Method for rapidly processing interphase short circuit fault of three-phase power supply system
By using power electronic switches and mechanical switches in parallel in a three-phase power supply system, the phase-to-phase short-circuit faults are quickly dealt with, and the problems of long fault handling time and large impact on the line in the prior art are solved, achieving rapid and safe fault handling and reducing the power outage area.
Patent Information
- Application Number
- CN202410422975.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-09
- Publication Date
- 2025-03-11
AI Technical Summary
When there are short circuits between phases, the existing three-phase power supply system has a long fault processing time, the reclosing gate has a large impact on the line, and it is difficult to reduce the power outage area.
The power electronic switch is connected in parallel with the mechanical switch. After a phase-to-phase short circuit fault occurs, the mechanical switch jumps out and the power electronic switch is closed. The rapid on-off capability of the power electronic switch is used to quickly determine the fault point position and quickly disconnect when the disconnection condition is reached, thereby shortening the fault processing time.
By quickly handling faults, shorten the fault handling time, reduce the impact on the line, and allow multiple mechanical switches to be set up to reduce the power outage area, meeting the need to quickly troubleshoot faults within the reclosing time.
Smart Images
Figure CN119602187A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of power supply system fault processing, and in particular to a method for quickly processing an interphase short circuit fault in a three-phase power supply system. Background Art
[0002] When a short circuit occurs in the three-phase power supply system, the outgoing circuit breaker of the substation detects the fault and trips. The mechanical switch below the circuit breaker opens due to the loss of pressure, and then the circuit breaker delays closing. If it is an instantaneous fault, the mechanical switch delays closing step by step, and the line resumes power supply; if it is a permanent fault, the mechanical switch senses the incoming power step by step and delays the first period of time (the time to confirm that the line has pressure) before closing and sending out. When closing to the fault section, the circuit breaker trips again. The mechanical switch upstream of the fault point closes and remains closed for less than the second period of time to lock the forward incoming power closing. The rear switch of the fault point locks the reverse closing due to sensing the instantaneous incoming power (not maintained for the first period of time). The first period of time is generally 7 seconds, and the second period of time is 0.5 seconds. The disadvantage of this method is that the fault handling time is long, and the reclosing of the fault has a great impact on the line. Summary of the invention
[0003] The purpose of the present invention is to provide a method for quickly handling interphase short circuit faults in a three-phase power supply system, which method has a short fault handling time, small impact on the line, and allows the setting of multiple mechanical switches to reduce the power outage area.
[0004] In order to achieve the above object, the present invention adopts the following technical scheme:
[0005] A method for quickly handling an interphase short circuit fault in a three-phase power supply system comprises a power supply and a busbar, wherein at least one outgoing line is arranged on the busbar, a circuit breaker is arranged on the outgoing line, a plurality of mechanical switches are arranged below the circuit breaker, a fault handling switch is arranged at the lower port of the circuit breaker, the fault handling switch can connect at least one phase of the lower port of the circuit breaker to the power supply, each of the mechanical switches is respectively connected in parallel with a power electronic switch in an off state, the power electronic switch can connect and disconnect at least one phase of the upper port and the lower port of the mechanical switch, a PT is respectively installed to measure the voltage of the upper port of each power electronic switch, and a CT is respectively installed to measure the current of each power electronic switch; when an interphase short circuit fault occurs, the The circuit breaker and the mechanical switch both trip at least one fault phase, the fault processing switch connects the fault phase tripped by the circuit breaker to the power supply, and then if the PT voltage at the port of a certain power electronic switch exceeds a first preset voltage value and lasts for a first preset time period, the certain power electronic switch is turned on, and if the CT current signal of the certain power electronic switch exceeds the first preset current value within a second preset time period after the certain power electronic switch is turned on, the certain power electronic switch is turned off; after the turned-on power electronic switch is turned off again or all the power electronic switches remain turned on, each of the mechanical switches copies the on-off state of the power electronic switch connected in parallel therewith.
[0006] Preferably, after each of the mechanical switches copies the on / off state of the power electronic switch connected in parallel therewith, all of the power electronic switches are turned off.
[0007] Preferably, a CT is installed to measure the current of the fault handling switch. Within a third preset time period after the fault handling switch connects the faulty phase of the circuit breaker to the power supply, if the CT current signal of the fault handling switch exceeds a second preset current value, the fault handling switch is disconnected.
[0008] Preferably, the fault handling switches are three single-phase control switches and are respectively connected in parallel to the three phases of the upper and lower ports of the circuit breaker.
[0009] Preferably, resistors are connected in series to two or three of the single-phase control switches.
[0010] Preferably, the fault handling switch includes a first switch capable of connecting at least one phase of the lower port of the circuit breaker to the earth or a common conductor and a second switch capable of connecting a busbar or a system neutral point to the earth or a common conductor.
[0011] In the present invention, if the fault point is between the first power electronic switch and the second power electronic switch, then after the fault handling switch is closed, the PT at the top of the first power electronic switch detects that the voltage exceeds the first preset voltage value and lasts for the first preset time period. At this time, the first power electronic switch is turned on and forms a fault detection loop including a power supply, a bus, two fault lines and a fault point. The first power electronic switch is disconnected when the current exceeds the first preset current value within the second preset time, thereby determining the position of the fault point; if the fault point is between the second power electronic switch and the third power electronic switch, then after the fault handling switch is closed, the PT at the top of the first power electronic switch detects that the voltage exceeds the first preset voltage value and lasts for the first preset time. After the first stage, the first power electronic switch is turned on, but because the second power electronic switch is not turned on at this time, the phase-to-phase short circuit fault point is cut off. At this time, the detection loop cannot be formed. The current of the first power electronic switch in the second preset time does not exceed the first preset current value. As the first power electronic switch is turned on, the PT at the port of the second power electronic switch detects the voltage and can last for the first preset time period. Then the second power electronic switch is turned on, and the first power electronic switch will not detect the current exceeding the limit in the second preset time period (the second preset time period is generally shorter than the first preset time period). The first electronic switch remains on, and the second power electronic switch will be disconnected in the second preset time period due to the detection of the current exceeding the limit. For instantaneous faults, the instantaneous faults have disappeared after each power electronic switch is turned on, and the current exceeding the limit will not occur, so each power electronic switch remains on. Finally, the mechanical switch can copy the on-off state of the power electronic switch. If there is a fault point between the circuit breaker and the first power electronic switch, after the fault handling switch is closed, the current of the fault handling switch will exceed the second preset current value in the third preset time period, and the fault handling switch will be disconnected at this time.
[0012] The beneficial effect of the present invention is that the power electronic switch is connected in parallel with the mechanical switch, and the mechanical switch is tripped and the power electronic switch is closed after a phase-to-phase short circuit fault occurs. In this way, the fast switching capability of the power electronic switch can be utilized. When the disconnection condition of the power electronic switch is met, the power electronic switch can be quickly disconnected, and this time is much shorter than the tripping time of the mechanical switch. Therefore, the number of mechanical switches can be increased while still being able to eliminate the fault in a short time, thereby refining and reducing the power outage area, while meeting the need to eliminate the fault within the reclosing time. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 This is a wiring diagram of an embodiment of the method of the present invention;
[0014] Figure 2 It is a wiring diagram of another embodiment of the method of the present invention. DETAILED DESCRIPTION
[0015] The present invention will be further described below by means of specific embodiments in conjunction with the accompanying drawings:
[0016] like Figure 1 As shown, the three-phase non-effectively grounded power supply system has a power supply 100, a busbar 101 and an outgoing line 102. There can be multiple outgoing lines and they are all branched from the busbar. The following takes the outgoing line 102 as an example to illustrate the method for handling the phase-to-phase short circuit fault. The handling of other outgoing lines is consistent with that of the outgoing line 102.
[0017] A circuit breaker 90 is provided on the outgoing line 102, and a plurality of mechanical switches are provided below the circuit breaker 90. Four, five, six or more mechanical switches may be provided, such as mechanical switch 91, mechanical switch 92, mechanical switch 93, etc. The mechanical switch may be a circuit breaker or an ordinary load switch. A fault handling switch 1 is connected in parallel at the circuit breaker 90. The fault handling switch 1 is provided between the lower port of the circuit breaker 1 and the bus 101. When the fault handling switch 1 is closed, one phase, two phases or three phases between the lower port of the circuit breaker 90 and the bus 101 may be connected, thereby also being connected to the power source 100. A power electronic switch is connected in parallel at each mechanical switch, such as a power electronic switch 2 is connected in parallel at the mechanical switch 91, a power electronic switch 3 is connected in parallel at the mechanical switch 92, and a power electronic switch 4 is connected in parallel at the mechanical switch 93. When the power electronic switch is closed, one phase, two phases or three phases between the upper port and the lower port of the mechanical switch may be connected. Voltage transformer 6 (PT6), voltage transformer 7 (PT7) and voltage transformer 8 (PT8) are installed on the upper ports of power electronic switches 2, 3, 4 respectively, current transformer 9 (CT9), current transformer 10 (CT10) and current transformer 18 (CT18) are installed on power electronic switches 2, 3, 4 respectively, and current transformer 17 (CT17) is installed on fault handling switch 1.
[0018] When the line is transmitting power normally, the circuit breaker 90 is closed, the mechanical switches 91, 92, 93 are closed, the fault handling switch 1 is opened, and the power electronic switches 2, 3, 4 are opened.
[0019] When a phase-to-phase short circuit fault occurs, if the fault point F is between the two phases BC and between the mechanical switch 92 and the mechanical switch 93, the circuit breaker 90 will trip the three phases according to the overcurrent, and at the same time, the mechanical switches 91, 92, 93, etc. will all trip the three phases due to the lack of line pressure. Then the switches 11 and 12 of the fault handling switch 1 are closed (the switch 13 can be closed or not); because the fault point is after the power electronic switch 3, the closing of the fault handling switch 1 will not form a fault detection loop including the power supply 100, the bus 101, the fault phase B and the fault phase C, and the fault point. The fault handling switch 1 cannot detect the fault current within a preset time period (the preset time period is set to a third preset time period, such as 5ms or 10ms, etc.), and remains turned on. The fault detection current is the current generated by the fault detection circuit including the power supply 100, the bus 101, the fault phase B and the fault phase C and the fault point. This current is generally much larger than the load current (for example, after the power electronic switch 2 is closed, although there is no fault detection current, there will be a load current flowing through the load 20). Therefore, the setting of the first preset current value should be able to distinguish between the fault detection current and the load current. The first preset current value is smaller than the fault detection current but larger than the load current. The setting of the second preset current value below is the same.
[0020] PT6 detects that the line has pressure and lasts for the first preset time period (such as 20ms) due to the closure of the fault handling switch 1, and then the power electronic switch 2 is closed. Since the fault point is after the power electronic switch 3, the closure of the power electronic switch 2 will not form the above-mentioned fault detection loop. Within the second preset time period (generally less than the first preset time period, such as 5ms), CT9 cannot detect the fault detection current of the power electronic switch 2 and remains turned on.
[0021] PT7 detects that the line has pressure and lasts for the first preset time period due to the closing of the power electronic switch 2, and then the power electronic switch 3 is turned on. Since the fault point is after the power electronic switch 3, the closing of the power electronic switch 3 forms the above-mentioned fault detection loop. The power electronic switch 3 is disconnected within the second preset time period because CT10 detects that the current exceeds the first preset current value.
[0022] Before the power electronic switch 3 is disconnected, the fault detection current will flow through the fault handling switch 1 and the power electronic switch 2 at the same time, but the CT17 of the fault handling switch 1 will not detect that the current exceeds the second preset current value (which may be equal to or different from the second preset time period, but is generally shorter than the first preset time period, such as 5ms) within the third preset time period (which may be the same as or different from the second preset time period, but is generally shorter than the first preset time period, such as 5ms), and the CT9 of the power electronic switch 2 will not detect that the current exceeds the first preset current value within the second preset time period, so the fault handling switch 1 and the power electronic switch 2 will not trip and remain turned on.
[0023] Because the power electronic switch 3 is closed and then quickly opened, the PT8 will not detect that the line continues to have voltage (ie, the voltage will not last for the first preset time period), so the power electronic switch 4 remains open.
[0024] When a certain power electronic switch that is turned on is turned off again, or all power electronic switches remain turned on (this is a transient fault and disappears automatically), the mechanical switch copies the on-off state of the power electronic switch connected in parallel with it, that is, the mechanical switch 91 is closed, and the mechanical switches 92 and 93 remain open, and then all power electronic switches are turned off, that is, the power electronic switch 2 is turned off, and the power electronic switches 3 and 4 remain open. The fault handling switch 1 is turned off, and the circuit breaker 90 is closed to supply power.
[0025] The mechanical switches 91 and 92 can be disconnected due to detecting that the line has no pressure, or can be tripped due to detecting that an overcurrent occurs.
[0026] In one embodiment, the circuit breaker 90 may not cut off the three phases, but may cut off one or two faulty phases, and accordingly the fault handling switch 1 only closes one or two switches to connect the faulty phase disconnected by the circuit breaker 90. Similarly, the mechanical switch may only trip one or two faulty phases, and then the power electronic switch connects the faulty phase tripped by the mechanical switch.
[0027] Figure 2 Another embodiment is shown (PT and CT are omitted), in which the fault handling switch 1 does not directly connect the lower port of the circuit breaker 90 with the bus 101, but includes a first switch 31 and a second switch 32. The first switch 31 connects the lower port of the circuit breaker 90 with the earth (or a common wire), and the second switch 32 connects the bus (or the system neutral point) with the earth (or a common wire). In this way, the lower port of the circuit breaker can also be connected to the power supply. Other operations are the same as the above-mentioned embodiments.
[0028] In one embodiment, reference Figure 1 and Figure 2 , a resistor 5 is connected in series to the three phases (or any two phases) of the fault handling switch 1, and the resistor 5 can limit the current, thereby reducing the current of the detection circuit to avoid impact on the system. It should be pointed out that in the above embodiment, it is also feasible not to connect the resistor in series to the fault handling switch, because the use of power electronic switches makes the fault handling time very short, and even if the resistor is not connected in series, it will not cause a great impact on the system.
[0029] In the above embodiments, the power electronic switch is preferably an insulated gate bipolar transistor.
[0030] The above embodiments are only some illustrations of the concept and implementation of the present invention, and are not intended to limit the same. Under the concept of the present invention, technical solutions that have not been substantially changed are still within the scope of protection.
Claims
1. A method for quickly handling a phase-to-phase short circuit fault in a three-phase power supply system, comprising a power supply and a busbar, at least one outgoing line is provided on the busbar, a circuit breaker is provided on the outgoing line, a plurality of mechanical switches are provided below the circuit breaker, a fault handling switch is provided at the lower port of the circuit breaker, the fault handling switch can connect at least one phase at the lower port of the circuit breaker to the power supply, and is characterized in that: Each of the mechanical switches is connected in parallel with a power electronic switch in an off state, and the power electronic switch can connect and disconnect at least one phase of the upper port and the lower port of the mechanical switch, and a PT is installed to measure the voltage of the upper port of each power electronic switch, and a CT is installed to measure the current of each power electronic switch; When an interphase short circuit fault occurs, the circuit breaker and the mechanical switch both trip at least one faulty phase, and the fault handling switch connects the faulty phase tripped by the circuit breaker to the power supply, and then: If the PT voltage at a port of a certain power electronic switch exceeds a first preset voltage value and lasts for a first preset time period, the certain power electronic switch is turned on, and if the CT current signal of the certain power electronic switch exceeds the first preset current value within a second preset time period after the certain power electronic switch is turned on, the certain power electronic switch is turned off; After the turned-on power electronic switch is turned off again or all the power electronic switches remain turned on, each of the mechanical switches copies the on-off state of the power electronic switch connected in parallel therewith.
2. The method for quickly handling a phase-to-phase short circuit fault in a three-phase power supply system according to claim 1, characterized in that: After each of the mechanical switches copies the on / off state of the power electronic switch connected in parallel therewith, all of the power electronic switches are turned off.
3. The method for quickly handling a phase-to-phase short circuit fault in a three-phase power supply system according to claim 1, characterized in that: A CT is installed to measure the current of the fault handling switch. Within a third preset time period after the fault handling switch connects the fault phase of the circuit breaker to the power supply, if the CT current signal of the fault handling switch exceeds a second preset current value, the fault handling switch is disconnected.
4. The method for quickly handling a phase-to-phase short circuit fault in a three-phase power supply system according to claim 1, characterized in that: The fault handling switches are three single-phase control switches and are respectively connected in parallel to the three phases of the upper and lower ports of the circuit breaker.
5. The method for quickly processing a phase-to-phase short circuit fault in a three-phase power supply system according to claim 4, characterized in that: Resistors are connected in series to two or three of the single-phase control switches.
6. The method for quickly handling a phase-to-phase short circuit fault in a three-phase power supply system according to claim 1, characterized in that: The fault handling switch comprises a first switch capable of connecting at least one phase of the lower port of the circuit breaker to the earth or a common conductor and a second switch capable of connecting a busbar or a system neutral point to the earth or a common conductor.