JP3157386B2 - Ground fault detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault detecting device having a test device for checking whether or not the operation of the ground fault detecting device is abnormal.

[0002]

2. Description of the Related Art FIGS. 7 and 8 are circuit diagrams showing the configuration of a conventional ground fault detecting device. FIG. 7 shows a ground fault circuit breaker configured to detect a ground fault and cut off an AC electric circuit. Reference numeral 8 denotes a ground fault alarm which is configured to only output a contact signal or display upon detection of a ground fault and not to interrupt an AC electric circuit. In these figures, 1 is an AC circuit, 2 is a zero-phase current transformer, 2a
Is a secondary winding, 3 is a ground fault detection circuit connected to the secondary winding 2a, 4 is a switching element connected to an output terminal of the ground fault detection circuit 3, and 5 is a switching element 4
An output device, such as an electromagnetic device, driven by
Is a voltage drop circuit connected to a power supply circuit for the ground fault detection circuit 3, 8 is a test switch, 9 is a test winding wound around the zero-phase current transformer 2, 10 is a rectifier circuit, and 11 is a rectifier circuit. A capacitor, 12 is a contact of the circuit breaker, and 13 is a test resistor. In FIG. 7, the test device 14 is constituted by the test switch 8, the test winding 9, and the test resistor 13, and in FIG. 8, the test switch 8 and the test resistor 13 constitute the test device 14, respectively.

[0003] The operation of the conventional ground fault detecting device thus configured will be described. When a ground fault occurs in the AC circuit 1, the zero-phase current transformer 2 generates a ground fault detection signal in its secondary winding 2a, and this signal is input to the ground fault detection circuit 3. The ground fault detection circuit 3 determines the magnitude of the ground fault detection signal. If the magnitude of the ground fault detection signal exceeds a predetermined value, the output of the ground fault detection circuit drives the switching element 4 to activate the output device 5. In the circuit of FIG. 7, the contact 12 of the circuit breaker is opened by the operation of the output device 5, and the ground fault current is interrupted. In the circuit of FIG.
The operation of the output device 5 outputs a contact output or the like.

The rectifier circuit 10 rectifies the voltage of the AC circuit 1 to obtain a DC power supply of the ground fault detecting circuit 3, and the voltage drop circuit 6 uses the high voltage (for example, 1) of the AC circuit 1.
00V, 200V, 400V, etc.) to a low voltage (for example, 12V, 24V, etc.) required for the power supply of the ground fault detection circuit 3. Further, the capacitor 11 converts the pulsating current obtained by the rectifier circuit 10 to a ground fault. This is for smoothing to a direct current necessary as a power supply of the detection circuit 3.

In FIG. 7, when the test switch 8 is closed, an AC current flows to the test winding 9 through the test resistor 13 by the voltage of the AC circuit 1, and this current excites the zero-phase current transformer 2 to ground the ground. By operating the detection circuit 3, it can be confirmed that the ground fault detection device operates normally.
In the configuration of FIG. 7, immediately after the test switch 8 is closed, the contact 12 of the circuit breaker is actuated to cut off the AC circuit 1, so that the time during which power is applied to the test resistor 13 is short. A small resistor that can withstand only a short time is used.

Next, the configuration of FIG. 8 will be described. In this circuit configuration, even if a ground fault is detected and the output device 5 is activated, the AC circuit 1 is not cut off, so that the test device 14 can be used at a continuous rating. It has become. That is, an AC signal is extracted from the AC circuit 1 and is directly applied to the input terminal of the ground fault detection circuit 3 via the test switch 8 and the test resistor 13. The input terminal of the ground fault detection circuit 3 is operable by supplying a small signal.
Is small, and the test apparatus 14 can continuously operate within the allowable power even in the configuration shown in FIG. 8 in which the AC circuit 1 is not interrupted.

[0007]

By the way, in the configuration of FIG. 7, since the test device 14 is rated for a short time, the power supply side and the load side of the ground fault detecting device (that is, the point a in FIG. When the test switch 8 is closed continuously , the contact 12 of the circuit breaker does not open.
Therefore, there has been a problem that excessive power is continuously supplied to the test resistor 13 from the power supply side of the AC circuit 1 and the resistor 13 is burned out.

In the configuration of FIG. 8, since a signal for test is directly input to the ground fault detection circuit 3, the operation after the ground fault detection circuit 3 can be verified. 2 cannot be verified, for example, whether there is a disconnection of the secondary winding 2a, and the function as a test device is incomplete.

In each of the configurations shown in FIGS. 7 and 8, the magnitude of the signal generated by the test apparatus 14 has a dependency proportional to the voltage of the AC circuit 1. For example, in the case where the ground fault detection device is designed so that it can be used for the AC200V and AC400V electric circuits, the operation can be verified with a signal of an appropriate level suitable for the sensitivity current when used at AC200V.
When used at C400V, 2 at AC200V
The operation is verified with twice as large a signal level, and there is also a problem that a fault in which the sensitivity current of the ground fault detection device drifts in a dull direction cannot be found.

The present invention has been made in order to solve the above-mentioned problems, and the operation of the entire ground fault detecting device from the zero-phase current transformer 2 to the final output device 5 or the contact 12 of the circuit breaker will be described. Can be verified, even if the power supply side and load side are connected in reverse, the test switch does not burn out due to the continuous closing, and the signal level used for the test for various voltages of the AC circuit 1 It is an object of the present invention to provide a test apparatus capable of verifying an operation with a signal of an appropriate level without an excessively large signal.

[0011]

According to the present invention, there is provided a ground fault detecting apparatus comprising: a zero-phase current transformer inserted into an AC circuit; and the AC circuit operated by a current from a secondary winding of the current transformer. A ground fault detection circuit, a rectifier circuit that rectifies the voltage of the AC circuit and supplies power to the ground fault detection circuit, and a voltage drop circuit that adjusts a power supply voltage supplied to the ground fault detection circuit to a predetermined value. When, the locations are connected in series with the input side of the rectifier circuit
And a test winding wound around the zero-phase current transformer and connected to both ends of the impedance element via a test switch. It is provided. Also, a voltage drop circuit is inserted on the output side of the rectifier circuit, and the voltage drop circuit is connected between the voltage drop circuit and the impedance element .
A surge absorption capacitor for forming an L-shaped surge absorption circuit is connected between the two. Further, the voltage drop circuit is inserted on a side closer to the AC circuit than the impedance element on the input side of the rectifier circuit. Further, the voltage drop circuit is configured by a circuit or an element having a non-linear voltage-current characteristic.

[0012]

The ground fault detecting device according to the present invention excites a zero-phase current transformer by a test switch and a test winding by a voltage between both ends of an impedance element inserted in series with a power supply circuit of a ground fault detecting circuit. Get. Therefore, it is possible to perform a test of the entire ground fault detecting device from the zero-phase current transformer to the output device, and there is no fear that the test resistor is burned out even in repeated tests.

[0013]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1, 2a, 3, 4, 5, 6, 10,
Reference numerals 11 and 12 are the same as those of the above-mentioned conventional apparatus. Reference numeral 7 denotes an impedance element inserted in series between the AC circuit 1 and a rectifier circuit 10 for supplying power to the ground fault detection circuit 3. Reference numeral 8 denotes a test switch, which includes both ends of the impedance element 7 and a test winding. 9 is inserted in series in the circuit connecting
The impedance device 7, the test switch 8, and the test winding 9 constitute a test device 14. Reference numeral 21 denotes a capacitor, which is connected between the voltage dropping circuit 6 and the impedance element 7 on the output side of the rectifier circuit 10 so as to form an L-type filter with the impedance element 7.

Next, the operation will be described. In FIG.
The process from the detection of a ground fault current when a ground fault occurs to the operation of the output device 5 is the same as that of the conventional device. The operation of supplying power to the ground fault detection circuit 3 by the voltage drop circuit 6, the rectifier circuit 10, and the capacitor 11 is the same as that of the conventional one.

The operation of the test device 14 will be described.
An AC current for supplying power to the ground fault detection circuit 3 flows through the impedance element 7. When the test switch 8 is closed, a part of the AC current flowing through the impedance element 7 is shunted to the test winding 9 and the zero-phase current transformer 2
To generate a simulated signal. Therefore, by appropriately setting the impedance of the impedance element 7 and the number of turns of the test winding 9, the zero-phase current transformer 2 is excited, a test signal is supplied to the ground fault detection circuit 3, and the operation of the ground fault detection device is performed. Can be tested.

In general, the current consumption of the ground fault detection circuit 3 is several mA, the power consumption is several tens mW even if the impedance element 7 is set to, for example, 1 KΩ. Even if the circuit 8 is kept closed, it can withstand power consumption. Further, the current that can be diverted to the test winding 9 is several mA, but by increasing the number of turns of the test winding 9, a sufficient ampere-turn for a sufficient test can be obtained.

Embodiment 2 FIG. In the first embodiment, the rectifier circuit 10, the voltage drop circuit 6, and the surge absorbing capacitor 21 for protecting the switching element 4 from surge are connected to the impedance element 7 so as to form an L-shaped circuit. ,
The test impedance element 7 can be used as a surge absorbing element, and the number of components can be reduced.

Embodiment 3 FIG. In the first embodiment, the voltage drop circuit 6 is connected to the ground fault detection circuit 3 by the impedance element 7.
Although it is located closer, as shown in FIG. 2, the same operation can be obtained even if the voltage drop circuit 6 is connected to the side closer to the AC circuit 1 than the impedance element 7.

In the case of the configuration shown in FIG. 2, the voltage of the AC
Is dropped to a level close to the potential of the ground fault detection circuit 3 and the secondary winding 2a. Therefore, in this embodiment, electrical insulation between the secondary winding 2a and the test winding 9 is easy, and the entire zero-phase current transformer including the test winding 9 can be reduced in size at low cost. Become. In the embodiment shown in FIG. 2, the voltage drop circuit 6 is regarded as a simple circuit element, but as shown in FIG.
Even if 5 is used, the same effect can be exerted.

Embodiment 4 FIG. FIG. 4 shows an embodiment in which a constant voltage circuit of a series control system is used as the voltage drop circuit 6. FIG.
In the figure, 16 is a transistor, 17 is a resistor, 18 is a Zener diode, and these constitute the voltage drop circuit 6. The voltage drop circuit 6 exhibits a non-linear characteristic with respect to a change in the voltage value of the AC circuit 1.

FIG. 5 shows a change in the current flowing through the impedance element 7 with respect to a change in the voltage of the AC circuit 1. 4A shows a case where the voltage drop circuit 6 is a circuit (for example, a resistor) having a linear characteristic, and FIG. 4B shows a series control type constant voltage circuit having a non-linear characteristic as shown in FIG. The case of is shown. In the configuration of FIG. 4, the same operation of the test apparatus as in the first embodiment can be obtained. However, in the configuration of FIG. 4, as shown in FIG. , The current flowing through the impedance element 7 is substantially constant. Therefore, the current flowing through the test winding 9 can be set to a substantially constant value with respect to various voltages. When the voltage of the AC circuit 1 is high, an excessive test current flows through the test winding 9. There is no inconvenience of performing a test at a point larger than the predetermined sensitivity current of the ground fault detecting device, and a correct operation test can be performed with a current value close to the predetermined sensitivity current regardless of the voltage value of the AC circuit 1.

FIG. 4 shows a circuit in which the transistor 16 is analogously controlled by a zener diode 18 for generating a reference voltage as a voltage drop circuit. However, as shown in FIG. 6, a constant current diode is used instead of the voltage drop circuit. The same effect can be obtained even if 19 is used.

[0023]

As described above, according to the present invention, even if the test equipment is operated continuously, the test equipment does not burn out due to overpower, and therefore, also protects the reverse connection of the ground fault circuit breaker. Further, the present invention can be applied to a ground fault alarm device, and can further test the operation of the entire ground fault detecting device including the zero-phase current transformer.

Further, the test impedance element can be used also as a surge absorbing circuit element, and the voltage applied to the test apparatus is set to a value close to the potential of the secondary winding of the current transformer for ground fault detection. Thereby, the number of parts of the apparatus can be reduced and the apparatus can be downsized.

Further , the voltage drop circuit is connected to the input side of the rectifier circuit.
On the side closer to the AC circuit than the impedance element
The voltage applied to the test equipment is
Test for easy electrical insulation between secondary winding and test winding
Make the entire zero-phase current transformer, including the windings, smaller and cheaper
be able to. Furthermore, the voltage drop circuit for obtaining the power supply of the ground fault detection device has a non-linear characteristic with respect to the voltage, so that it is suitable for a constant test current regardless of the voltage value of the AC circuit. There is an effect that a test of a proper operation can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram illustrating a ground fault detecting device according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram illustrating a ground fault detection device according to a second embodiment of the present invention.

FIG. 3 is a circuit configuration diagram illustrating a ground fault detection device according to a modification of the second embodiment.

FIG. 4 is a circuit configuration diagram illustrating a ground fault detection device according to a third embodiment of the present invention.

FIG. 5 is a characteristic diagram for explaining the operation of the third embodiment.

FIG. 6 is a circuit configuration diagram illustrating a ground fault detection device according to a fourth embodiment of the present invention.

FIG. 7 is a circuit configuration diagram showing a conventional ground fault detection device.

FIG. 8 is a circuit configuration diagram showing a conventional ground fault detection device.

[Explanation of symbols]

1 AC circuit, 2 zero-phase current transformer, 2a secondary winding, 3
Ground fault detection circuit, 4 switching element, 5 output device, 6 voltage drop circuit, 7 impedance element, 8 test switch, 9 test winding, 10 rectifier circuit, 11 capacitor, 12 breaker contact, 13 test resistor, 14 Test equipment, 15 transformers, 16 transistors, 17 resistors, 18 Zener diodes, 19 constant current diodes, 21 surge absorption capacitors.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 3/32-3/347 H02H 3/05 H02H 3/16 H01H 83/02 H01H 83/04

Claims (4)

(57) [Claims] 1. A zero-phase current transformer inserted into an AC circuit, a ground fault detection circuit of the AC circuit operated by a current from a secondary winding of the zero-phase current transformer, and a rectification of a voltage of the AC circuit. rectifying circuit for supplying power to the ground fault detector circuit, the voltage drop circuit for adjusting the power supply voltage supplied to the ground fault detection circuit to a predetermined value, the connected in series to the input side of the rectifier circuit
An impedance element for generating a voltage due to a current consumption of a ground fault detection circuit ; a test winding wound around the zero-phase current transformer and connected to both ends of the impedance element via a test switch. A ground fault detecting device. 2. A voltage drop circuit is inserted at an output side of a rectifier circuit, and is provided between the voltage drop circuit and an impedance element.
Form an L-type surge absorption circuit between the impedance element
2. The ground fault detecting device according to claim 1, wherein a surge absorbing capacitor to be formed is connected. 3. The ground fault detecting device according to claim 1, wherein the voltage drop circuit is inserted on a side closer to the AC circuit than an impedance element on an input side of the rectifier circuit. 4. The ground fault detecting device according to claim 1, wherein the voltage drop circuit is constituted by a circuit or an element having a non-linear voltage-current characteristic. .