JP3317986B2 - Earth leakage breaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching sequence for switching off and alarming in an earth leakage circuit breaker, and is particularly suitable for a heater load with poor insulation at the time of starting or a computer circuit which requires evacuation of an important circuit before shutting down. Related to a short circuit breaker.

[0002]

2. Description of the Related Art As described in Japanese Patent Application Laid-Open No. 2-60411, a conventional device comprises a circuit breaker having an overcurrent tripping means,
An overcurrent pre-warning means, a ground fault tripping means, and a ground fault pre-warning means were provided.

[0003]

In the above-mentioned prior art, the leakage interruption and the leakage alarm are classified into two factors, that is, the magnitude of the ground fault (leakage) current and the operation time after the occurrence of the leakage. No consideration was given to the classification of interruptions and alarms over time. Also, no consideration has been given to the classification (switching) of interruption and warning by the elapsed time for the same ground fault current.

For this reason, when applied to a heater load or the like having poor insulation at the time of starting, it is necessary to set a tripping sensitivity current or a large operating time in order to avoid an operation at the time of starting. There was a problem.

[0005] In addition, there is a problem with respect to the protection coordination of the upper and lower circuit breakers that the set value width of each circuit breaker sensitivity current and operating time is narrowed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an earth leakage circuit breaker that outputs an alarm output from the time of starting until the current is reduced to a predetermined leakage current, and performs an interruption operation when a leakage current having a value exceeding the predetermined leakage current occurs. is there.

[0007] A second object of the present invention is to provide an alarm output when a predetermined leakage current is exceeded until a predetermined time elapses after the start, and thereafter to shut off when the predetermined leakage current is exceeded. An object of the present invention is to provide an earth leakage breaker for operation.

A third object of the present invention is to provide an earth leakage breaker which outputs an alarm when a predetermined leakage current is exceeded and reaches a cutoff operation after a predetermined time.

[0009]

An object of the present invention is to provide an operation signal when a leakage current is detected, and an operation signal when the leakage current is removed.
A leakage detection circuit that supplies a non-operation signal to the next output circuit and a pulse generation circuit that detects a breaker closing operation and generates a short-time pulse are provided. Is achieved by switching

A second object of the present invention is to provide the earth leakage detecting circuit and a timer circuit for generating a pulse for a predetermined time after the circuit breaker is turned on. This is achieved by shutting off the output after the termination by the output of the leakage detection circuit.

A third object of the present invention is to provide the electric leakage detection circuit and a timer circuit which starts operation in response to the operation signal, and generates an alarm output by the electric leakage detection circuit and causes the timer circuit to perform an interruption operation. This is achieved by:

[0012]

The leakage detection circuit generates an output when a leakage current exceeding a predetermined leakage current is detected, and the pulse generation circuit detects the closing of the circuit breaker and generates a short-time pulse. Thereby, an alarm is generated at the first OR output of the two outputs,
The shutoff operation can be performed by the second OR output.

The logical product output is input only for the shorter one of the leakage current continuation time and the timer output time. Thereby, the alarm output can be performed during the timer output, and the shutoff operation can be performed after the timer output is completed.

In the third object, since the timer starts operating by the output of the leakage detection circuit at the preceding stage, it is possible to temporally switch between alarm and cutoff for the same predetermined leakage current.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the present embodiment.

First, the block configuration will be described. The earth leakage breaker 2 is connected between the power supply 1 of the electric circuit and the load 3 and is built therein to open and close the electric circuit. A zero-phase current transformer 5 for detecting unbalance of an electric circuit on the load side; a leakage detection circuit 7 for detecting a leakage from an output of the zero-phase current transformer 5; a pulse generation circuit 9; a gate circuit 10;
1, 13, 17, trigger circuit 12, leak alarm output circuit 1
4 and a trip coil 6 connected to a trigger circuit 12.

The opening and closing mechanism 4 is opened and closed by operation of a handle (not shown) or operation of the trip coil 6.

A power supply circuit 8 is connected to connection points T1 and T2 on the load side of the zero-phase current transformer 5 inside the earth leakage breaker 2, and a stabilized voltage output of the power supply circuit 8 is a pulse generation circuit 9 and an earth leakage circuit. Each gate circuit 10 including the detection circuit 7 and the like,
17, 13, flip-flop circuit 11, trigger circuit 1
2 and the earth leakage alarm output circuit 14 (this connection is not shown).

The input of the trigger circuit 12 is connected to the output of the AND gate 17, and the output is connected to the trip coil 6 for tripping the opening / closing mechanism 4.

On the input side of the leakage detecting circuit 7, the opening / closing mechanism 4
Of the zero-phase current transformer (hereinafter abbreviated as ZCT) 5 through which the three-phase conductor on the load side passes. On the other hand, one of the outputs of the leakage detection circuit 7 is connected to one of the inputs of the two-input OR gate 10 and the other is connected to one of the inputs of the two-input AND gates 13 and 17.

The pulse generating circuit 9 is composed of, for example, a well-known one-shot multi-circuit, and its output is an OR gate 10
And the output of the OR gate 10 is connected to the input terminal of the T-FF 11 as the flip-flop circuit 11. Further, the output Q of the T-FF 11 is
The anti-Q output is connected to the other input of the AND gate 13, and the anti-Q output is connected to the other input of the AND gate 17, and the output of the AND gate 13 is sent to the earth leakage alarm output circuit 14 that drives the LED display 15 and the contact output 16. , AND gate 17 outputs
The tripping coil 6 is connected to the tripping coil 6 via the trigger circuit 12.

Next, the operation will be described. Symbols A to 2 in FIG.
E is a voltage waveform of each part of the same symbol in FIG. 1 and will be described in comparison with this. FIGS. 2A and 2B show a case where a load having a large leakage current after being turned on and a normal load are connected.

When the switching mechanism is closed by operating the handle of the earth leakage breaker, the load is energized. The leakage current of a load having a large leakage current at the time of starting the heater or the like gradually decreases, for example, as shown in FIG. 3 as the leakage current of the heater load. Now, considering the case where the sensitivity current value of the earth leakage breaker is set to the level indicated by the broken line in FIG.
The output shown in FIG. 2B is received in response to the secondary output of CT5.

On the other hand, the pulse generation circuit 9 composed of a well-known one-shot multi-circuit outputs the waveform shown in FIG. 2C, and outputs a leak alarm output circuit through a gate 10, a T-FF 11, and an AND gate 13 by an output D. 14 is operated. The operation of the leakage alarm output circuit 14 continues until the leakage current of the area A in FIG. 3, that is, the heater, which is the load, decreases below the leakage current breaker sensitivity current setting value shown by the broken line in FIG.
Next, after the area A, that is, in the cutoff standby range of the area B,
Since the output from the electric leakage detection circuit 7 disappears (becomes LOW level), the operation of the electric leakage alarm output 14 stops. still,
The operation of the trigger circuit remains stopped.

Next, when the leakage current exceeds the sensitivity current set value, the anti-Q output of the T-FF 11 becomes H level by the output of the OR gate 10 due to the output from the leakage detection circuit 7, Then, the trigger circuit is driven by the E output, and the tripping coil 4 closes the opening / closing mechanism 4. At this time, the Q output of the T-FF 11 is at the LOW level, and the operation of the leakage alarm output circuit 14 remains stopped.

In this embodiment, the switching from the alarm output to the cut-off output after the operation is started is performed by the sensitivity current set value, so that even if the load such as the heater has a large leakage current at the time of starting, the load insulation property reaches the normal value. Then, it is possible to shift to the cut-off possible area after reliably judging this.

The above function can be realized by simply increasing the number of circuit elements shown in a broken-line frame in FIG. 1 in a leakage detection circuit of a general leakage breaker.

Next, a second embodiment of the present invention will be described with reference to FIGS. 4, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. FIG.
Waveforms A to F are waveforms of portions denoted by the same reference numerals in FIG. FIGS. 5A and 5B show a case where a load having a large leakage current after being turned on and a normal load are connected.

The embodiment shown in FIG. 4 is a circuit breaker that detects a leakage current of a circuit or device and disconnects (disconnects) the circuit or device from a higher-level circuit. Either or both O
An earth leakage breaker capable of N / OFF switching, specifically, a timer circuit 18 that starts from the start of operation, and inputs the output of the timer circuit 18 and the output of the pulse generation circuit 9 to the OR gate 10 It is.

Next, the operation will be described.
Is closed and the timer circuit 18 starts operating, the output of the timer circuit 18 becomes HIGH, the output of which is supplied to one of the inputs of the three-input OR gate 10 and the inverter 20
And supplied to one input of a two-input AND gate 21. The other input of the two-input AND gate 21 is connected to the output of the leakage detection circuit 7. 2-input AND gate 2
1 is connected to the input terminal of the trigger circuit 12.

As a result, as shown in FIG. 6, a warning is issued until the output of the timer circuit 18 becomes LOW after a predetermined time,
After that, it will be in an electric leakage interruption standby state.

According to this embodiment, in addition to the first embodiment, when the timer circuit is turned off, the leakage current is compared with the predetermined value, so that it is possible to reliably shut off as a load insulation failure.

Next, a third embodiment will be described with reference to FIG. In FIG. 7, a circuit for calculating the differential coefficient of the leakage current (it is a well-known circuit and its description is omitted) is provided, and when the differential coefficient is zero, a predetermined leakage current (dashed line in FIG. 7) Then, the alarm is switched from the alarm to the cutoff standby state if the current is equal to or more than the current.

According to this embodiment, accurate protection can be provided even for a defective load.

Next, a fourth embodiment will be described with reference to FIG. In the present embodiment, an element that detects a leakage current of a circuit or a device and disconnects (disconnects) the circuit or the device from a higher-level circuit is used to store an element that stores a change in leakage current from when the leakage circuit breaker is turned on until a predetermined time. It is provided.

This storage element may be a known storage element, and stores a leakage current change pattern of a normal load. This stored leakage current change is compared with the actual leakage current, and when there is no difference between them and the predetermined leakage current is exceeded, only the leakage alarm is output, and when the leakage current falls below the predetermined leakage current, When the actual leak current exceeds a predetermined leak current, the shut-off operation is performed. When the actual leak current deviates from the stored change in the leak current, the shut-off operation is performed.

According to the present embodiment, it is possible to cut off a defective load at an early stage.

Next, a fifth embodiment will be described with reference to FIGS. FIG. 9 is a block diagram showing the configuration of the leakage detection circuit 7.
One of the outputs is input to the timer circuit 19, the other is input to the earth leakage alarm output circuit 14, and the output of the timer circuit 19 is input to the trigger circuit 12.

Next, the operation will be described. When the main circuit leakage current exceeds a predetermined value and the leakage detection circuit 7 operates, the leakage alarm output circuit 14 operates by the output A of the circuit 7, and the light emitting diode 15 is turned on. , The alarm output 16 operates. On the other hand, the timer circuit 19 receives the output of the detection circuit 7, generates an output B after a predetermined time delay, and energizes the tripping coil 6 via the trigger circuit 12. The output of the leakage detection circuit 7 is output for each of different leakage current values, and the output for the small leakage current is output to the leakage alarm output circuit 14.
If the output corresponding to the large leakage current is input to the timer circuit 19, the coordination of the alarm and the cutoff can be obtained.

According to the present embodiment, since the earth leakage warning is earlier than the interruption, it is possible to take precautionary measures such as evacuating an important load provided with a storage element within this delay time, and to cope with a sudden power failure due to the interruption. Become.

[0042]

According to the present invention, a sensitivity current settled for a load having a temporal change in leakage current, for example, a heater load whose insulation property is poor at start-up and whose insulation property gradually improves by energization, is used. Switching between alarm and cutoff is performed based on the standard. If a large leakage current occurs in a normal state, an alarm is output, and if an accident occurs, the alarm can be cut off. , An earth leakage breaker capable of protection can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram showing waveforms of respective parts of a circuit block of the earth leakage breaker according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram of an earth leakage breaker according to the first embodiment of the present invention.

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

FIG. 5 is a waveform diagram showing waveforms at various parts in a circuit block diagram of an earth leakage breaker according to a second embodiment of the present invention.

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

FIG. 7 is a characteristic diagram of an earth leakage breaker according to a third embodiment of the present invention.

FIG. 8 is a characteristic diagram of an earth leakage breaker according to a fourth embodiment of the present invention.

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

FIG. 10 is a waveform diagram showing waveforms of respective parts of a circuit block diagram of an earth leakage breaker according to a fifth embodiment of the present invention.

FIG. 11 is a characteristic diagram of an earth leakage breaker according to a fifth embodiment of the present invention.

[Explanation of symbols]

2: earth leakage breaker, 4: switching mechanism, 5: zero-phase current transformer,
6: trip coil, 16: alarm output contact

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Hayakawa 4-3 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi Techno Engineering Co., Ltd. (56) References JP-A-2-55517 (JP, A) JP-A-5 -176443 (JP, A) JP-A-2-60411 (JP, A) JP-A-3-93422 (JP, A) JP-A 55-148324 (JP, U) JP-B-57-14096 (JP, B2) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01H 83/02

Claims (4)

(57) [Claims] An open / close means for opening and closing an electric circuit, a main circuit conductor connected to a load side of the open / close means, a zero-phase current transformer for detecting an imbalance of a current flowing through the main circuit conductor, In an earth leakage breaker provided with a detection circuit for detecting an output of a phase current transformer and generating an output corresponding to the magnitude of the output, timing means for timing a time after the electric circuit is closed by the switching means Output determination means for determining the magnitude of the output of the detection circuit; alarm means connected to the output determination means for issuing an alarm based on the output; and signal generation means for generating a trip signal. A tripping means for opening and closing the opening / closing means based on an output of the signal generating means, wherein the output judging means has an output of the detection circuit equal to or more than a predetermined value from the start of timing of the timing means to the end of timing operation. When The output is supplied to said alarm means,
An earth leakage breaker configured to supply the output of the detection circuit to the tripping means when the output of the detection circuit exceeds a predetermined value after the operation of the time counting means is completed. 2. The earth leakage breaker according to claim 1, wherein said output judging means is configured to stop supplying an output to said alarm means after the operation of said timing means. 3. A switching means for opening and closing an electric circuit, a main circuit conductor connected to a load side of the switching means, a zero-phase current transformer for detecting imbalance of a current flowing through the main circuit conductor, and An earth leakage breaker provided with a detection circuit for detecting an output of a phase current transformer and generating an output corresponding to the magnitude of the output, wherein a timing means for timing a duration of an output of the detection means, and the detection circuit Output determination means for determining the magnitude of the output of
Alarm means connected to the output determining means for issuing an alarm based on the output, signal generating means for generating a trip signal, and trip means for opening and closing the opening / closing means based on the output of the signal generating means The output determination means calculates a derivative of the leakage current after the electric circuit is closed, and before the time when the derivative is zero reaches a predetermined time, the output of the detection means is set to a predetermined value or less. The output of the detection circuit is supplied to the alarm means until the time when the differential coefficient is zero reaches a predetermined time, and when the output of the detection circuit exceeds a predetermined value, An earth leakage breaker configured to supply an output to the tripping means. 4. The output judging means according to claim 1, wherein the output of said detection circuit becomes equal to or less than a predetermined value even before the time when the differential coefficient of said leakage current is zero reaches a predetermined time. 4. An earth leakage circuit breaker according to claim 3, wherein the output of said detection circuit is supplied to said tripping means when the value exceeds a predetermined value.