JPH09322383A - Leak detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leak detector, by which a testing device is not burnt even if the testing device is continuously operated, and the testing operation can be securely performed even for a control circuit for detecting leaking having the surge removing function based on polarity discrimination. SOLUTION: In a leak detector, which obtains control power supply from a main circuit 1 connected to an AC power supply, the AC side of a rectifier circuit 7, whose DC side is connected to the power supply of a control circuit 4, is connected to a main circuit 1 through a voltage dropping element 8. A constant voltage element 15 is connected to the DC side of the rectifier circuit 7. Furthermore, resistors 10a and 10b, which are constituted in series so that one end is connected to the ground of the control circuit, are connected to any one terminal on the AC side of the rectifier circuit 7 through a test switch 9. The signal, whose voltage is divided as specified at the connecting point of the resistors 10a and 10b, is connected to resistors 12 and 13b connected to both ends of the inputs of the control circuit 4 through a capacitor 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage detecting device for detecting an earth leakage or a ground fault generated in an AC electric line, and more particularly to an earth leakage detecting device having a test circuit.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a circuit configuration of a conventional leakage detecting device disclosed in, for example, Japanese Patent Laid-Open No. 5-182579. In the figure, 1 is an AC main circuit (hereinafter referred to as the main circuit), 2 is an opening / closing contact for opening and closing the main circuit 1, 3 is the main circuit 1 passing through, and a secondary winding 3a and a test winding 3b are wound. The zero-phase current transformer 4 is a control circuit in which the input side is connected between both ends of the secondary winding 3a of the zero-phase current transformer 3, and 7 is a rectifier circuit that supplies power to the control circuit 4. The alternating current side is connected to the main circuit 1 via the voltage drop element 8. Reference numeral 5 is a thyristor controlled by the output of the control circuit 4, the anode of which is connected to the AC main circuit 1 via the electromagnetic trip device 6 together with the voltage drop element 8 connected to one end of the rectifier circuit 7 on the AC side. The gate is connected to the output side of the control circuit 4, and the cathode is connected to the low voltage side of the control circuit 4. The electromagnetic trip device 6 is mechanically interlocked with the open / close contact 2. When the output of the control circuit 4 brings the thyristor 5 into conduction and the electromagnetic trip device 6 is excited, the open / close contact 2 is opened and closed. The main circuit 1 is configured to be opened. The high voltage side and the low voltage side of the power source of the control circuit 4 are connected to the direct current side of the rectifier circuit 7, respectively.
Reference numeral 9 is a test switch, and 10 is a test resistor, which are connected in series with each other and are connected to the test winding 3b of the zero-phase current transformer 3.
Is connected to the main circuit 1 via.

The conventional earth leakage detecting device is constructed as described above, and when earth leakage occurs in the main circuit 1, the zero-phase current transformer 3
Produces an output voltage on the secondary winding 3a. The control circuit 4 amplifies this output voltage and, at the same time, outputs a gate signal to the gate of the thyristor 5 to make the thyristor 5 conductive when the output voltage exceeds a predetermined level by an internal discriminator. As a result, the electromagnetic trip device 6 is excited, the open / close contact 2 is activated, and the main circuit 1 is opened. Further, when the test switch 9 is closed, a predetermined current flows from the AC power source of the main circuit 1 to the test winding 3b of the zero-phase current transformer 3 via the test switch 9 and the test resistor 10, thereby causing the secondary winding. Three
An output voltage similar to that described above is generated in a and the control circuit 4
Then, the electromagnetic tripping device 6 is excited by the thyristor 5 to open the circuit breaker 2.

FIG. 5 shows a circuit configuration of another conventional type of leakage detecting device, which includes a test switch 9 and a test resistor 1.
The connection position of 0 is different from the above-mentioned conventional example, and one end of the test switch 9 and the test resistor 10 connected in series is connected to the rectification circuit 7.
Is connected to the high-voltage side of the DC side, that is, the power supply of the control circuit 4, and the remaining one end is connected to either one end of the input side of the control circuit.

[0005]

In the conventional earth leakage detecting device shown in FIG. 4, a test signal is obtained from the main circuit 1 to which a commercial power source is energized via a test resistor 10 which limits a current. Therefore, the same potential as that of the main circuit 1 is applied to both ends of the test resistor 10 and the test switch 9, and it is necessary to use a test resistor and a test switch having high breakdown voltage. Further, the power supply voltage of the main circuit 1 is 100V,
Due to the high voltage of 200 V and 415 V, the power loss of the test resistor 10 during the test operation becomes very large, and not only a large test resistor for power is required, but also the test resistance is generated due to heat generation when the test operation is continuously performed. However, there was a problem that it was burnt out. Further, the zero-phase current transformer 3 needs to have a tertiary winding as the test winding 3b, which causes a problem of high cost.

Further, the conventional example of FIG. 5 is an example of an earth leakage detection device which prevents burnout of a test resistor during a continuous test operation, which is a problem of the conventional example of FIG. 4 described above, and is a low voltage control circuit 4. Of the control circuit 4 by forcing the signal to a predetermined level and inputting the signal to the input side of the control circuit 4 together with the output of the secondary winding 3a of the zero-phase current transformer 3.
Is operating. In this conventional example, the power supply of the control circuit whose voltage has been reduced is made small and input to the input side of the control circuit. However, this is a control circuit that operates when the input voltage of the control circuit becomes high. The case is shown as an example. On the contrary, in the case of the control circuit which operates when the input voltage becomes low, the resistor connected to the input side and one end of the test switch are connected to the low voltage side of the rectifier circuit.
In the conventional example of FIG. 5, the voltage applied to the test circuit is a low voltage and a small current, so that the test circuit can be downsized and the test resistor can be prevented from burning.

However, the problem with the conventional example of FIG. 5 is that the test operation cannot be performed unless the control circuit used here operates with a DC input signal. By the way, in many of today's leakage detection devices, a control circuit in the leakage detection device incorporates a discrimination circuit for distinguishing between a surge signal and an actual leakage signal so as not to malfunction due to a transient signal such as a lightning surge. However, in the conventional example shown in FIG. 5, the control circuit is forcibly operated by the DC signal, and it is not possible to test whether the discrimination circuit is normal or abnormal.

Further, as an example of a control circuit which prevents malfunction due to a transient signal such as lightning surge, Japanese Patent Laid-Open No. 2-194
Although there is a leakage detection device disclosed in Japanese Patent No. 68, when this leakage detection device is used as a control circuit, the test operation of the conventional test circuit of FIG. 5 cannot be performed. This is a leakage detection device characterized in that the leakage detection device is for the purpose of surge elimination, the leakage signal is a positive and negative alternating periodic signal, that is, not detected unless it is an AC signal,
The conventional example of FIG. 5 has a problem that a control circuit that does not malfunction due to such a lightning surge cannot be used.

The present invention has been made in order to solve these problems, and it is compact in size without using a test switch having a high breakdown voltage, a test resistor for electric power, and a zero-phase current transformer with a tertiary winding. The purpose is to obtain an earth leakage detection device that is inexpensive, does not burn out the test resistance even during continuous test operation, and can perform highly reliable test operation even with a control circuit that does not malfunction due to lightning surge. .

[0010]

A leakage detecting device according to the present invention is electromagnetically coupled to a main circuit connected to an AC power source, detects an unbalanced current in the main circuit, and outputs the unbalanced current to a secondary winding. A zero-phase current transformer, a control circuit that receives a signal from the secondary winding of the zero-phase current transformer on the input side, and generates a leakage detection signal when the magnitude of the signal is equal to or greater than a predetermined value, in the main circuit A rectifier circuit connected via a voltage drop element, and a DC side connected via a constant voltage element to the control circuit for power supply, an AC of the rectifier circuit via a test switch for checking the control function of the control circuit. A test circuit is provided that connects one end of the control circuit to the input end of the control circuit.
The AC component at one end of the rectifier circuit on the AC side is reduced in voltage, and the waveform is shaped and applied to the input end of the control circuit.

In the above structure, the test circuit is
After the AC component at one end on the AC side of the rectifier circuit is divided by a voltage dividing resistor, the DC component is cut off by a capacitor and is supplied to the control circuit input terminal.

In addition to the leakage detection function, the control circuit has
It has an active filter function for removing harmonics existing in the main circuit.

As the test switch, a switch composed of a photoelectric element is used.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. 1 is a diagram showing a circuit configuration of an earth leakage detection device according to Embodiment 1 of the present invention. In the figure, 1
Nos. 9 to 9 are the same as those in the conventional example. Reference numeral 4a is an amplifier provided in the control circuit 4, and 4b is an electric leakage discriminator provided in the control circuit 4 as well. Reference numerals 10a and 10b denote resistors for dividing (that is, attenuating) the signal including the AC component from the test switch 9 and attenuating the resistors to a predetermined magnitude by the resistance values of the resistors 10a and 10b. Reference numeral 11 is a capacitor for removing a DC component, which removes a DC component from the attenuated signal. Reference numeral 12 is a resistor that constitutes a differentiating circuit together with the capacitor 11, and a signal from which the direct current component is removed is generated at both ends of this resistor 12. Therefore, this resistor 12
Of the control circuit 4 on the opposite side of the
Control circuit 4 by connecting to the reference side of the input terminal of
AC waveform centered on the reference voltage of
It occurs at the connection point between 1 and resistor 12. Also 13a, 13b
Is an input resistance of the control circuit 4, and functions as an adder together with the resistance 17. By connecting resistors 13a, 13b and 17 to the amplifier 4a inside the control circuit 4 as shown in the figure, the resistors 13a and 13b are provided on the output side of the amplifier 4a.
The signals input to are amplified by the ratio with the resistor 17, respectively, and then added, that is, combined and output. In addition, 1
5 is a constant voltage element that limits the voltage across the DC side of the rectifying circuit 7, 16 is a smoothing capacitor that smoothes the full-wave rectified waveform rectified by the rectifying circuit 7, and 14 is a zero-phase current transformer. A resistor for converting the output current of the secondary winding 3a of No. 3 into a voltage, which is omitted in FIGS. 4 and 5 of the conventional example.

The test operation of the earth leakage detection device configured as described above will be described with reference to FIG. FIG. 2A shows the main circuit 1.
Are shown. FIG. 2B shows the voltage across the DC side of the rectifier circuit 7. The symbol Vz in the figure indicates the limiting voltage of the constant voltage element 15 connected to both ends of the rectifier circuit 7 on the DC side. FIG. 2C shows the voltage across the AC side of the rectifier circuit 7. The symbol Vf in the figure indicates the forward voltage of the rectifying element inside the rectifying circuit 7, and the forward voltage Vf is generally less than 1V. As is clear from FIG. 2 (c), even if the voltage of the main circuit 1 is high, most of it is applied to both ends of the voltage drop element 8, and the circuit portion after the rectifier circuit 7 has a voltage of Vz + 2Vf at the maximum, and Vz is 1
If the voltage is about 0 and several V, all the circuits after the rectifying circuit 7 can be the low voltage section. Next, the relationship of the voltage between the terminals of the rectifier circuit 7 will be described.
That is, in the figure, the side with the earth symbol is hereinafter referred to as the earth. The voltage of each terminal on the AC side of the rectifier circuit 7 with respect to this ground is shown in FIGS. 2 (d) and 2 (e). In addition,
The voltage of the high-voltage side terminal on the DC side with respect to earth is
Same as (b). As is apparent from FIGS. 2 (d) and 2 (e), the voltage waveforms of the terminals on the AC side of the rectifier circuit 7 when viewed from the ground have different phases, but both are connected to the main circuit 1 with a commercial power source. It is a waveform close to a rectangular wave of the same frequency as. Therefore, an AC voltage can be obtained between one of the terminals on the AC side of the rectifier circuit 7 and the ground.

After that, the test switch 9 during the test operation
Will be described in the closed state. When the test switch 9 is closed, a current flows to the ground through the resistors 10a and 10b, but since the resistors 10a and 10b are connected in series, the resistors 10a and 1
A voltage divided by the ratio of the resistance value of 0b is generated. When this voltage division ratio, that is, the amount of attenuation is set to a predetermined value, the voltage at the connection point between the resistors 10a and 10b is obtained as shown in FIG.
The waveform of is obtained. Here, Vref in the drawing is a reference voltage in the control circuit 4, which is a voltage applied to the positive phase input of the amplifier 4a, and when the attenuation amount of the voltage is appropriately set, the voltage Vref in FIG. The waveform of 2 (e) can be an AC waveform centered on Vref. Therefore, resistance 1
The functions of 0a and the resistor 10b are not for the purpose of attenuation but to obtain an AC waveform centered on the reference voltage Vref as much as possible.

As described above, the resistors 10a and 10b are provided.
Thus, although an AC waveform centered on the reference voltage Vref can be obtained, it cannot be directly input to the input side of the control circuit 4. This is because the central value of the AC waveform and the reference voltage Vr with respect to the magnitude of the signal handled by the control circuit 4.
This is because the deviation of ef is large, and if the reference voltage Vref changes or the power supply voltage changes, the deviation becomes extremely large. The capacitor 11 and the resistor 12 are for removing the deviation between the center value of the AC waveform and the reference voltage Vref, and the direct current component is cut by the differentiating circuit configured by the capacitor 11 and the resistor 12 to center the reference voltage Vref. To obtain the complete AC waveform. This AC waveform is shown in FIG.
Note that the voltage division by the resistors 10a and 10b is omitted,
A waveform centered on the reference voltage Vref can be obtained only by the differentiating circuit, but if the center of the waveform is not brought close to the reference voltage Vref in advance by dividing the voltage by the resistors 10a and 10b, a large amount of direct current will be applied to the differentiating circuit. As the minutes enter, the operation becomes unstable, that is, the operation immediately after the test switch 9 is closed becomes unstable and the test operation is delayed.
The voltage is divided by the resistors 10a and 10b in advance.

The test AC signal thus obtained is input to the control circuit 4 via the resistor 13b, and is combined with the signal of the zero-phase current transformer 3 and processed as described above.
As for the magnitude of the above-mentioned test signal, the amplification factor of the amplifier 4a is set by the resistors 13b and 17, and the test signal has an appropriate magnitude.

In short, in the earth leakage detecting device configured as described above, when the test switch is closed, the DC component of the signal containing the AC component obtained from the rectified circuit whose voltage is lowered is removed by the capacitor. At the same time, the waveform is shaped, added to the signal of the zero-phase current transformer, and input to the control circuit. By setting the above signal to a predetermined magnitude,
The control circuit operates and the test operation is performed as if the zero-phase current transformer detected the unbalanced current. The signal input to the control circuit at this time is an AC signal with the same frequency as the commercial power supply, and even if the control circuit waits for the surge removal function, the same signal as when the leakage of the commercial power supply occurs is input. Therefore, the control circuit can be surely tested.

Further, since the entire test circuit is constructed so as to operate at a low voltage and a small current, not only can it be constructed in a small size, but there is a concern that the test switch will be burned out even if the test operation is continued by being continuously pressed. There is no.

Embodiment 2 FIG. FIG. 3 shows a circuit configuration diagram of the second embodiment. In the first embodiment shown in FIG. 1, the amplifier 4a on the input side of the control circuit 4 is configured as a multi-input adder. The circuit of FIG. 3 is an embodiment in which the amplifier 4a is developed into an active filter which is a multi-input adder and serves as a low-pass filter. 20, 23
The capacitors 21 and 22 and the resistors 13a and 13b are components of the active filter based on the amplifier 4a. The circuit configuration shown in FIG. 3 is a well-known circuit configuration as a basic circuit of a second-order low-pass filter, but a resistor 13b is added together with a resistor 13a for inputting a signal of the zero-phase current transformer 3 to input a test signal. With this configuration, the same test operation as in the case of the first embodiment can be performed, and as an effect of the active filter, a leakage detection device that is not affected by the harmonics existing in the main circuit can be obtained.

In both the first and second embodiments, the test switch 9 for performing the test operation is described as a normal switch. However, in the present invention, a photoelectric element such as a photo coupler is used as the test switch 9. be able to. Conventionally, since the voltage of the main circuit is directly applied to both ends of the test switch, a photoelectric element such as a photocoupler having a low withstand voltage and a small current capacity can be used. In the present invention, since the entire test circuit is composed of low voltage and small signal,
These photo couplers and the like can be used as the test switch, and the test operation can be performed while being completely insulated from the main circuit.

Further, in the above-mentioned embodiment, the case where the leakage detecting device is used for the leakage breaker has been described, but it may be used for a leakage relay or the like, and the same effect as that of the above-mentioned embodiment is obtained.

[0024]

Since the present invention is constructed as described above, it is not necessary to provide a third winding in the zero-phase current transformer, and it can be constructed at low cost, and it is a component used in a test circuit. Since all can be used for small signals, the circuit can be made compact, and at the same time, even if there is a continuous test operation, there is no burnout of parts, and an AC signal with the same frequency as the power supply connected to the main circuit is used as a test signal. Therefore, it is possible to provide the control circuit with a surge eliminating function.

Further, since the amplifier on the input side of the control circuit has a function as an active filter, it is possible to eliminate the influence of malfunction due to harmonics of the main circuit.

Further, since a photo coupler or the like can be used as the test switch, it is possible to perform switching isolated from the main circuit.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an earth leakage detection device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram illustrating the operation of the present invention.

FIG. 3 is a circuit configuration diagram showing an electric leakage detector according to Embodiment 2 of the present invention.

FIG. 4 is a circuit configuration diagram showing a conventional leakage detection device.

FIG. 5 is a circuit configuration diagram showing another conventional leakage detection device.

[Explanation of symbols]

1 main circuit, 2 switching contacts, 3 zero-phase current transformer, 3a secondary winding, 4 control circuit, 4a amplifier, 4b earth leakage discriminator, 5 thyristor, 6 electromagnetic trip device, 7 rectifier circuit, 8 voltage drop element , 9 Test switch, 10a,
10b, 12, 13a, 13b, 14, 17, 21, 2
2 resistors, 11, 16, 20, 23 capacitors, 15
Constant voltage element.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H02J 3/01 H02J 3/01 B 17/00 17/00 B

Claims (4)

[Claims] 1. A zero-phase current transformer, which is electromagnetically coupled to a main circuit connected to an AC power source, detects an unbalanced current of the main circuit and outputs the unbalanced current to a secondary winding, and this zero-phase current transformer. The control circuit that receives the signal of the secondary winding at the input side and generates the leakage detection signal when the magnitude of the signal is a predetermined value or more, is connected to the main circuit through the voltage drop element, and the constant voltage element is connected. A rectifier circuit whose direct current side is connected to the control circuit for power supply via a test switch for checking the control function of the control circuit, and either one of the alternating current side of the rectifier circuit and the input end of the control circuit. Leakage detection, characterized in that the test circuit is configured to reduce the voltage of the AC component at one end of the rectifier circuit on the AC side and to shape the waveform of the AC component to be applied to the input end of the control circuit. apparatus. 2. The test circuit divides the AC component at one end on the AC side of the rectifier circuit with a voltage dividing resistor, and then cuts the DC component with a capacitor and supplies it to the control circuit input terminal. The leakage detection device according to claim 1, wherein 3. The leakage detection device according to claim 1, wherein the control circuit has an active filter function for removing harmonics existing in the main circuit, in addition to the leakage detection function. . 4. The leakage detection device according to claim 1, wherein the test switch is a switch including a photoelectric element.