A method for dealing with interphase short circuit in a dual-power three-phase power system

Abstract

The present invention discloses a method for dealing with interphase short circuits in a dual-power three-phase power system. In the dual-power three-phase power system, there is a sectionalizing switch, and a number of sectional switches are provided on the three-phase lines on both sides of the sectionalizing switch. The number of sectional switches divides the three-phase lines into a number of protection zones, and a number of sectionalizing switches are provided within the protection zones. When an interphase short circuit occurs, first, a detection circuit including the interphase short circuit fault point and two fault-phase conductors is created, so that the sectionalizing switch on the active side cuts off the fault point. Then, the sectionalizing switch closes, and then a detection circuit including the interphase short circuit fault point and two fault-phase conductors is created, and the fault point is cut off by using the sectionalizing switch on the new power source side. This method can cut off the connection between the interphase short circuit fault point and the power sources on both sides, thereby maximizing the coverage of the power supply area, reducing the adverse effects brought by the interphase short circuit, and at the same time being beneficial to reducing the use of large-current switches and lowering the cost.

Description

Technical Field

[0001] The present invention relates to the field of power system protection, and particularly to a method for handling phase-to-phase short circuits in a dual-power three-phase power system. Background Art

[0002] At present, when a phase-to-phase short circuit occurs in a certain line of a three-phase power system, the following processing methods are usually adopted: 1. Adopt the reclosing method: First, cut off the first circuit breaker on this line and then close the first circuit breaker. If it is an instantaneous phase-to-phase short circuit and is eliminated after closing the first circuit breaker, normal power supply continues. If the phase-to-phase short circuit fault still exists after closing the first circuit breaker, cut off the first circuit breaker and wait for maintenance. 2. Adopt the time differential cooperation method: That is, circuit breakers on the same line are set with different overcurrent tripping times according to their distances from the power source. The closer to the power source, the longer the tripping time. Generally, the set differential is 100 ms, which is determined by the mechanical action time of the switch and the time consumed by the algorithm. This method can isolate the fault area, but for faults where the fault point is close to the power source, the power supply system endures the short-circuit current for a long time, causing a large impact on the power grid. 3. First, trip the first circuit breaker due to overcurrent, then trip the last load switch without current (other load switches are in the closed state), then reclose the first circuit breaker. If the fault occurs below the last load switch, the fault can be eliminated. Otherwise, there is still a fault current after the first circuit breaker recloses. At this time, the first circuit breaker trips again due to overcurrent, then the penultimate load switch trips without current, and then the first circuit breaker recloses again. If the phase-to-phase short circuit occurs between the penultimate load switch and the last load switch, the fault can be eliminated. And so on, cut off the load switches without current upwards in turn until the fault is eliminated. However, during this operation process, the power supply system is repeatedly subjected to large short-circuit current impacts. If the number of times is too many, it will damage the line. In addition, the time for the line to eliminate the fault is also very long. 4. Circuit breakers with the ability to trip due to fault current are configured on the line. When a fault occurs, all circuit breakers are set to trip due to overcurrent, and then start closing from the first circuit breaker. If there is overcurrent, it trips, and the fault is eliminated. If the first circuit breaker closes successfully without overcurrent, the overcurrent tripping is blocked for a period of time. During this period, the second circuit breaker closes. Since the first circuit breaker has been blocked due to overcurrent, the second circuit breaker trips due to overcurrent, and the fault is eliminated. If there is no overcurrent, then close the next one, and so on. This scheme requires each circuit breaker to have the ability to cut off large currents, which has high requirements for circuit breakers, high manufacturing costs, complex logic, and a relatively long self-healing time. Therefore, the existing methods for handling phase-to-phase short circuits all have the problems of long fault handling time, large impact on the system, and high requirements for the ability of switches to cut off large currents.

[0003] Patent application for invention 2020114536325 and patent application for invention 2020114536310 provide two methods for dealing with phase - to - phase short - circuit. When a phase - to - phase short - circuit occurs, a detection loop including the faulty phase and the phase - to - phase short - circuit fault point is artificially constructed, and the number of current pulses or duration information of the current is detected by a switch on the detection loop to trigger a trip so as to cut off the fault point. This method does not perform zone protection. First, the first circuit breaker needs to trip, so that users on the entire line will be affected, and the power - off area is large. Moreover, this method does not clearly propose how to reduce the number of large - current switches used. Patent application for invention 2021106183754 discloses a method for dealing with phase - to - phase short - circuit in a three - phase power system. Zone switches and sectional switches are set on the line. The zone switches can cut off large current, and the sectional switches only need to cut off the load current. When a phase - to - phase short - circuit occurs, the zone switches are controlled to trip through differential protection, and then the sectional switches are tripped by the method based on current pulses or current duration, so as to remove the phase - to - phase short - circuit fault.

[0004] A dual - power supply system has two power supplies, which are separated by a sectionalizing switch in the middle. After one power supply stops power supply, the sectionalizing switch can be closed to continue power supply using the other power supply. However, after a phase - to - phase short - circuit fault occurs, when the sectional switch on one side of the fault point is cut off by the above - mentioned method to remove the short - circuit fault relative to one power supply, if the sectionalizing switch is closed to continue power supply to the powered - off line, the phase - to - phase short - circuit fault point still exists relative to the other power supply and must be removed, but the foregoing patents do not give corresponding treatment methods. Summary of the Invention

[0005] The object of the present invention is to provide a method for dealing with phase - to - phase short - circuit in a dual - power three - phase power system, which can cut off the connection between the phase - to - phase short - circuit fault point and the two - side power supplies, so as to maximize the coverage of the power - supply area, reduce the adverse effects brought by the phase - to - phase short - circuit, and at the same time is beneficial to reducing the use of large - current switches and lowering costs.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for dealing with phase - to - phase short - circuit in a dual - power three - phase power system, the dual - power three - phase power system is provided with a sectionalizing switch, and a plurality of zone switches are provided on the three - phase lines on both sides of the sectionalizing switch. The plurality of zone switches divide the three - phase lines into a plurality of protection zones, and a plurality of sectional switches are provided in the protection zones; when a phase - to - phase short - circuit fault occurs on one side of the sectionalizing switch, the following steps are taken for treatment:

[0008] S1: The sectionalizing switch on the source side of the phase-to-phase short-circuit fault point cuts off the fault current. Then, a first detection loop is constructed using the two faulty-phase conductors between the phase-to-phase short-circuit fault point and the sectionalizing switch on the source side and the phase-to-phase short-circuit fault point, and a first current signal is injected into the first detection loop. The sectionalizing switches within the protection zone detect the first current signal and trip according to a first preset condition to cut off the connection between the phase-to-phase short-circuit fault point and the sectionalizing switch on the source side. The first preset condition causes the sectionalizing switch closer to the sectionalizing switch on the source side to trip later than the sectionalizing switch farther from the sectionalizing switch on the source side according to the first current signal. The sectionalizing switch on the source side is the sectionalizing switch that can cut off the power transmission of the protection zone where the phase-to-phase short-circuit fault point is located before the sectionalizing switch at the boundary closes.

[0009] S2: The sectionalizing switch at the boundary closes. The sectionalizing switch on the new source side of the phase-to-phase short-circuit fault point cuts off the fault current. Then, a second detection loop is constructed using the two faulty-phase conductors between the phase-to-phase short-circuit fault point and the sectionalizing switch on the new source side and the phase-to-phase short-circuit fault point, and a second current signal is injected into the second detection loop. The sectionalizing switches within the protection zone detect the second current signal and trip according to a second preset condition to cut off the connection between the phase-to-phase short-circuit fault point and the sectionalizing switch on the new source side. The second preset condition causes the sectionalizing switch closer to the sectionalizing switch on the new source side to trip later than the sectionalizing switch farther from the sectionalizing switch on the new source side according to the second current signal. The sectionalizing switch on the new source side is the sectionalizing switch that can cut off the power transmission of the protection zone where the phase-to-phase short-circuit fault point is located after the sectionalizing switch at the boundary closes.

[0010] Preferably, the first current signal or the second current signal is generated using the electric energy of the dual-power three-phase power system.

[0011] Preferably, in step S1, the sectionalizing switch on the source side trips at least one faulty phase to cut off the fault current and maintains the conduction of the other faulty phase. Then, the tripped faulty phase is connected to the ground or a common conductor from the lower port of the sectionalizing switch on the source side. Next, a live phase other than the faulty phase that maintains conduction is connected to the ground or a common conductor from the upper port of the sectionalizing switch on the source side, or a neutral point of the dual-power three-phase power system is connected to the ground or a common conductor to generate the first current signal. In step S2, the sectionalizing switch on the new source side trips at least one faulty phase to cut off the fault current and maintains the conduction of the other faulty phase. Then, the tripped faulty phase is connected to the ground or a common conductor from the lower port of the sectionalizing switch on the new source side. Next, a live phase other than the faulty phase that maintains conduction is connected to the ground or a common conductor from the upper port of the sectionalizing switch on the new source side, or the other neutral point of the dual-power three-phase power system is connected to the ground or a common conductor to generate the second current signal.

[0012] Preferably, in the step S1, a first signal generating switch and a first current limiting resistor are provided between one end bus or a neutral point of the dual-power three-phase power system and the ground. The first signal generating switch is cyclically connected to and disconnected from the ground or a common wire to generate a first current pulse. The sectionalizing switch trips according to a preset number of current pulses, and the sectionalizing switch closer to the active side sectionalizing switch trips with a larger number of current pulses than the sectionalizing switch farther from the active side sectionalizing switch; or the first signal generating switch is continuously connected to the ground or a common wire to generate a first continuous current, and the sectionalizing switch trips according to a preset current duration, and the sectionalizing switch closer to the active side sectionalizing switch trips with a longer current duration than the sectionalizing switch farther from the active side sectionalizing switch. In the step S2, a second signal generating switch and a second current limiting resistor are provided between the other end bus or another neutral point of the dual-power three-phase power system and the ground. The second signal generating switch is cyclically connected to and disconnected from the ground or a common wire to generate a second current pulse. The sectionalizing switch trips according to a preset number of current pulses, and the sectionalizing switch closer to the new source side sectionalizing switch trips with a larger number of current pulses than the sectionalizing switch farther from the new source side sectionalizing switch; or the second signal generating switch is continuously connected to the ground or a common wire to generate a second continuous current, and the sectionalizing switch trips according to a preset current duration, and the sectionalizing switch closer to the new source side sectionalizing switch trips with a longer current duration than the sectionalizing switch farther from the new source side sectionalizing switch.

[0013] Preferably, in the step S1, connecting a tripped faulty phase from the lower port of the active side sectionalizing switch to the ground or a common wire includes using the active side sectionalizing switch to connect the tripped faulty phase from the lower port of the active side sectionalizing switch to the ground or a common wire after disconnecting the tripped faulty phase, or using the active side sectionalizing switch to disconnect the tripped faulty phase and then connecting the tripped faulty phase from the lower port of the active side sectionalizing switch to the ground or a common wire through another switch; in the step S2, connecting a tripped faulty phase from the lower port of the new source side sectionalizing switch to the ground or a common wire includes using the new source side sectionalizing switch to connect the tripped faulty phase from the lower port of the new source side sectionalizing switch to the ground or a common wire after disconnecting the tripped faulty phase, or using the new source side sectionalizing switch to disconnect the tripped faulty phase and then connecting the tripped faulty phase from the lower port of the new source side sectionalizing switch to the ground or a common wire through another switch.

[0014] Preferably, the first current signal or the second current signal is generated by a power source other than the power sources of the dual-power three-phase power system.

[0015] Preferably, a differential protection system is arranged on the protection area. When an interphase short-circuit fault occurs, the differential protection system issues a control signal to cause the active-side sectionalizing switch to trip at least one faulty phase to cut off the fault current, or to cause the new-source-side sectionalizing switch to trip at least one faulty phase to cut off the fault current.

[0016] Preferably, both the first signal generating switch and the second signal generating switch are a single-phase thyristor or two independent thyristors or three independent thyristors; both the first current-limiting resistor and the second current-limiting resistor are adjustable resistors or resistor selectors, or are resistors with fixed resistance values.

[0017] Preferably, a differential protection system is arranged on the protection area. When an interphase short-circuit fault occurs, in steps S1 and S2, the differential protection system controls the active-side sectionalizing switch and the new-source-side sectionalizing switch to act to cut off the fault current.

[0018] In the above solution, the line is divided into several protection areas. After an interphase short circuit occurs, the sectionalizing switches on both sides of the fault point can be cut off respectively, so that the interphase short-circuit fault point can be isolated from the dual-power supply system, and the power supply of other areas outside the sectionalizing switches on both sides of the fault point is not affected. This technical solution distinguishes between sectionalizing switches and segmenting switches. The sectionalizing switch cuts off the large short-circuit current, while the segmenting switch plays a role in cutting off in the constructed detection circuit. By setting the current-limiting resistor, a current signal with a smaller current value can be regulated, that is, the current in the detection circuit is a controllable current. In this way, the segmenting switch only needs to have the ability to cut off small current, and the requirement for the cutting-off performance is greatly reduced, thereby further effectively reducing the performance cost of the switch. Description of the Drawings

[0019] Figure 1 is a schematic diagram of the relevant structure of the dual-power three-phase power system in the present invention. Detailed Embodiments

[0020] The present invention will be further described below with reference to the drawings through specific embodiments:

[0021] As Figure 1As shown in the figure, the dual-power three-phase power system includes power source 1 and power source 2. A three-phase power supply line is erected between the two power sources, and a sectionalizing switch 3 is provided in the middle of the power supply line. The sectionalizing switch 3 is usually in the open state. A number of sectionalizing switches 4 are provided on the three-phase lines on both sides of the sectionalizing switch 3. A protection area is defined between two adjacent sectionalizing switches 4. A differential protection system can be set on the sectionalizing switch 4. When a phase-to-phase short circuit occurs in the protection area, the differential protection system controls the corresponding power inlet sectionalizing switch 4 to trip, thereby cutting off the fault current (the dotted box in the figure represents a certain sectionalizing switch and the area where it can cut off the power). A number of sectionalizing switches 5 can be installed inside each protection area. The sectionalizing switch 5 only needs to have the ability to cut off the load current and does not need to have the ability to cut off large short-circuit currents, so as to reduce costs.

[0022] Assume that a phase-to-phase short circuit fault occurs between phases B and C at point F, and the following method is adopted for handling: First, use the active-side sectionalizing switch 41 to cut off the fault current (assuming C is cut off and phase B is kept conducting. The specific method is to cut off both phases B and C simultaneously and then restore the conduction of phase B, or only cut off phase C while phase B remains conducting from the beginning). Then, connect phase C to the ground at the lower port of the active-side sectionalizing switch 41. Next, connect phase A or phase C to the ground cyclically or continuously at the upper port of the active-side sectionalizing switch 41 (both are energized, generally taken on the bus of power source 1, or can also be grounded through the neutral point). In this way, a detection loop including two faulty-phase conductors (i.e., phases B and C) and the phase-to-phase short circuit point F is constructed, and a current pulse or current duration serving as the first current signal will be generated. The sectionalizing switch 5 has the ability to detect the current pulse or current duration and can be cut off according to the first preset condition. The first preset condition is that the number of current pulses cut off near the active-side sectionalizing switch is more than the number of current pulses cut off far from the active-side sectionalizing switch, or the current duration cut off near the active-side sectionalizing switch is longer than the current duration cut off far from the active-side sectionalizing switch. In this way, it can be ensured that the closest sectionalizing switch 51 on the side of the active-side sectionalizing switch 41 to point F is cut off (for more detailed content, reference can be made to the invention patent application 2020114536325 and the invention patent application 2020114536310). Then, close the sectionalizing switch 3. Then, point F is still a phase-to-phase short circuit fault point relative to power source 2 and also needs to be handled and removed in a similar manner. Specifically, still control the new active-side sectionalizing switch 42 to operate through the differential protection system, so as to keep phase B conducting and phase C cut off (it can also be phase B cut off and phase C conducting. Hereinafter, the case of phase B conducting and phase C cut off is taken as an example). Then, connect phase C to the ground at the lower port of the new active-side sectionalizing switch 42 (in this specification, the upper port refers to the side where the switch is connected to the power source and is energized, and the lower port refers to the other side. Therefore, for the same sectionalizing switch, the upper and lower ports will be different depending on the power source). Then, connect phase A or phase C on the side of power source 2 to the ground cyclically or continuously at the upper port of the new active-side sectionalizing switch 42 (at this time, both are energized phases, generally taken on the bus of power source 2, or the neutral point of power source 2 can also be grounded). In this way, another detection loop including two faulty-phase conductors and the phase-to-phase short circuit point F is constructed again, and a current pulse or current duration serving as the second current signal is injected. Similarly, the closest sectionalizing switch 52 on the side of the new active-side sectionalizing switch 42 to point F will trip, so as to remove the short circuit fault of point F relative to power source 2 ( Figure 1Only one sectional switch is shown on each side of F for illustration purposes. In reality, there can be multiple sectional switches on each side. After the fault at point F is cleared, the sectional switch 41 on the active side and the sectional switch 42 on the new power source side close to restore power supply. In this embodiment, the sectional switch on the active side is the sectional switch that can cut off the power transmission in the protection area where the phase-to-phase short-circuit fault point is located before the sectional switch 3 (the boundary switch) closes; the sectional switch on the new power source side is the sectional switch that can cut off the power transmission in the protection area where the phase-to-phase short-circuit fault point is located after the sectional switch 3 closes (if the short-circuit fault point F falls on the other side of the sectional switch 3, the operating principle is the same).

[0023] As can be seen from the above, constructing a detection circuit using two faulty phase conductors and the phase-to-phase short-circuit fault point and injecting the first current signal and the second current signal, and presetting the sequential cut-off order of the sectional switches according to the corresponding current signals are the keys to solving the problem. In this way, no matter where the phase-to-phase short-circuit fault point occurs in which protection area, the nearest sectional switches can be smoothly cut off from both sides of the fault point, so as to eliminate the faults relative to both power source 1 and power source 2. In the above example, the current signals are generated using the electrical energy of the dual-power power system itself, which is relatively convenient. However, those skilled in the art should be able to understand that even with the help of a power source outside this system, the above purpose can still be achieved (at this time, the two faulty phases can be cut off simultaneously, and then the power supply ends can be connected from the cut-off points, and current pulses or continuous currents can still be created).

[0024] Some embodiments of constructing the above detection circuit are further described below:

[0025] In one embodiment, the sectional switch 41 on the active side has a phase-separated control function, that is, it can cut off only the C phase while keeping the B phase conducting, so that the fault current can be smoothly cut off. Then, the C phase is connected to the ground through the grounding switch 6 at the lower port of the sectional switch 41 on the active side. Then, the A phase (or C phase) is cyclically grounded or continuously grounded at the upper port of the sectional switch 41 on the active side using the first signal generation switch 7, so as to generate current pulses or continuous currents, thus constructing a detection circuit that meets the requirements. Or in another embodiment, a conducting switch 8 is provided in parallel with the sectional switch 41 on the active side. The sectional switch 41 on the active side cuts off all three phases simultaneously, and then the B phase is made conducting again by closing the conducting switch 8 single-phase. In the above embodiments, the first signal generation switch 7 can also make the grounding switch 6 or the conducting switch 8 conduct cyclically instead of conducting cyclically itself, so as to generate current pulses. After the sectional switch 3 closes, the sectional switch on the new power source side can also cut off one faulty phase and keep the other faulty phase conducting from the beginning, or cut off all three phases simultaneously, and then make one faulty phase conducting again through the corresponding conducting switch. Then, a second detection circuit is constructed through the grounding switch and the second signal switch 12.

[0026] In one embodiment, the first signal generating switch and the grounding switch may not be grounded, but instead are both connected to the same common wire, and a first detection circuit can also be created. Similarly, the second signal generating switch and the grounding switch may not be grounded, but instead are both connected to the same common wire, and a second detection circuit can also be created.

[0027] Preferably, in the above embodiment, a first current-limiting resistor 9 and a second current-limiting resistor 10 are connected in series to limit the short-circuit current.

[0028] Preferably, the first signal generating switch 7 and the second signal generating switch 12 are both a single-phase thyristor or two independent thyristors or three independent thyristors; the first current-limiting resistor 9 and the second current-limiting resistor 10 are both adjustable resistors or resistor selectors, or are resistors with fixed resistance values.

[0029] If a three-phase interphase short-circuit fault occurs, two faulty phases need to be cut off simultaneously, one faulty phase needs to be maintained in conduction, and then one of the cut-off faulty phases is grounded at the lower port of the corresponding sectionalizing switch. The other operations are the same. If an external power source is selected, three phases need to be cut off simultaneously, and then any two faulty phases are connected to the external power source to generate current pulses or a continuous power source. Obviously, using an external power source is generally more cumbersome than using the system's own power source and is not as convenient as using its own electrical energy.

[0030] The present invention is an extension of the patent application for invention 2021106183754. Regarding some implementation details, reference can also be made to the content of this patent application for invention.

[0031] The above embodiments are only illustrative of the concept and implementation of the present invention and do not limit it. Under the concept of the present invention, technical solutions without substantial transformation are still within the scope of protection.

Claims

1. A method for dealing with interphase short circuits in a dual-power three-phase power system. The dual-power three-phase power system is provided with a sectionalizing switch, and a number of sectional switches are provided on the three-phase lines on both sides of the sectionalizing switch. The number of sectional switches divides the three-phase lines into a number of protection zones, and a number of sectionalizing switches are provided within the protection zones; characterized in that When an interphase short - circuit fault occurs on one side of the sectionalizing switch, handle it according to the following steps: S1: The sectionalizing switch on the active side of the interphase short - circuit fault point cuts off the fault current. Then, use the two fault - phase conductors between the interphase short - circuit fault point and the sectionalizing switch on the active side and the interphase short - circuit fault point to construct a first detection loop and inject a first current signal into the first detection loop. The sectionalizing switches within the protection zone detect the first current signal and trip according to a first preset condition, thereby cutting off the connection between the interphase short - circuit fault point and the sectionalizing switch on the active side. The first preset condition enables the sectionalizing switch closer to the sectionalizing switch on the active side to trip later than the sectionalizing switch farther from the sectionalizing switch on the active side according to the first current signal. The sectionalizing switch on the active side is the sectionalizing switch that can cut off the power transmission of the protection zone where the interphase short - circuit fault point is located before the sectionalizing switch is closed; S2: The sectionalizing switch is closed. The sectionalizing switch on the new active side of the interphase short - circuit fault point cuts off the fault current. Then, use the two fault - phase conductors between the interphase short - circuit fault point and the sectionalizing switch on the new active side and the interphase short - circuit fault point to construct a second detection loop and inject a second current signal into the second detection loop. The sectionalizing switches within the protection zone detect the second current signal and trip according to a second preset condition, thereby cutting off the connection between the interphase short - circuit fault point and the sectionalizing switch on the new active side. The second preset condition enables the sectionalizing switch closer to the sectionalizing switch on the new active side to trip later than the sectionalizing switch farther from the sectionalizing switch on the new active side according to the second current signal. The sectionalizing switch on the new active side is the sectionalizing switch that can cut off the power transmission of the protection zone where the interphase short - circuit fault point is located after the sectionalizing switch is closed.

2. The method for handling phase-to-phase short circuit in a dual-power three-phase power system according to claim 1, characterized in that, Use the electric energy of the dual - power three - phase power system to generate the first current signal or the second current signal.

3. The method for handling the interphase short circuit of a dual-power three-phase power system according to claim 2, characterized in that, In step S1, the sectionalizing switch on the active side trips at least one fault phase to cut off the fault current and maintains the conduction of the other fault phase. Then, connect the tripped fault phase from the lower port of the sectionalizing switch on the active side to the ground or a common conductor. Next, connect one of the energized phases except the fault phase maintained in conduction to the ground or a common conductor at the upper port of the sectionalizing switch on the active side or connect a neutral point of the dual - power three - phase power system to the ground or a common conductor to generate the first current signal; In step S2, the sectionalizing switch on the new active side trips at least one fault phase to cut off the fault current and maintains the conduction of the other fault phase. Then, connect the tripped fault phase from the lower port of the sectionalizing switch on the new active side to the ground or a common conductor. Next, connect one of the energized phases except the fault phase maintained in conduction to the ground or a common conductor at the upper port of the sectionalizing switch on the new active side or connect the other neutral point of the dual - power three - phase power system to the ground or a common conductor to generate the second current signal.

4. The method for handling inter-phase short circuit of a dual-power three-phase power system according to claim 3, characterized in that, In the step S1, a first signal generating switch and a first current limiting resistor are provided between one end bus or a neutral point of the dual-power three-phase power system and the ground. The first signal generating switch is cyclically connected to and disconnected from the ground or a common wire to generate a first current pulse. The sectionalizing switch trips according to a preset number of current pulses, and the sectionalizing switch closer to the active side sectionalizing switch trips with a larger number of current pulses than the sectionalizing switch farther from the active side sectionalizing switch; Alternatively, the first signal generating switch is continuously connected to the ground or a common wire to generate a first continuous current. The sectionalizing switch trips according to a preset current duration, and the sectionalizing switch closer to the active side sectionalizing switch trips with a longer current duration than the sectionalizing switch farther from the active side sectionalizing switch; In the step S2, a second signal generating switch and a second current limiting resistor are provided between the other end bus or another neutral point of the dual-power three-phase power system and the ground. The second signal generating switch is cyclically connected to and disconnected from the ground or a common wire to generate a second current pulse. The sectionalizing switch trips according to a preset number of current pulses, and the sectionalizing switch closer to the new source side sectionalizing switch trips with a larger number of current pulses than the sectionalizing switch farther from the new source side sectionalizing switch; Alternatively, the second signal generating switch is continuously connected to the ground or a common wire to generate a second continuous current. The sectionalizing switch trips according to a preset current duration, and the sectionalizing switch closer to the new source side sectionalizing switch trips with a longer current duration than the sectionalizing switch farther from the new source side sectionalizing switch.

5. The method for processing inter-phase short circuit of a dual-power three-phase power system according to claim 3, wherein In the steps S1 and S2, maintaining the conduction of the other faulty phase includes disconnecting and then reconnecting the other faulty phase, or not disconnecting the other faulty phase and thus conducting it from the beginning.

6. The method for handling phase-to-phase short circuit in a dual-power three-phase power system according to claim 3, wherein, In the step S1, connecting the tripped faulty phase from the lower port of the active side sectionalizing switch to the ground or a common wire includes using the active side sectionalizing switch to connect the tripped faulty phase from the lower port of the active side sectionalizing switch to the ground or a common wire after disconnecting the tripped faulty phase, or using the active side sectionalizing switch to disconnect the tripped faulty phase and then connecting the tripped faulty phase from the lower port of the active side sectionalizing switch to the ground or a common wire through another switch; In the step S2, connecting the tripped faulty phase from the lower port of the new source side sectionalizing switch to the ground or a common wire includes using the new source side sectionalizing switch to connect the tripped faulty phase from the lower port of the new source side sectionalizing switch to the ground or a common wire after disconnecting the tripped faulty phase, or using the new source side sectionalizing switch to disconnect the tripped faulty phase and then connecting the tripped faulty phase from the lower port of the new source side sectionalizing switch to the ground or a common wire through another switch.

7. The method for handling inter-phase short circuit of a dual-power three-phase power system according to claim 1, characterized in that, Generate the first current signal or the second current signal by using a power source other than the power sources of the dual-power three-phase power system.

8. The method for handling inter-phase short circuit of a dual-power three-phase power system according to claim 1, characterized in that, A differential protection system is arranged on the protected area. When an interphase short-circuit fault occurs, the differential protection system issues a control signal to cause the active-side sectionalizing switch to trip at least one faulty phase to cut off the fault current, or cause the new-source-side sectionalizing switch to trip at least one faulty phase to cut off the fault current.

9. The method for handling phase-to-phase short circuit in a dual-power three-phase power system according to claim 4, characterized in that, Both the first signal generating switch and the second signal generating switch are a single-phase thyristor or two independent thyristors or three independent thyristors; both the first current-limiting resistor and the second current-limiting resistor are adjustable resistors or resistor selectors, or resistors with fixed resistance values.

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