JP2008084596A - Earth leakage circuit breaker of three-phase four-wire system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an earth leakage circuit breaker of a three-phase four-wire system without causing a dead time in earth leakage detection even if timings at which the respective phases are closed are shifted from one another. <P>SOLUTION: Power of an electronic control circuit 6 determining earth leakage from a zero-phase current value detected by a zero-phase current transformer 4, and power of a trip coil 8 tripping a main circuit 1 are supplied from all of three-phase voltage phases R, S and T based on a neutral phase N. Power lines 12a-13d are connected to all the four wires of the main circuit 1, and a direct current is generated between a power line 12 formed by uniting power lines 12a-13d of the phases R, S and T through rectifier elements D3-D5, and a power line 12d of the neutral phase N and supplied to the electronic control circuit 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a three-phase four-wire earth leakage breaker that interrupts an electric circuit when a leakage occurs in the three-phase four-wire electric circuit.

The earth leakage circuit breaker includes a zero-phase current transformer that detects a zero-phase current in the electric circuit and an electronic control circuit that determines an electric leakage from the detected zero-phase current value, and is a three-phase circuit installed in a three-phase four-wire circuit. The configuration of the 4-wire earth leakage breaker is the same. In this case, the electronic control circuit is supplied with power from the circuit to be interrupted. However, in the case of a three-phase four-wire earth leakage breaker, there are three voltage lines. Had been supplied with power.
However, if one of the phases used as the power source is disconnected, there is a risk of leakage in the other two voltage lines, but the electronic control circuit will not operate. For this reason, there is a three-phase leakage breaker in which the power source of the electronic control circuit is taken from three voltage lines so that the leakage can be detected and cut off even if a break occurs (see, for example, Patent Document 1).
JP 2005-216829 A

By configuring as in Patent Document 1, even if one of the three phases (R-phase, S-phase, and T-phase) is disconnected, the leakage operation can be detected and the interruption operation can be performed. However, when looking at the breaking operation speed (breaking operation time) at the moment when the circuit breaker is closed, the three-phase four-wire earth leakage breaker is used when the N phase is closed first and then tripped. Is configured so that the N phase is opened last, and all the contacts do not close or open simultaneously.
In the case of such a three-phase four-wire earth leakage breaker, if all the voltage phases are reliably closed simultaneously after the N phase is closed, the electronic control circuit controls the electric circuit in which the leakage path exists at the same time as the occurrence of the electric leakage. It can operate to detect a leakage and issue a circuit interruption signal.

However, it is difficult to provide such a contact structure, and a slight time difference actually occurs. For example, if the contacts are closed in the order of neutral phase (N phase) → R phase → S phase → T phase, there is a possibility that leakage will occur at the time of closing from N phase to R phase. Since only one phase is connected, power is not yet supplied to the electronic control circuit that determines the occurrence of leakage. Accordingly, it is not possible to detect a leakage at this point. Thereafter, after closing the circuit to the S phase, the electronic control circuit performs a leakage detection operation, and a contact releasing operation is performed.
In this way, in the case of an earth leakage breaker used for a three-phase four-wire electric circuit, since all contacts are not configured to be closed simultaneously, electric leakage cannot be detected instantaneously in the case of an electric circuit in which electric leakage occurs simultaneously with turning on. In other words, there was a slight dead time.

  Therefore, in view of such problems, the present invention has an object to provide a three-phase four-wire earth leakage breaker in which no dead time is generated in leakage detection even when there is a deviation in the timing at which each phase is closed. And

In order to solve the above-mentioned problem, the invention of claim 1 is directed to a zero-phase current transformer for detecting a zero-phase current of a three-phase four-wire circuit, a shut-off means for shut-off operation of the circuit from a power source, and a detected zero A three-phase four-wire earth leakage breaker comprising an electronic control circuit for operating the breaker by judging leakage from a phase current value, wherein the electronic control circuit includes a neutral phase and a three-phase voltage line It is characterized by receiving power supply from all phases.
With this configuration, when closing the circuit breaker, there is no dead time during which the electronic control circuit does not operate due to the order in which the contacts close or the time difference, and the occurrence of leakage can be detected without delay even when the power is turned on. . In addition, even if an open phase occurs, if a leakage occurs, the operation is reliably interrupted.

The invention according to claim 2 is the invention according to claim 1, wherein the shut-off means is a trip coil, and the operating power source of the trip coil is common to the power source of the electronic control circuit, and the neutral phase and the three-phase power source. The power supply is received from all phases of the voltage line.
With this configuration, even when the power is turned on, the interruption operation can be performed in accordance with the leakage detection operation of the electronic control circuit.

  According to the present invention, when performing the closing operation of the circuit breaker to close the electric circuit, there is no dead time during which the electronic control circuit inside the circuit breaker does not operate due to the order of closing the contacts or the time difference, and the closing operation Even at times, the occurrence of electrical leakage can be detected and blocked without delay.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an example of a three-phase four-wire earth leakage breaker according to the present invention, wherein 1 is a main circuit comprising four R, S, T three phases and a neutral phase N, and 2 is a power source. Side connection terminal, 3 is a load side connection terminal, 4 is a zero phase current transformer for detecting a zero phase current of the main electric circuit 1, and 5 is a circuit breaker control unit equipped with an electronic control circuit 6 which is made into an IC for judging leakage. , 7 is an open / close contact, 8 is a trip coil for opening (breaking) the open / close contact 7, and 9 is a test switch for testing the electronic control circuit.

  The zero-phase current transformer 4 is arranged by inserting the four conductors constituting the main circuit 1 and the one conductor constituting the test circuit 10, and detecting the zero phase current detected in the main circuit 1. The phase current is converted into voltage information and input to the electronic control circuit 6. D1 and D2 are protective elements for protecting the circuit, and the test circuit 10 having the test switch 9 is disposed between the R phase and the N phase via the zero-phase current transformer 4.

Power supply lines 12 a to 12 d are connected to all phases of the R, S, T phase and the neutral phase N, and are arranged in the electronic control circuit 6. The power supply lines 12a to 12c connected to the respective voltage lines are respectively provided with rectifying elements D3 to D5 and star-connected to form one power supply line 12, and a DC voltage based on the neutral phase N is applied. It is generated and supplied to the electronic control circuit 6 via the three-stage constant current diodes D6 to D8.
Z1 to Z3 are varistors, and are provided between the power supply lines 12a to 12c connected to the R, S, and T phases and the power supply line 12d connected to the neutral phase N in order to protect the circuit from lightning surges. Is provided. The constant current diodes D6 to D8 are provided for supplying a constant current to the electronic control circuit 6.

  On the other hand, the power lines 12a to 12d are also power lines of the trip coil 8. When the thyristor 13 is turned on, the trip current is connected to the R, S, T voltage phases via the trip coil 8. It flows between the power supply line 12d connected to 12c and the neutral phase N. However, at this time, the value of the current flowing through the trip coil 8 is regulated by the constant current diodes D6 to D8, but the trip operation is performed when the discharge current of the capacitor C1 flows. As a result, the switching contact 7 is cut off, and the main electric circuit 1 is cut off from the power source.

The operation of the circuit breaker configured in this way when the power is turned on is specifically as follows. When the switching contact 7 is closed and the power is turned on, the neutral phase N is closed first, and then the voltage phases R, S, and T are closed in any order.
At this time, it is assumed that there is a leakage path in the R phase of the main circuit 1. First, if the neutral phase N is closed, and then the R phase is closed first among the three phases, for example, the R phase has a leakage path, and thus leakage occurs at this point. However, power is supplied to the electronic control circuit 6 when the R phase is energized, and power is also supplied to the trip coil 8 at the same time. Therefore, if a leakage occurs, it is detected instantaneously and the interruption operation is performed.
Further, if the S phase or the T phase is closed next to the neutral phase N, no leakage occurs as long as the R phase is not closed in either case. After that, leakage occurs due to the closing of the R phase, but since the power is supplied to the electronic control circuit 6 and the trip coil 8 when the earlier of the S phase or the T phase is closed, the circuit breaks without delay. Can work.

In this way, when closing the circuit breaker, there is no dead time during which the electronic control circuit does not operate due to the order in which the contacts close or the time difference, and the occurrence of leakage can be detected without delay even when the power is turned on. . In addition, even if an open phase occurs, power is supplied from the remaining voltage phase.
Further, since power is supplied to the trip coil at the same time as the electronic control circuit, even when the power is turned on, an electric leakage is detected and an instantaneous interruption operation is performed.

  In the above embodiment, the power supply circuit of the electronic control circuit 6 and the energization path of the trip coil 8 are a common circuit, but can be an independent electric circuit.

It is a circuit diagram showing an example of an embodiment of a three-phase four-wire earth leakage breaker according to the present invention.

Explanation of symbols

  1 .... Main circuit, 4 .... Zero phase current transformer, 6 .... Electronic control circuit, 7 .... Switch contact, 8 .... Trip coil, 12, 12a to 12d ... Power line.

Claims (2)

A zero-phase current transformer for detecting a zero-phase current of a three-phase four-wire circuit, a shut-off means for shutting off the power circuit from a power source, and determining the leakage from the detected zero-phase current value and operating the shut-off means A three-phase four-wire earth leakage breaker with an electronic control circuit for
The electronic control circuit receives a power supply from all phases of a neutral phase and a three-phase voltage line. 2. The tripping coil is a trip coil, and an operating power source of the trip coil is common to a power source of an electronic control circuit and is supplied with power from all phases of a neutral phase and a three-phase voltage line. Three-phase four-wire earth leakage breaker.

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