JP5788713B2 - Earth leakage breaker - Google Patents

Description

  The present invention relates to an earth leakage circuit breaker, and more particularly to an earth leakage circuit breaker that can detect and interrupt even a pulsating current leakage in which a direct current component is superimposed in addition to an alternating current leakage.

In recent years, solar power generation facilities and electric vehicle charging facilities have begun to spread to ordinary households. Since such equipment is subjected to AC / DC conversion, when leakage occurs, leakage due to a pulsating current superimposed with a DC component can be considered. However, the conventional earth leakage breaker has a circuit configuration as shown in FIG. 3, and cannot correctly detect the pulsating current.
Specifically, in FIG. 3, 21 is a zero-phase current transformer that detects a zero-phase current in the electric circuit L, 22 is an IC leakage detection circuit, 23 is a trip coil that cuts off the electric circuit L, and 24 is a rectifier circuit. The leakage of the electric circuit L is detected using the zero-phase current transformer 21.

The leakage detection circuit 22 includes a constant voltage circuit 22a, a reference voltage generation circuit 22b that generates a reference voltage for determining leakage, and a comparison circuit that includes a differential boost circuit that compares the detected zero-phase current with the reference voltage. 22c, a latch circuit 22d for holding the determination result, etc., and the comparison circuit 22c makes a half wave of either positive or negative polarity with respect to the zero phase current waveform (leakage current waveform) detected by the zero phase current transformer 21. On the other hand, a determination operation is performed in comparison with a threshold value (reference voltage). For example, in the configuration in which the comparison circuit 22c performs a determination operation on the positive half-wave, even if the negative half-wave is larger than the positive half-wave, that is, if a leakage current with a negative DC component superimposed is generated, Even if this occurred, a situation where it could not be detected unless the positive half-wave exceeded the threshold value occurred.
From such a background, an earth leakage circuit breaker called “A-type” has been proposed that detects an earth leakage if the current leakage exceeds a predetermined value even if the earth leakage current has a DC component superimposed thereon (for example, Patent Documents). 1).

JP 2010-14478 A

  However, the A-type leakage breaker disclosed in Patent Document 1 uses a plurality of zero-phase current transformers, Hall elements, and a DC conversion circuit in addition to an IC leakage detection circuit. Therefore, in addition to one zero-phase current transformer and one IC leakage detection circuit, a Hall element, a further zero-phase current transformer, a DC conversion circuit, and the like are necessary, which is expensive. However, a space was required to install multiple zero-phase current transformers.

  Therefore, in view of such problems, the present invention requires only one zero-phase current transformer and does not require a large space, and in addition to conventional AC leakage, pulsating leakage including DC components is also good. An object of the present invention is to provide an earth leakage circuit breaker that detects and interrupts the operation.

In order to solve the above problem, the invention described in claim 1 is directed to a zero-phase current transformer for detecting a zero-phase current in an electric circuit composed of two power lines, a predetermined reference voltage, and the zero-phase current transformer. A leakage detection circuit that is integrated into an IC to determine the occurrence of leakage by comparing the waveform of one of the output voltage waveforms of the voltage detector, and a blocking means for blocking the switching means provided on the electric circuit when it is determined that leakage has occurred And an earth leakage test circuit that tests the earth leakage detection circuit by generating a pseudo earth leakage current , wherein the earth leakage detection circuit performs the same determination operation with the same reference voltage. When the output of the zero-phase current transformer is input in opposite phases to both of the leakage detection circuits, and at least one of the leakage detection circuits determines that leakage has occurred, the interruption means Shuts down and the leakage The strike circuit includes a first current path connected between the power lines on the load side of the zero-phase current transformer through the zero-phase current transformer and one of the zero-phase current transformer on the power supply side. A second current path connected between the power line of the zero-phase current transformer and the other power line on the load side of the zero-phase current transformer without passing through the zero-phase current transformer, and a specific one-way connection to the first current path. A first rectifying means for flowing current, a second rectifying means for flowing a current in one specific direction through the second current path, and one of the first current path and the second current path. A closing means for selecting and closing the current path, and switching the both current paths by the closing means to perform a closing operation to generate a zero-phase current having a reverse polarity .
According to this configuration, using one zero-phase current transformer and two conventional leakage detection circuits in the form of an IC, the leakage current can be reliably detected even if the leakage is superimposed with either positive or negative DC components. Thus, the electric circuit can be interrupted. Therefore, with a space-saving and low-cost circuit configuration, even if there is pulsating leakage, it reliably detects and shuts off when a predetermined reference voltage is exceeded.
Further, the pseudo-leakage current can be generated by switching the first current path and the second current path by operating the closing means. Therefore, it is possible to select and generate a leakage current having both positive and negative polarities, and to individually test the two leakage detection circuits. Therefore, when any one of the leakage detection circuits fails, it can be reliably detected.

According to a second aspect of the present invention, in the configuration according to the first aspect, both of the leakage detection circuits include a reference voltage generation circuit that generates a predetermined reference voltage, the generated reference voltage, and an output of the zero-phase current transformer. A comparator circuit for comparing the voltage to determine the occurrence of leakage, and a latch circuit for holding the output of the comparator circuit, the outputs of both the comparator circuits being input to one of the latch circuits, The blocking means operates in response to the output of the latch circuit.
According to this configuration, since only one of the two latch circuits is used, the input / output terminal of the other latch circuit may be open, and the number of elements to be assembled can be reduced.

According to a third aspect of the present invention, in the configuration according to the first or second aspect , the first current path is wired so that a current flows from one specific power line to the load side from the power supply side of the zero-phase current transformer. On the other hand, the second current path is configured such that a current flows from the one specific power line on the power supply side of the zero-phase current transformer to the other power line on the load side, and reaches the other power line. In the path, the first current path and the second current path have a common current path, and the first rectifying means and the second rectifying means are common rectifying means arranged in the common current path. It is characterized by being.
According to this configuration, only one rectifying means is required.

According to a fourth aspect of the present invention, in the configuration according to the third aspect , the common rectifier circuit is a rectifier circuit for supplying a DC power to the leakage detection circuit.
According to this configuration, since the rectifying means also serves as the rectifying circuit of the power supply circuit, it is not necessary to separately provide the rectifying means for the leakage test circuit, and can be configured at low cost.

  According to the present invention, by using one zero-phase current transformer and two conventional leakage detection circuits that are integrated into an IC, the leakage current is reliably detected even if the leakage current is a combination of positive and negative DC components. Thus, the electric circuit can be interrupted. Therefore, with a space-saving and low-cost circuit configuration, even if there is pulsating leakage, it reliably detects and shuts off when a predetermined reference voltage is exceeded.

It is a circuit diagram which shows an example of the earth-leakage circuit breaker which concerns on this invention. It is a circuit diagram of a ground-fault circuit breaker provided with a ground-fault test circuit. It is a circuit diagram of the conventional earth-leakage circuit breaker.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an example of an earth leakage breaker according to the present invention, where 1 is a power supply side terminal, 2 is a load side terminal, and 3 is an electric circuit L between the power supply side terminal 1 and the load side terminal 2. Open / close contact, 4 is a zero-phase current transformer, 5 is a trip coil for opening the open / close contact to cut off the electric circuit, 6 is a leakage breaker circuit that outputs a cut-off signal when a leak occurs, and 7 is judged to be leaked This is an IC leakage detection circuit.

  The leakage detection circuit 7 is composed of the same two ICs (first leakage detection circuit 7a and second leakage detection circuit 7b). For example, a bipolar analog integrated circuit μPC1702 manufactured by NEC Corporation is used. This circuit has the same circuit configuration as the leakage breaker circuit 22 shown in FIG. 3, and is composed of a constant voltage circuit, a reference voltage generation circuit, and a differential boost circuit that compares the detected zero-phase current with the reference voltage. A circuit, a latch circuit for holding a determination result, and the like are incorporated. The first terminal is a reference voltage generating terminal, the second terminal is a comparison circuit input terminal, the third terminal is a GND terminal, the fourth terminal is a comparison circuit output terminal, the fifth terminal is a latch circuit input terminal, Seven terminals are latch circuit output terminals, and the eighth terminal is a power supply terminal. The electric circuit L is composed of two power lines L1 and L2.

  The earth leakage breaker circuit 6 takes an operating power source such as the earth leakage detection circuit 7 from the load-side electric circuit L that has passed through the zero-phase current transformer 4, and the power terminals of both earth leakage detection circuits 7 a and 7 b via the trip coil 5. Connected to. Further, a resistor RL is connected between the output terminals of the zero-phase current transformer 4, and the detected zero-phase current is converted into a voltage. This voltage information is input to the comparison circuit input terminals of both leakage detection circuits 7a and 7b. However, in the first leakage detection circuit 7a and the second leakage detection circuit 7b, the connection lines are connected to each other so that reverse phase voltage information is input. Then, both comparison circuit outputs are input to the latch circuit input terminal (fifth terminal) of the first leakage detection circuit 7a via the OR circuit using the diodes D2 and D3.

  The earth leakage circuit breaker thus configured operates as follows. However, as described above, since the first leakage detection circuit 7a and the second leakage detection circuit 7b determine the voltage information of opposite phases, the first leakage detection circuit 7a is here the zero-phase current transformer 4. Is compared with a predetermined reference voltage output from the reference voltage generating terminal (first terminal), and the second leakage detection circuit 7b is connected to the zero-phase current transformer 4. Of the AC voltage waveform to be output, the negative voltage waveform is compared with a predetermined reference voltage output from the reference voltage generation terminal (first terminal).

Assuming that a leakage current with a positive direct current superimposed is generated, the output AC voltage waveform of the zero-phase current transformer 4 is an AC voltage waveform having a larger positive polarity waveform than a negative waveform. . Then, the positive voltage waveform first reaches the reference voltage. The reference voltage of the first leakage detection circuit 7a and the second leakage detection circuit 7b is set to the same value.
Accordingly, the comparison circuit of the first leakage detection circuit 7a first detects the occurrence of leakage, and a leakage detection signal is output from the comparison circuit output terminal (fourth terminal).

On the other hand, when a leakage current in which a negative direct current is superimposed is generated, the output AC voltage waveform of the zero-phase current transformer 4 is an AC voltage waveform having a larger negative polarity waveform than the positive polarity. In this case, the comparison circuit of the second leakage detection circuit 7b detects the occurrence of leakage, and a leakage detection signal is output from the comparison circuit output terminal (fourth terminal). As a result, if any of the positive and negative polarities output from the zero-phase current transformer 4 exceeds the reference voltage, the occurrence of leakage is determined.
Further, in the case of normal leakage in which a positive / negative symmetric AC voltage waveform having no DC component is output from the zero-phase current transformer 4, the one that exceeds the reference voltage first of the two leakage detection circuits 7a and 7b A detection signal is output.

Thus, the leakage detection signal output from the fourth terminal of the first leakage detection circuit 7a or the second leakage detection circuit 7b is input to the latch circuit input terminal (fifth terminal) of the first leakage detection circuit 7a. At this time, the leakage detection signals of both leakage detection circuits 7a and 7b are input to the latch circuit input terminal of the first leakage detection circuit via the OR circuit using the diodes D2 and D3.
When the leakage detection signal is input to the latch circuit, an activation signal for the trip coil 5 is output from the latch circuit output terminal (seventh terminal), the thyristor Z1 is turned on, and the trip coil 5 performs a trip operation. In this way, the switching contact 3 opens and the electric circuit L is interrupted.

In this way, by using one zero-phase current transformer 4 and two conventional leakage detection circuits 7a and 7b that are integrated into an IC, the leakage current can be reliably ensured even if the leakage is superimposed on any positive or negative DC component. It is possible to cut off the electric circuit by detecting the current. Therefore, with a space-saving and low-cost circuit configuration, even if there is pulsating leakage, it reliably detects and shuts off when a predetermined reference voltage is exceeded.
Further, since only one latch circuit is used among the latch circuits of the first leakage detection circuit 7a and the second leakage detection circuit 7b, the input / output terminals of the other latch circuit may be in an open state, and the IC is connected. Even if two elements are used, the number of elements to be assembled can be reduced.

FIG. 2 shows another embodiment of the leakage breaker of the present invention. The difference from the configuration of FIG. 1 is that a leakage test circuit 10 is provided, and the function of detecting the leakage and cutting off the electric circuit L is the same as that of FIG.
Hereinafter, the leakage test circuit 10 will be described. The leakage test circuit 10 is configured to cause two current paths 11 (first current path 11a and second current path 11b) through which current flows in one specific direction and current to flow through one of the current paths 11. And a changeover switch 12.

  Specifically, of the two current paths 11a and 11b, the first current path 11a is connected to one power line L1 on the load side with respect to the installation position of the zero-phase current transformer 4 on the circuit L, and then zero. The phase current transformer 4 is inserted from the power supply side and connected to the other power line L2 on the load side of the electric circuit L. The other second current path 11b is formed by connecting to one power line L1 on the power source side of the circuit L and connecting to the other power line L2 on the load side without passing through the zero-phase current transformer 4.

However, the first current path 11a and the second current path 11b after the insertion of the zero-phase current transformer 4 have a common path through the changeover switch 12 until they are connected to the other power line L2. In this way, the selector switch 12 can select a current path to be energized out of the both current paths 11a and 11b, and only one of them can be energized. Note that the current flowing through the current path 11 is adjusted by the resistor Rt provided in the common current path 11 to a specific value at which the leakage detection circuit 7 performs the leakage determination operation.
Further, the common current path 11 is connected to the other power line L2 via the anode of the diode D1 constituting a rectifier circuit for supplying DC power to the leakage detection circuit 7, and the current path 11 is connected to the current path 11 by the diode D1. A specific unidirectional current to be regulated is energized.

By providing such a leakage test circuit 10, a pseudo leakage current is generated by operating the changeover switch 12, and the trip coil 5 is tripped and cut off.
Specifically, when the changeover switch 12 is first connected so that the first current path 11 a is closed, a constant current flows through the zero-phase current transformer 4. Therefore, it appears as if the current on the one power line L1 side is larger than the power line L2, and the zero-phase current transformer 4 detects this as a zero-phase current. Furthermore, since the current flowing through the first current path 11a at this time is a current of one specific polarity by the diode D1, the zero-phase current transformer 4 outputs a voltage signal having a large waveform of this specific polarity. If this polarity is, for example, a positive waveform, the first leakage detection circuit 7a detects this and outputs a leakage detection signal in the same manner as the leakage detection operation described above. As a result, the trip coil 5 trips and shuts off.

On the other hand, when the changeover switch 12 is connected so that the second current path 11b is closed, the current of one power line L1 seems to have decreased with respect to the current of the other power line L2, and the zero-phase current transformer 4 detects this as a zero-phase current. At this time, since the current flowing through the second current path 11b is a current having one specific polarity regulated by the diode D1, the zero-phase current transformer 4 outputs a voltage signal having a large waveform having this specific polarity. To do.
At this time, since the positive polarity of the voltage waveform output from the zero-phase current transformer 4 is smaller than that of the negative polarity, the second leakage detection circuit 7b that performs a detection operation on the negative waveform detects the leakage and detects leakage. Output a signal. As a result, the trip coil 5 trips and shuts off. The change-over switch 12 is normally in an open state, and no current flows through the current path 11.

As described above, the pseudo-leakage current can be generated by switching the first current path 11a and the second current path 11b by operating the changeover switch 12. Therefore, it is possible to select and generate a leakage current having both positive and negative polarities, and the two leakage detection circuits 7a and 7b can be individually tested. Therefore, if one of the leakage detection circuits 7 fails, the leakage current is detected and cut off as long as the leakage current is generated by an alternating current, but if a leakage due to a pulsating current superimposed with a direct current occurs, The situation that cannot be detected can be surely prevented.
In addition, the rectifier circuit that defines the direction of the current flowing through both current paths 11 of the leakage test circuit 10 is shared by the diode D1 that constitutes the power supply circuit of the leakage detection circuit 7, so that the leakage test circuit 10 Therefore, it is not necessary to provide a separate rectifier circuit and can be configured at low cost.

  In the above embodiment, the first current path 11a is formed so that the current is taken out from the load-side electric path L of the zero-phase current transformer 4 and passed again through the zero-phase current transformer 4, and the apparent power line L1 is formed. However, the apparent current of one power line L1 may be decreased by passing the zero-phase current transformer 4 in the reverse direction. In this case, the second current path 11b may be provided so that a current flows from one power line L1 on the load side of the zero-phase current transformer 4 to the other power line L2 on the power source side so that the current of the other power line L2 decreases. . In short, by switching the changeover switch 12, wiring may be performed so that a positive or negative DC component is superimposed on the zero-phase current detected by the zero-phase current transformer 4.

  1 .... Power supply side terminal 2 .... Load side terminal 3 .... Opening / closing contact (switching means) 4 .... Zero phase current transformer 5 .... Trip coil (breaking means) 6 .... 7 .... Leakage detection circuit, 7a ... First leakage detection circuit, 7b ... Second leakage detection circuit, 10 .... Leakage test circuit, 11 .... Current path, 11a ... First current path, 11b ... 2 current paths, 12... Changeover switch (closing means), L .. electric circuit, 22 b .. reference voltage generation circuit, 22 c .. comparison circuit, 22 d .. latch circuit, D1 .. diode (first rectification means, first 2 rectifying means).

Claims (4)

A zero-phase current transformer that detects a zero-phase current in a circuit constituted by two power lines, and a leakage current by comparing a predetermined reference voltage with a waveform of one polarity of the output voltage waveform of the zero-phase current transformer A leakage detection circuit that is integrated into an IC for determining occurrence, a blocking unit that switches off an opening / closing unit provided on the circuit when it is determined that leakage has occurred, and a leakage that tests the leakage detection circuit by generating a pseudo leakage current An earth leakage circuit breaker with a test circuit ,
The leakage detection circuit is composed of two circuits that perform the same determination operation with the same reference voltage,
The outputs of the zero-phase current transformers are input in opposite phases to both of the leakage detection circuits, and when at least one of the leakage detection circuits determines that leakage has occurred, the blocking means performs a blocking operation ,
The leakage test circuit includes a first current path connected between the power lines on the load side of the zero-phase current transformer through the zero-phase current transformer,
A second current path connected between one power line on the power source side of the zero-phase current transformer and the other power line on the load side of the zero-phase current transformer without passing through the zero-phase current transformer;
A first rectifying means for flowing a current in one specific direction in the first current path; and a second rectifying means for flowing a current in a specific one direction in the second current path;
Closing means for selecting and closing any one of the first current path and the second current path;
An earth leakage circuit breaker characterized by generating a zero-phase current having a reverse polarity by switching both current paths by the closing means and performing a closing operation . Both of the leakage detection circuits include a reference voltage generation circuit that generates a predetermined reference voltage, a comparison circuit that compares the generated reference voltage with the output voltage of the zero-phase current transformer to determine the occurrence of leakage, and the It has a latch circuit that holds the output of the comparison circuit,
2. The earth leakage circuit breaker according to claim 1 , wherein the outputs of both of the comparison circuits are input to any one of the latch circuits, and the interruption means operates upon receiving the output of the one latch circuit. The first current path is wired so that a current flows from a specific one power line to the load side from the power source side of the zero-phase current transformer, while the second current path is a power source of the zero-phase current transformer The specific one power line on the side is wired so that current flows from the other power line to the load side,
In the path to the other power line, the first current path and the second current path have a common current path,
3. The leakage breaker circuit according to claim 1, wherein the first rectifying unit and the second rectifying unit are common rectifying units arranged in the common current path. 4. The leakage breaker according to claim 3, wherein the common rectifying means is a rectifier circuit for supplying a DC power to the leakage detection circuit.

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