JP2000156929A - Ground direction relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take measures without replacing ground direction relay, by switching a function for operation without zero-phase voltage in conjunction with the sensitivity setting of a sensitivity setting circuit, and a function for operating after generation of the prescribed zero-phase voltage. SOLUTION: A performance-switching means 10 is composed of a rotary switch 37 and a rotary switch 11, which are operated in conjunction with each other. When performance is set to high sensitivity range, the contactor of the rotary switch 11 is in contact with contact (a) or (b) when the performance is set to the low sensitivity, a contactor is in contact with the desired contact (n-1) or (n), the contact (a) or (b) is connected to an OR circuit and the contacts (n-1), (n) become idle contacts. Therefore, when the voltage of the zero-phase voltage element 30 is set at a prescribed high sensitivity, operation is possible only with the zero-phase current without generation of the zero-phase voltage, when a voltage is set to the prescribed low sensitivity, operation is possible with the preset voltage of the zero-phase voltage element after generation of the zero-phase voltage. As a result, it is no longer required to replace the ground direction relay.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault directional relay, and more particularly to a non-grounded three-phase three-wire type distribution line or the like, in which a ground fault current at the time of a one-line complete ground fault is large and a zero-phase voltage is generated. The present invention relates to an improvement of a ground fault directional relay suitable for detecting a ground fault in a difficult distribution system.

[0002]

2. Description of the Related Art A ground fault directional relay detects a zero-sequence voltage and a zero-sequence current generated at the time of a ground fault, and when both detection signals exceed a set level, the phase of the signal of these voltage and current components is detected. This is a relay that performs comparison and determines the direction of the power supply side or the load side with respect to the zero-phase current transformer as a boundary, and performs a protection operation in the event of a ground fault on the load side.

[0003] A normal earth fault relay operates only when both the zero-phase current and the zero-phase voltage are equal to or higher than a set level. However, a non-grounded three-phase three-wire system is used. In a power distribution system in which a ground fault current is large when a wire is completely grounded, a zero-phase voltage is hardly generated, and high resistance cannot be detected. That is, even though a ground fault has occurred, the zero-phase voltage does not reach the set level, so that the ground fault directional relay does not operate.

As described above, in a distribution system in which a ground fault current at the time of a one-line complete ground fault is large, it is meaningless to increase the ground fault current sensitivity, and a ground fault directional relay of a power company operates first and is unnecessary. This will cause a power outage accident.

Accordingly, the applicant of the present application has proposed a ground fault directional relay having a function of reliably operating even when the generation of a zero-sequence voltage is small in a ground fault in a distribution system having a large ground fault current at the time of a one-line complete ground fault. (Japanese Patent No. 2554217).

An outline of a ground fault directional relay (hereinafter, referred to as a prior application) according to this proposal will be described with reference to FIG. In FIG. 3, reference numeral 20 denotes a zero-phase current element, which is a filter 21 for extracting a fundamental wave component of the zero-phase current Io detected by a zero-phase current transformer (not shown), and an output of the filter 21 for an amplifier 2.
2, a level detection circuit 23 for outputting an output signal when the output level exceeds a set level, a waveform shaping circuit 24 for shaping the output of the filter 21 into a rectangular wave, and an output of the waveform shaping circuit 24 and the level detection circuit 23. An AND circuit 25 outputs a signal corresponding to the zero-phase current when the output AND condition is satisfied.

Reference numeral 30 denotes a zero-phase voltage element, which is a filter 31 for extracting a fundamental wave component of the zero-phase voltage Vo detected by a zero-phase voltage detector (not shown), an amplifier 32 for amplifying the same, and an amplifier 32 for the amplifier. A level detection circuit 33 for outputting an output signal when the output exceeds a set level, and a waveform shaping circuit 3 for shaping the output of the filter 31 into a rectangular wave or a pulse.
4. An AND circuit 35 which takes the AND condition of the waveform shaping 34 and the output signal of the level detection circuit 33 and outputs a signal corresponding to the zero-phase voltage when the AND condition is satisfied.

Reference numeral 40 denotes a phase discriminating circuit, which inputs signals for the zero-phase current and the zero-phase voltage, compares the phases of the two signals, and detects a ground fault at the power supply side or the load side of the zero-phase current transformer. The output is sent to the time limit circuit 50 when it is on the load side. When this output is input, the timing circuit 50 closes the contact of the output relay X after a lapse of a predetermined time and performs a predetermined protection operation such as shutting off the circuit breaker.

Reference numeral 60 denotes a zero-phase current operation circuit. The zero-phase current operation circuit 60 includes an AND circuit 61. One input of the AND circuit 61 receives the output of the level detection circuit 23 on the zero-phase current element side. It is input to the other input side from the level detection circuit 33 on the zero-phase voltage element side via the inverter circuit 62. The output signal of the AND circuit 61 is input to the timed circuit 50 directly or via the OR circuit OR. The inverter circuit 62 includes a level detection circuit 3 on the zero-phase voltage element side.
When the output signal of the level detector 3 is 0, that is, when the zero-phase voltage is lower than the set level, the output signal is output to the AND circuit 61.
Stop output to.

With this configuration, even when the detected value on the zero-phase voltage element 30 side is equal to or less than the operation set value (sensitivity value), if the detected value on the zero-phase current element 20 side is equal to or greater than the operation set value, Under these two conditions, the AND circuit 61 outputs a ground fault detection signal, and operates the output relay X after a predetermined time period elapses via the time circuit 50.

When the detected value on the side of the zero-phase voltage element 30 exceeds the operation set value, the zero-phase current operation circuit 60 is locked so as not to output an output signal. Therefore, the original operation of the ground fault directional relay is not hindered.

[0012]

The above-described ground fault directional relay is a distribution system having a large ground fault current at the time of a one-line complete ground fault, and can perform high resistance detection even when a zero-phase voltage is unlikely to be generated, and operate reliably. It has a beneficial effect of achieving full protection coordination with electric power companies and has been put to practical use.

However, this ground fault directional relay was installed at the time of the first construction of a distribution substation or substation to protect a distribution system in which a ground fault current at the time of a one-line complete ground fault is large and a zero-phase voltage is hardly generated. Later, if the protection conditions change due to a change or expansion of distribution / substation equipment, unnecessary operation may occur.

That is, operating only with the zero-phase current before the generation of the zero-phase voltage becomes a non-directional ground fault relay during that time, and may operate even if a ground fault occurs on the power supply side or another line.

This phenomenon will be described with reference to FIG. 4. The zero-phase current flowing in the zero-phase current transformer ZCT at the time of a ground fault on the power supply side or another line is reversed through the ground capacitance on the load side as shown in FIG. And the zero-phase current value is determined by the magnitude of the ground capacitance on the load side.

That is, assuming that a ground fault occurs on the power supply side of the zero-phase current transformer ZCT, the ground capacitance CL on the load side is assumed.
When the current flowing to the Ig _L, flowing the current Ig _L penetrates the zero-phase current transformer ZCT.

[0017] Now, taking an example Nonreferenced 6KV distribution line, the current Ig _L flowing through CL when fully ground fault occurs in the power supply side and 4A, the power supply-side zero-phase voltage of 5% earth fault When this occurs, a current of 0.2 A flows experimentally through CL.

Therefore, the sensitivity setting of the earth fault directional relay is set to Io.
= 0.2A, Vo = 5%, Vo =
In order to prevent unnecessary operation (operation in a ground fault outside the self-protection range) for a ground fault of 5% or less, the current Lg _L flowing through the load-side ground capacitance CL is 4 A. Must be: Range of CL at this time depends on the thickness and the length L of the cable, the cable 1 of computationally 38mm ²
In the case of 0.33 μF / km, the length L is L <3.3 km, and unnecessary operation does not occur when the cable length is about 1 km as in a private substation.

However, after the installation, if the thickness or length of the facility cable changes due to a change or extension of the facility, or if the load capacity increases and the ground capacitance increases, unnecessary operation may occur. Comes out.

In addition, a voltage regulator may be installed in a distribution line due to a change or extension of equipment, and an imbalance may occur in the electric circuit, resulting in a residual voltage (apparent zero-sequence voltage) due to the imbalance. In such a case, if the set value of the zero-sequence voltage element is set in a high sensitivity range (for example, 2.5% or 5%), the possibility of performing unnecessary operation increases.
10% or 15%).

If the sensitivity is set to be low, accurate and accurate protection operation cannot be expected.

Therefore, since it is impossible to cope with such a change in the protection condition after the construction, it is necessary to replace the ground fault direction relay installed first with a ground fault direction relay which meets the protection condition.

An object of the present invention is to provide a ground fault directional relay having a function capable of coping with such a case.

[0024]

In the present invention, a means for solving the above-mentioned problem is to provide a zero-phase current signal having a waveform-shaped zero-phase current signal when the zero-phase current reaches a level set by a level detection circuit. A current element, a zero-phase voltage element for outputting a waveform-shaped zero-phase voltage signal when the zero-phase voltage reaches a set level of the level detection circuit, and a phase by inputting the zero-phase current signal and the zero-phase voltage signal. A phase discrimination circuit that outputs a ground fault detection signal when the ground fault is on the load side, an output signal of the zero-phase current element-side level detection circuit, and an output signal of the zero-phase voltage element level detection circuit. Even if the zero-phase voltage is equal to or less than a set value, a ground fault detection signal is output when the zero-phase current exceeds a set level, and a ground fault detection is performed when the zero-phase voltage reaches the set level. A zero-phase current operation circuit that stops signal output, A performance switching means is provided in an output circuit for outputting a ground fault detection signal of the phase current operation circuit, and switches performance in conjunction with switching of a set value of a sensitivity setting circuit included in the zero-sequence voltage element. And a function that operates in the absence of a zero-sequence voltage in conjunction with sensitivity setting by a sensitivity setting circuit and a function that operates after a predetermined zero-sequence voltage is generated.

With this configuration, in the high sensitivity setting range, the operation is performed only by generating the zero-phase current without waiting for the generation of the zero-phase voltage, and in the low sensitivity setting range, the predetermined zero-phase voltage is generated. Waiting for operation and coordination with the power company's ground fault directional relay.

In another embodiment, the performance switching means comprises an on / off switch, and the on / off operation of the on / off switch depends on the nature of the load, so that the operation is performed after the zero-phase voltage is generated. Function that operates only with zero-phase current without waiting for the generation of zero-sequence voltage. Can be handled without replacing the relay.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a first embodiment of the present invention, which has many points in common with the conventional example of FIG. 3, and therefore, portions having the same names or the same functions as those in FIG. The same reference numerals are given and the detailed description is omitted.

Reference numeral 36 denotes a sensitivity setting circuit provided in the zero-phase voltage element 30, for example, the rotary switch 3
7, which is provided on the output side of the filter 31 and sets the sensitivity of the zero-phase voltage element 30.

Numeral 10 denotes a performance switching means, which comprises a rotary switch 11 similar to the rotary switch 37, and these rotary switches 37 and 11 are linked with each other. The rotary switch 37 of the sensitivity setting circuit 36 calculates the zero-phase voltage percentage% (generated zero-phase voltage / voltage at complete ground fault × 10
0%), for example, 2.5%, 5.0%, 7.5%, 10%
% And 15%.

The performance of the rotary switch 11 of the performance switching means 10 is switched in conjunction therewith. The switching of the performance is performed by, for example, 2.5% or 5.
When the high sensitivity range of 0% is set, the rotary switch 11
Contact the contacts a or b, and 10% or 1
When a low sensitivity range such as 5% is set, the contact is made to contact any of the contacts n-1 or n. The contacts a or b are connected to an OR circuit, and the contacts n−1 and n are vacant contacts that are not connected anywhere.

Therefore, when the voltage setting of the zero-phase voltage element 30 is set to a predetermined high sensitivity range, the operation is performed only with the zero-phase current without waiting for generation of the zero-phase voltage, and the predetermined low sensitivity setting range is set. In this case, the operation waits for generation of the zero-phase voltage, that is, when the voltage reaches the set voltage of the zero-phase voltage element.

FIG. 2 is a circuit diagram of a second embodiment of the present invention. The performance switching means 10 of the first embodiment does not comprise a rotary switch, but is simply opened and closed by an on / off operation. Performance switching means 1 composed of switch 10S
0 '.

When the open / close switch 10S is turned on, the zero-phase current operation circuit 60 functions to provide a ground fault directional relay which operates only with the zero-phase current without waiting for generation of the zero-phase voltage. This is a ground fault directional relay that operates after the occurrence of the fault.

It should be noted that E in the figure is a ground, and the signal is always low when the open / close switch 10 'is off regardless of the logic element of the OR circuit to prevent malfunction.

Since the present invention is configured as described above,
If a ground fault directional relay according to the present invention is installed at the time of construction of a substation or a distribution substation, the protection conditions at the time of construction, for example, the ground fault current when the distribution system is a complete one-ground fault, a zero-phase voltage is generated. If it is easy, the sensitivity setting circuit 36 in FIG.
By setting the sensitivity setting to a low sensitivity range and turning off the open / close switch in FIG. 2, the output circuit of the zero-phase current operation circuit 60 is turned off, and the zero-phase current element 20 and the zero-phase voltage element 30 are turned off. The protection operation is performed by the set value and the phase determination by the phase determination circuit 40.

Later, when the protection conditions change due to the change or extension of the equipment at the substation or distribution station, for example, when the distribution system becomes large in the case of a large ground fault current at the time of a complete ground fault in one line and it is difficult to generate a zero-phase voltage. 1, the setting value of the sensitivity setting circuit 36 is set in a high sensitivity range, and in FIG.
Turn S on. By this operation, the zero-phase current operation circuit 60
Is connected to an OR circuit, and operates even when the zero-phase current is equal to or greater than the set value, even if the zero-phase voltage is equal to or less than the set value.

Therefore, no matter how the protection conditions of the system change after the installation, it is possible to respond by operating only the rotary switch or the open / close switch, and it is not necessary to replace the earth fault directional relay.

In particular, the sensitivity setting circuit 36 is provided with a rotary switch for setting the sensitivity.
By rotating the operation unit protruding from the surface plate (display plate) of the ground fault directional relay, the open / close switch in FIG. 2 can also be operated on the surface plate by causing the operation pin to protrude from the surface plate. It can be realized with a very simple configuration.

[0040]

As described above, the present invention is very simple in structure, but has the following significant effects in performance.

That is, in the invention of the prior application, when the value is equal to or less than the set value of the zero-phase voltage element, the relay becomes a non-directional ground-fault relay, and can be applied only to a power distribution system in which the load-side capacitance is equal to or less than a predetermined value.
If the ground capacitance on the load side changes and becomes very large due to the change or addition of facilities at power plants and substations, if the ground fault occurs below the zero-phase voltage set value, it will exceed the zero-phase current set value. There are cases. In such a case, there is a possibility of performing unnecessary operation, and it is necessary to cooperate with a ground fault directional relay of a power company, so it is necessary to replace the general ground fault directional relay, but the ground fault directional relay of the present invention is installed. This eliminates the need for replacement.

If a voltage regulator is provided in the distribution line to cause an imbalance in the electric circuit and a residual voltage (apparent zero-phase voltage) due to the imbalance, a setting of the sensitivity setting circuit is required. If the high sensitivity range is set to about 2.5% or 5%, unnecessary operation may occur. Therefore, it is necessary to set the low sensitivity range to about 10% or less in consideration of the residual voltage. When set in the low sensitivity range, the function becomes a non-directional function up to the set zero-sequence voltage value, so that the original ground fault directional relay having the directional function can provide more reliable protection. In such a case, in the example of FIG. 1, since the function is automatically switched at the time of setting the sensitivity, there is an excellent effect that it is not necessary to replace the ground fault directional relay.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of another embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a conventional ground fault direction relay.

FIG. 4 is an explanatory diagram of a ground fault current.

[Explanation of symbols]

 10, 10 'performance switching means 11 rotary switch 10S on / off switch 20 zero-phase current element 30 zero-phase voltage element 21, 31 filters 22, 32 amplifiers 23, 33 level detection circuits 24, 34 ... waveform shaping circuits 25, 35 ... AND circuit 36 ... sensitivity setting circuit 37 ... rotary switch 40 ... phase discriminating circuit 50 ... timed circuit 60 ... zero-phase current operation circuit 61 ... AND circuit 62 ... inverter circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsuro Taguchi 7-4-14 Ginza, Chuo-ku, Tokyo F-term (reference) 2G033 AA02 AB03 AC02 AD13 AF05 AG12 5G058 EE06 EF03 EG05 EH01

Claims (2)

[Claims] A zero-phase current element for outputting a waveform-shaped zero-phase current signal when the zero-phase current reaches a set level of the level detection circuit; A zero-phase voltage element that outputs a waveform-shaped zero-phase voltage signal, a phase that inputs these zero-phase current signals and a zero-phase voltage signal, compares the phases, and outputs a ground fault detection signal when a ground fault occurs on the load side. A determination circuit, an output signal of the level detection circuit on the zero-phase current element side, and an output signal of the level detection circuit of the zero-phase voltage element are input, and even if the zero-phase voltage is equal to or less than a set value, the zero-phase current A zero-phase current operating circuit that outputs a ground fault detection signal when the voltage exceeds a set level, and stops outputting the ground fault detection signal when the zero-phase voltage reaches the set level; Is provided in an output circuit that outputs a ground fault detection signal of Performance switching means for switching the performance in response to the switching of the set value of the sensitivity setting circuit of the phase voltage element, the performance switching means having a function of operating without a zero-phase voltage in response to the sensitivity setting by the sensitivity setting circuit; A ground fault relay, wherein a function of operating after waiting for generation of a predetermined zero-sequence voltage is switchable. 2. A ground fault directional relay, wherein the performance switching means according to claim 1 is constituted by an on / off switch.