KR100431561B1 - An Auto Voltage Source Changer - Google Patents

Abstract

A busbar breaker and busbar breaker for power connection between busbars are used to allow a power plant-substation-receiver, which selectively uses two or more busbars, to switch buses that supply power to specific areas of the power network. In the voltage source switching device for a power substation comprising: a control control room which is installed in the bus disconnector and busbar contact breaker, and operates in conjunction with the operation of the bus disconnector and busbar contact breaker to control the power network by sending a signal indicating the status. Generates sequential control signal through processing according to its own configuration by receiving the current state value of bus voltage source measured from a number of auxiliary contact terminals and auxiliary contact terminals for monitoring and remote control of bus disconnector and bus contact breaker According to the predetermined bus switching order Including the logic circuit to implement a bus switch, a voltage source for automatically switching device to the substation, characterized in that to perform an operation for switching a bus bar to power without temporal interruption it is started.

Description

Voltage Source Automatic Switching Device for Power Substations {An Auto Voltage Source Changer}

The present invention relates to a voltage source automatic switching device for a substation, and more particularly, to protect the power system in the case of changing the power source in the power system between the power plant-substation-recipient, especially in the dual bus configuration of the power substation. The present invention relates to a voltage switching device that enables the maintenance and management of substations smoothly by measuring, controlling, and preventing malfunction of various devices.

The power generation of a power plant is configured through a nationwide network so that it can be stepped down or distributed through substations and supplied to each customer, so that any part of the substation in the power network of the power plant-substation-acceptor or section failure of the power system is generated. In this case, an error occurs in the entire power system.

In view of this point, the conventional power supply system between the power generation substation selectively supplies and receives power through two buses of the first bus and the second bus, as shown in FIG. This is because the power system between the substation and the substation is composed of an annular network, and the flow of the power current changes with the time load.

In such a double bus system, the voltage switching switch is operated manually or automatically for the operation of protection relays (breaker disconnection, distance measurement, inter-communication between relay substations and counter substations), power metering, and indicators. There is a need for a device for switching in a manner. This is an essential component to perform continuous power supply by immediately switching to another healthy bus in case of failure or work outage of one bus system.

In particular, in the case of an unmanned substation installed in a large number of remote locations or mountain walls, an automatic voltage switching device such as 43 PDA is widely used as a switching device. However, this 43PDA requires separate installation of control cables between devices in order to use the auxiliary contact point of the main machine in the field. Therefore, the construction cost is excessive, the efficiency of use of the duct, the reinforcement cost of the nonconformity after installation, maintenance There are several problems such as spending and lack of function. In addition, the 43PDA generates a dead time of power system protection during manual or automatic switching, and a warm-up time of the latest digital relay occurs in a few seconds to several minutes when restarted by simultaneous switching with a control DC power supply. In addition, since 43PDA uses a motor for driving, that is, a mechanical driving method, a separate driving and control power source, a motor, a driving mechanism, and the like are required. In addition, when the operation and the wiring are complicated and the operator misoperates, for example, an unnecessary power failure may occur or the operation may be extended to a large failure when the operation sequence is not identical.

The present invention is to solve the problems of the conventional automatic voltage switching device, to provide an intelligent circuit configuration, eliminating dead time by procuring and operating the control power itself. In addition, the operation is automatically performed according to the priorities set in advance, and in case of short circuit or ground fault, the protective distance relay is the first priority to properly measure the distance when the bus voltage drops. It is aimed at making it possible.

It aims to automatically detect and alarm fuse break of voltage source, phase unbalance, coil break of transfer auxiliary relay, and other abnormalities, and to automatically switch voltage source to the best bus line which is easy to install and matches the operating conditions.

In addition, it provides a configuration that can be automatically switched in accordance with the operating conditions without the operator, and further provides a configuration for preventing mistakes by various operators. It also includes status monitoring, current operating position, voltage source error indication, and self-test. It also provides a configuration that can be switched without time interruption depending on which bus is connected to multiple lines. Through this, it is aimed at minimizing the power interruption of some sections of substations and transmission / output line input / output lines due to failures in the power system, and enhancing the convenience of operation such as stabilizing the entire power system and management system.

Figure 1A, B is a disconnection wiring diagram of a conventional substation to which a voltage source automatic switching device for a substation is applied.

2 is a conceptual block diagram of a voltage source automatic switching and low frequency relay malfunction prevention apparatus of a power substation of the present invention;

3 is a circuit diagram showing a state in which a control cable is unnecessary by using an auxiliary contact of an existing circuit breaker and a disconnector according to the present invention;

4 is a schematic circuit diagram of a voltage source automatic switching device for a power substation of the present invention;

5A and 5B show a conventional voltage source automatic switching circuit diagram;

6 is a specific circuit diagram of a voltage source automatic switching device for a power substation of the present invention;

7 is a circuit diagram of a frequency counter for suppressing malfunction of a low frequency relay that may be added to the present invention;

8 is a circuit diagram of rectifying and signal source of a voltage source in the voltage source automatic switching device for a power substation of the present invention;

9 is a circuit diagram for determining priority switching order by source type in a voltage source automatic switching device for a power substation according to the present invention;

10 is a circuit diagram of mutually controlling on / off speed of set priority memory and bus selection auxiliary relay period in a voltage source automatic switching operation of a power substation of the present invention;

11 is a circuit diagram of an operation of a voltage source automatic switching device for a power substation of the present invention and a control power supply of the device.

12 is a sequential self-test circuit diagram of the one-button operation of the voltage source automatic switching device for the substation of the present invention; and

FIG. 13 is an explanatory diagram of a low frequency relay malfunction prevention circuit according to iron resonance during bus switching by a switch in the present invention. FIG.

Explanation of symbols on the main parts of the drawing

# 1,2: 1st, 2nd bus bar

52-1, 52-2, ..., CB: High Voltage, Ultra High Voltage Circuit Breakers

89-1, 89-2, ..., DS: high and ultra high voltage power breakers

PT: Voltage Transformer CT: Current Transformer

52 "a", 52 "b": ON auxiliary contact and breaker OFF auxiliary contact

89 "a", 89 "b": ON auxiliary contactor and breaker OFF auxiliary contact

R lamp, G lamp: breaker or disconnector ON / OFF position monitoring indicator lamp

BD1, BD2, ...: bridge diode

PC: Photocoupler

RY1, RY2, X, Y, ...: Aux Relay 1, 2 or X, Y

ZD1, ZD2: Zener Diode

X-tal: crystal or crystal oscillator

Q1, Q2, ...: Transistor PTT: Voltage Element Tester Terminal

L1, L2: Indicator lamp (LED) TNR: Surge absorbing element

IC1, IC2, ...: Integrated circuits T1, T2, ...: Timers

43 PDA: Automatic voltage switch

In order to achieve the above object, the present invention provides a logic circuit in which the current position state value of each auxiliary contact point from the power switching circuit breaker and the load circuit breaker to the first bus line and the second bus line, each bus voltage source state value, and a line fault state value are logic circuits. The present invention provides a voltage source automatic switching device which is inputted to and operated to a bus position to be automatically switched by a previously assigned priority according to its signal value.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration and effect of the voltage source automatic switching Ming UFR malfunction prevention device for substation of the present invention.

Fig. 1 shows a part of the entire power supply line to a power plant-substation-acceptor where power lines are installed. A national or regional network is formed by various branch lines or branch lines from a power plant or other substation, and FIG. 1 shows only a part of such a power system, so that the total power such as branch lines and lead lines to other power plants or other substations is shown. The network is shown schematically.

In general power supply system, two buses, the first bus and the second bus, are supplied in parallel to disconnect power uninterrupted for fault check and renovation of some sections or regions. It is designed to receive power from.

Therefore, a number of power consumers are arranged on the entire power supply network by forming the first bus and the second bus in parallel, and in Fig. 2, such various types of customer A line, B line, C line, D line, etc. Is shown. For example, (A) Co., Ltd., (B) Hospital, and (C) School, which are the power users of the substation in Gyeongsan, Daegu, are the customer's line A, B, C, C. It is displayed on the control panel of the control room.

In case of abnormality in these various types of customers or substation lines, setting a minimum power supply stop area is a voltage source automatic switching and UFR malfunction prevention device for the substation, and selects power between the first bus and the second bus. It provides a switching function to control the switching to be supplied with.

In case of a failure of the power system of the A line area, the A line area receives three-phase power from one of the first bus and the second bus, so that the first bus and the second bus are stable. And is selectively powered from any one of the following.

In this case, in order to switch the power supply of the A line from the first bus to the second bus, the first bus disconnector is first turned on, and the first bus disconnector is artificially switched to the second bus position. Must be OFF. At this time, if the first bus disconnector is opened first, the entire substation as well as the area A line are blackout. This is because the disconnector cannot open the load. In other words, if the switching sequence is not followed, it may be extended to the bus fault and supply may be interrupted, causing undesired damage, and a surge current may be induced in all control signals, thus affecting the control system or controlling all central control stations at once. The supply system can be paralyzed by being terminated or making it impossible to determine the condition. Therefore, the switching order must be followed.

In general, a power system has a plurality of auxiliary contact terminals (hereinafter referred to as auxiliary contacts) that interlock with driving of a switching switch for monitoring and remote control in a control control room.

In Fig. 1, box-type 52-1, 52-2, ... 52-N are the load-load breakers, and 89A1 and 89B1 are the power switching circuit breakers, respectively, connected between the first bus and the second bus to load the bus Selectively open and close the no-load.

In Fig. 1, the bus disconnectors 89A1 and 89B1 between the first bus and the second bus are the no-load power switch of the substation for power disconnection, and the lower terminals a and b of the bus disconnector control the state of the bus disconnector as auxiliary contacts. And generate the respective data in the central control station at the remote site.

An additional logic determination circuit is provided to the terminal lead-out line drawn out from the auxiliary contact (a, b), and the corresponding bus line is selected according to the judgment of the logic circuit, and voltage switching is automatically performed according to the disconnection state without artificial manipulation. To lose.

Hereinafter, the configuration and operation of the voltage source automatic switching and UFR malfunction prevention apparatus of the substation of the present invention centering on the customer 89L1 will be described.

The A line is selectively supplied with electric power from the first bus and the second bus by 89A1, 89B1 and the load breaker and disconnecting switch 52BT, BT89A, BT89B.

By the configuration of the logic circuit, the first bus disconnector 89A1 or the second bus disconnector 89B1 for switching the power supply between the first bus and the second bus from the power supply state of the A line at the operator or the remote control position. When the circuit is to be operated, the logic circuit automatically determines which disconnector is operated and automatically switches to the bus side by the operation of auxiliary relays for signal transmission and control to all central control stations according to voltage switching in advance. Prevents misjudgement and uncontrollable conditions caused by conventional manual operation.

Each data signal drawn from the auxiliary contacts (a, b) of 89A1, 89B1, 52BT is passed through each photocoupler (PC) as shown in FIG. 3 for the surge current and the electrical isolation. It is fed to the output part (G) which automatically controls the automatic switching and UFR malfunction prevention device.

Fig. 2 shows a schematic configuration of the circuit configuration of the voltage source automatic switching and UFR malfunction preventing apparatus of the present invention.

The output unit G includes a DC converter C having the configuration shown in FIG. 11 to be used as its power source for transferring voltage from the first bus voltage transformer 1 and the second bus voltage transformer 2, PT abnormality detection circuit part (D), priority selection circuit part (P), PT abnormality detection and priority designation comparison alarm circuit part (R), self operation test part (T), CB / DS opening and closing discrimination part (S) The first bus voltage source 1 and the second bus voltage source 2 are selectively connected to each other. 4 and 6 show an exemplary circuit diagram of the output portion G. As shown in FIG.

5A and 5B are schematic diagrams of a conventional voltage source automatic switching circuit, in which an auxiliary cable (a) of a power circuit breaker installed at each bus line is required to draw a signal by installing a control cable when a line is changed. In the present invention, the breaker and disconnector auxiliary contacts are used to optimize the PT switching, but the photocoupler (PC) is used at each of the existing auxiliary contacts (a, b), even if the distance between the main unit and the apparatus is separated. Alternatively, it is possible to transmit the on / off state of the main unit in a remote control device or other insulated state, thus eliminating the need for a separate cable.

FIG. 8 is a circuit configuration for inputting signals for power supply and control, and is configured to have a double bus or more structure in consideration of electricity supply flexibility in case of failure in order to smoothly and uninterrupted or minimize equipment operation of a substation. In Fig. 8, the voltages of the first bus bar PT (1) and the second bus bar PT (2) are input as a source. In the drawings, a phase image of part A will be described as an example.

PT (A) -R1-Bridgediode (BD1) -R2, C1-Zenerdiode (ZD) -Schmidbuffer IC (IC1):

After passing the current limiting R1 and passing through the bridge diode, the PT current 60mA is full-wave rectified and becomes a sinusoidal pulse of 120㎐, but it is smoothed by the capacitor of C1, and the average current passes through R2. Connected to the same potential as the earth of the neutral wire, the alternating current is converted into direct current, and a voltage of a size suitable for use as an IC input signal source voltage can be obtained. Here, it must be greater than the dresshold voltage (about 1/2 of the power supply voltage) of IC1.

PT (A) -R1-diode (D1) -C2, R4-R5, C3-S1:

When two diodes D1 (surge protection and reverse voltage consideration) are passed through the current limiting R1, a smooth direct current is obtained. In addition, after passing the limiting resistance of R4, it is connected to R5 and C3, where R5 is a bleed resistor for lowering the DC crest voltage and supplying a stable voltage, and C3 accumulating the DC voltage to allow for instantaneous voltage fluctuation. This is necessary. The resistance value of R1 and R4 is selected by considering the idle bus and fault 1 phase in order to obtain the equivalent DC current of 15-20mA. The reason for using several resistors of R4 is to make it small and able to withstand heat capacity.

3. It is input to PT (A) -R1-R18 (UFR malfunction prevention circuit).

It is an input circuit to suppress the malfunction of URT when iron resonance occurs due to PT, breaker pole, bus-to-earth capacitance, residual charge, even though it is not a real low frequency in 170㎸ class gas insulated switchgear. Low frequency relay operation is associated with power plant output, causing widespread outages. Therefore, load blocking due to errors should be suppressed.

4. R4 (common point a):

Normally, two busbars of the first busbar PT (1) and the second busbar PT (2) may be in operation, but only one busbar, such as work, is operated, and due to a fuse shortage, etc. This is a circuit that is used for detection and supplementation of current automatically when there is a lack of necessary current because there is a possibility of malfunction or non-operation at the time of DC low voltage.

9 is to detect, judge, and determine which bus is connected to a PT voltage source for each bus, and to determine priorities, output priorities, include alarms, include line faults, current elements, and buses. It is for the contact breaker to cut off, i.e., disconnect the bus, so that it is the first priority when driving, so that it can be transferred in accordance with the position of the breaker connected to the bus.

1) First bus voltage source ① IC1-IC2-IC4-IC11:

The first bus signal source is an analog signal, is added to the IC11 by adding the three elements of the IC2 via the Schmitt buffer of the IC1, and inputted to A3 of the priority IC22. When all three phases are normal, the signal from IC2 is "1".

2) 1st bus voltage signal source ①-IC3-R9-Q1:

The first bus signal source is converted into a digital signal when the analog signal passes through IC1. If the voltage source is abnormal and there is a mismatch, the output of " 1 " operates Q1 through R9 to operate LED L1 and RY1 simultaneously. Make an alarm. This signal can be sent as a remote failure signal.

3) 1st bus voltage signal source ①-IC6-IC22 (A5):

The digital signal passing through IC1 is input to IC6, and one element of IC6 has outputs of "1" and "0" according to the state of the bus disconnection device. This output is input to terminal A5 of IC22 to become the top 3 priority.

4) + 5V-1, 2nd CB (a) -IC7-IC22 (A1):

The signal of + 5V is input to the A1 terminal of IC22 via the EX-OR circuit of IC7 when the auxiliary contact of the primary and secondary circuit breakers matches the a contact of the bus disconnect. Top 5 priority.

In the case of the second bus voltage signal source, only the number of the IC used is the same as that of the first bus voltage signal source. The output code of IC22 is shown in the right input / output table of FIG.

R8 is to suppress various IC input / output errors and to maintain low when no signal is present.

For example, if the highest rank is reversed, A22 terminal-IC4-bus circuit breaker (a) -1, 2nd circuit breaker (a)-+ 5V DC of IC22, i.e. there is a fault in the line or bus disconnector is connected to the first bus It's time. To sum this up,

1st priority: when the bus disconnecter is in operation and the track fails, it automatically switches to the 1st bus,

2nd priority: when the bus disconnector is in operation and the track fails, it automatically switches to the second bus,

3rd priority: Automatic transfer to the 1st bus when the transmission and distribution line is operating with the 1st bus and there is no error in the 1st bus voltage source,

4th priority: Automatic transfer to the second bus when the transmission and distribution line is operating with the second bus and there is no error in the voltage source of the second bus.

5th priority: Automatic transfer to the 1st bus when the power distribution line is in operation with the 2nd bus or there is an error in the 2nd bus voltage source and the 1st bus is pressurized and normal.

6th priority: Automatic transfer to the second bus when the transmission and distribution line is operating as the first bus but there is a problem in the voltage source of the first bus and the second bus is pressurized and normal.

7th priority: Automatic transfer to the 1st bus when the power distribution line is operating on the 1st bus or there is a fault in the 1st bus voltage source and the 2nd bus is in operation.

8th priority: Automatic transfer to the second bus when the power distribution line is operating on the second bus or there is an error in the voltage source of the second bus and the first bus is idle.

Fig. 10 shows that the output according to the priority is coded and the selected signal separated into the first and second busbars is inputted to the memory circuit so as to be maintained until the next input signal and the voltage source switching auxiliary relay is turned on / off. The off time was adjusted so that there was no time interruption during transfer.

In order to switch to the first bus line, the code signal output from IC22 is a combination signal of IC15, IC16, IC17, IC18 is input to the RS latch circuit first, and the output is Q3 operated via R14 to the LED1 light emitting diode of PC1. As a result, the high breakdown transistor of PC1 conducts, so that RY3 is operated. Therefore, the final bus voltage source output G is determined by RY3 and RY4. The operation of RY3 and RY4 can be controlled by the constants of the capacitors C1 and C2. If the selection is made as shown in the table on the right side of Fig. 10, it is possible to change over time without interruption. That is, the on operation of the RY operates at about 80% of the rated voltage, and when the off operation is performed at about 20% of the rated voltage. Combining the values of capacitor and capacitor can overlap several power cycles when switching contacts. A detailed circuit of the latch memory circuit is shown in the lower part of FIG.

11 is a self-controlled power supply circuit using a PT voltage source.

The first bus PT voltage source passes through the limiting resistor R1, passes through two diodes D1, and obtains a smoothed direct current by the capacitor C2. Normally, PT secondary voltage is 110V AC, so it is good to combine resistors R1 and R4 well to obtain rated DC 125V, and 5V is suitable for control power such as IC, so it is possible to form a regular DC / DC converter to obtain a constant voltage of 5V. have.

Since the PT rectified voltage and the negative side of the converter are not common, the converter must be isolated between 1st and 2nd order, and the capacitor C3 and the battery backup device are to maintain the instantaneous voltage drop or short-time compensation of the device.

Fig. 12 is a circuit for self-testing the present invention, comprising a test signal oscillator, a sequential test circuit, and a monostable timer circuit.

The X-Tal, connected to IC15, is a crystal oscillator oscillating to 32.768 용 for wristwatches and can achieve 1 ㎐ / sec at Q14. IC16 AND output is continuously oscillated in combination with Q14 + Q12 = 1.25sec. R12 is for obtaining a solid signal, and C4, C5, and C6 are for frequency fine tuning. IC14 is a three-stage buffer that requires a "1" signal on the side of the enable terminal to conduct the LEDs of L3. If there is a "1" signal at the T1-T6 terminals of IC13, Q3 is conducted through R20. The potential of R2, ZD and r connected to the selector of Q3 becomes 0V and acts like PT disconnection. Since it is lower than the dresshold voltage of IC1 Schmitt buffer, it cannot be passed and appears abnormal, and is automatically switched in parallel with the alarm. The monostable circuit returns a signal to the input side only once within the time constant range in which the "1" signal is combined with RC. The output signal of IC13 is the same as the operation chart of Fig. 12, and the output signal widths of T1 and T2-T6 are the same as the clock signal of the oscillator during the monostable timer. Reset is done at T7, so one stroke is over. IC13 is a shift register.

FIG. 13 can cause iron resonance on the basis of the capacitance of the breaker, the bus and the ground, and the PT of the breaker at the time of no-load switching. That is, it is a circuit which suppresses the malfunction of the low frequency relay by comparing the PT frequency of the first bus and the PT frequency of the second bus. When 60 Hz is inputted from PT, the wave rectification of the BD1 passes through the wave rectification of BD1 in the waveform shaping and frequency multiplying circuit. The first stage of the three-stage NOT circuit is a signal amplifier preamplifier, and the next two stages and three stages are Schmitt-trigger circuits for digitizing the square wave. It is a circuit shaped by a square wave of 10 Hz-1 MHz and 50 Hz or more. The diode D1 is to protect the IC against excessive inputs. This circuit is a square wave exactly like the frequency of the AC waveform even if the AC contains noise. By using the EX-OR gate of IC2 in the in-dotted waveform shaping and frequency multiplying circuit in Fig. 13, the frequency twice the input pulse can be obtained. Since this circuit has three stages, an eight times frequency, or 960 Hz, can be obtained. 960 Hz is input to the TA terminal of IC5 through the T1 electronic contact. The first stage is 1's seat, the second stage is 10's seat, and the third stage is 100's seat. When the output of the first bus side PT input is connected to the lower comparison circuits A, B, and C of FIG. 13 and D, E, F are input to the comparison circuit, that is, according to the comparison result between the first bus frequency and the second bus frequency. Alarms and breakers can be suppressed (breaker isolation). 1Hz of 960㎐ corresponds to 0.0625 sec, and the low frequency relay operation time is about 0.1sec. Therefore, the operation time of the auxiliary relay (approximately 10-20㎳) should be within 0.1 second to separate the UFR blocking circuit. You can give it. IC3's three stages and DS are for program setting.

According to the voltage source automatic switching and UFR malfunction prevention device for substations having the above configurations and functions, two or more buses (first, second or A, B) in the power network between the power station and the substation, the substation and the substation, and the customer Based on the current value of the auxiliary switching switch of the power switch disconnector, the bus contact breaker auxiliary switch and the bus voltage source, the operation condition to the bus side to be selected according to which operation bus is connected by the logical priority judgment circuit. It can be automatically controlled continuously without dead time, and can be operated at high speed without motor drive and switch mechanism. Voltage source fault detection and control power supply It can be solved by itself by rectifying and using it. Can. In addition, the present invention is characterized by low consumption and low burden because it uses an electronic circuit. In addition, with one button, each bus and phase of the voltage source can be sequentially tested to detect the bus voltage abnormality and to detect and alert the abnormality of the switching operation magnet coil.

There is no need for external manpower, and there is no need to write a changeover operator, so there is no fear of human error or misoperation, and operation efficiency can be increased. The auxiliary contact of the existing main power equipment can be used without affecting other equipment, so it is economical because no separate long-distance control cable is required, and it is easy to install due to its small volume. In addition, in case of 170㎸ class gas insulated switchgear, iron resonance may occur due to capacitance between ground and electrodes at the time when one bus becomes no load by bus operation, and low frequency relay due to iron resonance frequency shift In order to prevent such a power outage, a high speed operation is performed by comparing the sound voltage source with the iron resonance frequency to suppress unnecessary power failure.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not limited to these embodiments, and has been claimed by those of ordinary skill in the art to which the invention pertains. It includes all variants of various forms that can be implemented without departing from the technical idea.

Claims (5)

A busbar breaker and busbar breaker for power connection between busbars are used to allow a power plant-substation-receiver, which selectively uses two or more busbars, to switch buses that supply power to specific areas of the power network. In the voltage source switching device for a power substation comprising: It is installed in the bus disconnector and the bus contact breaker, and operates in conjunction with the operation of the bus disconnector and the busbar contact breaker while monitoring the bus disconnector and the busbar breaker by generating a signal indicating the position state and the bus voltage source state. And a plurality of auxiliary contact terminals for remote control; And Including a logic circuit for receiving the current state value of the bus voltage source measured from the auxiliary contact terminal immediately generates a sequential control signal through a process according to its own configuration to implement automatic bus switching according to the prescribed bus switching order, A voltage source automatic switching device for a substation for performing a task of switching the bus to supply power without time interruption. The method of claim 1, An automatic switching device for a voltage substation for a power generation substation, characterized in that it further comprises selectively or both an alarm for alarming when the bus voltage source is abnormal and a lighting display for visual confirmation of abnormality. The method of claim 2, The button, the alarm, and the lighting indicator are connected to detect the alarm of the bus voltage and to detect the abnormality of the magnet coil in the sequential test of each bus and each phase of the voltage source with only one button. Voltage source automatic switching device for power substation. The method of claim 2, It further includes a rectifier for rectifying and converting the AC voltage of each phase of two or more bus voltage sources into direct current, and is used as a power source for controlling the logic circuit part, the alarm part, and the lighting display part, thereby eliminating the need for a separate external power source. Voltage source automatic switching device for a substation. The method of claim 1, And a photo coupler connected to the auxiliary contact terminal, thereby minimizing the influence of a surge current by achieving electrical insulation.