KR101638632B1 - Leakage current breaking apparatus - Google Patents

Abstract

Disclosed is a leakage preventing device capable of distinguishing between a surge current and a leakage current by using a duration time, operating only when a leakage current occurs, and further varying an operation time.

According to the present invention, there is provided a leakage current cut-off device including a power supply unit for supplying power to the inside of a vehicle, comprising: a zero-current transformer (ZCT) for detecting a surge current and a leakage current generated in a distribution line; A controller for outputting a signal corresponding to a voltage induced in the secondary coil of the video current transformer by the surge current or leakage current and operating the earth leakage shutoff device when an operation signal for the operation of the earth leakage shutoff device is received; And a surge protector for determining whether a surge current or a leakage current is generated according to the duration of the signal output from the controller and outputting an operation signal of the earth leakage interrupter to the controller when a leakage current is generated; The present invention provides an electric leakage preventing device comprising:

Surge current, Leakage current, Leakage current, Shutdown, Video current transformer, Resistor, Capacitor

Description

{LEAKAGE CURRENT BREAKING APPARATUS}

The present invention relates to a leakage preventing device, and more particularly, to a leakage preventing device that distinguishes between a surge current and a leakage current, operates only when a leakage current is generated, and can further change an operation time.

In general, a leakage current breaker is a type of leakage current breaker in which when a leakage current due to insulation deterioration of an electric device connected to a line or a line and a leakage current due to a human body contact of a load- It is a device to prevent in advance. Electrical circuits of transformers with high-voltage currents, and electrical facilities in pots with explosion hazards must be equipped with earth-leakage circuit breakers for safety reasons. Also, it is recommended to install an earth leakage circuit breaker to prevent electric shocks in electric circuits installed in places with high humidity and in places where outdoor people can easily reach.

However, it is a reality that such an earth leakage breaker is inconvenient to use due to a large number of malfunctions due to an unexpected surge current. Generally, both the surge voltage and the leakage current are larger than the preset reference voltage in the circuit. Therefore, the surge current is recognized as the leakage current in the earth leakage breaker, and the surge current often operates even when the surge current is generated. In order to prevent such a malfunction due to the surge current, a technique has been proposed in which a circuit for blocking or filtering the surge current is provided in the earth leakage breaker.

1 is a configuration diagram of a conventional earth leakage breaker.

Referring to FIG. 1, in the conventional earth leakage breaker 10, a current flowing in a primary coil is induced to a secondary coil through a ZCT (Zero Current Transformer) 11, 12 to the signal voltage. The signal voltage is input to the IC chip 14 through a surge protection circuit 13 for filtering a surge voltage using a filter composed of a resistor R and a capacitor C for distinguishing the signal voltage from a surge voltage And is compared with the reference voltage of the op-amp (OP-AMP) in the IC chip 14 to output an output signal. This output signal is used as a switching signal through the noise filter 15. [ The IC chip 14 receives the voltage from the power supply unit 16.

The circuit breaker 10 filters the surge current by forming the surge protection circuit 13 at the front end of the IC chip 14. However, there is a limit when the primary side current is large. In this case, the capacity of the capacitor C3 must be increased. This is because the ZCT 11 is connected to the input terminal of the zero- The impedance of the circuit is increased and the sensitivity current is changed, which makes it impossible to use the device.

In addition, the surge current itself can be reduced by increasing the number of turns of the ZCT 11. This increases the size of the bridge transformer 11, increases the price in proportion thereto, There is a problem in that it is difficult to apply it. In addition, since the operation time of the conventional earth leakage breaker 10 is characteristic of the product, it is fixed when it is determined once, so that it is impossible to apply it according to the situation, and the use width of the product is limited.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electric leakage preventing device capable of operating a electric leakage arrester only when a leakage current is generated by using a duration of a surge current and a leakage current in a distribution line .

It is another object of the present invention to make it possible to vary the operation time of the earth leakage breaker.

According to an aspect of the present invention,

(ZCT) for detecting a surge current and a leakage current generated in a power distribution line; A controller for outputting a signal corresponding to a voltage induced in the secondary coil of the video current transformer by the surge current or leakage current and operating the earth leakage shutoff device when an operation signal for the operation of the earth leakage shutoff device is received; And a surge protector for determining whether a surge current or a leakage current is generated according to the duration of the signal output from the controller and outputting an operation signal of the earth leakage interrupter to the controller when a leakage current is generated; The present invention provides an electric leakage preventing device comprising:

In one embodiment of the present invention, the surge protector receives a signal output from the control unit as a switching signal, and has a first switch connected to the power source through the first resistor (R1) (TR1); A voltage at a connection point between the first switch TR1 and the first resistor R1 is input as a switching signal through the second resistor R2 and one end is connected to the power source through the third resistor R3, A second switch TR2 connected to ground; A fourth resistor R4 and a fifth resistor R5 connected in parallel to the second switch TR2 between a connection point between the second switch TR2 and the third resistor R3 and the ground; And a capacitor (C) connected in parallel to the fifth resistor (R5) between a connection point of the fourth resistor (R4) and a fifth resistor (R5) and ground, and the capacitor (C) (R5), and outputs an operation signal to the control unit when the capacitor (C) is charged.

In this case, when the control unit outputs a signal corresponding to the induced voltage due to the leakage current, the capacitor C is preferably fully charged, and the control unit outputs a signal corresponding to the induced voltage by the surge current It is preferable that the capacitor C is not fully charged.

In an embodiment of the present invention, the control unit may further include a filtering unit for removing a noise signal included in the signal output from the control unit.

In an embodiment of the present invention, the controller compares the voltage induced in the secondary coil of the video current transformer with the predetermined reference voltage by the surge current or the leakage current, and when the induced voltage is greater than the reference voltage, It is preferable to output a voltage.

In another embodiment of the present invention, the surge protector receives a signal output from the control unit as a switching signal, and has a first end connected to the power source through the first resistor (R1) Switch TR1; A voltage at a connection point between the first switch TR1 and the first resistor R1 is input as a switching signal through the second resistor R2 and one end is connected to the power source through the third resistor R3, A second switch TR2 connected to ground; A fourth resistor R4 and a fifth resistor R5 connected in parallel to the second switch TR2 between a connection point between the second switch TR2 and the third resistor R3 and the ground; At least two capacitors (C1 to Cn) connected in parallel to the fifth resistor (R5) between the connection point of the fourth resistor (R4) and the fifth resistor (R5) and the ground; And a third switch SW for selectively connecting a connection point between the fourth resistor R4 and the fifth resistor R5 and any one of the at least two capacitors C1 through Cn. The selectively coupled capacitor charges a voltage across the fifth resistor (R5) and outputs an operation signal to the controller when the connected capacitor is charged.

Preferably, the operation time of the earth leakage protection device is adjusted by varying the output time of the operation signal by selectively connecting the two or more capacitors.

Also, it is preferable that the operation time of the earth leakage blocking device is determined by the capacitance of the fifth resistor (R5) and the selectively connected capacitor.

When the control unit outputs a signal corresponding to the induced voltage due to the leakage current, the selectively connected capacitor is preferably fully charged. Further, the control unit may control the signal corresponding to the induced voltage by the surge current When outputting, the selectively coupled capacitor is preferably not fully charged.

According to the present invention, it is possible to distinguish the leakage current from the leakage current by using the characteristic that the surge current is shorter than the leakage current in the leakage current interrupter, and by operating the leakage current interrupter only when the leakage current occurs, So that the reliability of operation can be increased in the electric leakage screening device.

In addition, according to the present invention, since the operation time of the electric leakage screening device can be varied, it is possible to broaden the use width according to a necessary situation.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The present invention provides a short circuit breaking device. The leakage current blocking device of the present invention operates only when a leakage current is generated without generating a surge current, thereby preventing malfunction due to an unexpected surge current. As described above, in the present invention, the leakage current is distinguished from the leakage current, so that the leakage preventing device operates when a leakage current occurs. In the present invention, the distinction between the surge current and the leakage current uses the duration of the surge current and the leakage current. Further, according to the present invention, the operation time of the electric leakage screening device is varied, so that the use width of the electric leakage screener can be widened according to the situation.

2 is a graph comparing the duration of the surge current and the leakage current according to the present invention.

As shown in FIG. 2, the surge current and leakage current detected in the distribution line are larger than the reference voltage Vref, and the surge current is shorter in duration than the leakage current. That is, when the duration of the surge current is t1 and the duration of the leakage current is t2, t1 and t2 have a relationship of t1 < t2. The present invention distinguishes between the occurrence of a surge current and a leakage current by using the difference between the duration of the surge current and the leakage current and makes it possible to operate the leakage breaker only when a leakage current occurs. .

3 is a configuration diagram of an electrical leakage preventing device according to an embodiment of the present invention.

3, an earth leakage protection device 100 according to an exemplary embodiment of the present invention includes a ZCT 110, a controller 120, a power source 130, a filter 140, 150).

The ZCT 110 is a device for detecting a leakage current to a distribution line. In particular, when an accidental current such as a leakage current or a surge current is generated in the distribution line, a current is induced in the secondary coil of the video current transformer 110, and the current of the secondary coil is converted into a voltage by a predetermined resistance. The thus induced voltage is supplied to the control unit 120. [

The control unit 120 includes an operational amplifier (OP-AMP) (not shown), and the output voltage is determined by comparing the induced voltage with the predetermined reference voltage by the operational amplifier. When an accidental current such as a surge current or a leakage current occurs, the induced voltage is detected to be larger than the reference voltage as shown in FIG. 2, and the operational amplifier outputs the output through the output terminal. These outputs correspond to surge currents and leakage currents, and the magnitude and duration of the output signal depend on the magnitude and duration of the surge current or leakage current.

The power supply unit 130 supplies operating power to the control unit 120 and the surge protection unit 150.

The filter 140 is connected in parallel with a resistor and a capacitor to filter the noise signal included in the output signal from the controller 120.

The surge protector 150 determines whether the output signal is due to surge current or leakage current depending on the duration of the signal output from the controller 120. If the output signal is due to a surge current, It outputs an operation signal. In other words, the output signal from the control unit 120 is caused by the surge current or the leakage current, and determines whether or not to output the operation signal according to the duration of the output signal. Whether or not the operation of the electric leakage preventing device is determined according to whether the operation signal is output or not is determined. Accordingly, the surge protector 150 does not output an operation signal when a surge current having a short duration is generated, thereby preventing the electric leakage shield device from operating. When a leakage current having a relatively long duration is generated, the surge protector 150 outputs an operation signal So that the electric leakage preventing device operates.

To this end, the surge protection unit 150 includes a first switch TR1, a second switch TR2, a plurality of resistors R1 to R5, and a capacitor C. [ The first switch TR1 uses a signal output from the control unit 120 as a switching signal. One end of the first switch TR1 is connected to the power supply unit 120 through the first resistor R1 and the other end is connected to the ground. Further, the second switch TR2 uses the voltage at the connection point of the first switch TR1 and the first resistor R1 as a switching signal. One end of the second switch TR2 is connected to the power supply unit 120 through the third resistor R3 and the other end is connected to the ground. The power source at the connection point of the second switch TR2 and the third resistor R3 is distributed by the fourth resistor R4 and the fifth resistor R5. The connection point of the fourth resistor R4 and the fifth resistor R5 is connected to the output terminal. The output signal of the output terminal is input to the control unit 120. The fifth resistor R5 is connected in parallel with the capacitor C and the voltage across the fifth resistor R5 is charged to the capacitor C.

Referring to FIG. 3, the operation of the earth leakage protection device 100 according to an embodiment of the present invention will be described. When a surge current or a leakage current occurs in the distribution line, a current is induced in the secondary coil of the video current transformer 110 in the earth leakage breaker 100 of the present invention. The current induced in the secondary coil is converted into a voltage by the sensitivity resistor 111 and input to the controller 120. The control unit 120 compares the induced voltage with the reference voltage by an internal operational amplifier, and outputs a signal determined by the comparison. The magnitude and duration of this output signal is determined by surge current or leakage current.

First, when the leakage current occurs, the induced voltage due to the leakage current is output to the operational amplifier of the control unit 120 because the induced voltage is higher than the reference voltage. This high signal has a magnitude and duration corresponding to the induced voltage by the leakage current. When the high signal is output as described above, the first switch TR1 is turned on. When the first switch TR1 is turned on, the switching signal of the second switch TR2 by the power supply unit 130 goes out to the ground via the first switch TR1 and the second switch TR2 is turned off. The second switch TR2 is turned off and the operating power from the power supply unit 130 is distributed to the fourth resistor R4 and the fifth resistor R5 through the third resistor R3 and is supplied to the fifth resistor R5 Voltage is applied. The capacitor C is charged by the voltage distributed to the fifth resistor R5. When charging of the capacitor C is completed, an operation signal is outputted to the output terminal and inputted to the control unit 120. [ When the operation signal is received, the control unit 120 operates the earth leakage protection device 100. The leakage current is maintained until the capacitor C is fully charged because its duration is relatively long, and when it is fully charged, the operation signal is output to the output terminal. In this way, when a normal leakage current occurs, the leakage current is maintained so that the capacitor C is fully charged up to the voltage applied to the fifth resistor R5, and an operation signal is outputted to the output terminal, 100 are operated.

On the other hand, when the surge current is generated, the induced voltage due to the surge current is output to the operational amplifier of the control unit 120 because the induced voltage is higher than the reference voltage. This high signal has a magnitude and duration corresponding to the induced voltage by the surge current. Thus, when the high signal is output, the first switch TR1 is turned on. When the first switch TR1 is turned on, the switching signal of the second switch TR2 by the power supply unit 130 goes out to the ground via the first switch TR1 and the second switch TR2 is turned off. When the second switch TR2 is turned off, the operating power from the power supply unit 130 passes through the third resistor R3 and is distributed to the fourth resistor R4 and the fifth resistor R5, . The capacitor C is charged by the voltage distributed to the fifth resistor R5. However, since the surge current has a short duration, the capacitor C can not be fully charged and is destroyed. That is, the surge current can not fully charge the capacitor C until the operation signal is output from the output terminal, and then it disappears. Accordingly, since the operation signal is not output, the controller 120 does not operate the earth leakage breaker 100. [ In this way, when the surge current is generated, the surge current can not be maintained until the capacitor C is completely charged to the voltage applied to the fifth resistor R5, so that the capacitor C is not charged and the operation signal is outputted to the output terminal The electric leakage preventing device 100 is not operated by the control part 120.

Here, the voltage applied to the fifth resistor R5 can be expressed by the following equation (1), and the time to charge the capacitor C up to the voltage applied to the fifth resistor R5, that is, the time Can be controlled by the time constant (RC) shown in Equation (2).

[Equation 1]

[Equation 2]

Where Vi is the voltage across the fifth resistor, C is the capacitance of the capacitor, and R is the fifth resistor value.

4 is a configuration diagram of an electrical leakage preventing device according to another embodiment of the present invention.

4, an earth leakage blocking device 200 according to another embodiment of the present invention includes a ZCT 210, a controller 220, a power source 230, a filter 240, a surge protector 240, 250 and an operation time adjustment unit 260. Here, the earth leakage protection device 200 according to another embodiment of the present invention is the one in which the operation time adjustment unit 260 is added to the configuration of the earth leakage protection device 100 shown in FIG. Therefore, the ZCT 110 and 210, the control units 120 and 220, the power supply units 130 and 230, and the filter units 140 and 240 shown in FIGS. 3 and 4 respectively perform the same operations. The surge protector 250 includes an operation time adjuster 260. The operation time adjustment unit 260 serves to vary the operation time of the earth leakage protection device 100. The operation time adjustment unit 260 includes a fifth resistor R5 and a plurality of capacitors C1 to Cn connected in parallel and a third switch SW for switching the capacitors C1 to Cn. The capacitor to be charged with the voltage across the fifth resistor R5 is determined according to the switching operation of the third switch SW. As the charging is completed in the selected capacitors C1 to Cn, an operation signal is outputted to the output terminal and inputted to the controller 120, so that the time for outputting the operation signal can be adjusted according to the capacity of each of the capacitors C1 to Cn, This makes it possible to control the operation time of the electric leakage screening device.

Referring to FIG. 4, the operation of the earth leakage protection device 200 according to another embodiment of the present invention will be described. When a surge current or a leakage current occurs in the distribution line, a voltage induced in the video current transformer 210 is input to the control unit 120, and the operational amplifier of the control unit 120 outputs a high signal because the induced voltage is greater than the reference voltage. When the signal is output, the first switch TR1 is turned on. When the first switch TR1 is turned on, the power source of the power source unit 130 goes out to the ground through the first switch TR1 and the second switch TR2 turns off. When the second switch TR2 is turned off, the operating power from the power supply unit 130 passes through the third resistor R3 and is distributed to the fourth resistor R4 and the fifth resistor R5, . Any one capacitor selected by the third switch SW is charged by the voltage distributed to the fifth resistor R5. The charging time is determined by the capacity of the selected capacitor since it is determined by the time constant (RC) of the above-mentioned equation (2). In this way, the operation time of the electric leakage blocking device can be varied by connecting a plurality of capacitors C1 to Cn in parallel and selecting any one of them.

5 is a diagram illustrating signals according to surge current and leakage current generation according to an embodiment of the present invention.

5 (a) shows a signal when a surge current is generated, and Fig. 5 (b) shows a signal when a leakage current is generated. In the drawings, A, B, C, and D indicate positions in the circuit of the earth leakage breaker shown in Figs. 3 and 4.

5 (a), when the surge current is larger than the reference voltage Vref set in the operational amplifier, the operational amplifier outputs a high signal, and the A position (the first switch TR1) A high signal is shown for a time when the surge current is larger than the reference voltage Vref. At this time, when the first switch TR1 is turned on, the second switch TR2 is turned off because there is no signal at the B position (switching signal of the second switch TR2). At the C position (voltage of the fifth resistor), a voltage is applied to the fifth resistor R5, and thus a high signal is outputted. Charging starts at the D position (voltage across the capacitor). However, since the duration of the surge current is short and the surge current disappears after being charged, the battery can not be charged until Vc. As a result, since the operation signal is not output to the output terminal, the earth leakage cutoff device does not operate.

On the other hand, as shown in FIG. 5 (b), the leakage current has a longer duration than the surge current. As a result, the signal holding time at the positions A, B, C, and D is also long. Referring to the drawing, when a leakage current occurs, the leakage current appears larger than the reference voltage (Vref) set in the operational amplifier, so that the operational amplifier outputs a high signal, and at the A position (switching signal of the first switch TR1) And a high signal for a time when the surge current is greater than the reference voltage (Vref). At this time, when the first switch TR1 is turned on, the second switch TR2 is turned off because there is no signal at the B position (switching signal of the second switch TR2). At the C position (voltage of the fifth resistor), a voltage is applied to the fifth resistor R5, and thus a high signal is outputted. Charging starts at the D position (voltage across the capacitor). The leakage current is charged up to the capacity of the capacitor because of the long duration. As a result, an operation signal is output to the output terminal and the earth leakage breaker operates.

As described above, in order to prevent erroneous operation due to the surge current, the leakage current blocking device of the present invention distinguishes the surge current from the leakage current by using the characteristic that the surge current is shorter than the leakage current, The circuit breaker shall be operated only when a surge current has occurred and no leakage current has occurred. Also, the operation time of the electric leakage blocking device can be arbitrarily changed by selectively using any one of a plurality of capacitors having different capacities by changing the operation signal for operating the electric leakage screening device according to the charging time of the capacitor .

While the invention has been shown and described with reference to certain preferred embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the appended claims, The genius will be so self-evident. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

The earth leakage protection device shall be installed in a high-voltage distribution line. Such a leakage current interrupting device may cause a malfunction of the electric device due to the surge current. Therefore, a surge protection circuit must be provided to protect the device from surge currents.

In this respect, the leakage current blocking device according to the present invention detects the occurrence of leakage current by using the surge current and the duration of the leakage current and operates only when leakage current is generated, thereby protecting the device and preventing malfunction have. In addition, since the operation time of the electric leakage screening device can be arbitrarily adjusted, the use width can be widened.

Therefore, the earth leakage breaker according to the present invention can be very usefully used in a power system such as a distribution line.

1 is a configuration diagram of a conventional earth leakage breaker.

2 is a graph comparing the duration of the surge current and the leakage current according to the present invention.

3 is a configuration diagram of an electrical leakage preventing device according to an embodiment of the present invention.

4 is a configuration diagram of an electrical leakage preventing device according to another embodiment of the present invention.

5 is a diagram illustrating signals according to surge current and leakage current generation according to an embodiment of the present invention.

 Description of the Related Art [0002]

110: Video transformer 120:

130: power supply unit 140: filter unit

150: surge protection unit 160: operation time adjustment unit

Claims (11)

1. An earth leakage breaker comprising: A video current transformer (ZCT) for detecting a surge current and a leakage current generated in a distribution line; A controller for outputting a signal corresponding to a voltage induced in the secondary coil of the video current transformer by the surge current or leakage current and operating the earth leakage shutoff device when an operation signal for the operation of the earth leakage shutoff device is received; And And a surge protector for determining whether a surge current or a leakage current is generated according to the duration of the signal output from the controller and outputting an operation signal of the earth leakage interrupter to the controller when a leakage current is generated, The surge protector includes: A first switch (TR1) receiving a signal output from the control unit as a switching signal, one end connected to the power source through a first resistor (R1) and the other end connected to a ground; A voltage at a connection point between the first switch TR1 and the first resistor R1 is input as a switching signal through a second resistor R2 and one end is connected to the power source through a third resistor R3, A second switch TR2 connected to ground; A fourth resistor R4 and a fifth resistor R5 connected in parallel to the second switch TR2 between a connection point between the second switch TR2 and the third resistor R3 and the ground; And And a capacitor (C) connected in parallel to the fifth resistor (R5) between a connection point of the fourth resistor (R4) and the fifth resistor (R5) and the ground, The capacitor C charges a voltage applied to the fifth resistor R5 and outputs an operation signal to the controller when the capacitor C is charged. The capacitor (C) is fully charged when a leakage current occurs in the distribution line, and is not fully charged when a surge current is generated in the distribution line. delete The method according to claim 1, And the capacitor (C) is fully charged when the control unit outputs a signal corresponding to the induced voltage due to the leakage current. The method according to claim 1, And the capacitor (C) is not fully charged when the control unit outputs a signal corresponding to the induced voltage by the surge current. The method according to claim 1, Further comprising a filtering unit for removing the noise signal included in the signal output from the control unit. The apparatus of claim 1, Wherein the voltage detection circuit compares a voltage induced in a secondary coil of the video current transformer with a preset reference voltage by the surge current or leakage current and outputs the induced voltage when the induced voltage is greater than the reference voltage. Device. 1. An earth leakage breaker comprising: A video current transformer (ZCT) for detecting a surge current and a leakage current generated in a distribution line; A controller for outputting a signal corresponding to a voltage induced in the secondary coil of the video current transformer by the surge current or leakage current and operating the earth leakage shutoff device when an operation signal for the operation of the earth leakage shutoff device is received; And A surge protector configured to determine whether a surge current or a leakage current is generated according to a duration of a signal output from the controller and output an operation signal of the earth leakage interrupter to the controller when a leakage current is generated; &Lt; / RTI &gt; The surge protector includes: A first switch (TR1) receiving a signal output from the control unit as a switching signal, one end connected to the power source through a first resistor (R1) and the other end connected to a ground; A voltage at a connection point between the first switch TR1 and the first resistor R1 is input as a switching signal through a second resistor R2 and one end is connected to the power source through a third resistor R3, A second switch TR2 connected to ground; A fourth resistor R4 and a fifth resistor R5 connected in parallel to the second switch TR2 between a connection point between the second switch TR2 and the third resistor R3 and the ground; At least two capacitors (C1 to Cn) connected in parallel to the fifth resistor (R5) between the connection point of the fourth resistor (R4) and the fifth resistor (R5) and the ground; And A third switch SW for selectively connecting a connection point between the fourth resistor R4 and the fifth resistor R5 and any one of the at least two capacitors C1 through Cn; Lt; / RTI &gt; The selectively coupled capacitor charges a voltage across the fifth resistor (R5) and outputs an operation signal to the controller when the connected capacitor is charged, Wherein the connected capacitor is fully charged when a leakage current occurs in the distribution line and is not fully charged when a surge current is generated in the distribution line. The method of claim 7, Wherein an operation time of the earth leakage blocking device is adjusted by varying a time at which the operation signal is outputted by selectively connecting the two or more capacitors. The method of claim 7, Wherein the operation time of the earth leakage blocking device is determined by the fifth resistor (R5) and the capacity of the selectively connected capacitor. The method of claim 7, Wherein the selectively connected capacitor is fully charged when the controller outputs a signal corresponding to the induced voltage due to the leakage current. The method of claim 7, Wherein when the control unit outputs a signal corresponding to an induced voltage by the surge current, the selectively connected capacitor is not fully charged.

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