KR102153851B1 - Miswiring detection method for power surge protective device with preventing malfunction of residual current detector - Google Patents

Abstract

The present invention relates to a miswiring detection method for a power surge protective device (SPD) considering malfunction prevention of a residual current detector. According to the present invention, the miswiring detection method comprises: a detection step of allowing a detection unit to detect a voltage between a phase and the ground and a voltage between a neutral line and the earth to transfer the voltages to a micro control unit (MCU) (500); and a detection step of allowing the MCU (500) to compare the transferred voltages with a preset reference voltage to determine whether connection of the phase and the neutral line is normal, wherein at AC 220 V, the preset reference voltage is AC 220 V measured between the phase and the earth and is AC 1-30 V measured between the neutral line and the earth, and it is determined that the connection is normal within the range of the detected voltage. Moreover, the residual current detector is installed in a distribution panel having the power SPD installed therein and is operated by a rated sensitivity current of 5 mA or more. Accordingly, the miswiring detection method provides a significant effect of informing a worker of miswiring information through a speaker installed in the SPD and a display unit, such as an LED, an LCD, a 7-segment, and the like, to prevent an accident when the phase and the neutral line are exchanged by a mistake of the worker. Moreover, current and time flowing during operation of a miswiring detection circuit are minimized, thereby providing a significant effect of preventing a trip effect due to inactivation of the residual current detector.

Description

Miswiring detection method for power surge protective device with preventing malfunction of residual current detector, considering the prevention of malfunction of earth leakage circuit breaker

The present invention relates to a method of detecting a faulty connection of an SPD for power supply considering the malfunction prevention of an earth leakage breaker, and more particularly, when a power surge protector is installed in a power system, the voltage between the phase and the ground, and the neutral wire and the ground is Because it is detected and judged, current flows toward the ground and may cause a trip of the earth leakage breaker, and when a trip occurs, the electricity supply may be interrupted. Accordingly, the present invention relates to a method for detecting a faulty wire that is considered so as not to cause a trip of an earth leakage breaker.

In general, the surge protector for power supply uses KS C IEC61643-11 and KS C IEC61643-12, which are domestic surge protector standards for power supply.

In Korea, the TT system and the TN system are used interchangeably, and according to the international standards of the International Electrotechnical Commission (IEC), the SPD and the earth leakage breaker can be installed as shown in Fig. 3 in the TT/TN system. In general, varistors are used, and gas discharge pipes are used between N-PEs.

As another conventional technique, there is provided a surge protector capable of determining a grounding state of Patent Registration No. 10-0941962, comprising: first and second input terminals; First and second output terminals electrically connected to the first and second input terminals, respectively; A ground terminal connected to the ground line; A first surge isolator connected in series between the first input terminal and the ground terminal; A second surge isolator connected in series between the second input terminal and the ground terminal; A measuring unit for measuring voltage or current of the first surge blocking unit and the second surge blocking unit; A control unit that calculates a ground resistance value of the ground terminal based on the voltage or current value measured by the measurement unit and compares it with a reference resistance value to determine a ground fault; It is described as a surge protector capable of determining a grounding state, characterized in that it includes a display unit that displays whether or not there is a ground fault according to an output signal according to the determination of the ground fault of the control unit.

However, the conventional technology as described above cannot detect the wrong wiring between the phase and the neutral wire, so if the phase and the neutral wire are changed due to the installer's mistake when installing the SPD, the gas discharge pipe is connected between the phase and the ground wire. Due to the operation, a fire, product damage, or power supply interruption may occur due to the rapid flow, which may lead to a large loss, and there is a problem that may lead to personal injury.

In addition, as a conventional technology, the resistance type grounding state display device of Korean Patent Application Publication No. 10-2003-0083472 includes: a transformer 10 for dropping an AC high voltage supplied through a voltage line and a neutral line to an AC low voltage;

A rectifier 12 for full-wave rectification for the lowered AC low voltage;

A smoothing unit 14 for smoothing the rectified voltage and converting it into a DC voltage;

A power polarity determination unit 16 including a power polarity determination terminal (T P) for determining power polarity between the voltage line and the neutral wire;

A first capacitor (C1), a first variable resistor (VR1), a second variable resistor (VR2), and a third resistor (R3) are connected in series between the voltage line and the enclosure connection terminal (TC). 1 Connect one end of the second capacitor C2 to the contact point between the capacitor C1 and the voltage line,

The other end of the second capacitor C2 connects a fourth resistor R4 having one end connected to a neutral wire, and a contact point between the first variable resistor VR1 and the second variable resistor VR2 and the second capacitor C2 ) And a voltage detector 182 formed by continuously connecting and connecting a third capacitor C3 and a fourth capacitor C4 between a contact point between the contact point between the fourth resistor R4 and the third capacitor C3. 4 A first Zener diode D8 and a second Zener diode D9 interposed between the capacitor C4, and one end connected to the anode of the first Zener diode D8, and the anode of the second Zener diode D9 A bridge circuit 18 including a sensitivity control unit 184 formed by forming a third variable resistor VR3 connected to the other end of the contact point of the fourth capacitor C;

It is driven by receiving the DC power supplied from the smoothing unit 14, and processing a signal for the presence or absence of a change in the voltage transmitted from the voltage detection unit 182 of the bridge circuit 18 is performed and at the same time corresponding to the signal processing. A control unit 20 which outputs a display control signal and performs signal processing for sensitivity control according to a resistance value adjusted from the sensitivity control unit 184 of the bridge circuit 18; And

A display unit 22 that is lit by a display control signal from the control unit 20;

A resistance-type grounding status display device, characterized in that it includes, has been disclosed, and it is possible to check whether the voltage line and the neutral line are changed by the display of the LED lamp, and the grounding status is to determine the grounding resistance by touching the hand to the electric enclosure. It is stated that it can be confirmed.

However, since the LED lamp indicates whether the voltage line and the neutral line are switched, several mA of current flows constantly to operate the LED. If an earth leakage breaker is installed, the leakage breaker may operate and a trip may occur. . In addition, the method by hand contact has a problem that can cause personal injury.

The present invention provides information indicating that the phase and neutral wires are changed by mistake of a contractor through a method of detecting a malfunction of an SPD for power supply considering the malfunction prevention of an earth leakage circuit breaker, and a speaker for generating a sound mounted in a surge protector, an LED, Installation stability is improved to prevent accidents in advance by notifying the presence or absence of faults and ground connection status through the display of LCD, 7 segments, etc., and the leakage breaker is not operated by minimizing the current and time flowing during the operation of the faulty detection circuit. This is to provide a method for detecting faulty wiring of SPD for power supply considering the prevention of malfunction of earth leakage breaker that does not cause trip phenomenon.

The present invention relates to a method for detecting a faulty wiring of a power supply SPD considering the malfunction of an earth leakage breaker, and by detecting the voltage between the phase and the ground and the voltage between the neutral and the earth by the detection unit, a microcontroller unit ( And a detecting step of transferring the transmitted voltage to the microcontroller unit 500; and a determining step of determining whether the connection between the phase and the neutral wire is normal by comparing the transmitted voltage with a preset reference voltage by the microcontroller unit 500. do.

As a means of detection, a high-output, high-voltage photocoupler and resistor that can separate the primary and secondary sides of the power supply are used, and a photocoupler with high CTR (Current Transfer Rate) characteristics is used to minimize the current to several mA and It is characterized in that the time flowing to the ground is minimized to tens of ms, so that the earth leakage circuit breaker does not malfunction when detecting a faulty connection.

In addition, the preset reference voltage is AC 220V, the voltage between the phase and the ground is measured as AC 220V, and the voltage between the neutral line and the ground appears as small as AC 1~30V. If the detected voltage is within the above range, the connection is normal. It characterized in that it is judged as.

In addition, in the case that a ground fault circuit breaker is installed in the switchboard where the power surge protector is installed, the operating current and time of the fault detection circuit are minimized, and the minimum operating current of the ground fault circuit breaker is adjusted to 5 mA and the minimum operating time of 30 ms or less. It is characterized in that it does not malfunction.

In the present invention, the faulty wiring detection method of the SPD for power supply considering the malfunction prevention of the earth leakage circuit breaker provides information that the phase and neutral wires are changed due to the mistake of a builder, and a speaker, LED, LCD, 7 There is a remarkable effect of preventing accidents in advance by notifying them through a display unit such as a segment. In addition, there is a remarkable effect that a trip phenomenon does not occur because the earth leakage breaker is not operated by minimizing the current and time flowing during the operation of the faulty construction detection circuit.

1 is a configuration diagram of a power surge protector and a method for determining a false construction with an erroneous construction prevention function of the present invention
FIG. 2 is a block diagram of a power surge protector equipped with a malfunction detection function of an SPD for power supply considering malfunction of the earth leakage circuit breaker of the present invention
3 is a configuration diagram of a power surge protector in which an earth leakage breaker is installed
Figure 4 is a software flow chart for preventing incorrect wiring of the present invention
5 is a software algorythm for preventing erroneous wiring of the present invention
6 is an exemplary view showing a ground fault of the present invention
7 is an exemplary diagram when the phase conductor and the neutral wire of the present invention are changed
8 is a circuit diagram for detecting a misconnection of the present invention

The present invention relates to a method of detecting a faulty wiring of an SPD for power supply considering the malfunction prevention of an earth leakage breaker, and the detection unit detects the voltage between the phase and the ground and the voltage between the neutral and the ground and transmits it to the Micro Controller Unit (500). And a determining step of determining whether a connection between a phase and a neutral wire is normal by comparing the transmitted voltage with a preset reference voltage by the microcontroller unit 500.

In addition, the preset reference voltage is AC 220V, the voltage between the phase and the ground is measured as AC 220V, and the voltage between the neutral line and the ground appears as small as AC 1~30V. If the detected voltage is within the above range, the connection is normal. It characterized in that it is judged as.

It is characterized in that it is determined that the connection is normal when the voltage is within the above range.

In addition, in the case that a ground fault circuit breaker is installed in the switchboard where the power surge protector is installed, the operating current and time of the fault detection circuit are minimized, and the minimum operating current of the ground fault circuit breaker is adjusted to 5 mA and the minimum operating time of 30 ms or less. It is characterized in that it is not operated.

The present invention will be described in detail with reference to the accompanying drawings. 1 is a configuration diagram of a surge protector for a power source equipped with an erroneous construction prevention function of the present invention and a method for determining erroneous construction, and FIG. 2 is a power supply with an erroneous connection detection function of an SPD for power supply considering the malfunction prevention of the earth leakage breaker of the present invention. A configuration diagram of a surge protector, FIG. 3 is a configuration diagram of a power surge protector in which an earth leakage circuit breaker is installed, FIG. 4 is a software flow chart for preventing erroneous wiring of the present invention, and FIG. 5 is a software algorythm for preventing erroneous wiring of the present invention. 6 is an exemplary diagram of a ground fault display according to the present invention, FIG. 7 is an exemplary diagram when the phase conductor and the neutral wire of the present invention are changed, and FIG. 8 is a circuit diagram for detecting an incorrect connection of the present invention.

The present invention relates to a method for detecting a faulty connection of an SPD for power supply considering the malfunction of an earth leakage breaker, and the detection unit detects the voltage between the phase and the ground and the voltage between the neutral and the ground and transmits it to a microcontroller unit. And a determining step of determining whether the connection between the phase and the neutral wire is normal by comparing the transmitted voltage with a preset reference voltage by the MCU.

As a means of detection, a high-output, high-voltage photocoupler and resistor that can separate the primary and secondary sides of the power supply are used, and a photocoupler with high CTR (Current Transfer Rate) characteristics is used to minimize the current to several mA and It is characterized in that the time flowing to the ground is minimized to tens of ms, so that the earth leakage circuit breaker does not malfunction when detecting a faulty connection.

The erroneous wiring detection circuit is designed so that the microprocessor is not affected by the surge by separating it into an AC primary side and a DC secondary side. Initially, when power was applied to the SPD, the GPIO (General Purpose Input Output) output of the microprocessor outputs high for several tens of ms and operates the relay to detect the phase and neutral lines at the GPIO input. During relay operation, the resistance value was selected so that the earth leakage breaker does not trip with the current flowing to the ground, and the leakage current was minimized to several mA and the detection time was minimized to tens of ms.

The software flow chart and algorythm for preventing erroneous wiring of the present invention are shown in FIGS. 4 and 5.

In addition, the preset reference voltage is that the voltage between the phase and the ground is measured as AC 220V in AC 220V, and the voltage between the neutral wire and the ground appears as small as AC 1 to 30V, and the detected voltage is within the above range. It is to judge as normal.

Further, an alarm step of outputting the result of the determination step to a speaker or a display mounted in the surge protector is further included.

In addition, the present invention relates to a method for detecting a faulty connection of a power supply SPD in consideration of preventing malfunction of an earth leakage breaker, which is installed inside a surge protector case, and detects a voltage between a phase and a ground and a voltage between a neutral wire and a ground, and a microcontroller unit ( A detection unit transmitting to the Micro Controller Unit); An output unit that generates an alarm; A microcontroller unit that compares the voltage transmitted from the detection unit with a preset reference voltage to determine whether a connection between a phase and a neutral wire is normal, and generates an alarm through an output unit; It consists of a power supply unit for supplying power; characterized in that it determines whether the connection between the phase and the neutral wire is normal.

In the present invention, the method for determining the faulty construction of a power surge protector includes a detection step of detecting a voltage between phase and ground and a voltage between neutral and ground by a detection unit and transferring the voltage to a microcontroller unit; A determination step of determining whether the connection between the phase and the neutral wire is normal by comparing with the set reference voltage; consists of.

The phase means L (Line), and the neutral line means N (Neutral).

The preset reference voltage is AC 220V, the voltage between the phase and the ground is measured as AC 220V, and the voltage between the N-PE appears as small as AC 1~30V. If the detected voltage is within the above range, the connection is normal. When the voltage between the phase and the ground is small and the voltage between the neutral and the ground becomes large, it is determined to be abnormal.

In the present invention, as a result of the determination step, a normal connection state and an abnormal connection state are output to a speaker or a display mounted in a surge protector to generate an alarm so that the operator can recognize it.

Speaker output outputs the recorded file input to the voice prompt IC to the speaker.

As an example, (normal state)

Ex) Sound: Outputs as "normally installed."

Display output part: Normal state output by LED or LCD or 7-segment.

(Abnormal state)

Yes)

-Check the position of the upper and neutral wires.

-Check the ground connection.

The display output unit may output an abnormal state or a normal state through an LED or LCD or 7-segment as shown in FIGS. 6 and 7.

The circuit of the surge protector of the present invention is as follows.

The circuit of the surge protector includes a detection unit; Power supply; A micro controller unit; It consists of an alarm section.

In the detection unit, the varistor 120 is connected between the phase, the neutral wire, and the ground wire, and the gas discharge pipe 130 is connected between the neutral wire and the ground. Leading ends of the phase and neutral wire are connected in series with the transformer 401 of the power supply, respectively.

A thermal fuse (110) is connected to the commercial line in the middle, and the commercial line is branched and grounded in the middle, but the resistor 711, photocoupler 710, relay 730, and transistor 731 are in series. It is connected sequentially and then grounded. In addition, a transistor 731 for on/off control of the relay 730 is connected to the microcomputer. The transformer 731 is connected in series with the bridge diode 402, and a varistor 613 is connected in parallel in front of the bridge diode 402 to protect from the transient voltage of the transformer 401. The output terminal of the bridge diode 402 is connected in series to the microcontroller unit through a voltage detector, and the other output terminal of the bridge diode is grounded.

The N line is branched in the middle to be grounded, and the resistor 721, the photocoupler 720, the relay 730, and the transistor 731 are sequentially connected in series and then grounded. In addition, a transistor 731 for on/off control of the relay 730 is connected to the microcomputer.

In the power supply unit, the two output terminals of the constant voltage supply device 403 are connected in series with the bridge diode 402 by two lines, and the bridge diode is connected in series with the transformer 401 by two lines. The transformer is connected in series to each of the leading ends of the phase wire and the neutral wire of the detection unit. The other output of the constant voltage supply is connected in series with the input of the microcontroller unit.

The output unit is connected in series with the amplifier 802 and a voice prompt 801 connected in series to the output terminal of the microcontroller unit, and the amplifying unit is connected in series to the speaker 803. Alternatively, the LED, LCD or 7-segment display unit 900 is connected in series to the microcontroller unit and displayed respectively.

One of the input terminals of the microcontroller unit is connected in series with the output terminal of the constant voltage supply device 403 of the power supply. One of the output terminals is connected in series with the voice prompt 801 of the output unit, and one of the output terminals is displayed by connecting the LED or LCD of the output unit or the 7-segment display unit 900 in series.

One of the output terminals of the microcontroller unit is connected to the transistor 731 to operate the relay 730 between the neutral line and the ground line. One of the input terminals of the microcontroller unit is connected in series to photocouplers 710 and 720 connected in series between the neutral wire and the ground.

One of the input terminals of the microcontroller unit is connected in series with the output terminal of the constant voltage supply device 403 of the power supply. One of the input terminals is connected in series with the input units of the photocouplers 710 and 720.

The voice output unit 800 includes a voice prompt 801 for determining a voice according to a signal from a microcontroller, and an audio-amp for amplifying a signal of the voice determined in the voice prompt 801 It includes 802 and a speaker 803 that outputs the sound amplified through the signal amplifier 802 as sound.

In the IC of the voice prompt 801, a voice file is previously stored.

The microcontroller 500 may determine whether the circuit unit is normally connected by determining through the voltage, and controls to output the status through the display unit 900 according to the state, or a voice prompt 801 ), the audio file stored in the integrated circuit (IC) is executed and the audio is output to the speaker 803 through the audio amplifier 802.

Typically, AC 220V is used, and the criterion for determining whether the connection of the circuit part by the microcontroller 500 is normal is the voltage between L(100) and PE(300) is measured as AC 220V, and N(200) and The voltage between the PEs 300 is AC 1~30V.

The display unit 900 may use a light emitting diode (LED), a liquid crystal display (LCD), a seven segment, or the like.

The microcontroller 500 determines a state by dividing it into a normal connection state and an abnormal connection state, and controls the information to be changed and output according to the determined state.

In addition, when the state is determined to be a normal connection state, signals are sent to the display unit 900 and the voice prompt 801, respectively, and the display unit 900 outputs it so that the normal state is known, and the voice prompt 801 Selects an audio file that is output during normal connection and outputs it to a speaker through a signal amplifier (Audio-Amp) 802.

As an embodiment, after determining that the microcontroller 500 is in a normal connection state, it sends a signal to the blue light emitting diode and the voice prompt 801, respectively, and the voice prompt 801 receiving the signal is output in the normal connection state among the voice files. The voice file is executed, but when the voice file is executed, the signal is transmitted to the signal amplifier (Audio-Amp), and the signal amplifier (Audio-Amp) amplifies the voice and makes a voice saying "It is installed normally" through the speaker. Is to print.

Conversely, when it is determined that the state is abnormally connected, the microcontroller 500 transmits signals to the display unit 900 and the voice prompt 801 respectively, and the display unit 900 can recognize the abnormal state. The voice prompt 801 selects a voice file output when abnormal connection is made, and outputs a voice file output when abnormal connection through a signal amplifier 802 to the speaker 803.

As an embodiment, after determining that the microcontroller 500 is in an abnormal connection state, it sends a signal to the voice prompt 801, respectively.

In addition, the voice prompt that received the signal executes a voice file that is output in an abnormal connection state among the voice files, but a corresponding voice file is selected according to the problem situation, and when the voice file is executed, the signal is signaled by an audio-amp. To pass.

The signal amplifier (Audio-Amp) amplifies the voice and outputs the voice through the speaker, and the voice of the selected voice file is output according to the problem situation. In this case, the problem situation can be determined when the phase and neutral wires of the surge protector to be used are changed and when the ground is not connected.

In particular, the output voice is "Please check the position of the phase and neutral wire.", "Please check the ground connection." Is to print one of them.

A detailed description of the operating sequence of the present invention is as follows. Normally, both the phase and neutral relay 730 are open so that no current flows between the phase and the ground, and the neutral and the ground. Therefore, when the main power is turned on from the power supply, the microcontroller unit operates, the relay of the phase and the middle wire is operated, and a very weak current flows between the phase and the ground, and the neutral and the ground. Then, the voltage between the phase and the ground and the voltage between the neutral and the ground are measured through the photocouplers 710 and 720 for detecting phase and ground and neutral and ground voltage.

The measured voltages are transmitted to the microcontroller unit, and the microcontroller unit judges the transmitted voltages, and if the voltage between the phase and the ground and the preset voltage between the neutral and the ground change each other, it is judged that the phase and the neutral wire are changed and are connected incorrectly. To output an alarm signal.

The earth leakage breaker, which is the technical point of the present invention, operates very sensitively to time and current magnitude, and the minimum rated sensitivity current of 5mA and the minimum operating time of 30ms should be considered as well, and both items should be adjusted within minimum conditions.

In other words, by minimizing the current and time flowing during the operation of the faulty construction detection circuit of the present invention, the earth leakage breaker does not operate, so that a trip phenomenon does not occur.

As shown in Fig. 8 of the present invention, the erroneous wiring detection circuit is designed so that the microprocessor is not affected by the surge by separating it into an AC primary side (black) and a DC secondary side (blue). Initially, when the power is applied to the SPD, the GPIO output (GPIO: General Purpose Input Output) of the microprocessor outputs high for 30ms and operates the relay to detect the phase and neutral lines at the GPIO input.

An optocoupler was used to detect the voltage between the phase and the ground, and the neutral and the ground, and an earth leakage breaker is sometimes used on the upper part of the SPD. Therefore, consider not to cause a trip phenomenon due to the current flowing from the phase to the ground during relay operation. Leakage current was minimized by selecting 330kΩ, and the detection time is 30ms, which is about 5 cycles based on 60Hz. The current flowing during this period is calculated by the formula of ohms, which is about 600 μA.

The international standard for an earth leakage breaker with an overcurrent protection device complies with IEC 61009-1 (RCBO with an overcurrent protection device for residential and similar purposes-Part 1: General requirements) and is less than the minimum rated sensitivity current of 6mA. It is not affected by much smaller values.

In addition, since the voltage between the neutral wire and the ground may increase according to the grounding environment and noise and harmonic voltage of peripheral devices, the detection was set to operate at 180V or more, which is about 80% of the normal voltage 220V.

Soon, since the minimum operating condition of the earth leakage breaker is 5mA, 30ms, the current detection value is adjusted to about 600uA by adjusting the resistance value, and it is detected by the output of the highly sensitive optocoupler.

In order to prevent malfunction due to noise, in the method of detecting by operating the relay once for 30ms, if the number of times is detected 5 times and all are detected as the same value, it is determined as a normal value.

100: L
110: thermal fuse
120, 613: Varistor
130: gas discharge pipe
200: N
300: PE
400: power supply
401: trans
402: bridge diode
403: constant voltage supply device
500: microcontroller
710, 720: photo coupler
711, 721: resistance
714, 724: coil
730: relay
731: transistor
800: audio output unit
801: voice prompt 802: signal amplifier 803: speaker
900: display unit
1: starting point of facility 2: switchboard
3: main ground short waveform or bar 4: surge protection device
5: ground connection of surge protection device, 5a or 5b
6: protected device
7: Residual current protective device (RCD)
F: Protection device specified by the SPD manufacturer (e.g. fuse, circuit breaker, RCD)
R _A : Ground electrode of facility (ground resistance)
R _g : Earth electrode of power system (ground resistance)

Claims (3)

A detection step of detecting the voltage between the phase and the ground and the voltage between the neutral wire and the ground by the detection unit and transferring the voltage to a microcontroller unit 500; And the microcontroller unit 500 uses a preset reference voltage and In a method for detecting a faulty connection of an SPD for a power source considering prevention of malfunction of an earth leakage circuit breaker comprising a determining step of determining whether the connection between the phase and the neutral wire is normal by comparison,
The preset reference voltage is AC 220V, the voltage between the phase and the ground is measured as AC 220V, the voltage between the neutral wire and the ground appears as small as AC 1 to 30V, and the detected voltage between the neutral wire and the ground is AC 1 The connection is judged as normal within the range of ~30V,
An earth leakage circuit breaker is installed in the switchboard where the power surge protector is installed, and the leakage circuit breaker is controlled within a minimum rated sensitivity current of 5 mA and a minimum operating time of 30 ms.By minimizing the current and time flowing during operation of the fault detection circuit The circuit breaker does not work, so no trip phenomenon occurs.
The mis-wiring detection circuit is separated into AC primary and DC secondary to prevent the microprocessor from being affected by surges, but when power is initially applied to the SPD, the microprocessor's GPIO output (GPIO: General Purpose Input Output) is used for a certain period of time. It outputs high while operating the relay to detect the phase and neutral wires at the GPIO input.
In order to detect the voltage between the phase and the ground and between the neutral and the ground, an optical coupler is installed and used. A method of detecting incorrect wiring of SPD for power supply considering the prevention of malfunction of an earth leakage circuit breaker. delete delete

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