JP4821992B2 - Ground fault detection device - Google Patents

Description

  The present invention relates to a ground fault detection device that detects a ground fault in a power transmission tower.

  As a conventional technique related to the present invention, for example, there is a ground fault point indicator and a short-circuit ground fault determination circuit of a power transmission and distribution line described in Patent Document 1. This is because the short-circuit relay and the ground fault relay provided in power plants and substations cut off the power transmission in a shorter time from the time of the failure than the ground fault relay. Thus, the ground fault point indicator is operated only in the case of a ground fault without being operated in the case of a short circuit fault. In other words, the time constant circuit is not charged up to a preset voltage in a short time span between the occurrence of a short-circuit fault and the transmission interruption by the short-circuit relay, and from the occurrence of the ground fault to the ground fault relay. Only in the case of a long time width until the power transmission is cut off, the time constant circuit is charged to the set voltage, so that only the ground fault is detected and displayed.

JP-A-11-142463

  Such Patent Document 1 functions effectively, but if only a ground fault can be detected without considering the operating time of a short circuit relay and a ground fault relay of a power plant or substation, Convenience can be improved, such as eliminating the need to make individual settings according to the operating time of the relay.

  The present invention has been made based on such a viewpoint, and prevents malfunction caused by a short circuit failure without considering the operation time of a short circuit relay and a ground fault relay of a power plant or substation. It is an object of the present invention to provide a ground fault detection device capable of accurately detecting only a ground fault.

In the present invention, two legs out of the four legs of the power transmission tower below the lowermost brace that supports the power transmission line of the power transmission tower having no overhead ground line are induced due to a short circuit failure. current flows in the reverse direction, the fault current due to the ground fault is provided on one leg of said two legs of the power transmission pylons flow in the same direction toward the earth, the one in the case of the short-circuit failure A first current transformer that detects an induced current flowing through the legs of the power supply, detects a fault current that flows through the one leg toward the ground in the case of a ground fault, and provides an AC voltage output; and An induced current that is provided on the other leg of the two legs, detects an induced current that flows in the opposite direction to the one leg that flows through the other leg in the case of the short-circuit fault, and the other leg in the case of the ground fault The one leg that flows toward the ground A second current transformer providing an AC voltage output by detecting a fault current flowing in the same direction, the combining unit for combining the AC voltage output of the first of said an AC voltage output of the current transformer second current transformer In addition, the above-described object is achieved by a ground fault detection device including detection means for detecting only a ground fault based on the combined output of the combining unit .

  According to this, it is possible to detect only a ground fault without considering the operating time of the short-circuit relay and the ground fault relay of the power plant or substation. The first and second current transformers detect induced currents flowing in opposite directions in the case of short-circuit faults and provide AC voltage outputs, respectively, and detect fault currents flowing in the same direction in the case of ground faults. AC voltage output is provided, so that there is a significant difference between the combined output in the case of a short-circuit fault and the combined output in the case of a ground fault, and only a ground fault can be accurately detected without detecting a short-circuit fault. Can be detected.

The first and second current transformers provide an AC voltage output having the same phase in the case of the ground fault to the detecting means, and an AC voltage output having the opposite phase in the case of the short circuit fault. Provided to the one leg and the other leg of the two legs of the power transmission tower so as to be provided to the detection means, and the combining part of the detection means is configured by a series connection of two bidirectional Zener diodes. The first and second bidirectional Zener diodes connected in series so that the fault currents are in the same direction and the induced currents are in opposite directions. A portion between the first current transformer and the second current transformer connected in series to the series connection of the current transformer and connected in series is the two of the series connection. The combined output from the amplitude limiting circuit via the amplitude limiting circuit that is connected between one and the other of the bidirectional Zener diodes to provide the combined output and a protective resistor that prevents inflow of current exceeding the rated current Rectifying circuit for full-wave rectification, and generating a large combined output that is full-wave rectified based on the AC voltage output of the same phase in the case of the ground fault, and mutually in the case of the short-circuit fault A full-wave rectified composite output that is much smaller than the composite output in the case of the ground fault is provided based on an anti-phase AC voltage output. This makes it possible to have a large combined output in the case of a ground fault, and a much smaller combined output in the case of a short-circuit fault, so that only a ground fault can be accurately detected without detecting a short-circuit fault. be able to.

  The detecting means is operated using the AC voltage output of the first and second current transformers as an operating power source. Therefore, it is not necessary to provide an operating power source such as a battery, maintenance such as battery replacement is unnecessary, and maintenance can be facilitated.

Further, the one leg provided with the first current transformer and the other leg provided with the second current transformer are substantially parallel to a power transmission line supported by a brace of the power transmission tower. Constructed to be two legs forming a surface.

In addition to the combining unit , the detecting means is charged by a combined output obtained by full-wave rectification of the combining unit, and the charging voltage of the charging circuit reaches the charging voltage in the case of a short-circuit fault. And a detection circuit for providing a detection output indicating detection of a ground fault when the charge voltage in the case of a ground fault is equal to or higher than a threshold set so as to be always reached. As a result, the charging circuit is charged with a large combined output at the time of a ground fault, so that it becomes easy to obtain a desired power as a detection output of the detection circuit at the time of a ground fault, and for example, when a display or the like is driven by this detection output A reliable operation of the display or the like can be achieved.

  According to the present invention, it is possible to detect only a ground fault without considering the operation time of a short-circuit relay and a ground fault relay in a power plant or substation, and it is possible to detect a combined output and a ground in the case of a short-circuit fault. It is possible to make a significant difference from the combined output in the case of a fault, and it is possible to accurately detect only a ground fault without detecting a short-circuit fault.

  Moreover, it is possible to reliably detect a ground fault even in a power transmission tower having no overhead ground wire.

  Further, it is not necessary to provide an operating power source such as a battery, and the ease of maintenance can be improved.

  In addition, it is possible to give a large composite output for ground faults and a much smaller composite output for short circuit faults, so that only ground faults can be detected accurately without detecting short circuit faults. Can do.

  Furthermore, it becomes easy to obtain desired power as a detection output of the detection circuit at the time of a ground fault, and when the display or the like is driven by the detection output, for example, a reliable operation of the display or the like can be achieved.

  As the best mode for carrying out the invention, an embodiment of the present invention will be described below.

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

  In FIG. 1, reference numeral 1 is a power transmission tower having four legs, a first leg 2, a second leg 3, a third leg 4, and a fourth leg 5. In this example, the power transmission tower 1 is not provided with an overhead wire. A power transmission line 7 is supported on each arm 6 of the power transmission tower 1 via an insulator (not shown).

  The ground fault detection device 10 includes a first current transformer 11, a second current transformer 12, a detection unit 13, and a display unit 14. The first and second current transformers 11 and 12 are located below the arm 6 of the power transmission tower 1 and are formed with a first and second legs 2 and 3 that form a surface ABCD substantially parallel to the power transmission line 7 or It is provided on the third and fourth legs 4 and 5 that form a surface EFGH that faces the surface ABCD and is also substantially parallel to the power transmission line 7. In this example, the first current transformer 11 is provided on the first leg 2 that forms the surface ABCD, detects the current flowing through the first leg 2, and provides an AC voltage output to the detection unit 13. Similarly, the second current transformer 12 is provided on the second leg 3 that similarly forms the surface ABCD, and the current flowing through the second leg 3 is detected to provide an AC voltage output to the detection unit 13. It has become. As will be described later, in the first leg 2 and the second leg 3, the fault current at the time of ground fault flows in the same direction toward the ground, and the induced currents at the time of the short-circuit fault flow in opposite directions. The same applies to the third leg 4 and the fourth leg 5. The detection unit 13 receives the AC voltage outputs of the first and second current transformers 11 and 12 and combines them, detects only a ground fault based on the combined output, and displays the detection output as the display unit 14. The display unit 14 is driven. The fault current at the time of ground fault flows in the same direction, and the induced currents at the time of short circuit fault flow in opposite directions, so there is a significant difference between the composite output in the case of a short fault and the composite output in the case of a ground fault. Therefore, only a ground fault can be accurately detected without detecting a short-circuit fault. The display unit 14 may be a conventionally known display unit such as a display unit using explosives or a display unit using a solenoid, and the detection output of the detection unit 13 is used as a detection signal for a ground fault. It can also be configured to transmit the occurrence of a ground fault.

  FIG. 2 is a diagram showing a fault current at the time of a ground fault and an induced current at the time of a short-circuit fault, and the same reference numerals as those in FIG. 1 denote the same parts.

  When a ground fault occurs in the power transmission tower 1 due to lightning or bird damage, the power transmission tower 1 having no overhead ground wire has several tens of A in the same direction toward the ground on the four legs 2 to 5 of the power transmission tower 1. Fault current Ia flows.

  On the other hand, when a short-circuit failure occurs in the transmission line 7, a short-circuit current Ib of several thousand A that is extremely large compared to the failure current Ia of several tens of A flows through the transmission line 7, and a magnetic field M thereby generated is transmitted to the transmission tower 1 The induced current Ic flows through the four legs 2 to 5 of the power transmission tower 1 through the plane ABCD and the plane EFGH in the horizontal direction. This induced current Ic flows so as to cancel the magnetic field M, and the direction of the induced current Ic is reversed between the first leg 2 and the second leg 3 of the plane ABCD, and the third leg of the plane EFGH. Similarly, the direction of the induced current Ic is reversed between the fourth leg 4 and the fourth leg 5.

  FIG. 3 is a diagram showing a mounting portion of the ground fault detection device in FIG. 1, and the same reference numerals as those in FIGS. 1 and 2 denote the same components. In this example, as described above, the first current transformer 11 is provided on the first leg 2 of the power transmission tower 1, and the second current transformer 12 is provided on the second leg 3. In the case of a ground fault, the fault current Ia flows in the same direction toward the ground in the first and second legs 2 and 3 of the transmission tower 1, and in the case of a short circuit fault, the first and second legs. 2 and 3, the induced current Ic flows in the opposite direction. The first and second current transformers 11 and 12 provide a sinusoidal AC voltage output having the same phase when the fault current Ia flowing in the same direction is detected, and when detecting the induced current Ic flowing in the reverse direction. It is provided to provide an antiphase sine wave AC voltage output.

  FIG. 4 is a circuit diagram showing an example of the detection unit 13 in FIG. 1, and the same reference numerals as those in FIGS. 1 and 2 denote the same components. The detection unit 13 constitutes detection means, and includes an amplitude limiting circuit 20, a rectifier circuit 21, a charging circuit 22, and a detection circuit 23. The amplitude limiting circuit 20 and the rectifier circuit 21 constitute a combining unit that combines the AC voltage output of the first current transformer 11 and the AC voltage output of the second current transformer 12 and gives the combined output.

  The amplitude limiting circuit 20 of the synthesizer includes two bidirectional Zener diodes 201 and 202 connected in series. The sine wave AC voltage output from the first and second current transformers 11 and 12 is input, The amplitude is limited and combined, and the combined output is supplied to the rectifier circuit 21 via the resistor 24. The resistor 24 is a protective resistor for the rectifier circuit 21 and prevents the current exceeding the rated current from flowing into the rectifier circuit 21 so that the diodes 210, 211, 212, and 213 constituting the rectifier circuit 21 are not destroyed. The rectifier circuit 21 of the synthesizer performs full-wave rectification on the combined output from the amplitude limiting circuit 20 and provides the combined output obtained by full-wave rectification to the charging circuit 22.

  FIG. 5 is a waveform diagram of the combining unit in the case of a ground fault, and FIG. 6 is a waveform diagram of the combining unit in the case of a short circuit failure.

  In the case of a ground fault, as shown in FIGS. 5A and 5B, the AC voltage output of the first current transformer 11 and the AC voltage output of the second current transformer 12 which are limited in amplitude are Are the same phase, and the combined output output from the amplitude limiting circuit 20 has substantially twice the amplitude in this example, as shown in FIG. The combined output is full-wave rectified, and the combined output subjected to full-wave rectification shown in FIG. As an example, the voltage of the AC voltage output of the first and second current transformers 11 and 12 whose amplitudes are limited is, for example, + 10V to −10V, and the voltage of the combined output is, for example, + 20V to −20V. A combined output of 20V is given as a combined output from the unit.

  On the other hand, in the case of a short-circuit failure, as shown in FIGS. 6E and 6F, the AC voltage output of the first current transformer 11 whose amplitude is limited and the second current transformer 12 The combined output output from the amplitude limiting circuit 20 has an amplitude of approximately 0 in this example, as shown in FIG. 6 (g). Then, the combined output is full-wave rectified, and the combined output subjected to full-wave rectification becomes substantially 0 in this example, as shown in FIG.

  Thus, in the case of a ground fault, a large combined output is given from the combining unit, and in the case of a short-circuit fault, a much smaller combined output is given compared to the case of a ground fault.

  Returning to FIG. 4, the charging circuit 22 includes a charging capacitor 220 and a resistor 221 inserted in parallel therewith, and the charging capacitor 220 is a full-wave rectified composite from the rectifier circuit 21 according to the time constant with the resistor 221. Charged by output. As described above, a ground fault fault results in a large combined output, and a short circuit fault results in a very small composite output.Therefore, the charging voltage increases in the case of a ground fault, and much smaller than that in the case of a ground fault. Thus, a significant difference occurs in the charging voltage.

  The detection circuit 23 includes a series connection of a resistor 230, a Zener diode 231, and a trigger resistor 232, a noise prevention capacitor 233 inserted in parallel with the trigger resistor 232, and a thyristor 234. The trigger resistor 232 applies a gate voltage to the gate of the thyristor 234, and the noise prevention capacitor 233 prevents the thyristor 234 from malfunctioning due to noise.

  A series connection of the resistor 230, the Zener diode 231 and the trigger resistor 232 is inserted in parallel in the charging circuit 22, and is connected to one output terminal 25a. The zener diode 231 gives a threshold that cannot be reached by the charging voltage of the charging circuit 22 in the case of a short circuit failure and that is always reached by the charging voltage of the charging circuit 22 in the case of a ground fault. The charging circuit 22 is turned on when the charging voltage is equal to or higher than a predetermined voltage. As an example, when a combined output of, for example, 20 V is given as a combined output subjected to full-wave rectification as described above at the time of a ground fault, the Zener diode 231 is set to turn on at a predetermined voltage value between 10 V and 20 V, for example. Is done. Thereby, at the time of a short circuit failure, one of the AC voltage outputs of the first current transformer 11 and the second current transformer 12 becomes small for some reason, and a difference occurs between the two AC voltage outputs. Even if the output is generated, the combined output does not exceed 10 V in the above example, so that the Zener diode 231 is not turned on.

  The thyristor 234 has a cathode and a gate inserted in parallel to a noise prevention capacitor 233 inserted in parallel with the trigger resistor 232, and an anode connected to the other output terminal 25b. A display unit 14 is connected to the output terminals 25a and 25b, and a detection output is given to the display unit 14 in the case of a ground fault.

  With such a configuration, when a short-circuit failure occurs, the AC voltage output of the opposite phase from the first and second current transformers 11 and 12 is detected from the first and second current transformers 11 and 12 by the detection of the induced current Ic resulting from the short-circuit failure. Given to. In the case of a short-circuit failure, since the AC voltage output is in reverse phase, the combined output output from the amplitude limiting circuit 20 has an amplitude of approximately 0 as shown in FIG. The combined output becomes substantially zero as shown in FIG. Therefore, the charging voltage of the charging circuit 22 is much smaller than the threshold value at which the Zener diode 231 of the detection circuit 23 is turned on, and no detection output is given due to a short circuit failure.

  On the other hand, when a ground fault occurs, an AC voltage output having the same phase is supplied from the first and second current transformers 11 and 12 to the amplitude limiting circuit 20 of the detection unit 13 by detecting the fault current Ia caused by the ground fault. It is done. In the case of a ground fault, since the AC voltage output is in phase, the combined output output from the amplitude limiting circuit 20 has a substantially double amplitude as shown in FIG. The combined output thus obtained has a high voltage value as shown in FIG. Therefore, the charging voltage of the charging circuit 22 becomes equal to or higher than a threshold value at which the Zener diode 231 of the detection circuit 23 is turned on, and the gate voltage is applied to the thyristor 234 via the trigger resistor 232 when the Zener diode 231 is turned on. As a result, the thyristor 234 is turned on, and the detection output is given to the display unit 14 from the output terminals 25a and 25b.

  As is apparent from the above, the detection unit 13 operates using the AC voltage output of the first and second current transformers 11 and 12 as an operation power supply. Therefore, it is not necessary to provide an operating power source such as a battery, maintenance such as battery replacement is unnecessary, and maintenance can be facilitated. In addition, since the charging circuit 22 is charged with a large combined output at the time of a ground fault, it is easy to obtain desired power as a detection output of the detection unit 13 at the time of a ground fault, and a display or the like is driven by this detection output. In addition, a reliable operation of the indicator or the like can be achieved.

  Further, the conventional ground fault point indicator according to Patent Document 1 described above could not be applied to a transmission line in which there is almost no difference in operating time between the short circuit relay and the ground fault relay, but according to the present invention. The ground fault detection device 10 can be applied to such a power transmission line without any problem. Furthermore, since the ground fault detection device 10 according to the present invention is configured to obtain a large composite output in the event of a ground fault, it can be applied to a minor ground fault that cannot be detected by a conventional ground fault indicator. Detection is possible, and the accuracy of ground fault detection can be improved.

  In the above-mentioned embodiment, the application to the transmission tower having no overhead ground wire was described. However, this does not exclude the application to the transmission tower having the overhead ground wire, and is applicable to the transmission tower having the overhead ground wire. can do. When applied to transmission towers with overhead ground wires, fault currents due to ground faults flow more into overhead ground wires with lower resistance than the ground, so the fault current at the time of ground faults can be detected effectively. From this point of view, it is desirable that the first and second current transformers 11 and 12 are provided on the legs of the transmission tower above the braces that support the transmission lines. Other configurations are as described above.

  The present invention can be used as a detection device that reliably detects only a ground fault without detecting a short-circuit failure even in a transmission tower having no overhead ground wire, and for a transmission tower having an overhead ground wire. However, it can be used as a detection device that reliably detects only ground faults.

FIG. 1 is a diagram showing an example of an embodiment of the present invention. FIG. 2 is a diagram showing a fault current at the time of a ground fault and an induced current at the time of a short-circuit fault. FIG. 3 is a diagram showing a mounting portion of the ground fault detection device in FIG. FIG. 4 is a circuit diagram showing an example of the detection unit 13 in FIG. FIG. 5 is a waveform diagram of the synthesis unit in the case of a ground fault. FIG. 6 is a waveform diagram of the synthesis unit in the case of a short circuit failure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission tower 2,3,4,5 Leg 6 Arm 7 Transmission line 10 Ground fault detection apparatus 11 1st current transformer 12 2nd current transformer 13 Detection part 20 Amplitude limiting circuit 21 Rectification circuit 22 Charging circuit 23 Detection circuit

Claims (5)

Two of the four legs of the transmission tower below the lower arm that supports the transmission line of the transmission tower that does not have an overhead ground line, the induced current caused by a short-circuit fault is reversed. induction flowing flow, fault current due to the ground fault is provided on one leg of said two legs of the power transmission pylons flow in the same direction towards the ground, the one leg in the case of the short-circuit failure A first current transformer for detecting an electric current, detecting a fault current flowing through the one leg toward the ground in the case of the ground fault, and providing an AC voltage output;
Provided on the other leg of the two legs of the power transmission tower, in the case of a short circuit failure, an induced current flowing in the opposite direction to the one leg flowing through the other leg is detected, and the ground fault A second current transformer for detecting a fault current flowing in the same direction as the one leg flowing in the other leg toward the ground and providing an AC voltage output;
A detecting unit that includes a combining unit that combines the AC voltage output of the first current transformer and the AC voltage output of the second current transformer, and that detects only a ground fault based on the combined output of the combining unit; A ground fault detection device comprising: The first and second current transformers provide an AC voltage output having the same phase in the case of the ground fault to the detecting means, and an AC voltage output having the opposite phase in the case of the short circuit fault is detected. Provided to the one leg and the other leg of the two legs of the power transmission tower to give to the means,
The combining unit of the detecting means is
An amplitude limiting circuit configured by series connection of two bidirectional Zener diodes, wherein the two bidirectional Zener diodes connected in series are configured such that the fault current is in the same direction and the induced currents are in opposite directions. A portion between the first current transformer and the second current transformer connected in series is inserted in parallel to the series connection of the first and second current transformers connected in series. The amplitude limiting circuit connected between one of the two bidirectional Zener diodes connected in series and the other to provide the combined output;
A rectifier circuit that full-wave rectifies the combined output from the amplitude limiting circuit via a protective resistor that prevents inflow of a current exceeding the rated current;
In the case of the ground fault, a large combined output that is full-wave rectified based on the AC voltage output in the same phase is generated, and in the case of the short-circuit fault, the ground fault is generated based on the AC voltage outputs that are opposite in phase to each other. The ground fault detection device according to claim 1, wherein the ground fault detection device is configured to provide a full-wave rectified composite output far smaller than the composite output in the case of a failure . The detection means further includes
A charging circuit charged by a combined output rectified by full wave of the combining unit;
When the charging voltage of the charging circuit cannot reach the charging voltage in the case of a short-circuit failure and exceeds a threshold value set so as to be always reached in the charging voltage in the case of a ground fault, The ground fault detection device according to claim 2 , further comprising a detection circuit that provides a detection output indicating detection of a failure . 4. The ground fault detection device according to claim 3 , wherein the detection means operates using the AC voltage output of the first and second current transformers as an operation power source . A surface in which the one leg provided with the first current transformer and the other leg provided with the second current transformer are substantially parallel to a transmission line supported by a brace of the power transmission tower. ground fault sensing device according to claim 2, characterized in that the two legs that form.

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