JPS60152224A - Shortcircuiting current suppressing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a method for suppressing short circuit current in a power system.

[Prior art and its problems]

1 is a distribution substation as an example of a power system configured to connect a source to a bus and supply power from the bus to a load via a load breaker. Figure 1 is a single-line system diagram for independent operation of transformer banks at a distribution substation, with transformer 81
The primary side of the converter has an extra high voltage, for example 70 kV, and transforms it to a high voltage, for example 6.6 kV.

This AC power transformed to 6.6 kV is supplied to the load via load breakers 83, 84, 85 connected to the bus bar 82. On the other hand, the transformer 91 similarly transforms the extra high voltage into a high voltage, and supplies power to the load from the bus bar 92 through the load breaker 93°94.95. Normally, the load breaker 93 is connected to the bus bar 92 by a connecting wire 96, and the connecting wire 86 does not exist. That is, transformers 81 and 91 each independently supply power to the load. At distribution substations, it is a general rule to operate transformer banks alone as described above, in order to standardize equipment and limit the spread of accidents when they occur. However, in the case of independent operation of such transformer banks, an imbalance may occur in the operating rate of each bank, and in such cases, the trap switches the load by switching the connection lines each time, and each The operating rates of the transformer banks are averaged out. For example, in FIG. 1, a load breaker 93 is connected to a bus bar 92 by a connecting wire 96, and this connecting wire 96 is cut to connect the connecting wire 8.
6, the load breaker 93 is reconnected to the bus bar 82 to equalize the roe I of the transformers 81 and 91. However, switching the connection lines each time requires a power outage to the busbar, and the switching work requires manpower and is complicated, so it is more suitable to operate transformer banks in parallel.

Figure 2 is a single line system diagram of transformer bank parallel operation,
Transformer 81 and its busbar 82 and load breakers 83 and 84
．． Bus bars 82 and 92 of the power system consisting of a transformer 91, its bus bar 92, and load breakers 93, 94.95 are connected by a bus interconnection breaker 99,
1 and 91 are operating in parallel to supply power to a load. By operating the transformer banks in parallel in this way, the equipment operating rate is improved. Improving the equipment operating rate is advantageous because even if the load increases to a certain extent, it can be handled without increasing power sources such as transformers, and as mentioned above, there will be no power outages due to switching work. Supply reliability will also improve.

However, in FIG. 2, for example, a problem occurs when a short circuit occurs at a short circuit point 100 on the load side of the load breaker 83. For now, transformers 81 and 91 are each IOMV
Assume that the capacity is A, and the percentage impedance is 7.5%.
Assuming that, the short circuit capacity when the secondary side of this transformer is shorted is 1070.075=133.3, which is 133
．． It is 3MVA. When the transformer bank is operating alone, that is, when the busbar interconnection breaker 99 is open, the short circuit current flowing into the short circuit fault point 100 is supplied only by the transformer 81, so the load breaker 83 has a current of 133.3 MVA. If there is a large breaking capacity, for example, 150 MVA, this short-circuit fault point 100 can be isolated from the bus bar 82.

If there is a running electric motor in the load, short circuit failure point 10
The short circuit current flowing into 0 is the current supplied by transformer 81,
It is necessary to calculate the short-circuit current supplied by the motor during operation, but this will not be explained hereafter as it is sufficient to add this amount when determining the breaking capacity of the load breaker. Tir + For simplicity, it is assumed that only the power supply supplies the short circuit current, and the motor supply is not considered.

In FIG. 2, the transformer 8 is
If a short-circuit accident occurs at the current fault point 100 when 1 and 91 are operating in parallel, the short final current of two transformers will flow through the load breaker 83, resulting in an interruption of 267 MVA or more. If there is no capacity, it will not be possible to shut off the circuit, which could lead to a major accident. Therefore, the breaking capacity is 1.50MV as mentioned above.
It is necessary to upgrade the breaking capacity from A, but this upgrade of the breaking capacity is necessary for all load breakers, which requires a large amount of cost, and also requires a large amount of space due to lack of installation space to upgrade the breaking capacity. There is a possibility that it may be possible to raise it or not.

In addition, even if the method of increasing the capacity of each transformer to cope with the increase in load instead of operating multiple transformers in parallel using state line interlocking circuit breakers 99, it is still necessary to upgrade the breaking capacity of the load breakers. .

In the current waveform when a short circuit occurs, a DC component is superimposed due to a transient phenomenon, and the current peak value is particularly large for several cycles after the short circuit occurs. Since this current peak value has a great effect on electrical equipment, it is desirable to eliminate this short circuit accident as soon as possible, but it is extremely difficult to deal with this accident within a very short time after the short circuit occurs. For example, in the case of Fig. 2, even if the bus-bar linked circuit breaker 99 is shut off, the shut-off time is 3.
~5 cycles and cannot deal with accidents. Constantly inserting a series reactor in the power supply circuit to limit the current in the event of a short circuit requires a large-capacity reactor, which increases equipment costs and installation space, and reduces voltage fluctuations in the circuit. This is not desirable because it becomes large and makes it impossible to supply high-quality electricity. On the other hand, the method of always short-circuiting this series reactor and inserting this series reactor into the circuit only when an accident occurs is difficult to operate within the extremely short time mentioned above.

In order to cope with the increase in the short-circuit capacity of the power supply due to the parallel operation of modified voltage transformer banks, it was necessary to upgrade the breaking capacity of the load breakers at great expense.

[Purpose of the invention]

This invention is useful when the short-circuit capacity of the power supply exceeds the breaking capacity of the load breaker connected to the bus due to an increase in power supply capacity or a change in the power supply from individual operation to parallel operation. It is an object of the present invention to provide a short-circuit current suppression method that limits the short-circuit current flowing through a load breaker to a permissible value or less without upgrading the breaking capacity of the load breaker.

[Key points of the invention]

In this invention, an artificial short circuit is prepared on the power supply side from the load breaker, and when a short circuit accident occurs on the load side,
The above-mentioned artificial short circuit is formed within the time until the short-circuit current flowing through the load breaker reaches the permissible value, and the short-term final current that should flow through the load breaker is bypassed by this artificial short circuit, and then the short circuit is The above purpose is achieved by reducing the current to a value that can be interrupted by this load breaker, releasing the short circuit of this artificial short circuit, and then disconnecting the short circuit fault point from the power supply by the load breaker. ing.

In addition, methods for reducing short circuit 1' current include methods of inserting an impedance between the power supply and the bus, methods of lowering the voltage of the power supply, methods of reducing the number of power supplies, methods of dividing the bus, and methods of inserting an impedance into the bus. There is a way to insert .

[Embodiments of the invention]

First, an artificial short circuit is formed in an extremely short period of time.
``3-Explain the need to do so using actual numbers.

If the capacity of the first transformer, which is the power supply, is 20 MVA and its percentage impedance is approximately 11°5, then the short circuit capacity of this transformer is 175 MVA, so when this transformer is operated in a single bank. It is sufficient that the load breaker has a breaking capacity of 175 MVA or more, that is, 250 MVA. However, as mentioned above, the second
If the transformer bank of
Since it is MVA, the breaking capacity of the load breaker is 350MV.
If it is not upgraded to A, there is a risk that it will become impossible to shut down.

Figure 3 is a short-circuit current waveform diagram. In Figure 3, the dashed line is the DC component of the short 1 fefJ current, which decreases exponentially with the passage of time.The magnitude of this DC component is It changes depending on the voltage phase when a short circuit occurs.The solid line is the actual short circuit current that includes this DC component, and is called an asymmetric short circuit current.Figure 3 shows a short circuit at a phase where the peak value of this asymmetric short circuit current is a shark dog. The asymmetric short-circuit current reaches its maximum when 0.5 cycles, or 10 milliseconds (at a frequency of 50 Hz, below, all times are shown at 50 Hz) after the short circuit occurs. When the circuit is a three-phase circuit, the maximum value 1p of this asymmetric short-circuit current is expressed by P, which is the short-circuit capacity, and ■, which is the circuit voltage.

Here, n is the magnitude of the DC component, and n=2.6 is the maximum. Assuming that the short-circuit capacity of the discharge source is 350 MVA and the circuit voltage is 6.6 kV, in the case of n-2,6 (1
), the maximum value of the short circuit current supplied by the power supply is 80 kA. On the other hand, if the breaking capacity of a load breaker is 250MVA, from equation (1), this breaker can withstand a maximum current of 57kA, but since the electromagnetic force is proportional to the square of the current, 80kA In this case, an electromagnetic force approximately twice that of 57 kA acts on the circuit breaker, causing it to be mechanically destroyed. As mentioned above, the breakdown occurs within a short period of time, within 10 milliseconds after the occurrence of the short circuit.

If the voltage phase at the time of a short circuit changes, the peak value of the short circuit current will decrease from the above value, but the time it takes to reach the current peak value of 57 kA, which is guaranteed not to cause damage, will be shorter (or less). Sometimes.

The secondary measured current of two 20MVA transformers is a voltage of 6.6.
kV, it is 3.5kA, so if a current approximately three times the rated current, or 10kA, flows through the circuit, it is detected as an abnormal current.After detecting this abnormal current, the 57kA current described above is detected. The shortest time to reach the peak value is 65 degrees in electrical angle and 3.6 milliseconds in time. Therefore, certain measures must be taken within 3.6 milliseconds after detecting an abnormal current.

Circuit breakers generally require 3 cycles (60 milliseconds) to 5 cycles (100 milliseconds) to complete interrupting, so
If the bus-linked circuit breaker or circuit breaker on the primary or secondary side of the transformer is shut off, it will not be enough, and if the transformer circuit breaker is shut off, it will result in a total power outage, which is a problem.

FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. 5 is a time chart showing the operation of this embodiment. The present invention will be explained in detail with reference to FIGS. 4 and 5.

In FIG. 4, 11 is a transformer, and this transformer 11
is connected to the bus 1, but a series reactor 14 is inserted between the transformer 11 and the bus 10, and a series reactor short-circuit breaker 15 is connected in parallel to this reactor 14. The short-circuit breaker 15 is normally closed, and the series reactor 14 is short-circuited. 16R9S, Ill is a current transformer inserted in each phase of the secondary side of this transformer 110, and 17R9S, +
p is an overcurrent relay that operates with the current detected by this current transformer. This bus 1 is provided with an artificial short circuit 30, and this artificial short circuit 30 has high-speed closing devices 33, S, and T that are always open and can operate for each phase. It consists of a short circuit breaker 34 and a smart circuit 35. 31RI+T has overcurrent relay 17 3,
This is a high-speed closing type drive circuit that operates in response to the signal 111, and 32 B, Ill is a high-speed closing coil. Load circuits 40, 50, 60 are connected to the bus 1, and these load circuits are connected to load breakers 41, 51, respectively.
．． 61 and current transformer 46, 56.66 and overcurrent relay 47,
It consists of 57.67. And this load breaker 41
, 5'l, and 61 are assumed to be smaller than the short-circuit capacity of the transformer 11.

100 is a short circuit accident point.

In the power system shown in FIG.
If a short circuit occurs between the first and second phases at the point 100 of 0, current transformers 16R and 168 inserted in the phase corresponding to the short circuit on the secondary side of the transformer will detect this fault current. do. When this fault current increases with the passage of time and reaches a certain predetermined value, for example, in the above-mentioned example, three times the rated current, the overcurrent relays 17R and 178 operate and the high-speed closing type drive circuit 31f (・High-speed dosing device 33 via high-speed dosing device making coil 32R and 328 via and 318
1 (, and 338 are thrown. This fast throwing device 33R,
As mentioned above, 33S is good if it has to be turned on within a very short time after detecting an abnormal current, but if it is a high-speed dosing device that applies the principle of electromagnetic repulsion, then the 36mm It is easy to complete loading within seconds; for example, there are anti-shock dispensers that can load in 2 milliseconds.

Since the short-circuit breaker 34 is always closed, the high-speed closing devices 33R and 338 are closed before the short-circuit fault current flowing through the load breaker 41 reaches the maximum current that the load breaker 41 can withstand. Once the artificial short circuit 30 is formed,
This short-circuit fault current is bypassed by the artificial short circuit 30, and a current exceeding the allowable value of the load breaker 41 does not flow through the load breaker 41. Therefore, when the series reactor short-circuit breaker 15 that short-circuits the series reactor 14 is cut off, the series reactor 14 is inserted in series with the transformer 11, so that the flow flows to the artificial short circuit 30 and the short-circuit fault point 100. The total short circuit current is significantly suppressed.

If the short-circuit breaker 34 is cut off at that point, all the short-circuit current suppressed by this series reactor 14 will be transferred to the short-circuit fault point 1.
00, the current transformer 46 detects this current, the overcurrent relay 47 is activated, and the load breaker 41 disconnects the short circuit fault point 100 from the power source. While the short-circuit breaker 34 is open, the high-speed closing switches 33 and 338 are opened, and when the short-circuit fault point 100 is disconnected from the power source transformer 11, the series reactor short-circuit breaker 15 and the short-circuit breaker are immediately connected. By turning on 34, the power system returns to the state before the accident occurred.

The above series of operations is shown in the time chart of FIG.

Figure 4 shows a case where there is only one transformer 11, but even if there are multiple transformers, the high-speed closing device can be turned on when the total value of abnormal current flowing through each transformer exceeds a preset value. do it.

@6 Figure is a circuit diagram showing a second embodiment of the present invention. In FIG. 6, 12 is a transformer having a tap changer on the high voltage side winding, and 18 is a tap changer for changing this tap. All other symbols and their contents are shown in FIG. Since it is the same as the first embodiment shown in , the explanation of the reference numerals will be omitted. Furthermore, when a short circuit accident occurs at the short circuit accident point 100, an artificial short circuit 30 is quickly formed and the short circuit current is bypassed to this artificial short circuit 30, similarly to the first embodiment shown in FIG. However, after that, operate the tap change operation device 18 to change the high voltage side coil of the transformer 12.
Change the tap on the transformer to reduce the voltage on the secondary side of the transformer.

When the secondary voltage of the transformer 12 decreases, the short-circuit capacity decreases, so the secondary voltage of the transformer is decreased until the current value falls below the allowable current value of the load breaker 41, and then the artificial short circuit 30 is short-circuited. Once released, the load breaker 41 can safely disconnect the short circuit fault point 100 from the power source. Thereafter, the tap change operator 18 may be operated to return the transformer secondary voltage to its original value. In the case of FIG. 6, there is one transformer 12, but even if there are multiple transformers, short circuit current can be suppressed by the same operations as long as care is taken to detect abnormal current.

FIG. 7 is a circuit diagram showing a third embodiment of the present invention. In FIG. 7, 11 and 21 are transformers, which are connected to the bus 1 via transformer secondary circuit breakers 13 and 23 on their respective secondary sides. 16R, S, T are transformers 1
A transformer for detecting each phase current on the 102nd secondary side,
26R, S, and T are current transformers for detecting each phase current on the secondary side of the transformer 21.

Overcurrent relay 27R is an overcurrent relay that operates when the total value of current 9 detected by current transformers 16R and 26 exceeds a certain value, and overcurrent relay 278 is also 27T.
The overcurrent relay also operates when the total value detected by current transformers 16S and 268, and the total value detected by current transformers 16T and 26T, respectively, exceed a set value. Reference numeral 30 denotes an artificial short circuit, which includes high-speed dosing devices 33R, S, and T, a high-speed dosing device drive circuit 31 S, T, and a high-speed dosing device making coil 32R for operating this dosing device. ,8,T
Short circuit breaker 34. The short circuit 35 has both its configuration and operation vJ
This is the same as FIG. 4, which is the embodiment of Embodiment 1. 40, 50, 6
0.70 is a load circuit, and each load breaker 41
．． It consists of 51.61°71, current transformers 46, 56, 66.76, and overcurrent relay 47°57.67.77.

100 is a short circuit accident point.

When a short circuit fault occurs at a short circuit fault point of 100 in Fig. 7, transformers 11 and 21 supply a short circuit current, but the impedance of the line from the transformer to the short circuit fault point is not necessarily the same for both transformers. Therefore, the short circuit currents shared by both transformers will be unequal. Therefore, current transformers 16 and 26R, 168 and 26
816T and 26T are connected. In the case of Figure 7, i
The first and second phase overcurrent relays 27 and 278 detect abnormal current. This abnormal current quickly activates the artificial short circuit 30 to form an artificial short circuit, and after bypassing the short circuit current flowing to the short circuit accident point 100 to this artificial short circuit 30, the transformer secondary circuit breaker 23 is closed. The circuit is cut off and the transformer 21 is disconnected from the bus bar. In other words, the capacity of the transformer that is the short circuit current supply source is reduced to reduce the magnitude of the short circuit current to within the allowable value of the load breaker 41. Thereafter, the short circuit breaker 34 is cut off to eliminate the artificially formed short circuit, and the reduced short circuit fault current is passed through the load breaker 41 and cut off.

FIG. 8 is a circuit diagram showing a fourth embodiment of the present invention. In FIG. 8, transformer 11 is connected to bus 2, to which load circuits 40 and 50 are connected. A transformer 21 is connected to another bus 3, load circuits 60 and 70 are connected as loads, and an artificial short circuit 30 is connected. The two busbars 2 and 3 are connected by a busbar interconnection breaker 4 which is normally closed. In the case of the embodiment shown in FIG. 8, when a short circuit accident occurs, the short circuit current is bypassed to the artificial short circuit 30, and then the bus interconnection breaker 4 is shut off to divide the bus bars to reduce the power supply capacity and short circuit current by °C. let In the case of this diagram where the short-circuit fault point 100 is in the load circuit 40, when the bus-linked circuit breaker 4 is disconnected, the short-circuit current supplied only by the transformer 11 automatically passes through the load circuit breaker 41. 41 disconnects the short-circuit fault point 100 from the power supply. When the short-circuit fault point is in the load circuit 70, the bus link circuit breaker 4 is cut off to divide the bus bar, reduce the power capacity, and then the short-circuit breaker 34 is cut off to shorten the bypassed short-circuit current. After returning to the final fault point, the load breaker-71 is disconnected.

FIG. 9 is a circuit diagram showing a fifth embodiment of the present invention. In FIG. 9, the bus 2 includes a transformer 11 and a load circuit 40.
and 50 are connected to the other bus bar 3, and the transformer 21, load circuits 60 and 70, and an artificial short circuit 30 are connected to the other bus bar 3. The two buses 2 and 3 are connected via a bus reactor 5, and a bus reactor short circuit breaker 6 is connected in parallel to the bus reactor 5, but this bus reactor short circuit breaker 6 is always closed. Therefore, the busbar accelerator 5 is short-circuited. When a short-terminal fault occurs at a short-circuit fault point of 100 in the load circuit 40, the short-circuit flow at this time is bypassed to the artificial short circuit 30, as in the other embodiments. Subsequently, when the bus reactor short-circuit interrupter 6 is cut off, the bus reactor 5 is inserted into the bus, and the short-circuit breaker 34 is cut off, the short-circuit current flowing through the load breaker 41 is equal to the current supplied by the transformer 11, Bus line react) /
This is the sum of the current supplied by transformer 21 via L-5.

Since the short-circuit current supplied by the transformer 21 from the aJ line soliactor 5 is significantly reduced, the short-circuit fault current flowing through the load breaker 41 is within the allowable value of this breaker, and the short-circuit fault point 100 is separated from the power supply by 9 nodes. You can let go.

〔Effect of the invention〕

According to the present invention, when a short circuit fault occurs, the short circuit fault current is bypassed to the artificial short circuit within a very short time, and then the short final current supplied by the power supply is reduced before the load breaker is activated. Since the structure is such that the short-circuit fault point is isolated from the source, it is possible to cope with an increase in the short-circuit capacity of the power supply by simply adding an artificial short circuit and a current suppression circuit. 71 This eliminates the need to extend the breaking vessels of a large number of load breakers at great expense.

Furthermore, there is no need to shut down the power grid when disconnecting the short-circuit fault point (there is no constant voltage fluctuation, which improves the quality and reliability of the supplied power. Furthermore, the artificial short-circuit can eliminate 5 faults in a short period of time). It is intended to move from the point of short circuit to this artificial short circuit, and the magnitude of the short circuit constant current has no relation to the operation or non-operation of this artificial short circuit.

[Brief explanation of the drawing]

FIG. 1 is a single-leg system diagram for single operation with a punctured transformer, FIG. 2 is a single-leg system diagram for parallel operation of transformer banks, and FIG. 3 is a short-circuit current waveform diagram. FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. 5 is a time chart diagram of the circuit shown in FIG. 6 is a circuit diagram showing a second embodiment 91j of the present invention, FIG. 7 is a circuit diagram of a third embodiment of the present invention, FIG. 8 is a circuit diagram of a fourth embodiment of the present invention, and FIG. 9 is a circuit diagram of a fourth embodiment of the present invention. FIG. 5 is a circuit diagram of a fifth embodiment of the present invention. 1.2.3...Bus bar, 4...Bus link circuit breaker, 5...Bus reactor, 6...
・Bus bar reactor short circuit breaker, 11.21...
Transformer, 12.・・・・・Tag Changer Publication Transformer, 13
．． 23...Transformer secondary side circuit breaker, 14...
・・Series reactor, 15・・Curved-series reactor short circuit breaker, 16, 26・・・Current transformer, 17.27・
...Overcurrent relay, 18...Tag change operation device, 3゜・°°°゛°artificial short circuit, 31...
...High-speed dosing device drive circuit, 32...High-speed dosing device making coil, 33...High-speed dosing device, 34...
...Short circuit breaker, 35...Short circuit, 40.
50, 60, 70... Load circuit, 41, 51
,61,71... Load breaker, 46.56,6
6.76... Current transformer, 47.57, 67.77
...Overcurrent relay, 81.91...Transformer, 82.92 Old bus, 83, 84, 85, 9
3゜94.95...Load breaker, 86.96.
...Connection line, 99...Bus bar linkage circuit breaker,
100...Short circuit accident point ◇Fig. 1 Fig. 2 Fig. 3 Fig. 6 Fig. 7

Claims (1)

[Claims] 1) A power system in which a power source is connected to a bus and the bus supplies power to a load circuit via a load breaker,
In a power system where the short-circuit current value that a power source can supply is greater than the allowable value of the load breaker, an artificial short circuit that can artificially short a desired phase of the power system is connected to the power source side from the load breaker. , the step of detecting abnormal current due to a short-circuit accident in a load circuit, and the artificial short-circuiting of the phase corresponding to the phase where the accident occurred or all phases at once at a speed that does not cause a short-circuit current exceeding an allowable value to flow to the load breaker. a step of inserting a reactor having an impedance that can limit the short circuit current value to below the F [capacity value of the load breaker] between the power supply and the bus, and a step of eliminating the artificial short circuit. Features short-circuit current suppression method. 2) In a power system that connects a power source to a bus and supplies power from the bus to a load circuit via a load breaker, the short-circuit current value that the power source can supply is greater than or equal to the allowable value of the self-load breaker. In a power system, an artificial short circuit capable of artificially shorting a desired phase of the power system is connected to the power source side from the load breaker, and an abnormal current due to a short circuit accident in the load circuit is detected; forming the artificial short circuit on the phase corresponding to the phase in which the fault occurred or all phases at once at a speed that prevents a short circuit current exceeding an allowable value from occurring; and the short circuit current value becomes less than the allowable value of the load breaker. %i Lf up to voltage. A short-circuiting method comprising the steps of lowering the voltage and eliminating the artificial short circuit. 3) In a power system in which a power source is connected to a busbar and power is supplied from the busbar to a load circuit via a load breaker, the short-circuit current value that the power supply can supply is greater than the allowable value of the load breaker. In a certain power system, there are two steps: connecting an artificial short circuit that can artificially short a desired phase of the power system to the power source side from the load breaker and detecting abnormal current due to a short circuit accident in the load circuit; A step in which a short circuit current exceeding the allowable value flows through the device at an extremely fast rate, forming the artificial short circuit on the phase corresponding to the phase where the accident occurred or all phases at once, and disconnecting a part of the power supply from the bus bar to reduce the short circuit current value. A method for suppressing short-circuit current, comprising the steps of: reducing the power supply capacity so that the current is less than the allowable value of a load breaker; and eliminating the artificial short circuit. 4) Connect the power supply to the bus, and connect the negative from the nuclear bus? In a power system that supplies power to a load circuit via a fiI circuit breaker, in which the short-circuit current value that can be supplied by the power supply is greater than or equal to the allowable value of the load breaker, a desired phase of the power system is artificially connected. connecting an artificial short circuit capable of shorting to the power source side from the load breaker to detect an abnormal current due to a short circuit accident in the load circuit; The step of forming the artificial short circuit for the phase corresponding to the phase where the fault occurred or all phases at once, and the power supply capacity such that the short circuit current value supplied from the power source connected to each bus bar is equal to or less than the allowable value of the load breaker. A method for suppressing short circuit current, comprising the steps of: dividing a bus bar at a position; and eliminating the artificial short circuit. 5) A power system that connects a power source to a bus and supplies power from the bus to a load circuit via a load breaker, where the short-circuit current value that the power source can supply is greater than or equal to the allowable value of the load breaker. In this step, an artificial short circuit capable of artificially shorting a desired phase of the power system is connected to the power supply side from the load breaker, and an abnormal current due to a short circuit accident in the load circuit is detected, and an allowable value is set in the load breaker. forming the artificial short circuit by collectively forming the phase or metal phase corresponding to the phase in which the accident occurred at such a speed that the above short circuit current cannot flow, and dividing the bus bar via a reactor to inserting a reactor having a predetermined impedance at a predetermined position on the bus bar such that the combined value of the short-circuit current supplied from the power supply and the short-circuit current supplied directly from the power supply is equal to or less than the allowable value of the load breaker; and the artificial short circuit. A method for suppressing short circuit current, comprising the steps of eliminating the circuit.