JPH06121449A - Grounding overcurrent relay device - Google Patents

Abstract

PURPOSE:To detect ground faults of a power receiving and distributing system at a high speed by producing an operation output, when both positive-side and negative-side currents are above the level of a set value. CONSTITUTION:A positive-current-value detecting means 14 and a negative- current-value detecting means 15 take in the secondary current of a potential current transformer connected to a power system, and find them by separating positive and negative waveform components respectively. An operation output judging means 19 produces an operation output for a grounding overcurrent relay 20, on condition that both operation outputs of the positive-current-value detecting means 14 and the negative-current-value detecting means 15 are being produced. As the result, it becomes possible to prevent the malfunctioning of the grounding overcurrent relay 20 and the misinterruption of the system circuit- breakers of a power receiving and distributing system caused by this malfunctioning, at the time of a transformer being connected, and it is possible to detect ground faults of the power receiving and distributing system surely and at a high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a ground fault current flowing in a power system when a ground fault occurs in a power receiving and distributing facility having a plurality of power supply facilities which can be operated in parallel and which are composed of a power transmitting facility or a power generating facility. The present invention relates to an operating ground fault overcurrent relay device.

[0002]

2. Description of the Related Art Conventionally, in power receiving and distributing equipment, a ground fault overcurrent relay and a circuit breaker are provided at a cooperative branch point of a power system, and when a ground fault occurs, the branch point breaker is opened to disconnect the ground fault system. Is configured so that the operation of the sound system can be continued.

FIG. 3 is a conventional system configuration diagram in which a ground fault overcurrent relay device is provided in a power receiving and distributing facility which is supplied with power from a power generating facility. In the figure, 1 is a power supply facility, 2 is a power receiving / distributing facility, and 3 and 5 are circuit breakers for cooperative branching, which are connected to or disconnected from the power supply facility 1. Electric power from the power supply facility 1 is supplied to the load B through the load A and the transformer 6 through the cooperative branching breakers 3 and 5. 8 is a ground fault overcurrent relay device installed at the grid connection separation point of the power distribution equipment,
The zero-phase current I _o taken out by the neutral phase (residual circuit) of the secondary three-phase three-wire circuit of the current transformer 4 is input. Therefore, when a ground fault occurs in the power path of the transformer 6 from the system isolation breaker 3, the ground fault current I _o flowing to the ground fault via the neutral point ground resistance 7 of the power supply equipment 1 is changed. It is detected by the ground fault overcurrent relay device 8 and the operation output thereof cuts off the cooperative branch breaker 3.

FIG. 4 is a block diagram of a conventional ground fault overcurrent relay device. As shown in the figure, when a ground fault occurs on the primary side of the transformer 6, the ground fault current I flowing to the ground fault point I
_o is input via the current transformer 4 provided at the cooperation branch point. Ground fault current I input to the overcurrent relay device 8
_{The o} is digitally converted via the analog / digital conversion element 9, sampled at regular intervals, and sent to the current value detection element 10. In the current value detection element 10,
Ground fault current (zero phase current) I calculated by sampling data
_Find the actual value of _o . The detection value data obtained by the current value detection element 10 is sent to the operation determination element 11, and the operation determination element 11 makes a comparison determination with the operation current value I _set from the preset operation setting value storage device 12. Is executed, and when I _o ≧ I _set , an operation signal for operating the ground fault overcurrent relay device is output.

[0005]

By the way, in the conventional ground fault overcurrent relay device 8, when the cooperative branch breaker 5 of FIG. 3 is turned on and the power of the power supply equipment 1 is applied to the transformer 6, An exciting inrush current due to the saturation of the iron core flows through the container 6. The phase of the exciting inrush current is saturated, the magnitude of the exciting inrush current value, the content rate of the direct current component, and the like.
It is clear from many actual measurement data as a real phenomenon that the current value balance of the three phases is largely biased, since most of the current flows in one phase, though it is not constant and contains a large amount of direct current, although it is not constant. .

As described above, when a large amount of direct current is contained and the current value balance of the three phases is largely biased to one of the three phases and flows to each phase of the current transformer 4 at the cooperation branch point, the three phases are separated. Since the excitation characteristics of the current transformer 4 change under the influence of the direct current component, the residual current obtained by synthesizing each phase of the current transformer 4 causes a combined current due to the characteristic error of each phase of the current transformer 4 ( An apparent zero-phase current I _o ) is generated, and the ground current overcurrent relay 8 operates by this combined current value, trips the cooperative branch circuit breaker 3, and stops the power supply to the load A. May occur.

Next, the operation of the ground fault overcurrent relay device 8 due to the magnetizing inrush current when the transformer is turned on will be described with reference to FIG.
Excitation inrush current I ₁ of the transformer 6 flowing in each of the three phases,
I ₂ and I ₃ have waveforms as shown in FIGS. 5A to 5C and include a large DC component, and the influence of this DC component causes a change in the excitation characteristics of each current transformer 4. As shown in FIG. 5D, the combined current on the secondary side of the current transformer 4 that is input to the ground fault overcurrent relay 8 flows as a current I _o having a high DC content rate. This combined current I _o is positive (I _o
^When either the value of ⁺ ) or the value of negative (I _o ⁻ ) exceeds the operation set value I _SET of the ground fault overcurrent relay device 8, an operation signal is output. The magnitude of the exciting inrush current of the transformer 6 is
Generally, it may reach about 8 times the rated current of the steady transformer. Since the detected value of the ground fault overcurrent in the resistance grounded power system is set to a value much smaller than the rated current of the steady transformer, the probability that the ground fault overcurrent relay 8 malfunctions due to the transformer inrush current is low. Extremely high.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a ground fault overcurrent relay device capable of detecting at a high speed without causing a malfunction due to an exciting inrush current when a transformer is turned on. is there.

[0009]

In order to achieve the above object, the present invention provides a ground fault overcurrent relay device for detecting a ground fault current flowing in a power system of a power supply facility or a power receiving and distributing facility. Positive current value detecting means and negative current value detecting means for obtaining a secondary current of the connected current transformer as an input current and separating the positive waveform component and the negative waveform component of the input current respectively, and the positive current value detecting means. It is characterized by comprising an operation output judging means for sending out an operation output of the ground fault overcurrent relay device on condition that the operation outputs of the current value detecting means and the negative current value detecting means are both established. .

[0010]

According to the present invention, since the exciting inrush current of the transformer contains a large amount of DC component, the waveform is deviated to the positive side or the negative side, and both the positive side current and the negative side current are detected. Since the operation output is performed when the level is above the set value level, it is possible to prevent malfunction due to the magnetizing inrush current of the transformer, and it is possible to detect the ground fault that should be detected at high speed.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a ground fault overcurrent relay device 20 according to an embodiment of the present invention.
4 is a block diagram of the configuration of FIG. 3, which is applied instead of the ground fault overcurrent relay device 8 in the power system shown in FIG. 3.

The ground fault overcurrent relay device 20 of this embodiment is connected to the three-phase combined residual circuit of the current transformer 4 provided at the power system cooperation branch point of the power receiving and distributing equipment 2 of FIG. The input current I _o from the device 4 is digitally converted through the analog / digital conversion element 13 of the ground fault overcurrent relay device 20 as shown in FIG. 1, and the positive waveform component current detection element 14 and the negative waveform component current detection are performed. The data is sampled and sent to the element 15 at regular intervals.

In the positive waveform component current detection element 14 and the negative waveform component current detection element 15, sampling data are calculated to obtain respective effective current values I _o ⁺ and I _o ⁻ . The positive waveform current effective value I _o ⁺ and the negative waveform current effective value I _o ⁻ are sent to the positive waveform component current operation determination element 16 and the negative waveform component current operation determination element 17, respectively, so that the positive waveform component and the negative waveform component are obtained. Both of the current operation determination elements 16 and 17 perform a comparison determination with the operation current I _SET from the operation setting value storage device 18 which is set in advance. The positive waveform component current operation determination element 16 sends an operation signal to the output determination element 19 when I _o ⁺ ≧ I _SET . Similarly, the negative waveform component current operation determination element 17 sends an operation signal to the output determination element 18 when | I _o ⁻ | ≧ I _SET .

In the output judging element 18, when both the operation outputs of the positive waveform component current operation judging element 16 and the negative waveform component current operation judging element 17 are both established, the operation signal as the ground fault overcurrent relay device 20 concerned. Is output.

According to this structure, the exciting inrush current component generated when the transformer is turned on is positive side (I ⁺ ) or negative side (I ⁺ ).
^- ) Is greatly biased to one side, so the change in the excitation characteristics due to the DC bias of the current transformer with respect to the inrush current when the transformer is turned on, and the fact that the secondary phase currents of the transformer are combined apparently positive waveform component I _o of the zero-phase current I _o which is generated residual circuit ^+, a negative waveform components I _o ^- and the positive waveform component of zero-phase current I _o apparent that occur residual circuit I _o ^+, the negative waveform components I _o ⁻ is greatly biased as shown in FIG. FIG. 2 shows a combined current I _o (apparent zero-phase current) generated in the residual circuit in which the secondary of each phase of the current transformer 4 is combined with the exciting inrush current generated when a voltage is applied to the transformer 6 of FIG. ² is an example showing a current I _o ⁺ of a positive waveform component and a current I _o ⁻ of a negative waveform component of the above.

[0016] Thus, according to this embodiment, the positive waveform component I _o ^+, the negative waveform components I _o ^- since any detectable current becomes less than the set value, the transformer inrush current due to earth fault overcurrent relay device It is possible to block the operation output of
It is possible to prevent accidental interruption of the system breaker of the power distribution system.

[0017]

As described above, according to the present invention, in a power distribution system having a plurality of power supply facilities, a malfunction of a ground fault overcurrent relay at the time of turning on a transformer and a system breaker of the power distribution system due to this malfunction. Accidental interruption can be prevented, and a ground fault in the power distribution system can be detected reliably and at high speed, and the stability of the power supply of the power distribution facility can be improved.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an embodiment of a ground fault overcurrent relay device of the present invention.

FIG. 2 is a waveform diagram showing both positive and negative waveform components of an apparent zero-phase current I _o generated in a transformer secondary residual circuit due to a transformer exciting inrush current in a ground fault overcurrent relay device of the present invention.

FIG. 3 is a system configuration diagram of power distribution equipment to which the ground fault overcurrent relay device of the present invention is applied.

FIG. 4 is a block configuration diagram of a conventional ground fault overcurrent relay device.

5 is a waveform diagram for explaining the operation of the conventional ground fault overcurrent relay device of FIG.

[Explanation of symbols]

1 ... Power supply equipment, 2 ... Power receiving / distributing equipment, 3, 5 ... Coupling branch breaker, 4 ... Current transformer, 6 ... Transformer, 7 ... Neutral ground resistance, 8 ... Ground fault overcurrent relay device, 9 ... analog / digital conversion element, 10 ... current value detection element, 11 ... operation determination element, 12 ... operation set value storage device, 13 ... analog / digital conversion element, 14 ... positive waveform component current detection element, 15
... Negative waveform component current detection element, 16 ... Positive waveform component current operation determination element, 17 ... Negative waveform component current operation determination element, 18 ...
Operation set value storage device, 19 ... Output determination element, 20 ... Ground fault overcurrent relay device.

Claims (1)

[Claims] 1. A ground fault overcurrent relay device for detecting a ground fault current flowing in a power system of a power supply facility or a power receiving and distributing facility, wherein a secondary current of an instrument current transformer connected to the power system is used as an input current. The positive current value detecting means and the negative current value detecting means, which take in and separately obtain the positive waveform component and the negative waveform component of the input current, and the operation outputs of the positive current value detecting means and the negative current value detecting means are both established. A ground fault overcurrent relay device, comprising: an operation output determination means for transmitting the operation output of the ground fault overcurrent relay device on condition that the ground fault overcurrent relay device operates.