JP2000102158A - Earth leakage circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform break operation in a specified time in response to the magnitude of an earth leakage current, and at the same time to prevent unnecessary operation in a grounding current due to a lightning surge. SOLUTION: In an earth leakage circuit, output with a specific value or large of an amplification circuit 6 for amplifying the output of a zero-phase current transformer 3 is changed into pulse by a first comparator 7, a capacitor 8b of an integration circuit 8 is charged for the amount of time of the pulse width, and a break signal γis outputted for operating a tripping coil 11 when the charge voltage exceeds a threshold of a second comparator. In this case, by a current mirror current generation circuit 13 being inserted into the feedback circuit of the amplification circuit 6, the capacitor 8b is discharged by current with the same value as that of a feedback current being proportional to the current flowing in a ZCT 3. When an earth leakage current flows, break operation is made at a specific time. On the other hand, when a grounding current due to a lightning surge flows, the charge voltage of the capacitor 8b does not exceed the threshold of the second comparator 9, thus preventing the break operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage circuit breaker, and more particularly to an earth leakage circuit breaker capable of avoiding unnecessary interruption due to a lightning surge.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional earth leakage breaker.
FIG. 5 shows a time chart thereof. 4 and 5, when a leakage current or a ground fault current due to a lightning surge flows through the main conductor 2 of the earth leakage breaker 1, a zero-phase current transformer (hereinafter referred to as ZCT) 3 through which the main conductor 2 penetrates. A secondary current is generated in the secondary winding, and this secondary current is converted into a voltage by the resistor 4. This voltage is amplified by the amplifier 6 after the impulse noise and the secondary high-frequency leakage current of the inverter are absorbed by the low-pulse filter 5, and the output is amplified by the threshold of the first comparator 7. The pulse is divided into negative electrodes and is synthesized by an OR circuit (OR1). Furthermore, O
The output of the first comparator 7 from R1 is integrated by the integrating circuit 8, and when the value exceeds the threshold value of the second comparator 9, the leakage signal from the cutoff signal output circuit 10 is output based on the output signal α. A trip signal γ is output to the trip coil 11 of the circuit breaker 1, and the earth leakage breaker 1 is opened.

[0003]

The cut-off time of the earth leakage circuit breaker is specified by the cut-off rule of the IEC standard. The rated sensitivity current is within 300 ms, the rated sensitivity current is twice within 150 ms, and the rated sensitivity current is 40 times in 5 times.
Although there is a condition of ms, the conventional earth leakage breaker is designed to shut off within 40 ms regardless of the earth leakage current in order to keep the shortest interruption time of the standard, and therefore, it is as follows. That is, the mechanical operation time of the earth leakage circuit breaker is usually about 23 ms at the maximum, and in that case, the judgment time until the interruption signal is sent to the trip coil is 40−23 = 17 ms.
Now, assuming that the time when the output of the amplifier 6 exceeds the threshold value of the first comparator 7 shown in FIG. 4, that is, the pulse width of the output of the first comparator 7 is, for example, 7 ms and the interval between pulses is 3 ms, The sum of the pulse widths required to output the cutoff signal γ within 17 ms, that is, the setting of the integration time of the integration circuit 8 is 17-3 =
14 ms.

On the other hand, in the case of a ground fault current due to a lightning surge that the user does not want to cut off, if the time exceeding the threshold of the first comparator 7 is, for example, 5 ms for the positive electrode and 25 ms for the negative electrode, the total
30 ms, which exceeds the above 14 ms. Therefore, if the interval between pulses is 2 ms, a cutoff signal γ is issued in 16 ms, and unnecessary cutoff occurs. An object of the present invention is to prevent unnecessary interruption due to such a lightning surge.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a zero-phase current transformer through which a main conductor passes, an amplifying circuit for amplifying an output of the zero-phase current transformer, and an amplifying circuit. A first comparator for detecting an output of a predetermined value or more of the circuit, an integrating circuit for integrating the output of the first comparator, and a second comparator for detecting an output of a predetermined value or more of the integrating circuit; A shutoff signal output circuit that outputs a shutoff signal to a tripping coil based on an output of the second comparator, wherein the capacitor of the integration circuit is connected to a current flowing through the zero-phase current transformer. The battery is charged with a proportional current. As a result, the rated sensitivity current is 30
Within 0 ms, within 150 ms at twice the rated sensitivity current, same as 5
If the capacity (time constant) of the integration circuit is set so as to be 40 ms in double, unnecessary interruption does not occur when a ground fault current flows due to a lightning surge.

In order to charge the capacitor of the integrating circuit with a current proportional to the current flowing through the zero-phase current transformer, the capacitor of the integrating circuit is charged with a current equal to the current flowing through the feedback loop of the amplifier circuit. Is good.

[0007]

FIG. 1 is a block diagram of an earth leakage breaker showing an embodiment of the present invention, and FIG. 2 is a time chart thereof. Note that the same reference numerals are used for the portions corresponding to the conventional example. 1 and 2, when a leakage current of the rated sensitivity current flows through the main conductor 2 penetrating the ZCT 3, a secondary current is generated in the secondary winding of the ZCT 3, and this current is converted into a voltage by the resistor 4. . This voltage is input to a low-pass filter 5 for absorbing impulsive noise and a high-frequency leakage current on the secondary side of the inverter, and its output is full-wave rectified by a full-wave rectifier circuit 12 and then amplified by an amplifier circuit 6. You.

The amplified output of the amplifier circuit 6 is pulsed by a first comparator 7 in which a threshold value for pulsing when a leakage current having a rated sensitivity current flows is set. The analog switch 8a of the integration circuit 8 is turned on,
The current mirror current generating circuit 13 inserted in the feedback circuit of the amplifier circuit 6 charges the capacitor 8b of the integration circuit 8 with a current having the same value as the feedback current proportional to the current flowing through the ZCT 3. Here, the capacity of the capacitor 8b is set so that the charging voltage exceeds the threshold value of the second comparator 9 within 277 ms, which is obtained by subtracting the mechanical operation time of 23 ms from the IEC standard of 300 ms. The shutoff signal γ is tripped from the shutoff signal output circuit 10 and output to the coil 11 within 277 ms by the output of the comparator 9.

When a leakage current of five times the rated sensitivity current flows through main conductor 2 penetrating ZCT 3, capacitor 8b of integrating circuit 8 is charged by the same operation as described above.
Here, the charging time constant of the integration circuit 8 is set so that the charging voltage exceeds the threshold value of the second comparator 9 within 17 ms, and the cutoff signal γ is output within 17 ms by the output of the second comparator 9.
Is output.

That is, the capacitor 8b of the integrating circuit 8
If leakage current of rated sensitivity current flows, for example,
It shuts off in about 220 ms (adjusted between 300 and 150 ms because it is specified within 150 ms with twice the rated sensitivity current), and shuts off within 40 ms when a leakage current of 5 times the rated sensitivity current flows. On the other hand, when a ground fault current due to a lightning surge flows through the main conductor 2 penetrating through the ZCT 3, the capacitor 8 b of the integrating circuit 8 is charged in the same manner as described above. It does not reach the threshold and does not shut off.

FIG. 3 is a block diagram of an earth leakage breaker showing another embodiment of the present invention. In FIG. 3, FIG.
The present embodiment is different from the first embodiment in that a current detector 14 for detecting a secondary current of ZCT 3 is provided, and a current mirror current generating circuit 13 detects the ZCT 3 based on the output of the current detector 14.
3 is that the capacitor 8b of the integration circuit 8 is charged with a current proportional to the secondary current. Other configurations and operations are shown in FIG.
The embodiment is the same as that of the first embodiment, and the time chart is also common to FIG.

When a leakage current of the rated sensitivity current flows through the main conductor 2 penetrating the ZCT 3, a secondary current is generated in the secondary winding of the ZCT 3, and this current is detected by the current detector 14 while the amount of the current is detected. , And is converted into a voltage by the resistor 4. This voltage is input to the low-pass filter 5, further subjected to full-wave rectification by the full-wave rectifier circuit 12, and then amplified by the amplifier circuit 6. The amplified output of the amplifier circuit 6 has a first threshold value which is set to a threshold value for pulsing when a leakage current of the rated sensitivity current flows.
And the analog switch 8a is turned on for the time corresponding to the pulse width.

As a result, the current mirror current generating circuit 13 connected to the current detector charges the capacitor 8b of the integrating circuit 8 with a current proportional to the current flowing through the ZCT 3. The capacity of the capacitor 8b is IEC standard 3
The charging voltage is set so as to exceed the threshold value of the second comparator 9 within 277 ms obtained by subtracting the mechanical operation time of 23 ms from 00 ms.
Within this time, the cutoff signal γ is output from the cutoff signal output circuit 10 to the tripping coil 11.

When a leakage current of five times the rated sensitivity current flows through the main conductor 2 penetrating the ZCT 3, the capacitor 8b of the integrating circuit 8 is charged by the same operation as described above. The charging voltage is set so as to exceed the threshold value of the second comparator 9 within 17 ms, and the cutoff signal γ is output within 17 ms by the output signal from the second comparator 9.

That is, the capacitor 8b of the integrating circuit 8
Is about 220 ms when leakage current of rated sensitivity current flows (because it is twice as large as rated sensitivity current and within 150 ms, 3
(Adjusted between 00 and 150 ms). If a leakage current of 5 times the rated sensitivity current flows, it will be shut off within 40 ms. On the other hand, when a ground fault current due to a lightning surge flows through the main conductor 2 penetrating the ZCT 3, the capacitor 8 b of the integrating circuit 8 is charged in the same manner as described above. It does not reach the threshold and does not shut off.

[0016]

As described above, according to the present invention, when a leakage current flows, the rated sensitivity current specified by the IEC is 300 ms.
Within 150ms at twice the rated sensitivity current and within 40ms at five times the rated sensitivity current. If a ground fault current due to a lightning surge flows, it will not be interrupted.

[Brief description of the drawings]

FIG. 1 is a block diagram of an earth leakage breaker showing an embodiment of the present invention.

FIG. 2 is a time chart showing the operation of the earth leakage breaker of FIG.

FIG. 3 is a block diagram of an earth leakage breaker showing another embodiment of the present invention.

FIG. 4 is a block diagram of a leakage breaker showing a conventional example.

FIG. 5 is a time chart showing an operation of the earth leakage breaker of FIG. 4;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 earth leakage breaker 2 main conductor 3 zero-phase current transformer 4 resistor 5 low-pass filter 6 amplifier circuit 7 first comparator 8 integration circuit 9 second comparator 10 cut-off signal output circuit 11 trip coil 12 full-wave rectifier circuit 13 Current mirror current generation circuit 14 Current detector γ cutoff signal

Claims (2)

[Claims] 1. A zero-phase current transformer through which a main conductor passes, an amplifier circuit for amplifying an output of the zero-phase current transformer, and a first comparator for detecting an output of a predetermined value or more of the amplifier circuit. An integrating circuit for integrating the output of the first comparator, a second comparator for detecting an output equal to or greater than a predetermined value of the integrating circuit, and a trip coil based on the output of the second comparator. An earth leakage circuit breaker having an interruption signal output circuit for outputting an interruption signal, wherein the capacitor of the integration circuit is charged with a current proportional to a current flowing through the zero-phase current transformer. vessel. 2. The earth leakage breaker according to claim 1, wherein a capacitor of the integration circuit is charged with a current equal to a current flowing in a feedback loop of the amplification circuit.