JPH06121448A - Grounding overcurrent relay device - Google Patents

Abstract

PURPOSE:To detect at a high speed a grounding accident in a power receiving/ distributing system by constituting a device of a positive current value detecting means, negative current value detecting means, current ratio deciding means and an operating output deciding means. CONSTITUTION:In positive and negative current value detecting means 14, 15, a secondary current of an instrument current transformer, connected to a power system, is fetched as an input data, to obtain positive and negative waveform components of this input current respectively separated. In a current ratio deciding mans 18, ratio of a difference between positive and negative current values is obtained from the respective data of the positive and negative current value detecting means 14, 15. In an operating output deciding means 20, operation is output on condition that both the positive and negative current value detecting means 14, 15 are a preset value or more and further ratio of the positive current value to the negative current value is a preset value or less in the current ratio deciding means 18. In this way, wrong operation is prevented due to an exciting rush current in a transformer, and an earth accident in a power receiving/distributing system can be detected at a high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when a ground fault occurs in a power receiving and distribution facility having a plurality of power supply facilities that can be operated in parallel,
The present invention relates to a ground fault overcurrent relay that operates by detecting a ground fault current flowing in a power system.

[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 and distributing facility, and 3 and 5 are breakers for cooperative branching, which are connected to or disconnected from the power supply facility 1. The breaker for this cooperative branch 3,
Electric power from the power supply equipment 1 is supplied to the load B through the load A and the transformer 6 through the transformer 6. Reference numeral 8 denotes a ground fault overcurrent relay device provided at a system cooperation branch point of the power receiving and distributing equipment, and a zero-phase current I ₀ extracted from a neutral phase (residual circuit) of the secondary three-phase three-wire circuit of the current transformer 4 If a ground fault occurs in the power path of the transformer 6 from the breaker 3 for cooperative branching, the ground fault current I flowing to the ground fault via the neutral point ground resistance 7 of the power supply facility 1 is input. _{When 0} is detected and the operation output is output, the breaker 3 for cooperative branching is cut off.

Now, in FIG. 3, 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
₀ is input to the ground fault overcurrent relay device 8 via the current transformer 4 provided at the cooperation branch point. The ground fault current I ₀ input to the ground fault overcurrent relay 8 is, as shown in FIG.
It is digitally converted by the digital conversion element 9, sampled at regular intervals, and sent to the current value detection element 10. The current value detecting element 10 calculates the effective value of the zero-phase current I ₀ by calculating sampling data.

The detection value data obtained by the current value detecting element 10 is sent to the operation judging element 11, and the operation current value I _set from the operation set value storage device 12 preset by the operation judging element 11 is _set . Is compared and I ₀ ≧
When I _set , an operation signal as the ground fault overcurrent relay device 8 is output.

[0006]

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. This exciting inrush current varies depending on which phase is saturated, the magnitude of the exciting inrush current value, the content ratio of the direct current component, and the like, and includes a large amount of direct current component although it is not constant. A large amount of actual measurement data has revealed that a large amount of current flows in one phase and the current value balance of the three phases is largely biased.

As described above, when a large amount of direct current is included and the current value balance of the three phases is largely biased to one of the three phases and flows into each phase of the current transformer 4 at the cooperative branch point, the influence of the direct current is exerted. Therefore, the excitation characteristics of the current transformer 4 of each phase change, and a combined current (not flowing to the primary side) due to a characteristic error of each phase of the current transformer in the residual circuit in which each phase of the current transformer 4 is combined. An apparent zero-phase current I ₀ ) is generated, and the ground current overcurrent relay 8 operates due to this combined current value, causing the cooperative branch breaker 3 to trip and stopping the power supply to the load A. There is.

Next, the operation of the ground fault overcurrent relay device 8 due to the exciting inrush current when the transformer is turned on will be described with reference to FIG.
As described above, the exciting inrush currents I ₁ , I ₂ , and I ₃ of the transformers flowing in each of the three phases when the transformer 6 is turned on are as shown in FIG.
The waveform shown in (a) contains a large DC component,
Since the excitation characteristics of each current transformer 4 change due to the influence of this DC component, the combined current on the secondary side of the current transformer 4 input to the ground fault overcurrent relay 8 is as shown in FIG. As shown in, a current I ₀ having a high DC content rate flows. Positive current (I ₀ ⁺⁾ or a negative current of the current I ₀ (I ₀ ^-) either one of the values of the operation signal is output to exceed the operation set value I _{The set} of earth fault overcurrent relay device 8 . The magnitude of the exciting inrush current of the transformer 6 may reach about eight times the rated current of the steady transformer in general. 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 transformer rated current, 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.

[0010]

In order to achieve the above-mentioned object, the present invention is a ground fault overcurrent relay device provided in a power system of a power supply facility or a power receiving and distributing facility, and a transformer for an instrument connected to the power system. Positive current value detecting means and negative current value detecting means, which obtains the secondary current of the current transformer as input data and separately obtains the positive waveform component and the negative waveform component of the input current, the positive current value detecting means and the negative current value detecting means. The current ratio determination means for obtaining the ratio of the difference between the positive current value and the negative current value from the respective data of the current value detection means, and both of the positive current value detection means and the negative current value detection means are set values or more, and It is characterized in that the current ratio determining means comprises an operation output determining means for performing an operation output on condition that the ratio of the positive current value and the negative current value is equal to or less than a set value.

[0011]

In the present invention, since the exciting inrush current of the transformer contains a large amount of direct current component, the waveform is largely deviated to the positive side or the negative side, and both the positive side current and the negative side current are detected. The operation output is performed when the ratio of the difference between the positive side current value and the negative side current value is equal to or less than the set value level, but the input current waveform is greatly biased to either the positive side or the negative side. It acts so that the operation output is blocked. Therefore, it is possible to prevent a malfunction due to the inrush current of the transformer, and it is possible to detect the ground fault that should be detected at high speed.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a ground fault overcurrent relay device 21 according to an embodiment of the present invention.
It is a block diagram of this ground fault overcurrent relay device 21
Is installed in, for example, a power system similar to that in FIG. FIG. 2 shows a combined current I ₀ (apparent zero-phase current) generated in a residual circuit in which the secondary side 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 in the present invention. ) Is an example showing the current I ₀ ⁺ of the positive waveform component and the current I ₀ ⁻ of the negative waveform component.

As shown in FIG. 1, the input current I ₀ input through 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. Digitally converted through the digital conversion element 13, a positive waveform component current detection element 14 and a negative waveform component current detection element 15
Is sampled at regular intervals and transmitted.

[0014] Positive waveform component current detection element 14, a negative waveform component current sensing element 15 in each of the current effective value by calculating the sampled data I ₀ ^+, I ₀ ^- a finding. The positive waveform component current effective value I ₀ ⁺ and the negative waveform component current effective value I ₀ ⁻ are
It is sent to the positive waveform component current operation determination element 16, the negative waveform component current operation determination element 17, and the current ratio determination element 18 of the positive waveform component current effective value I ₀ ⁺ and the negative waveform component current effective value I ₀ ⁻ , respectively. The current operation determination elements 16 and 17 for both the positive waveform component and the negative waveform component both _perform comparison determination with the operation current I _set from the preset operation setting value storage element 19. The positive waveform component current operation determination element 16 outputs an operation signal when I ₀ ⁺ ≧ I _set.
Send to. Similarly, the negative waveform component current operation determination element 17
Then, when | I ₀ ⁻ | ≧ I _set , the operation signal is sent to the output determination element 20.

Meanwhile, the current ratio judging element in 18 positive waveform current effective value I ₀ ⁺ and the negative waveform current effective value I ₀ ^- ratio of the difference between ^{_{(| 1- (I 0 + /}} I 0 -) |) of the calculated , The detection ratio and the set value K preset in the operation set value storage element 19 are compared and determined to be less than or equal to the set value K (| 1- (I ₀
⁺ / I ₀ ^-) | outputs an operation signal when ≦ K) determination factor 2
Send to 0.

In the output determination element 20, both the positive waveform component current operation determination element 16 and the negative waveform component current operation determination element 17 are satisfied, and the current ratio determination element 18 is also satisfied. When it is present, the operation signal as the ground fault overcurrent relay device 21 is output.

[0017] With this construction, the magnetizing inrush current component, positive (I ⁺⁾ or negative side that occurs when the transformer is turned ^- relative to one largely inrush current when the transformer is turned so biased in (I) A change in the excitation characteristic due to the DC bias of the current transformer occurs, and a positive waveform component I ₀ ^{+ of} the zero-phase current I ₀ apparently generated in the residual circuit due to the synthesis of the secondary-phase currents of the transformer The negative waveform component I ₀ ⁻ and the positive waveform component I ₀ ⁺ and the negative waveform component I ₀ ^{− of} the apparent zero-phase current I ₀ generated in the residual circuit also largely deviate as shown in the waveform diagram of FIG. Thus, the positive waveform components I ₀ ^+, the negative waveform components I ₀ ^-
One of the detected currents becomes less than the set value, and it becomes possible to prevent the operation output of the ground fault overcurrent relay device due to the transformer inrush current.

[0018]

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 ₀ generated in a transformer secondary residual circuit due to a transformer exciting inrush current according to the present invention.

FIG. 3 is a system configuration diagram of power reception and distribution equipment to which the ground fault overcurrent relay 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 illustrating 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 ... Coupling branch breaker, 4 ... Current transformer, 5 ... Coupling branch breaker, 6 ... Transformer, 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 ... Current ratio determination element, 19 ... Operation set value storage element, 20 ... Output determination element, 21 ... Ground fault overcurrent relay device.

Claims (1)

[Claims] 1. In a ground fault overcurrent relay device provided in a power system of a power supply facility or a power receiving and distributing facility, a secondary current of a current transformer for an instrument connected to the power system is taken as input data, and this input current Positive current value detecting means and negative current value detecting means, which are obtained by separately separating the positive waveform component and the negative waveform component, respectively, and the positive current value and the negative current from the respective data of the positive current value detecting means and the negative current value detecting means. The current ratio determination means for obtaining the ratio of the difference between the values and the positive current value detection means and the negative current value detection means both have a set value or more, and the current ratio determination means determines the ratio of the positive current value and the negative current value. A ground fault overcurrent relay device, comprising: an operation output determination means that outputs an operation on condition that the value is less than or equal to a set value.