JPH1094161A - Earth leakage breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the needless break caused by lightning surge. SOLUTION: This earth leakage breaker discriminates the grounding current by lightning surge or heavy grounding from a leak current with a third comparator 12 larger in threshold than a first comparator 7 which detects a leak current, and also discriminates the lightning surge and the heavy grounding by detecting, with a three-wave counter 14, whether the pulses of three waves or over are outputted from the first comparator 7 or not during the period of the time gate that the single stability multivibrator 13 started by the output of a third comparator 12 makes, and outputs a break signal γ from a break signal output circuit 10 only in the case of leakage and heavy grounding.

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. 26 is a block diagram of a conventional earth leakage breaker, and FIG. 27 is a time chart thereof. 26 and 27, when a leakage current or a ground fault current due to a lightning surge flows through the main circuit conductor 2 of the earth leakage breaker 1, a zero-phase current transformer (hereinafter referred to as ZCT) 3 through which the main circuit conductor 2 passes. , 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). Further, the output of the first comparator 7 from the OR 1 is integrated by the integrating circuit 8 and the value is added to the second comparator 9
Is exceeded, the tripping signal γ is output from the tripping signal output circuit 10 to the tripping coil 11 based on the output α, and the earth leakage breaker 1 is opened.

[0003]

The interruption time of the high-speed earth leakage circuit breaker is specified to be within 40 ms in the IEC standard for protecting the human body. On the other hand, the mechanical operation time of the earth leakage breaker is usually about 23 ms at the maximum, and in that case, the judgment time until sending the cutoff signal 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. 27, 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, the time exceeding the threshold of the first comparator 7 is 25 ms in total, for example, 5 ms for the positive electrode and 20 ms for the negative electrode. When the pulse interval is set to 2 ms, an interruption signal γ is generated in 16 ms, and unnecessary interruption occurs. An object of the present invention is to prevent unnecessary interruption due to such a lightning surge, while ensuring not only normal leakage but also periodic short-circuit leakage (heavy ground fault). Another object of the present invention is to improve the operation characteristics of the earth leakage breaker.

[0005]

According to the present invention, when a lightning surge or a heavy ground fault occurs, a ZCT secondary output that is much larger than that during a normal earth leakage occurs, and the output waveform of the ZCT due to the lightning surge is one-shot. On the other hand, attention is paid to the fact that the output waveform due to a heavy ground fault is continuous and repetitive, and these phenomena are distinguished to avoid unnecessary interruption due to lightning surge. Current transformer, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, an integration circuit for integrating the output of the first comparator, and an output of the integration circuit of a predetermined value or more In the earth leakage breaker provided with a second comparator for detecting a current, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator, the following means are taken. Things.

First, according to the first aspect of the present invention, a third comparator for detecting a ZCT secondary output larger than the first comparator for detecting an earth leakage is provided to detect the occurrence of a lightning surge or a heavy ground fault. In addition, a monostable multivibrator activated by the output is provided, and a gate is created for a certain time. Further, a counter is provided which counts the number of output pulses of the first comparator by a counter during the output period of the monostable multivibrator and counts the number of pulses equal to or more than a predetermined number, for example, three waves. Then, the counter output and the inverted output of the monostable multivibrator are OR-connected, and the AND output of the OR output and the output of the second comparator is ANDed.
The output is input to the cutoff signal output circuit.

In such an earth leakage breaker, a monostable multivibrator is activated when a lightning surge occurs, and its inverted output becomes L. On the other hand, no counter output is generated by a single lightning surge. AND condition with the output is not satisfied, and no cutoff signal is output. On the other hand, in the case of a continuous and repeated ground fault, the counter can count more than a predetermined number of pulses, so that the cutoff signal is output after the output of the counter. In addition, since the monostable multivibrator does not start at the time of normal leakage, the AND condition between the inverted output and the output of the second comparator is satisfied,
A shutoff signal is output.

According to a second aspect of the present invention, the occurrence of a lightning surge or a ground fault is detected by a third comparator.
AND of the signal inverted by the output of the monostable multivibrator activated by the output and the output of the second comparator
While the interruption due to the lightning surge is prohibited depending on the condition, a double ground fault is detected by counting a predetermined number or more of the number of output pulses of the first comparator during the output period of the monostable multivibrator, and the interruption signal is output. This is common to the invention described in Item 1, but is different in that an RS flip-flop is used.

That is, when a lightning surge occurs, an AND operation between the output of the monostable multivibrator and the output of the second comparator is performed.
An RS flip-flop is set by the output, and an inverted output thereof sets an AND condition with the output of the second comparator to be unsatisfied, thereby inhibiting the output of the cutoff signal. On the other hand, when a double ground fault occurs, the RS flip-flop is reset by the output of the counter that counts the output pulse of the first comparator, and the inverted output satisfies the AND condition to output the cutoff signal.

According to a third aspect of the present invention, there is provided a charging time switching circuit for switching a charging condition such that the integration time of the integrating circuit output to the second comparator is increased in the case of a lightning surge or a heavy ground fault. Surges and heavy ground faults are distinguished from earth leakage. That is, ZC larger than the first comparator
A third comparator that detects the T secondary output detects the occurrence of a lightning surge or a heavy ground fault, and creates a gate for a certain time by a monostable multivibrator activated by the output. Then, only during the output period of the monostable multivibrator, the charging condition of the charging condition switching circuit is switched to extend the integration time.

Thus, in the case of a single lightning surge,
Before the output of the integration circuit reaches the detection level of the second comparator, the output from the first comparator is interrupted, and the output from the second comparator to the cutoff signal output circuit can be suppressed. In this case, in the case of a double ground fault in which the output from the first comparator is repeatedly and continuously performed, although the integration time is longer than that during the electric leakage, the output of the integration circuit reaches the detection level of the second comparator. It is possible, and at that time, the drive of the cutoff signal output circuit by the output of the second comparator is performed.

According to a fourth aspect of the present invention, there is provided a monostable multivibrator activated by the output of the second comparator, and the output of the monostable multivibrator and the first monostable multivibrator.
And the output of the second comparator is connected with the output of the second comparator by distinguishing the lightning surge from leakage or a ground fault based on the presence or absence of the AND output.
By inputting the output to a cutoff signal output circuit, a cutoff signal is not output in the case of a lightning surge. That is, in the case of a single lightning surge, after the output from the second comparator, the output from the first comparator does not occur within a certain time period by the monostable multivibrator, and the monostable The AND condition with the output of the multivibrator is not satisfied. On the other hand, in the case of a ground fault and a heavy ground fault, there is an output from the first comparator even after the start of the monostable multivibrator, and the AND condition is satisfied.

According to a fifth aspect of the present invention, there is provided a monostable multivibrator activated by the output of the second comparator, and the positive and negative outputs from the first comparator during the output period of the monostable multivibrator. A polarity discriminating circuit for discriminating alternately input signals and outputting the same; an output of the polarity discriminating circuit and an output of the monostable multivibrator
A D connection is made to distinguish lightning surge from leakage or heavy ground fault depending on the presence or absence of this AND output.
In other words, in the case of a single lightning surge, after the output from the second comparator, the polarity of the polarity different from that of the output immediately before from the first comparator is set within the gate for a certain period of time by the monostable multivibrator. There is no output, and the AND condition with the output of the monostable multivibrator does not hold.

On the other hand, in the case of repeated and continuous earth leakage and heavy ground fault, there is an output of a different polarity from the first comparator even after the start of the monostable multivibrator, and the AND condition is satisfied. Then, by inputting the AND output of the AND output and the output of the second comparator to the cutoff signal output circuit, it is possible to prevent the cutoff signal from being output in the case of a lightning surge.

According to a sixth aspect of the present invention, there is provided a third comparator for detecting an output of an integration circuit smaller than the second comparator, and an output pulse of the first comparator based on an output of the third comparator. A counter that counts the number of pulses and outputs the count when the number of pulses exceeds a predetermined number, and outputs an AND output of the output of the counter and the output of the second comparator to a cutoff signal output circuit. is there. In the case of repeated continuous earth leakage and heavy ground fault, there is a counter output, whereas in the case of a single lightning surge, there is no counter output.
Since the condition is not satisfied, no cutoff signal is output.

The first aspect of the present invention has no problem when the voltage (current) waveform of the lightning surge is simple. However, the discharge waveform due to lightning in the field may include chattering at the time of rising. This is chattering with a large current, which cannot be completely absorbed by the filter circuit and an output due to chattering is generated up to the output of the second comparator. When the counter counts the pulses due to the chattering, an unnecessary cutoff operation is performed. May be. Therefore, a seventh aspect of the present invention, in the first aspect of the present invention, includes a count prohibition circuit for prohibiting the counter from counting for a certain time when the monostable multivibrator is activated. This eliminates the need to count pulses due to chattering, and prevents unnecessary interruption.

According to the first aspect of the present invention, there is provided a counter for counting the number of output pulses of the first comparator during an output period of the monostable multivibrator, and outputting when the number of pulses is counted over a predetermined number. In the case of a heavy ground fault, a cutoff signal is output based on the counter output. In this case, at least three count pulses are required to distinguish a heavy ground fault from a lightning surge.
When three waves are counted at the commercial frequency of, the judgment time until the counter output, that is, until the shut-off signal is sent to the trip coil becomes 20 ms (see FIG. 3), and there is a risk of adversely affecting the equipment connected to the load side.

Therefore, the invention according to an eighth aspect of the present invention provides a signal transmission inhibiting circuit for inhibiting transmission of an output signal of a third comparator for a predetermined time in place of a counter, an output of the signal transmission inhibiting circuit, and a monostable multivibrator. A latch circuit for setting and inputting an AND output with the output of the monostable multivibrator and reset inputting the inverted output of the monostable multivibrator; and ORing the output of the latch circuit with the inverted output of the monostable multivibrator; An AND output of the OR output and the output of the second comparator is input to a cutoff signal output circuit.
Here, the signal transmission inhibition time is set to the maximum time during which the double ground fault exceeds the threshold value of the third comparator, for example, 5 ms. Thus, when the third comparator detects two waves, it is determined that a double ground fault has occurred, and the determination time is 10 ms. On the other hand, in the case of a lightning surge, the output of the third comparator is extinguished within the above-mentioned prohibition time.
The ND condition is not satisfied, and no cutoff signal is output.

According to a ninth aspect of the present invention, a lightning surge is distinguished from a heavy ground fault by focusing on the difference between the waveform widths of the positive electrode and the negative electrode, and is a zero-phase current transformer larger than the first comparator. Only during the output period of the monostable multivibrator activated by the output of the third comparator which detects the secondary output of the first comparator, the first comparator is charged by only the first wave of each of the positive and negative output pulses of the first comparator. A positive-pulse charging circuit and a negative-pulse charging circuit; and a comparator that compares charging voltages of the positive and negative charging circuits and outputs a signal when the voltage difference exceeds a predetermined value. The inverted output of the comparator and the monostable multivibrator are provided. And an OR connection between the inverted output of the second comparator and the AND output of the OR output and the output of the second comparator.

Since the lightning surge has different waveform widths between the positive and negative waveforms, a voltage difference occurs between the positive and negative charging circuits, and the output of the comparator becomes H, and therefore the inverted output thereof becomes L, and no cutoff signal is generated. However, in the case of a double ground fault, the waveforms of the positive electrode and the negative electrode are almost the same, so that there is almost no voltage difference.

According to a tenth aspect of the present invention, a lightning surge is distinguished from a heavy ground fault by focusing on the difference between the heights of the waveforms of the positive electrode and the negative electrode, and the zero-phase current is larger than that of the first comparator. A monostable multivibrator activated by an output of a third comparator for detecting a secondary output of the transformer, and each first wave of positive and negative outputs of the zero-phase current transformer only during an output period of the monostable multivibrator. A positive peak hold circuit and a negative peak hold circuit that respectively hold only the peak voltage of each of them, and a comparator that compares the hold voltages of these positive and negative hold circuits and outputs when the voltage difference exceeds a predetermined value. The inverted output and the inverted output of the monostable multivibrator are OR-connected, and the AND output of the OR output and the output of the second comparator is output to a cutoff signal output circuit. Forces.

In the lightning surge, since the heights of the positive and negative waveforms are different from each other, a voltage difference occurs between the peak voltages of the positive and negative peak hold circuits. Although this does not occur, since the waveforms of the positive and negative electrodes are almost the same in the case of a double ground fault, there is almost no voltage difference, so that the inverted output of the comparator becomes H and a cutoff signal is generated.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Note that the same reference numerals are used for the portions corresponding to the conventional example. Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the invention described in claim 1, and FIGS. 2 and 3 are time charts thereof. 1 and 2, when a leakage current of, for example, 15 mA flows through the main circuit conductor 2 penetrating the ZCT 3, a secondary current is generated in the secondary winding of the ZCT 3, and this secondary current is converted into a voltage by the resistor 4. Is done. This voltage is passed through a low-pass filter 5 and then amplified by an amplifier 6 and divided into a positive electrode and a negative electrode by a first comparator 7 which sets a threshold value for pulsing the leakage current of 15 mA. Pulse width 7
The pulse is made into ms and the pulse interval is made into 3 ms, and is synthesized by an OR circuit (OR1). This output charges the integrating circuit 8 by the pulse width, and the second comparator 9 is set by setting a charging time constant such that the sum of the pulse widths exceeds the threshold value of the second comparator 9 if the total is 14 ms, for example. Is H.

On the other hand, ZCT larger than the first comparator 7
The third set the threshold value to detect the secondary output of the third
Is connected to both ends of the resistor 4, and a current of, for example, 1 A level or more flowing through the main circuit conductor 2 is supplied to the third comparator 12
The pulse is divided into a positive electrode and a negative electrode, and is combined by an OR circuit (OR2). Then, a monostable multivibrator 13 activated by an output from OR2 is provided, and a gate is created for a time of, for example, 30 ms. Also, a counter (hereinafter referred to as a three-wave counter) 14 that counts the number of output pulses of the first comparator 7 and counts three waves only during the output period is provided, and its output is inverted by an inverting circuit 15. OR the inverted output of the monostable multivibrator 13
Input to the circuit (OR3), its output β and the second comparator 9
AND output with the output α is input to the cutoff signal output circuit 10.

When the leakage current of 15 mA flows through the main circuit conductor 2, the third comparator 12 does not detect the leakage current and the monostable multivibrator 13 does not start.
The inverted output becomes H and is input to OR3. as a result,
The α signal and the β signal both become H and are input to AND 1, and the cutoff signal γ is tripped from the cutoff signal output circuit 10 and sent to the coil 11.

If a ground fault current due to a lightning surge flows through the main circuit conductor 2 and the pulse width pulsed at the threshold value of the first comparator 7 is, for example, 25 ms in total as shown in FIG. Output exceeds the threshold of the second comparator, and exceeds the integration time of 14 ms, so that the output α of the second comparator becomes H. In addition, Z equivalent to 1A level or more in terms of leakage current
Since the CT secondary current is generated, the output of the third comparator 12 becomes H, and hence the output of OR2 becomes H, the monostable multivibrator 13 is activated, and a gate is created for a time of 30 ms. , The three-wave counter 14 is the first comparator 7
The output pulse of is counted. However, as can be seen from FIG. 2, since only two waves are input, the output of the three-wave counter 14 is L, the inverted output of the monostable multivibrator 13 is also L, and the output β of the OR3 is L. Therefore, the output of AND1 becomes L and the cutoff signal γ is not output.

When a heavy ground fault current flows through the main circuit conductor 2, the sum of the pulse widths pulsed by the threshold value of the first comparator 7 exceeds 14 ms as shown in FIG.
Output exceeds the threshold value of the second comparator 9 and its output α
Becomes H. In addition, since a ZCT secondary current corresponding to a level of 1 A or more in terms of leakage current is generated, the third comparator 1
The output of 2 becomes H, and the monostable multivibrator 13 is activated. During the output period, the three-wave counter 14 counts the output pulse of the first comparator 7. Then, when three rising edges of the pulse are input, the output of the three-wave counter 14 becomes H, and the output β of OR3 becomes H, and AND1
Becomes H, and the cutoff signal γ is output.

Embodiment 2 FIG. 4 is a block diagram showing an embodiment of the second aspect of the present invention, and FIG. 5 is a time chart thereof. In FIG.
Output α of second comparator 9 and monostable multivibrator 1
3 is connected to an AND circuit (AND2), and the output is set and input to the RS flip-flop 16. Further, the inverted output of the second comparator 9 inverted by the inverting circuit 17 and the output of the three-wave counter 14 are connected to an OR circuit (OR3), and the output is reset input to the RS flip-flop 16. Then, the output α of the second comparator 9 and the inverted output (Q bar) β of the RS flip-flop 16 are connected to the AND circuit (AND1), and the output is input to the cutoff signal output circuit 10.

When a leakage current of 15 mA flows through the main circuit conductor 2,
As described above, the output α of the second comparator is H, and its inverted output is L. On the other hand, the third comparator 12 has a leakage current
No 15 mA is detected, the output of the monostable multivibrator 13 is L, and therefore the output of the three-wave counter 14 is also L. Therefore, the β signal becomes H while the RS flip-flop 16 remains in the reset state. As a result, the output of AND1 becomes H, and the cutoff signal γ is output from the cutoff signal output circuit 10.

4 and 5, when a ground fault current due to a lightning surge flows through the main circuit conductor 2, the output α of the second comparator 9 and the output of the monostable multivibrator 13 become H as described above. However, the output of the three-wave counter 14 is L
Remains. Therefore, the RS flip-flop 16 is set, and the inverted output β is the output α of the second comparator 9.
Is H while L is H. As a result, the AND1 output becomes L, and the cutoff signal γ is not output.

When a heavy ground fault current flows through the main circuit conductor 2, the output of the monostable multivibrator 13 becomes H by the detection of the third comparator as described above, and then the output α of the second comparator 9 becomes When it becomes H, the output of AND2 becomes H
And the RS flip-flop 16 is set and output is inhibited. Thereafter, when the three-wave counter 14 becomes H at the time when three outputs of the first comparator 7 are inputted, the RS flip-flop 16 is reset, and the inverted output β becomes H. As a result, the output of AND1 becomes H, and the cutoff signal γ
Is output.

Third Embodiment FIG. 6 is a block diagram showing a third embodiment of the invention, and FIGS. 7 and 8 are time charts thereof. In FIG. 6, the output of the monostable multivibrator 13 activated by the output of the third comparator 12, which detects the ZCT secondary output larger than the first comparator 7, is inverted by the inverting circuit 18 and charged by the output. The charging condition of the condition switching circuit 19 is switched, and the integration time of the integration circuit 8 is extended only during the output period of the monostable multivibrator 13.

Here, the charging condition switching circuit 19 has the circuit configuration shown in FIG.
1, the collector current of the transistor 22 is increased, and the collector current of the transistor 23 having this collector current as the base current, that is, the current supplied to the integration circuit 8 is increased, and the integration circuit 8 is charged in a normal integration time. Is completed. On the other hand, when the analog switch 20 is in the OFF state, the collector current of the transistor 22, that is, the base current of the transistor 23 is limited by the resistor 21, so that the collector current of the transistor 23 is reduced and the current supplied to the integration circuit is reduced. Decrease the charge time.

In FIGS. 6 and 7, when the leakage current of 15 mA flows through the main circuit conductor 2, the third comparator 12 does not detect this and the monostable multivibrator 13 does not start. Therefore, the output of the monostable multivibrator 13 becomes L and the inverted output becomes H, and the analog switch 2
0 is ON. As a result, as described above, the output of the integration circuit 8 exceeds the threshold value of the second comparator 9 in the normal integration time, the output α becomes H, and the cutoff signal γ is output.

When a ground fault current due to a lightning surge flows through the main circuit conductor 2, the output of the third comparator 12 becomes H, the monostable multivibrator 13 is activated, and its inverted output becomes L.
Becomes Therefore, during the output period of the monostable multivibrator 13, the analog switch 20 is turned off, the charging current is reduced, and the integration time of the integration circuit 8 becomes longer. As a result, as shown in FIG. 7, the output from the first comparator 7 ends before the output of the integration circuit 8 reaches the threshold value of the second comparator 9, and eventually the second comparator 9 9, the output α remains at L, so that the cutoff signal γ is not output.

When a heavy ground current flows through the main circuit conductor 2, the output of the monostable multivibrator 13 becomes H by the detection of the third comparator 12, as shown in FIG. Becomes longer. Therefore, the time required for the output of the integration circuit 8 to reach the threshold value of the second comparator 9 is prolonged, but the output of the integration circuit 8 is eventually output because the output of the first comparator 7 continues. Second comparator 9
Exceeds the threshold value, the output α becomes H, and the cutoff signal γ
Is output.

Fourth Embodiment FIG. 9 is a block diagram showing a fourth embodiment of the invention, and FIGS. 10 and 11 are time charts thereof. In FIG. 9, the output of the monostable multivibrator 13 activated by the output α of the second comparator 9 and the first comparator 7
Is connected to an AND circuit (AND2), and an AND output of the output β and the output α of the second comparator 9 is input to the cutoff signal output circuit 10.

9 and 10, when a leakage current flows through the main circuit conductor 2, the output α of the second comparator 9 becomes H as described above, and therefore the monostable multivibrator 13 is activated, For example, a time gate of 15 ms is created. Next, when the output of the first comparator 7 rises, the output β of AND2 becomes H, and therefore the output of AND1 becomes H, and the cutoff signal γ is output.

On the other hand, even if a ground-fault current due to a lightning surge flows through the main circuit conductor 2 and the output α of the second comparator 9 becomes H and the monostable multivibrator 13 is started, FIG. As can be seen, since there is no rising signal of the output of the first comparator 7, AND2 remains at L, and the cutoff signal γ is not output. On the other hand, in the case of a heavy ground fault, as shown in FIG. 11, there is an output from the first comparator 7 after the activation of the monostable multivibrator 13, so that the output β of the AND2
, And the output of AND1 becomes H, and the cutoff signal γ is output.

Fifth Embodiment FIG. 12 is a block diagram showing a fifth embodiment of the present invention, and FIG. 13 is a time chart thereof. In FIG. 12, it is determined that the monostable multivibrator 13 activated by the output α of the second comparator 9 and the positive and negative outputs are alternately input from the first comparator 7 during the output period. And an output of the polarity discriminating circuit 24 and the output of the monostable multivibrator 13 are connected to an AND circuit (AND2), and the output β and the output α of the second comparator 9 are provided. Is input to the cutoff signal output circuit 10.

12 and 13, the main circuit conductor 2
When the output α of the second comparator 9 becomes H and the monostable multivibrator 13 is started, the polarity discrimination circuit 24 alternately outputs the positive and negative outputs from the first comparator 7. At the time when it is input to
Becomes H, and the cutoff signal γ is output.

On the other hand, even if a ground-fault current due to a lightning surge flows through the main circuit conductor 2 and the output α of the second comparator 9 becomes H and the monostable multivibrator 13 is started, FIG. As can be seen, since the output from the first comparator 7 remains negative, the output of the polarity discrimination circuit 24 does not become H, the output β of AND2 remains L, and the cutoff signal γ is not output. On the other hand, although a time chart is omitted, in the case of repeated and continuous ground faults, the positive and negative outputs from the first comparator 7 are alternately input to the polarity determination circuit 24 even after the monostable multivibrator 13 is started. As a result, the cutoff signal γ is output.

Embodiment 6 FIG. 14 is a block diagram showing an embodiment of the invention according to claim 6, and FIG. 15 is a time chart thereof. In FIG. 14, a third comparator 25 for detecting the output of the integrating circuit 8 smaller than the second comparator 9 and the number of output pulses of the first comparator 7 are counted based on the output thereof. 3
A three-wave counter 14 for outputting when the wave count is performed,
An AND output of the output β of the three-wave counter 14 and the output α of the second comparator 9 is input to the cutoff signal output circuit 10.

14 and 15, the main circuit conductor 2
When the output of the amplifier 6 exceeds the threshold value of the first comparator 7, the integration circuit 8 starts outputting. Then, when the output of the integrating circuit 8 exceeds the threshold value of the third comparator 25, the three-wave counter 14 starts counting the output pulses of the first comparator 7, and the third pulse of FIG. The output β becomes H at the time when the rising edge is input. Further, since the output α of the second comparator 9 is H at that time, the output of AND1 becomes H and the cutoff signal γ is output.

On the other hand, a ground fault current due to a lightning surge flows through the main circuit conductor 2, the output of the third comparator 25 becomes H, and the three-wave counter 14 outputs the output pulse of the first comparator 7. Even when counting is started, only the pulse as can be seen from FIG. 15 is input, so that the output β remains L,
No cutoff signal γ is output. On the other hand, although a time chart is omitted, in the case of a double ground fault,
Since the waves can be counted, the cutoff signal γ is output.

Embodiment 7 FIG. 16 is a block diagram showing an embodiment of the invention according to claim 7, and FIG. 17 is a time chart thereof. Here, FIGS. 18 and 19 show the waveform of the lightning surge, in which the vertical axis represents the voltage V (or current I) and the horizontal axis represents the time t. FIG.
Is a case where the waveform is simple, and there is no problem even in the first embodiment. However, as shown in FIG. 19, the lightning surge sometimes includes chattering at the time of rising.
In that case, in the first embodiment, there is a danger that the pulse is counted and the cutoff operation is performed.

In the seventh embodiment of FIG. 16, the countermeasure is taken. In contrast to the earth leakage breaker of FIG. 1, when the monostable multivibrator 13 is activated, the counting operation of the three-wave counter 14 is performed for a certain time, In the case shown, a count prohibition circuit 26 for prohibiting for 1 ms is provided. Figure 1 Lightning surge
In the case where chattering is included at the time of rising as shown in FIG. 9, the pulse also appears in the OR1 output of the first comparator 7 in FIG. Therefore, the count prohibition circuit 26
17 (FIG. 1), as shown in the left column of FIG.
When the wave counter 14 counts three waves including the chattering pulse, the OR3 output β becomes H, and when the output α of the second comparator 9 becomes H, the output of AND1 becomes H and the cutoff signal γ becomes Will be output.

On the other hand, in the circuit provided with the count prohibition circuit 26 (FIG. 16), as shown in the right column of FIG.
In the first 1 ms of the ms time gate, the counting of the OR1 output of the comparator 7 in FIG. 1 by the three-wave counter 14 is prohibited. On the other hand, lightning surge chattering converges in tens of μs. As a result, during the remaining 29ms gate period,
The OR1 output counts only two waves, and the three-wave counter 1
4 is L, the inverted output of the monostable multivibrator 13 is L, and the OR3 output β is also L, thus AND1
Is L, and the cutoff signal γ is not output. In addition,
Although not shown, when a heavy ground fault current occurs, three waves are counted during the gate period of the remaining 29 ms despite the count prohibition time of 1 ms, so that the interruption operation is not hindered.

Eighth Embodiment FIG. 20 is a block diagram showing an eighth embodiment of the invention, and FIG. 21 is a time chart thereof. In FIG. 20, the transmission of the output signal of the third comparator 12 is performed for a certain period of time.
In the case shown, a signal transmission inhibition circuit 27 for inhibiting 5 ms,
A latch circuit 28 comprising an R flip-flop;
The AND output of the output of the signal transmission inhibition circuit 27 and the output of the monostable multivibrator 13 is set and input to the latch circuit 28, and the inverted output of the monostable multivibrator 13 is reset input to the latch circuit 28. Then, the Q output of the latch circuit 28 and the inverted output of the monostable multivibrator 13 are input to an OR circuit (OR3), and an AND output of the output β and the output α of the second comparator is output to the cutoff signal output circuit 10. To enter. Normally, the output of AND2 is L and the inverted output of the monostable multivibrator 13 is H. Therefore, the latch circuit 28 is in a reset state and its Q output is L.

In FIG. 21, when a double ground fault occurs, a gate of the monostable multivibrator 13 is created for 20 ms by the output of the third comparator 12, but the first output signal of the third comparator 12 is Since the transmission is blocked by the signal transmission inhibition circuit 27, the output of AND2 remains L, and the inverted output of the monostable multivibrator 13 is also L, so that the Q output of the latch circuit 28 is maintained at L, and OR3 Is L, and therefore the cutoff signal γ is not output. However, since the pulse output of the second wave of the third comparator 12 is after 10 ms, it is not blocked by the signal transmission inhibition circuit 27 and AND
The output of 2 becomes H, the latch circuit 28 is set, the Q output thereof becomes H, and the cutoff signal γ is output. That is, the determination time of the occurrence of the double ground fault in the eighth embodiment is 10 ms as illustrated. When a lightning surge occurs, the pulse output of the third comparator 12 is single-shot (see FIG. 2), and its output signal is blocked from being transmitted by the signal transmission inhibiting circuit 27, so that no interruption operation is performed.

Ninth Embodiment FIG. 22 is a block diagram showing a ninth embodiment of the present invention, and FIG. 23 is a time chart thereof. In FIG. 22, only during the output period of the monostable multivibrator 13, the positive pulse charging circuit 29 and the negative pulse charging circuit 30, which are charged by only the first wave of the positive and negative output pulses of the first comparator 7, respectively. These positive and negative charging circuits 29, 3
And a comparator 31 for comparing the charging voltage of 0 and outputting when the voltage difference exceeds a predetermined value.
1 and an inverted output of the monostable multivibrator 13 are inverted by an OR circuit (OR
3), and the AND output of the output β and the output α of the second comparator 9 is input to the cutoff signal output circuit 10.

In FIG. 23, when a lightning surge or a heavy ground fault occurs, the monostable multivibrator 13
During the time gate period of ms, the positive pulse charging circuit 29 and the negative pulse charging circuit 30 are charged by only the first wave of the positive and negative output pulses of the first comparator 7, respectively. Is done. In the case of a lightning surge, the width of the waveform is different between the positive electrode and the negative electrode, and a voltage difference occurs, so that the output of the comparator 31 is H and its inverted output is L,
Also, since the inverted output of the monostable multivibrator 13 is L, the output β of OR3 is L, and the output of AND1 is L
Does not output the cutoff signal γ. On the other hand, in the case of a double ground fault, the waveforms of the positive electrode and the negative electrode are almost the same, and there is almost no voltage difference between the charging voltages. Therefore, the output of the comparator 31 is L, the inverted output thereof is H, and the output β of the OR3 is H. AND
One output is H, and the cutoff signal γ is output.

Embodiment 10 FIG. 24 is a block diagram showing an embodiment of the invention according to claim 10, and FIG. 25 is a time chart thereof. In FIG. 24, only during the output period of the monostable multivibrator 13, the positive peak hold circuit 33 for holding the peak voltage of only the first wave of each of the positive and negative outputs of the zero-phase current transformer 3 amplified by the amplifier 6; Negative electrode peak hold circuit 3
And a comparator 31 that compares the hold voltages of the positive and negative hold circuits 33 and 34 and outputs a signal when the voltage difference exceeds a predetermined value. An inverted output obtained by inverting the output of the comparator 31 by an inverting circuit 32 is provided. The inverted output of the monostable multivibrator 13 and the inverted circuit are input to an OR circuit (OR3), and the output β of the output β and the output α of the second comparator 9 are A
The ND output is input to the cutoff signal output circuit 10.

In FIG. 24, when a lightning surge or a heavy ground fault occurs, the monostable multivibrator 13
During the time gate period of ms, the peak voltage of only the first wave of each of the positive and negative outputs of the zero-phase current transformer 3 is changed to the positive peak hold circuit 33.
And the negative peak hold circuit 34 respectively. Each hold voltage is compared by the comparator 31. In the case of a lightning surge, the height of the waveform is different between the positive electrode and the negative electrode, and a voltage difference occurs. Therefore, the output of the comparator 31 is H, the inverted output is L, and the inverted output of the monostable multivibrator 13 is L. , OR3 output β
Is L, the output of AND1 is L, and the cutoff signal γ is not output. On the other hand, in the case of a heavy ground fault, the waveforms of the positive electrode and the negative electrode are almost the same, and there is almost no voltage difference between the hold voltages.
The output β of OR3 is H, and the output of AND1 is H, and the cutoff signal γ is output.

[0055]

As described above, according to the present invention, when a leakage current flows, it can be cut off within 40 ms according to the IEC standard, and can be cut off even in the case of a heavy ground fault. In the case of a short-circuit current, an unnecessary interruption operation can be reliably avoided.

[Brief description of the drawings]

FIG. 1 is a block diagram of an earth leakage breaker according to Embodiment 1 of the present invention.

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

FIG. 3 is a time chart showing another operation of the earth leakage breaker of FIG. 1;

FIG. 4 is a block diagram of an earth leakage breaker according to a second embodiment of the present invention.

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

FIG. 6 is a block diagram of an earth leakage breaker according to a third embodiment of the present invention.

FIG. 7 is a time chart showing the operation of the earth leakage breaker of FIG. 6;

FIG. 8 is a time chart illustrating another operation of the earth leakage breaker of FIG. 6;

FIG. 9 is a block diagram of an earth leakage breaker according to a fourth embodiment of the present invention.

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

11 is a time chart illustrating another operation of the earth leakage breaker of FIG. 9;

FIG. 12 is a block diagram of an earth leakage breaker according to a fifth embodiment of the present invention.

FIG. 13 is a time chart illustrating an operation of the earth leakage breaker of FIG. 12;

FIG. 14 is a block diagram of an earth leakage breaker according to Embodiment 6 of the present invention.

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

FIG. 16 is a block diagram of an earth leakage breaker according to a seventh embodiment of the present invention.

17 is a time chart illustrating an operation of the earth leakage breaker of FIG. 16;

FIG. 18 is a waveform diagram of a simple lightning surge.

FIG. 19 is a waveform diagram of a lightning surge including chattering at the time of rising.

FIG. 20 is a block diagram of an earth leakage breaker showing an eighth embodiment of the present invention.

FIG. 21 is a time chart illustrating the operation of the earth leakage breaker of FIG. 20.

FIG. 22 is a block diagram of an earth leakage breaker according to Embodiment 9 of the present invention.

23 is a time chart illustrating an operation of the earth leakage breaker of FIG. 22.

FIG. 24 is a block diagram of an earth leakage breaker according to Embodiment 10 of the present invention.

FIG. 25 is a time chart showing the operation of the earth leakage breaker of FIG. 24.

FIG. 26 is a block diagram of an earth leakage breaker showing a conventional example.

FIG. 27 is a time chart showing the operation of the earth leakage breaker of FIG. 26.

[Description of Signs] 1 earth leakage breaker 2 main circuit conductor 3 zero-phase current transformer 4 resistance 5 low-pass filter 6 amplifier 7 first comparator 8 integration circuit 9 second comparator 10 cut-off signal output circuit 11 trip coil Reference Signs List 12 third comparator 14 three-wave counter 15 inversion circuit 16 RS flip-flop 19 charging condition switching circuit 20 analog switch 22 transistor 23 transistor 24 polarity discrimination circuit 25 third comparator 26 count inhibition circuit 27 signal transmission inhibition circuit 28 latch Circuit 29 Positive pulse charging circuit 30 Negative pulse charging circuit 31 Comparator 32 Inverting circuit 33 Positive peak hold circuit 34 Negative peak hold circuit γ Cutoff signal

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsumi Watanabe 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (10)

[Claims] 1. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and an output of the first comparator integrated. An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. A third comparator for detecting a secondary output of the zero-phase current transformer larger than the first comparator, and a monostable activated by an output of the third comparator. A multivibrator, and a counter that counts the number of output pulses of the first comparator only during the output period of the monostable multivibrator and outputs when the number of pulses is counted to a predetermined number or more. Inversion of monostable multivibrator And an OR connection between the output and the output of the second comparator and an AND output of the OR output and the output of the second comparator. 2. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and an output of the first comparator integrated. An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. A third comparator for detecting a secondary output of the zero-phase current transformer larger than the first comparator, and a monostable activated by an output of the third comparator. A multivibrator, a counter that counts the number of output pulses of the first comparator only during the output period of the monostable multivibrator, and outputs a signal when the number of pulses is counted over a predetermined number; an output of the counter; The OR output with the inverted output of the comparator An RS flip-flop for setting and inputting an AND output of the output of the monostable multivibrator and the output of the second comparator; and providing an inverted output of the RS flip-flop and an output of the second comparator. AN with output
An earth leakage breaker characterized in that a D output is input to the cutoff signal output circuit. 3. A zero-phase current transformer through which a main circuit conductor penetrates, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and integrating an output of the first comparator. An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. A third comparator for detecting a secondary output of the zero-phase current transformer larger than the first comparator, and a monostable activated by an output of the third comparator. An earth leakage breaker, comprising: a multivibrator; and a charging condition switching circuit for switching a charging condition of the integration circuit so that an integration time becomes longer only during an output period of the monostable multivibrator. 4. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and integrating an output of the first comparator. An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. In the earth leakage breaker provided, a monostable multivibrator activated by an output of the second comparator is provided, and an output of the monostable multivibrator and an output of the first comparator are AND-connected. A of the AND output and the output of the second comparator
An earth leakage breaker, wherein an ND output is input to the cutoff signal output circuit. 5. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and integrating an output of the first comparator. An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. A monostable multivibrator activated by the output of the second comparator; and the positive and negative outputs from the first comparator alternately during the output period of the monostable multivibrator. A polarity discriminating circuit for discriminating that the signal has been input and outputting the signal; an AND connection between an output of the polarity discriminating circuit and an output of the monostable multivibrator;
An earth leakage breaker, wherein an AND output of an ND output and an output of the second comparator is input to the cutoff signal output circuit. 6. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and integrating an output of the first comparator. An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. A third comparator for detecting an output of the integration circuit that is smaller than the second comparator, and an output pulse number of the first comparator based on an output of the third comparator. A counter for counting the number of pulses and outputting the count when the number of pulses exceeds a predetermined number, and an AND output of the output of the counter and the output of the second comparator is input to the cutoff signal output circuit. A ground fault circuit breaker. 7. The earth leakage breaker according to claim 1, further comprising a count prohibition circuit for prohibiting a counting operation of the counter for a predetermined time when the monostable multivibrator is activated. 8. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output equal to or greater than a predetermined value of the zero-phase current transformer, and integrating an output of the first comparator. An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. A third comparator for detecting a secondary output of the zero-phase current transformer larger than the first comparator, and a monostable activated by an output of the third comparator. A multivibrator, a signal transmission prohibition circuit for prohibiting transmission of an output signal of the third comparator for a certain period of time, and an AND output of an output of the signal transmission prohibition circuit and an output of the monostable multivibrator; Reset the inverted output of the monostable multivibrator. And a latch circuit for inputting the output of the monostable multivibrator.
The earth leakage breaker is connected, and an AND output of the OR output and the output of the second comparator is input to the shutdown signal output circuit. 9. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and integrating an output of the first comparator An integrator circuit, a second comparator for detecting an output equal to or more than a predetermined value of the integrator circuit, and a shutoff signal output circuit for outputting a shutoff signal to a trip coil based on the output of the second comparator. A third comparator for detecting a secondary output of the zero-phase current transformer larger than the first comparator, and a monostable activated by an output of the third comparator. A multivibrator, a positive pulse charging circuit and a negative pulse charging circuit that are charged only by the first wave of each of the positive and negative output pulses of the first comparator only during the output period of the monostable multivibrator;
Comparing the charging voltages of these positive and negative charging circuits, and providing a comparator that outputs when the voltage difference exceeds a predetermined value,
The inverted output of the comparator and the inverted output of the monostable multivibrator are OR-connected, and the OR
An earth leakage breaker characterized in that an AND output of an output and an output of the second comparator is inputted to the cutoff signal output circuit. 10. A zero-phase current transformer through which a main circuit conductor passes, a first comparator for detecting an output of a predetermined value or more of the zero-phase current transformer, and integrating the output of the first comparator. An integrating circuit that performs
An earth leakage breaker comprising: a second comparator for detecting an output equal to or greater than a predetermined value of the integration circuit; and a cutoff signal output circuit for outputting a cutoff signal to a trip coil based on the output of the second comparator. , A third comparator for detecting a secondary output of the zero-phase current transformer larger than the first comparator, a monostable multivibrator activated by an output of the third comparator, A positive-polarity peak hold circuit and a negative-polarity peak hold circuit for respectively holding only the peak voltage of each of the positive and negative outputs of the zero-phase current transformer only during the output period of the monostable multivibrator, and a hold for these positive and negative hold circuits A comparator for comparing voltages and outputting when the voltage difference becomes equal to or greater than a predetermined value, and ORing the inverted output of the comparator with the inverted output of the monostable multivibrator; And an AND output of the OR output and the output of the second comparator is input to the cutoff signal output circuit.