simulated substation to generate an oil discharge. This dielectric breakdown of the insulating oil causes a one-wire ground fault. Zero-sequence voltage V and zero-sequence current I in the simulated substation at the time of this failure.

The waveform was recorded. However, the insertion capacitance C1 on the bus bar side simulating the high voltage distribution lines of all other feeders is 2.5 μF, and the insertion capacitance C2 on the line side simulating the high voltage distribution lines of the feeder is 0.5 μF. did.

The above-mentioned FIGS. 4(a), (b) and 5(aHb) show the zero-sequence voltage V and zero-sequence current I in the case of a ground fault caused by dielectric breakdown of the insulating oil obtained in this way. FIG.

Zero-sequence current I in the case of dielectric breakdown of insulating oil as shown in FIGS. 4(b) and 5(b). The waveform is very similar to the ground fault waveform of the high-voltage pin insulator shown in Figure 3 (b) and is difficult to distinguish, but in the case of the high-voltage pin insulator, the wave crest is sharp, whereas in the case of insulating oil, the wave crest is sharp. has a unique rounded waveform. In other words, the cause of the ground fault can be identified as dielectric breakdown of the insulating oil, using the appearance of roundness at the wavefront of the zero-sequence current lo as a discrimination condition.

Figures 6(a) and 6(b) show the zero-sequence voltage V and zero-sequence current in the case of a ground fault in a gap arrester. FIG.

As shown in the figure (b), the zero-sequence current I. 5mS to 16m
The cause of the ground fault failure is identified in the lightning arrester using the appearance of intermittent high-frequency vibrations with a duration of 5 as a discrimination condition. When using the frequency analysis method, the zero-sequence current I. The determination condition is that the 7th and 9th harmonics of the harmonic components become intermittently large. The occurrence of this intermittent high-frequency vibration is a sign of failure of the lightning arrester, and the zero-sequence current I. The size of is 100
It is a minute area of about mA to several A. Therefore, this slight ground fault in the lightning arrester could not be detected by the conventional ground fault directional relay. However, according to the present method, even this slight ground fault can be detected and can be dealt with before both relays operate and a power outage occurs.

FIGS. 7(a) and 7(b) show the zero-sequence voltage V and the zero-sequence current I in the case of a ground fault caused by contact of an animal with a live part of the high-voltage distribution line 22. FIG.

As shown in the figure (b), the zero-sequence current I. The cause of the ground fault is determined to be contact of an animal with a live part of the distribution line, using the presence of a dent in the crest of the wave. When using the frequency analysis method, the zero-sequence current I. The determination condition is that the third harmonic among the harmonic components of is larger, and the harmonic components of the zero-sequence current IO are smaller in the order of the third, fifth, and seventh harmonics. Furthermore, the zero-sequence voltage V. When using the waveform of V to identify the cause of failure, zero-sequence voltage V.

An additional AND condition for these discrimination conditions is that the harmonic component of is small.

FIGS. 8(a) and 8(b) show the zero-sequence voltage V and zero-sequence current I in the case of a ground fault caused by a tree contacting a live part of the high-voltage distribution line 22. FIG.

As shown in (a) and (b) of the same figure, the zero-sequence voltage ■. The cause of the ground fault failure is determined to be contact of a tree with a live portion of the distribution line, using the condition that the harmonic components of both the zero-sequence current IO and the zero-sequence current IO are small.

Note that the waveform record analysis device 20 may automatically determine the cause of failure according to the above conditions, and a lamp provided for each cause of failure may be lit based on the determination result. It is also convenient to display the time when the failure occurred.

[Effects of the Invention] As explained above, the method for determining the cause of a ground fault fault in a high-voltage distribution line according to the present invention is based on the difference in the cause of the fault in the waveforms of zero-sequence voltage and zero-sequence current that occur at the time of a ground fault fault. Because it takes advantage of its unique characteristics, ground faults can be caused by cables,
Not only can the cause of failure be identified to each item when it is caused by failure of each item such as high-voltage pin insulators, pole transformers, or lightning arresters, but also ground faults can be caused by contact of animals or trees with live parts of distribution lines. The cause of failure can be identified even when

Therefore, when the cause of a ground fault is determined to be a high-voltage pin insulator using the method of the present invention, it is only necessary to investigate which high-voltage pin has caused the abnormality, such as cables, pole transformers, lightning arresters, etc. There is no need to inspect local supplies. Furthermore, if the method of the present invention identifies the cause of the ground fault as contact of an animal or tree with a live portion of the distribution line, there is no need to inspect items on the distribution line.

Since the investigation range for the cause of failure can be narrowed down in this way, the cause of the ground fault can be investigated quickly and easily. In other words, it is possible to simplify and ensure maintenance and inspection work, and it is also possible to prevent serious failures. Furthermore, it is possible to detect even slight ground faults that could not be detected with conventional relays, making it possible to deal with them before a power outage occurs due to the operation of this relay.

[Brief explanation of the drawing]

FIG. 1 is a single-line diagram showing an example of an ungrounded three-phase AC high-voltage distribution line to which the method for determining the cause of a ground fault failure in a high-voltage distribution line according to an embodiment of the present invention is applied, and FIG. b) is a waveform diagram of the zero-sequence voltage and zero-sequence current in the case of a cable ground fault, and Figure 3 (a) and (b) are the zero-sequence voltage and zero-sequence current in the case of a ground fault in the high-voltage bottle insulator. Waveform diagram with current, Figure 4 (a)
(b) is a waveform diagram of the zero-sequence voltage and zero-sequence current in the case of a ground fault caused by dielectric breakdown of the insulating oil in the pole transformer. Figure 5 (a) and (b) are the times of the previous waveform diagram. Enlarged view of the axis,
Figure 6 (a) and (b) are waveform diagrams of zero-sequence voltage and zero-sequence current in the case of a ground fault in a lightning arrester. Figure 8 (a) and (b) are waveform diagrams of zero-sequence voltage and zero-sequence current in the case of a ground fault caused by a ground fault. It is a waveform diagram of the zero-sequence voltage and zero-sequence current of. Explanation of symbols 2...Power transmission line, 4...Distribution substation, 6...Main transformer, 10...GPTSlB... Automatic switch, I8
...ZCT. 20... Waveform recording analysis device, 22... High voltage distribution line,
24... Ground fault point. Figure 2 Figure 5 Figure 6

Claims (1)

[Claims] 1. Zero-sequence voltage and zero-sequence current of an ungrounded three-phase AC high-voltage distribution line are detected, and the waveform of the zero-sequence voltage has a staircase waveform or a rectangular waveform, and A method for determining the cause of a ground fault in a high-voltage distribution line, which identifies the cause of a ground fault in a cable, on the condition that a pulse with a pulse width of 0.1 to 1 mS appears in the current. 2. Detect the zero-sequence voltage and zero-sequence current of an ungrounded three-phase AC high-voltage distribution line, and detect if the zero-sequence voltage contains large odd harmonics and the fifth harmonic component of the zero-sequence current. , a method for determining the cause of a ground fault in a high-voltage distribution line, which identifies the cause of the fault in the cable, on the condition that the seventh and ninth harmonics are large. 3. Detect the zero-sequence current of the ungrounded three-phase AC high-voltage distribution line,
A method for determining the cause of a ground fault in a high-voltage power distribution line, which identifies the cause of the fault as a high-voltage pin insulator, on the condition that a peak appears at the wave crest of this zero-sequence current. 4. Detect the zero-sequence current of the ungrounded three-phase AC high-voltage distribution line,
The third harmonic among the harmonic components of the zero-sequence current is large, and
A method for determining the cause of a ground fault in a high-voltage power distribution line, which identifies the cause of the fault as a high-voltage pin insulator, on the condition that the fifth and seventh harmonics are small. 5. Further detect the zero-sequence voltage of the ungrounded three-phase AC high-voltage distribution line, and if the harmonic component of the zero-sequence voltage is small, add an additional logical product condition to identify the cause of the ground fault failure as the high-voltage pin interlock. The method for determining the cause of a ground fault in a high-voltage distribution line according to claim 3 or 4. 6. Detect the zero-sequence current of the ungrounded three-phase AC high-voltage distribution line,
A method for determining the cause of a ground fault in a high-voltage distribution line, which specifies the cause of the ground fault as dielectric breakdown of insulating oil in the distribution line equipment, on the condition that a roundness appears in the wave crest of this zero-sequence current. 7. Detect the zero-sequence current of the ungrounded three-phase AC high-voltage distribution line,
A method for determining the cause of a ground fault in a high-voltage distribution line, which identifies the cause of the fault in a lightning arrester on the condition that intermittent high-frequency vibration appears in this zero-sequence current. 8. Detect the zero-sequence current of the ungrounded three-phase AC high-voltage distribution line,
A method for determining the cause of a ground fault in a high-voltage power distribution line, in which the cause of the fault in a ground fault is identified as a lightning arrester, on the condition that the seventh and ninth harmonics among the harmonic components of a zero-sequence current become intermittently large. 9. Detect the zero-sequence current of the ungrounded three-phase AC high-voltage distribution line,
A method for determining the cause of a ground fault in a high-voltage power distribution line, which identifies the cause of the fault as an animal contacting a live part of the power distribution line, on the condition that a dent appears in the wavefront of this zero-sequence current. 10. Detect the zero-sequence current of an ungrounded three-phase AC high-voltage power distribution line, and determine if the third harmonic among the harmonic components of the zero-sequence current is large and the third, fifth, and seventh harmonics are zero in that order. A method for determining the cause of a ground fault in a high-voltage power distribution line, which identifies the cause of the fault as an animal's contact with a live part of the power distribution line, on the condition that the harmonic components of the phase current become small. 11. Further detect the zero-sequence voltage of the ungrounded three-phase AC high-voltage distribution line, and confirm that the harmonic component of the zero-sequence voltage is small in order to identify the cause of the ground fault failure as an animal contacting the live part of the distribution line. 11. The method for determining the cause of a ground fault in a high-voltage distribution line according to claim 9 or 10, wherein an additional AND condition is used. 12. Detect the zero-sequence voltage and zero-sequence current of an ungrounded three-phase AC high-voltage distribution line, and determine the cause of the ground fault on the condition that the harmonic components of both the zero-sequence voltage and zero-sequence current are small. A method for determining the cause of ground faults in high-voltage distribution lines by identifying the contact of trees with live parts of the wires.