Open-phase detection method and device suitable for system with multiple starting standby transformers

Abstract

The invention discloses an open-phase detection method and device suitable for a system with multiple starting standby transformers. The method comprises the following steps: measuring a three-phase current on an incoming line, measuring a neutral point zero sequence voltage of each starting standby transformer, and collecting a neutral point grounding knife switch position of each starting standby transformer; based on the three-phase current on the incoming line, calculating an incoming line positive sequence current and an incoming line zero sequence current by using a symmetric component method; and according to the incoming line zero-sequence current, the neutral point zero-sequence voltage of each starting standby transformer and the position of a neutral point grounding knife switch, judging whether an open-phase fault occurs and positioning a fault interval. The method is suitable for a parallel connection mode of a plurality of starting and standby transformers, is also suitable for a transformer neutral point grounding or non-grounding system, and can effectively identify open-phase faults on a high-voltage side and a line of the starting and standby transformer under no-load and light-load working conditions.

Description

Technical Field

[0001] The present invention relates to the field of main equipment protection and monitoring in power plants, and more specifically to the phase loss detection and device for a multi-start-up standby transformer system in a power plant. Background Art

[0002] In the power system, the unbalanced operation of the circuit breaker caused by faults in the circuit breaker operating mechanism and its electrical control circuit, etc., leading to overheating or burning accidents of the generator, not only causes a major loss to the power plant, but also poses a great threat to the safe operation of the power system. Since the phase loss fault occurred at the Byron Nuclear Power Plant in Illinois, USA in 2012, it has attracted the high attention of the Institute of Nuclear Power Operations (INPO) and the World Association of Nuclear Operators (WANO). However, similar incidents still occur from time to time in global nuclear power units to this day.

[0003] According to incomplete statistics, domestic nuclear power start-up standby transformers basically adopt the wiring methods of Ynd or Yny-d, and are in an unloaded state for a long time, with a very small load current (mainly the no-load excitation current, generally about 0.06% of the rated current). Once a phase loss fault occurs on the high-voltage side of the start-up standby transformer, the conventional electromagnetic CT basically cannot respond. Coupled with the influence of the delta winding, there is no obvious change in the 220 kV bus voltage of the start-up standby transformer system, that is, it cannot be reflected by conventional electrical quantities under no-load conditions. At this time, once an important load is connected, the three-phase voltage and current will become unbalanced, thus causing multiple protections with negative sequence components as the starting elements to malfunction, and ultimately resulting in a series of fault events in the nuclear power plant.

[0004] According to patent retrieval, a patent of Xuji Group Co., Ltd., "CN108649532B An injection type transformer line phase loss protection method and device", obtains the zero-sequence impedance by injecting current into the transformer neutral point to reflect the phase loss fault of the transformer; a patent of Nanjing Nanrui Relay & Protection Electric Co., Ltd., "CN108169615B A phase loss detection method for start-up standby transformers based on optical CT", uses optical CT to detect the three-phase current on the primary side of the nuclear power plant standby transformer to reflect the phase loss fault of the transformer. The above methods are only applicable to the phase loss faults near the high-voltage side of a single transformer. Therefore, there is no detection method applicable to discriminating different phase loss points in a multi-start-up standby transformer system. Summary of the Invention

[0005] The object of the present invention is to propose a phase loss detection method and device applicable to a multi-start-up standby transformer system, which can sensitively and accurately identify the phase loss faults on the high-voltage side and the line of the start-up standby transformer under no-load or light-load conditions, and is also applicable to both the transformer neutral point grounded and ungrounded systems, improving the safety and reliability of the operation of the start-up standby transformer system.

[0006] To achieve the above object, the solution of the present application is as follows:

[0007] According to the first aspect of the present application, a phase loss detection method applicable to a multi-start standby transformer system is proposed, including:

[0008] Measure the three-phase current on the incoming line, measure the zero-sequence voltage of the neutral point of each start standby transformer, and collect the position of the neutral point grounding switch of each start standby transformer;

[0009] Based on the three-phase current on the incoming line, use the symmetrical component method to calculate the positive-sequence current and zero-sequence current of the incoming line;

[0010] According to the zero-sequence current of the incoming line, the zero-sequence voltage of the neutral point of each start standby transformer, and the position of the neutral point grounding switch, determine whether a phase loss fault occurs and locate the fault interval.

[0011] According to some embodiments, the method further includes: in response to determining that a phase loss fault has occurred, judging the phase of the phase loss fault according to the three-phase current on the incoming line.

[0012] According to some embodiments, the measurement of the three-phase current on the incoming line and the zero-sequence voltage of the neutral point of the start standby transformer has sufficient accuracy when all start standby transformers are in no-load and light-load conditions.

[0013] According to some embodiments, the determining whether a phase loss fault occurs and locating the fault interval according to the zero-sequence current of the incoming line, the zero-sequence voltage of the neutral point of each start standby transformer, and the position of the neutral point grounding switch specifically includes:

[0014] By judging whether the amplitude of the zero-sequence voltage of the neutral point of the start standby transformer with the neutral point grounding switch in the off position exceeds a preset zero-sequence voltage threshold of the neutral point, and judging whether the amplitude of the zero-sequence current of the incoming line is greater than a first preset zero-sequence current threshold and whether the amplitude of the zero-sequence current of the incoming line is greater than a second preset zero-sequence current threshold, comprehensively determine whether a phase loss fault occurs and locate the fault interval.

[0015] According to some embodiments, the determining whether a phase loss fault occurs and locating the fault interval according to the zero-sequence current of the incoming line, the zero-sequence voltage of the neutral point of each start standby transformer, and the position of the neutral point grounding switch specifically includes:

[0016] Judge whether the amplitude of the zero-sequence voltage of the neutral point of the start standby transformer with the neutral point grounding switch in the off position is greater than a preset zero-sequence voltage threshold of the neutral point. If so, determine that a phase loss fault has occurred in the start standby transformer with the neutral point grounding switch in the off position; otherwise, determine that no phase loss fault has occurred in the start standby transformer with the neutral point grounding switch in the off position;

[0017] If none of the starting standby transformers with neutral grounding switches in the off position have phase break faults, further determine whether the magnitude of the incoming line zero-sequence current is greater than a preset first zero-sequence current threshold. If not, it is determined that no phase break fault has occurred. If so, further determine whether the magnitude of the incoming line zero-sequence current is greater than a preset second zero-sequence current threshold. If so, it is determined that a phase break fault has occurred in the incoming line. If not, it is determined that a phase break fault has occurred on the high-voltage side of the starting standby transformer with the neutral grounding switch in the on position; the second zero-sequence current threshold is greater than the first zero-sequence current threshold.

[0018] According to some embodiments, the neutral point zero-sequence voltage threshold is k 1 ×U n , where U n is the rated value of the phase voltage on the high-voltage side of the starting standby transformer, and k 1 is a reliability coefficient, taking a value of 0.2 to 0.4.

[0019] According to some embodiments, the first zero-sequence current threshold is the larger of a fixed threshold and a floating threshold. The fixed threshold needs to be greater than the magnitude of the zero-sequence unbalance current measured on-site. The floating threshold is where is the magnitude of the positive-sequence current of the incoming line, k 2 is a reliability coefficient, taking a value of 0.6 to 0.8, and N is the number of starting standby transformers.

[0020] According to some embodiments, the second zero-sequence current threshold is the larger of a fixed threshold and a floating threshold. The fixed threshold needs to be greater than the magnitude of the zero-sequence unbalance current measured on-site. The floating threshold is where is the magnitude of the positive-sequence current of the incoming line, k 3 is a reliability coefficient, taking a value of 0.5 to 0.9.

[0021] According to some embodiments, determining the phase of the phase break fault based on the three-phase currents on the incoming line specifically includes: comparing the magnitudes of the phase currents of the three-phase currents, and the phase with the smallest current magnitude is the fault phase.

[0022] According to some embodiments, the method further includes: in response to determining that a phase break fault has occurred, sending an alarm signal or operating a trip after a set delay.

[0023] According to a second aspect of the present application, a phase break detection device applicable to a multi-starting standby transformer system is proposed, including:

[0024] A data acquisition unit for measuring the three-phase currents on the incoming line, measuring the neutral point zero-sequence voltage of each starting standby transformer, and collecting the position of the neutral point grounding switch of each starting standby transformer;

[0025] A sequence current calculation unit, configured to calculate a positive sequence current and a zero sequence current of an incoming line by using a symmetrical component method based on three-phase currents on the incoming line; and,

[0026] A fault determination unit, configured to determine whether a phase break fault occurs and locate a fault section according to the zero sequence current of the incoming line, the zero sequence voltage of the neutral point of each starting standby transformer, and the position of the neutral point earthing switch.

[0027] According to some embodiments, the apparatus further includes: a phase discrimination unit, configured to, in response to determining that a phase break fault has occurred, determine the phase in which the phase break fault occurs according to three-phase currents on the incoming line.

[0028] According to some embodiments, the apparatus further includes: an action unit, configured to, in response to determining that a phase break fault has occurred, send an alarm signal or actuate a trip after a set delay.

[0029] According to a third aspect of the present application, an electronic device is provided, including a processor and a memory, where a program is stored on the memory, and the program can be loaded and executed by the processor to perform the foregoing phase break detection method applicable to a multi-starting standby transformer system.

[0030] According to a fourth aspect of the present application, a computer-readable storage medium is provided, storing a computer program, where when the computer program is executed by a processor, the foregoing phase break detection method applicable to a multi-starting standby transformer system is implemented.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: By analyzing the zero sequence current of the incoming line and the zero sequence voltages of the neutral points of all starting standby transformers, the present application can effectively identify phase break faults on the high-voltage side of the starting standby transformer and on the line under no-load and light-load conditions, and is applicable to both transformer neutral point grounding and non-grounding systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic flow chart of a phase break detection method applicable to a multi-starting standby transformer system according to an embodiment of the present application.

[0033] Figure 2 It is a schematic flow chart of a second phase break detection method applicable to a multi-starting standby transformer system according to an embodiment of the present application.

[0034] Figure 3 It is a schematic flow chart of a third phase break detection method applicable to a multi-starting standby transformer system according to an embodiment of the present application.

[0035] Figure 4 It is a schematic flow chart of a fourth phase break detection method applicable to a multi-starting standby transformer system according to an embodiment of the present application.

[0036] Figure 5 This is a typical application wiring diagram provided by the embodiments of the present application.

[0037] Figure 6 It is a schematic flow diagram of another phase loss detection method applicable to a multi-start standby transformer system according to the embodiments of the present application.

[0038] Figure 7 It is a schematic structural diagram of a phase loss detection device applicable to a multi-start standby transformer system according to the embodiments of the present application.

[0039] Figure 8 It is a schematic structural diagram of a second phase loss detection device applicable to a multi-start standby transformer system according to the embodiments of the present application.

[0040] Figure 9 It is a schematic structural diagram of a third phase loss detection device applicable to a multi-start standby transformer system according to the embodiments of the present application.

[0041] Figure 10 It is a schematic structural diagram of a fourth phase loss detection device applicable to a multi-start standby transformer system according to the embodiments of the present application.

[0042] Figure 11 The figure shows a structural diagram of an electronic device provided by the present application. Detailed implementation manners

[0043] The present invention will be further described below with reference to the accompanying drawings.

[0044] Since the unbalanced operation of the transformer will cause overheating or burning of the equipment, bringing losses and safety threats to the power system, and the existing phase loss detection technologies are all used for the phase loss faults at the proximal end of the high-voltage side of a single transformer, lacking research on the phase loss detection of a multi-start standby transformer system. In view of this, the embodiments of the present application propose a phase loss detection method applicable to a multi-start standby transformer system, as Figure 1 shown, including the following steps:

[0045] S101. Measure the three-phase currents on the incoming line, measure the zero-sequence voltages at the neutral points of each start standby transformer, and collect the positions of the neutral point earthing switches of each start standby transformer.

[0046] Collect the three-phase currents and the zero-sequence voltages at the neutral points through the current transformers installed on the incoming line and the voltage transformers at the neutral points of each start standby transformer. The three-phase currents on the line are respectively denoted as and The zero-sequence voltages at the neutral points of each start standby transformer are respectively denoted as N is the number of start standby transformers, and N is an integer greater than or equal to 2.

[0047] Among them, the current transformers used to measure the three-phase current on the incoming line and the voltage transformers used for the zero-sequence voltage of the neutral point of each start-up standby transformer have sufficient accuracy when all start-up standby transformers are in no-load and light-load conditions.

[0048] In some embodiments, the position of the neutral point earthing switch of each start-up standby transformer is collected by introducing the off-position contact of the neutral point earthing switch of each start-up standby transformer, which are respectively S 1 、S 2 、…、S N , and the off-position of the neutral point earthing switch is 1, otherwise it is 0.

[0049] S102. Calculate the positive-sequence current and zero-sequence current of the incoming line by using the symmetrical component method based on the three-phase current on the incoming line.

[0050] According to the three-phase current on the incoming line and calculate the positive-sequence and zero-sequence components of the current by using the symmetrical component method to obtain the positive-sequence current of the incoming line and the zero-sequence current

[0051]

[0052] In the formula:

[0053] S103. Determine whether a single-phase open circuit fault occurs and locate the fault interval according to the zero-sequence current of the incoming line, the zero-sequence voltage of the neutral point of each start-up standby transformer, and the position of the neutral point earthing switch.

[0054] Specifically, determine whether a single-phase open circuit fault occurs and locate the fault interval by judging whether the amplitude of the zero-sequence voltage of the neutral point of the start-up standby transformer with the neutral point earthing switch in the off position exceeds the preset zero-sequence voltage threshold of the neutral point, and by judging whether the amplitude of the zero-sequence current at the incoming line position exceeds the preset first zero-sequence current threshold and whether the amplitude of the line zero-sequence current is greater than the preset second zero-sequence current threshold.

[0055] In some embodiments, the determining whether a single-phase open circuit fault occurs and locating the fault interval according to the zero-sequence current of the incoming line, the zero-sequence voltage of the neutral point of each start-up standby transformer, and the position of the neutral point earthing switch specifically includes:

[0056] Judge whether the amplitude of the zero-sequence voltage of the neutral point of the start-up standby transformer with the neutral point earthing switch in the off position is greater than the preset zero-sequence voltage threshold of the neutral point. If so, it is determined that a single-phase open circuit fault has occurred in the start-up standby transformer with the neutral point earthing switch in the off position; otherwise, it is determined that no single-phase open circuit fault has occurred in the start-up standby transformer with the neutral point earthing switch in the off position;

[0057] If there is no open-phase fault in any of the start-up standby transformers with neutral grounding switches in the off position, further determine whether the amplitude of the incoming line zero-sequence current is greater than a preset first zero-sequence current threshold. If not, it is determined that there is no open-phase fault. If so, further determine whether the amplitude of the incoming line zero-sequence current is greater than a preset second zero-sequence current threshold. If so, it is determined that an open-phase fault has occurred in the incoming line. If not, it is determined that an open-phase fault has occurred on the high-voltage side of the start-up standby transformer with the neutral grounding switch in the on position; the second zero-sequence current threshold is greater than the first zero-sequence current threshold.

[0058] In some embodiments, the neutral zero-sequence voltage threshold is k 1 ×U n , where U n is the rated value of the phase voltage on the high-voltage side of the start-up standby transformer, and k 1 is a reliability coefficient, taking a value of 0.2 to 0.4, preferably 0.2.

[0059] In some embodiments, the first zero-sequence current threshold is the larger of a fixed threshold and a floating threshold. The fixed threshold needs to be greater than the amplitude of the zero-sequence unbalance current measured on site. The floating threshold is where is the amplitude of the positive-sequence current on the incoming line side, and k 2 is a reliability coefficient, taking a value of 0.6 to 0.8, preferably 0.8.

[0060] In some embodiments, the second zero-sequence current threshold is the larger of a fixed threshold and a floating threshold. The fixed threshold needs to be greater than the amplitude of the zero-sequence unbalance current measured on site. The floating threshold is where is the amplitude of the positive-sequence current on the incoming line side, and k 3 is a reliability coefficient, taking a value of 0.5 to 0.9, preferably 0.6.

[0061] In some embodiments, as Figure 2 shown in the embodiment, based on the foregoing embodiment, the open-phase detection method applicable to a multi-start-up standby transformer system further includes: Step S104, after determining that an open-phase fault has occurred, determine the phase of the open-phase fault according to the three-phase current of the incoming line.

[0062] Specifically, compare the amplitudes of the three-phase currents. The phase with the smallest current amplitude is the fault phase.

[0063] In some embodiments, the amplitudes of the three-phase currents of the incoming line can be obtained as and The phase with the smallest current amplitude among the three phases is the fault phase, that is:

[0064] If is satisfied, the fault phase is phase A;

[0065] If the following conditions are met then the faulty phase is Phase B;

[0066] If the following conditions are met then the faulty phase is Phase C.

[0067] In some embodiments, as shown in the embodiments of Figure 3 and Figure 4 Based on the above two embodiments, the phase loss detection method applicable to the multi-start standby transformer system may further include step S105: when it is determined that a phase loss fault has occurred, an alarm signal is sent after a set delay or an action is taken to trip. The value range of the set delay is 0.1 s to 30.0 s, and preferably 20 s is taken.

[0068] Next, in combination with Figure 5 The typical application wiring diagram of the 220 kV start-up standby transformer system of a certain nuclear power plant shown below is used to specifically introduce a phase loss detection method applicable to the multi-start standby transformer system of the present application. The electrical main wiring diagram, the schematic diagram of the phase loss fault detection of the start-up standby transformer, and the fault points are as shown in the appendix Figure 2 shown. The start-up standby transformer is a three-phase double-winding transformer, with Yn / D-11 connection, and there are 2 units in total. The phase loss fault detection is realized by measuring the three-phase current on the incoming line and the zero-sequence voltage of the neutral point of each transformer. As Figure 6 shown, the specific steps for implementing the phase loss detection applicable to the multi-start standby transformer system are as follows:

[0069] S201. Measure the three-phase current on the incoming line through a high-precision optical current transformer Measure the zero-sequence voltage of the neutral points of the two start-up standby transformers through electromagnetic voltage transformers Collect the positions of the neutral point earthing switches of the two start-up standby transformers. If the neutral point earthing switch of the No. 1 start-up standby transformer is in the closed position, then S 1 = 0; if the neutral point earthing switch of the No. 2 start-up standby transformer is in the open position, then S 2 = 1.

[0070] S202. According to the three-phase current on the incoming line and Use the symmetrical component method to calculate the positive-sequence and zero-sequence components of the current, and obtain the incoming line positive-sequence current and the incoming line zero-sequence current

[0071] S203. Identification of the faulty phase for phase loss:

[0072] Step S203.1: In this embodiment, the neutral earthing switch of the No. 2 starting standby transformer is in the off position. Therefore, it is determined whether the amplitude of the zero-sequence voltage of the neutral point of the No. 2 starting standby transformer exceeds the preset zero-sequence voltage threshold of the neutral point. If so, it is determined that a single-phase open fault has occurred in the No. 2 starting standby transformer, and step S204 is entered; otherwise, it is determined that no single-phase open fault has occurred, and step S203.2 is entered.

[0073] The method for realizing single-phase open discrimination based on the amplitude of the zero-sequence voltage of the neutral point in this embodiment is as follows:

[0074]

[0075] In this embodiment, take k 1 = 0.2, U n = 127 kV, then when the amplitude of the zero-sequence voltage of the neutral point of the Nth starting standby transformer is greater than or equal to 25.4 kV, it is determined that a single-phase open fault has occurred in this transformer.

[0076] S203.2: Determine whether the amplitude of the zero-sequence current at the incoming line position exceeds the preset first threshold of the zero-sequence current. If so, enter step S203.3; otherwise, it is determined that no single-phase open fault has occurred, and the process ends.

[0077] The method for discriminating whether the amplitude of the zero-sequence current at the incoming line position exceeds the preset first threshold of the zero-sequence current in this embodiment is as follows:

[0078]

[0079] In this embodiment, take k 2 = 0.8, N = 2, I 0_set = 0.2 A.

[0080] S203.3: Determine whether the amplitude of the zero-sequence current at the incoming line position exceeds the preset second threshold of the zero-sequence current. If so, it is determined that a single-phase open fault has occurred in the incoming line. If not, it is determined that a single-phase open fault has occurred in the high-voltage side of the starting standby transformer with the neutral earthing switch in the on position, and step S204 is entered.

[0081] The method for discriminating whether the amplitude of the zero-sequence current at the incoming line position exceeds the preset second threshold of the zero-sequence current in this embodiment is as follows:

[0082]

[0083] In this embodiment, take k 3 = 0.6, I 0_set = 0.2 A.

[0084] S204: Determine the phase of the single-phase open fault according to the magnitudes of the three-phase current amplitudes of the incoming line.

[0085] In this embodiment, the amplitudes of the incoming three-phase currents are respectively and The phase with the minimum current amplitude among the three phases is the faulty phase, that is:

[0086] If is satisfied, the faulty phase is phase A;

[0087] If is satisfied, the faulty phase is phase B;

[0088] If is satisfied, the faulty phase is phase C.

[0089] S205. When it is determined that a single-phase open fault has occurred, an alarm signal is sent after a set delay or an operation is performed to trip. The value range of the set delay is 0.1 s to 30.0 s, and preferably 20 s is taken.

[0090] The following is an application of this discrimination method in combination with different fault conditions:

[0091] Case 1: When all starting standby transformers are in no-load conditions, as Figure 2 shown at the position of the single-phase open point 1, a single-phase open fault of phase B occurs. The three-phase currents on the incoming line, the calculated sequence components, and the zero-sequence voltages of the neutral points of the two starting standby transformers are as follows:

[0092] 0.197∠52.97°, 0.113∠132.51°

[0093] 3.675∠-74.58°, 1.391∠146.23°, 3.670∠7.23°

[0094] 2.777∠-93.68°, 1.387∠-33.68°

[0095] In formula (2), k 1 = 0.2, U n = 127 kV, the amplitude of the zero-sequence voltage of the neutral point of the No. 2 starting standby transformer is 0.113 kV, which is much smaller than the zero-sequence voltage threshold of 25.4 kV. It is determined that the No. 2 starting standby transformer with the neutral grounding switch in the off position has not had a single-phase open fault.

[0096] Furthermore, in formula (3), k 2 = 0.8, N = 2, I 0_set = 0.2 A, and the positive-sequence current amplitude is 2.777 A. Then the first threshold of the zero-sequence current is 1.111 A, and the zero-sequence current amplitude is 1.387 A. Formula (3) is satisfied.

[0097] Furthermore, in formula (4), k3 = 0.6, I 0_set = 0.2 A, the positive-sequence current amplitude is 2.777 A, then the second threshold of the zero-sequence current is 1.666 A, while the zero-sequence current amplitude is 1.387 A, and Equation (4) is not satisfied.

[0098] Therefore, it is judged that the No. 1 start-up standby transformer with the neutral grounding switch in the closed position has a phase-breaking fault. Further comparing the amplitudes of the three-phase currents of the incoming line, it is found that the amplitude of the B-phase current is the smallest, so the faulty phase is the B-phase.

[0099] Case 2: When all start-up standby transformers are in no-load operation, as Figure 2 shown at the phase-breaking point 2, an A-phase breaking fault occurs. The three-phase currents on the incoming line, their calculated sequence components, and the zero-sequence voltages of the neutral points of the two start-up standby transformers are as follows:

[0100] 0, 56.56∠116.84°

[0101] 1.538∠-90.44°, 2.497∠160.06°, 2.458∠16.33°

[0102] 2.129∠-91.41°, 0

[0103] Let k in Equation (2) 1 = 0.2, U n = 127 kV, the zero-sequence voltage amplitude of the neutral point of the No. 2 start-up standby transformer is 56.56 kV, which is much greater than the zero-sequence voltage threshold of 25.4 kV. Then it is judged that the No. 2 start-up standby transformer has a phase-breaking fault. Further comparing the amplitudes of the three-phase currents of the incoming line, it is found that the amplitude of the A-phase current is the smallest, so the faulty phase is the A-phase.

[0104] Case 3: When all start-up standby transformers are in no-load operation, as Figure 2 shown at the phase-breaking point 3, a C-phase breaking fault occurs. The three-phase currents on the incoming line, their calculated sequence components, and the zero-sequence voltages of the neutral points of the two start-up standby transformers are as follows:

[0105] 0.393∠-67.03°, 0.393∠-67.03°

[0106] 4.797∠-123.59°, 4.800∠176.14°, 0

[0107] 2.774∠-93.70°, 2.767∠-153.73°

[0108] In formula (2), k 1 = 0.2, U n = 127 kV. The zero-sequence voltage amplitude of the neutral point of the No. 2 startup standby transformer is 0.393 kV, which is much less than the zero-sequence voltage threshold of 25.4 kV at the neutral point. It is determined that the No. 2 startup standby transformer with the neutral grounding switch in the off position has no phase-breaking fault.

[0109] Furthermore, in formula (3), k 2 = 0.8, N = 2, I 0_set = 0.2 A. The positive-sequence current amplitude is 2.774 A. Then the first threshold of the zero-sequence current is 1.110 A, and the zero-sequence current amplitude is 2.767 A. Formula (3) is satisfied.

[0110] Furthermore, in formula (4), k 3 = 0.6, I 0_set = 0.2 A. The positive-sequence current amplitude is 2.774 A. Then the second threshold of the zero-sequence current is 1.664 A, and the zero-sequence current amplitude is 2.767 A. Formula (4) is satisfied.

[0111] Therefore, it is determined that a phase-breaking fault has occurred in the incoming line. Further comparing the amplitudes of the three-phase currents of the incoming line, it is found that the amplitude of the C-phase current is the smallest. Then the fault phase is the C-phase.

[0112] By using the above method, by real-time monitoring the three-phase currents on the incoming line and the zero-sequence voltages of the neutral points of each startup standby transformer, when the above phase-breaking criterion is met, it is determined as a phase-breaking fault, and an alarm signal is sent after a set delay to remind the operator to handle it in time.

[0113] This method can sensitively and accurately identify the phase-breaking faults on the high-voltage side of the startup standby transformer and the line under no-load or light-load conditions, and is applicable to both the transformer neutral grounding and non-grounding systems, improving the safety and reliability of the operation of the startup standby transformer system.

[0114] Figure 7 Shown is a phase-breaking detection device 300 applicable to a multi-startup standby transformer system provided by an embodiment of the present application, including: a data acquisition unit 301, a sequence current calculation unit 302, and a fault determination unit 303. Among them:

[0115] The data acquisition unit 301 is used to measure the three-phase currents on the incoming line, measure the zero-sequence voltages of the neutral points of each startup standby transformer, and collect the positions of the neutral grounding switches of each startup standby transformer.

[0116] The sequence current calculation unit 302 is used to calculate the positive-sequence current and the zero-sequence current of the incoming line based on the three-phase currents on the incoming line by using the symmetrical component method.

[0117] A fault determination unit 303 is configured to determine whether a phase break fault occurs and locate the fault interval based on the incoming line zero - sequence current, the zero - sequence voltage of the neutral point of each start - up standby transformer, and the position of the neutral - point earthing switch.

[0118] In some embodiments, as Figure 8 shown, a phase break detection device 300 applicable to a multi - start - up standby transformer system further includes a phase discrimination unit 304, configured to, in response to determining that a phase break fault has occurred, determine the phase of the phase break fault according to the three - phase currents on the incoming line.

[0119] In some embodiments, as Figure 9 and Figure 10 shown, a phase break detection device 300 applicable to a multi - start - up standby transformer system further includes: an action unit 305, configured to, in response to determining that a phase break fault has occurred, send an alarm signal or act on a trip after a set delay.

[0120] The phase break detection device 300 applicable to a multi - start - up standby transformer system in this application performs functions similar to those of the foregoing method. For details, reference can be made to the previous description and will not be elaborated here.

[0121] Figure 11 Shown is a structural diagram of an electronic device provided in this application. It includes a processor and a memory. The memory stores computer instructions. When the computer instructions are executed by the processor, the processor executes the computer instructions to implement the method and refinement scheme as Figures 1 to 4 shown.

[0122] It should be understood that the above - mentioned device embodiments are illustrative only, and the devices disclosed in the present invention can also be implemented in other ways. For example, the division of the above - mentioned units / modules is only a logical function division, and there can be other division methods in actual implementation. For example, multiple units, modules, or components can be combined, or can be integrated into another system, or some features can be ignored or not executed.

[0123] In addition, without special explanation, in each embodiment of the present invention, each functional unit / module can be integrated in one unit / module, or each unit / module can exist physically alone, or two or more units / modules can be integrated together. The above - mentioned integrated unit / module can be implemented in the form of hardware or in the form of a software program module.

[0124] When the integrated unit / module is implemented in the form of hardware, the hardware can be a digital circuit, an analog circuit, etc. The physical implementation of the hardware structure includes but is not limited to transistors, memristors, etc. Unless otherwise specified, the processor or chip can be any suitable hardware processor, such as a CPU, GPU, FPGA, DSP, and ASIC, etc. Unless otherwise specified, the on-chip cache, off-chip memory, and memory can be any suitable magnetic storage medium or magneto-optical storage medium, such as resistive random access memory (RRAM), dynamic random access memory (DRAM), static random access memory (SRAM), enhanced dynamic random access memory (EDRAM), high-bandwidth memory (HBM), hybrid memory cube (HMC), etc.

[0125] If the integrated unit / module is implemented in the form of a software program module and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this disclosure. The aforementioned memory includes: various media that can store program codes, such as USB flash drives, read-only memory (ROM), random access memory (RAM), mobile hard disks, magnetic disks, or optical discs.

[0126] The embodiments of this application also provide a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to execute as Figure 1 the methods and refinement schemes shown.

[0127] It should be clearly understood that this application describes how to form and use specific examples, but this application is not limited to any details of these examples. Instead, based on the teachings of the content disclosed in this application, these principles can be applied to many other embodiments.

[0128] In addition, it should be noted that the above-mentioned drawings are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, rather than for the purpose of limitation. It is easy to understand that the processes shown in the above-mentioned drawings do not indicate or limit the chronological order of these processes. Additionally, it is also easy to understand that these processes can be executed synchronously or asynchronously, for example, in multiple modules.

[0129] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are similarly included in the patent protection scope of the present invention.

Claims

1. A phase failure detection method applicable to a system of multiple startup standby transformers, characterized in that: include: Measure the three-phase current on the incoming line, measure the zero-sequence voltage at the neutral point of each starting standby transformer, and collect the position of the neutral point grounding switch of each starting standby transformer; Based on the three-phase current on the incoming line, a symmetrical component method is used to calculate the incoming line positive sequence current and the incoming line zero sequence current; Whether a phase failure occurs and the fault interval is located are determined based on the incoming line zero-sequence current, the neutral point zero-sequence voltage of each starting standby transformer and the position of the neutral point grounding switch.

2. A method for detecting phase failure in a system of multiple startup standby transformers as claimed in claim 1, characterized in that: Also includes: In response to determining that a phase failure has occurred, the phase where the phase failure has occurred is determined based on the three-phase current on the incoming line.

3. A method for detecting phase failure in a system of multiple startup standby transformers as claimed in claim 1, characterized in that: The three-phase current on the incoming line and the zero-sequence voltage at the neutral point of the starting standby transformer are measured with sufficient accuracy when all starting standby transformers are in no-load and light-load conditions.

4. A method for detecting phase failure in a system of multiple startup standby transformers as claimed in claim 1, characterized in that: The determining whether a phase failure occurs and locating the fault interval according to the incoming line zero-sequence current, the neutral point zero-sequence voltage of each starting standby transformer and the position of the neutral point grounding switch specifically includes: By judging whether the neutral point zero-sequence voltage amplitude of the starting standby transformer with the neutral point grounding switch in the open position exceeds the preset neutral point zero-sequence voltage threshold, and judging whether the incoming line zero-sequence current amplitude is greater than the preset zero-sequence current first threshold, and whether the incoming line zero-sequence current amplitude is greater than the preset zero-sequence current second threshold, it is comprehensively judged whether a phase failure occurs and the fault interval is located.

5. A method for detecting phase failure in a system of multiple startup standby transformers as claimed in claim 1, characterized in that: The determining whether a phase failure occurs and locating the fault interval according to the incoming line zero-sequence current, the neutral point zero-sequence voltage of each starting standby transformer and the position of the neutral point grounding switch specifically includes: Determine whether the neutral point zero-sequence voltage amplitude of the starting standby transformer with the neutral point grounding switch in the open position is greater than a preset neutral point zero-sequence voltage threshold value, if so, determine that the starting standby transformer with the neutral point grounding switch in the open position has a phase failure, otherwise determine that the starting standby transformer with the neutral point grounding switch in the open position has not a phase failure; If all the starting standby transformers with neutral point grounding switches in the open position have not experienced a phase failure, further determine whether the incoming line zero-sequence current amplitude is greater than the preset zero-sequence current first threshold value. If not, determine that no phase failure has occurred. If so, further determine whether the incoming line zero-sequence current amplitude is greater than the preset zero-sequence current second threshold value. If so, determine that a phase failure has occurred in the incoming line. If otherwise, determine that a phase failure has occurred on the high-voltage side of the starting standby transformer with the neutral point grounding switch in the closed position; the zero-sequence current second threshold value is greater than the zero-sequence current first threshold value.

6. A method for detecting phase failure in a system of multiple startup standby transformers as claimed in claim 5, characterized in that: The neutral point zero-sequence voltage threshold is k1×U n , where U n is the rated value of the high-voltage side phase voltage of the starting standby transformer, k1 is the reliability coefficient, which is taken as 0.2~0.

4.

7. A method for detecting phase failure in a system of multiple startup standby transformers as claimed in claim 5, characterized in that: The first zero-sequence current threshold is the larger of the fixed threshold and the floating threshold. The fixed threshold needs to be larger than the zero-sequence unbalanced current amplitude measured on site. The floating threshold is in is the positive sequence current amplitude of the incoming line, k2 is the reliability coefficient, which is 0.6~0.8, and N is the number of starting standby transformers.

8. A method for detecting phase failure in a system of multiple starting standby transformers as claimed in claim 5, characterized in that: The second zero-sequence current threshold is the larger of the fixed threshold and the floating threshold. The fixed threshold needs to be larger than the zero-sequence unbalanced current amplitude measured on site. The floating threshold is in is the positive sequence current amplitude of the incoming line, k3 is the reliability coefficient, which is between 0.5 and 0.

9.

9. A method for detecting phase failure in a system of multiple startup standby transformers as claimed in claim 2, characterized in that: The phase where the phase failure occurs is determined based on the three-phase current on the incoming line. Specifically, the current amplitudes of the three-phase currents are compared, and the phase with the smallest current amplitude is the fault phase.

10. A method for detecting phase failure applicable to a system of multiple startup standby transformers as claimed in claim 1, characterized in that: include: In response to determining that a phase failure has occurred, an alarm signal is issued or the circuit breaker trips after a set delay.

11. A phase failure detection device suitable for a system of multiple starting standby transformers, characterized in that: include: The data acquisition unit is used to measure the three-phase current on the incoming line, measure the neutral point zero-sequence voltage of each starting standby transformer, and collect the position of the neutral point grounding switch of each starting standby transformer; A sequence current calculation unit, used for calculating the incoming line positive sequence current and the incoming line zero sequence current by using a symmetrical component method based on the three-phase current on the incoming line; and The fault determination unit is used to determine whether a phase failure occurs and locate the fault interval according to the incoming line zero-sequence current, the neutral point zero-sequence voltage of each starting standby transformer and the position of the neutral point grounding switch.

12. A phase failure detection device suitable for a system of multiple starting standby transformers as claimed in claim 11, characterized in that: include: The phase difference judgment unit is used to respond to the judgment that a phase failure has occurred and judge the phase difference of the phase failure according to the three-phase current on the incoming line.

13. A phase failure detection device suitable for a system of multiple starting standby transformers as claimed in claim 11, characterized in that: include: The action unit is used to respond to the judgment that a phase failure has occurred and send out an alarm signal or trip after a set delay.

14. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores a program, and the program can be loaded by the processor to execute the method as claimed in any one of claims 1 to 10.

15. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 10 is implemented.

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