A fault location and busbar protection method and system

Abstract

This invention discloses a fault location and busbar protection method and system. The fault location and busbar protection method includes: acquiring simulation information and switch information of the fault location and busbar protection system; determining the area where the fault point is located based on the simulation information; and controlling the switch located in the area where the fault point is located to disconnect based on the area where the fault point is located and the switch information. In this embodiment, the fault location and busbar protection system determines the faulty area by acquiring simulation information from the secondary sides of the first and second main transformers; and disconnects the switch in the faulty area by acquiring switch information from the secondary sides of the first and second main transformers, thereby achieving accurate determination and precise isolation of the faulty area in the fault location and busbar protection system.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to a fault location and busbar protection method and system. Background Technology

[0002] The low-voltage side of the main transformer in a substation typically uses a delta connection, hence this side is called the delta side. Since a delta connection lacks a neutral point, a grounding point is usually artificially created using a grounding transformer to achieve grounding.

[0003] Among artificially created grounding points, the most common grounding method is grounding the busbar through a grounding transformer with reduced resistance. Since the delta-side busbar lacks busbar protection, grounding through the busbar with reduced resistance makes it impossible to accurately locate and isolate the fault area when a fault occurs in the system. Summary of the Invention

[0004] This invention provides a fault location and busbar protection method and system that can accurately locate and isolate fault areas.

[0005] According to one aspect of the present invention, a fault location and busbar protection method is provided, the method being applied to a fault location and busbar protection system, the fault location and busbar protection system including at least a main transformer and a busbar, the main transformer including a first main transformer and a second main transformer, the busbar including a first busbar and a second busbar; the first busbar is connected to the secondary side of the first main transformer, and the second busbar is connected to the secondary side of the second main transformer; a tie switch is provided between the first busbar and the second busbar; multiple feeders and a grounding transformer are connected to each busbar, the grounding transformer being grounded through a small resistor; a switch is provided between each busbar and the main transformer, the grounding transformer, and the feeders;

[0006] The method includes:

[0007] Collect simulation and switch information from the fault location and busbar protection system;

[0008] Based on the simulation information, the area where the fault point is located is determined;

[0009] Based on the area where the fault point is located and the switch information, control the switch located in the area where the fault point is located to be disconnected.

[0010] Optionally, the acquisition of the simulation information and switch information of the fault location and bus protection system includes:

[0011] Simulation information of the fault location and bus protection system is collected through a zero-sequence current transformer; wherein, the secondary side of the main transformer of the fault location and bus protection system is connected in a delta configuration; the simulation information includes the three-phase current and zero-sequence current of the secondary side of the main transformer, the three-phase current and zero-sequence current of each feeder, the three-phase current of the primary side of the grounding transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, as well as the capacitive current of each bay.

[0012] Collect the switch information of the fault location and bus protection system; wherein, the switch information includes the switch position of the secondary side of the main transformer, the position of the tie switch, the switch position of each feeder, and the switch position of the grounding transformer.

[0013] Optionally, determining the area where the fault point is located based on the simulation information includes:

[0014] The fault of the zero-sequence current transformer of the grounding transformer is determined based on the three-phase current on the primary side and the zero-sequence current on the secondary side of the grounding transformer.

[0015] Based on the fault location and the vector sum of the total zero-sequence current of the bus protection system and the threshold value of the zero-sequence vector sum, the bus area fault is determined; wherein, the bus area fault includes bus short-circuit fault, dead zone short-circuit fault near the tie switch, short-circuit fault of each feeder near the bus side, and short-circuit fault of the secondary side switch of the main transformer near the bus side.

[0016] Based on the magnitude and direction of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, it is determined that a high-resistance grounding fault occurs in the area between the secondary coil of the main transformer and the switch on the secondary side of the main transformer.

[0017] Based on the magnitude and direction of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, it is determined that a single-phase grounding fault has occurred on the feeder; or, it is determined that at least two feeders in the external ring network have experienced single-phase grounding faults.

[0018] Optionally, determining the fault of the zero-sequence current transformer of the grounding transformer based on the three-phase current on the primary side and the zero-sequence current on the secondary side of the grounding transformer includes:

[0019] Calculate the sum of the three-phase currents on the primary side of the grounding transformer based on the three-phase currents on the primary side of the grounding transformer.

[0020] Compare the sum of the three-phase currents on the primary side of the grounding transformer with the zero-sequence current on the secondary side of the grounding transformer. Based on the comparison result, determine the fault states of the current transformer on the primary side of the grounding transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the interior of the grounding transformer.

[0021] Optionally, the step of comparing the sum of the three-phase currents on the primary side of the grounding transformer with the zero-sequence current on the secondary side of the grounding transformer, and based on the comparison result, determining the fault states of the current transformer on the primary side of the grounding transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the interior of the grounding transformer, includes:

[0022] When |I jd - I j0 | > I z1 it is determined that there is a fault in the zero-sequence current transformer on the secondary side of the grounding transformer and the interior of the grounding transformer; where I z1 is the setting value, I jd is the sum of the three-phase currents on the primary side of the grounding transformer, and I j0 is the zero-sequence current on the secondary side of the grounding transformer.

[0023] Optionally, the step of determining a bus area fault based on the vector sum of the total zero-sequence current of the fault location and bus protection system and the zero-sequence vector sum threshold includes: [[ID=2,2]]

[0024] Compare the total zero-sequence current of the fault location and bus protection system with the zero-sequence vector sum threshold to generate a comparison result;

[0025] Based on the comparison result, determine the bus area fault.

[0026] Optionally, the step of determining a high-resistance grounding fault in the area between the secondary side coil of the main transformer and the switch on the secondary side of the main transformer based on the magnitude and direction of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer includes:

[0027] Compare the zero-sequence current on the secondary side of the main transformer with the zero-sequence current of the small resistor on the secondary side of the grounding transformer;

[0028] When the directions of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer are opposite and the vector sum of the opposite directions is zero, it is determined that there is a high-resistance grounding fault in the area between the secondary side coil of the main transformer and the switch on the secondary side of the main transformer.

[0029] Optionally, determining that a single-phase ground fault has occurred on the feeder based on the magnitude and direction of the zero-sequence current of the feeder and the zero-sequence current of the small resistance on the secondary side of the grounding transformer; or, determining that at least two feeders form a ring network outside the station and have experienced a single-phase ground fault, includes:

[0030] The zero-sequence current of the feeder is compared with the zero-sequence current of the small resistor on the secondary side of the grounding transformer;

[0031] When the zero-sequence current of the feeder is in the opposite direction to the zero-sequence current of the small resistor on the secondary side of the grounding transformer, the vector sum of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer is zero, and the maximum value of the zero-sequence current of the feeder is greater than X%*I. j0 When a single-phase ground fault occurs on the feeder, or at least two feeders form a loop network outside the station and a single-phase ground fault occurs, the system determines that X% has occurred. X% is a percentage; when the fault location and busbar protection system does not have an external loop network, X% is set to 80%; when two feeders on the same busbar are in an external loop network, X% is set to 40%; when three feeders on the same busbar are in an external loop network, X% is set to 30%.

[0032] Optionally, controlling the switch located in the area where the fault point is located to disconnect based on the area where the fault point is located and the switch information includes:

[0033] When the zero-sequence current transformer of the grounding transformer fails, the switch on the primary side of the grounding transformer is opened, and this protection is locked.

[0034] When a fault occurs in the busbar area, the switch of the busbar area is disconnected after one step and the standby automatic switching device is locked.

[0035] When a high-resistance ground fault occurs in the area between the secondary winding of the main transformer and the secondary switch of the main transformer, the secondary switch of the main transformer is disconnected after one step.

[0036] When a single-phase ground fault occurs on the feeder, or when at least two feeders in the external ring network experience a single-phase ground fault, the switch of the faulty feeder is disconnected after one level of differential control, and the feeder reclosing is blocked.

[0037] According to another aspect of the present invention, a fault location and busbar protection system is provided, characterized in that it comprises:

[0038] Main transformer and busbar,

[0039] The main transformer includes a first main transformer and a second main transformer, and the busbars include a first busbar and a second busbar; the first busbar is connected to the secondary side of the first main transformer, and the second busbar is connected to the secondary side of the second main transformer; a tie switch is provided between the first busbar and the second busbar; multiple feeders and a grounding transformer are connected to each busbar, and the grounding transformer is grounded through a small resistor; a switch is provided between each busbar and the main transformer, the grounding transformer, and the feeders;

[0040] Zero-sequence current transformers are used to collect analog and switching information from fault location and bus protection systems.

[0041] The fault location module is used to determine the area where the fault point is located based on the simulation information.

[0042] The control module is used to control the switch located in the area where the fault point is located to disconnect based on the area where the fault point is located and the switch information.

[0043] The technical solution of this invention identifies the fault location and busbar protection system fault area by collecting analog information from the secondary sides of the first and second main transformers; and disconnects the switches in the fault location and busbar protection system fault area by collecting switch information from the secondary sides of the first and second main transformers. Therefore, this invention can achieve accurate identification and precise isolation of the fault location and busbar protection system fault area.

[0044] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart illustrating a fault location and busbar protection method provided in an embodiment of the present invention;

[0047] Figure 2 This is a structural schematic diagram of a fault location and busbar protection system provided in an embodiment of the present invention;

[0048] Figure 3This is a flowchart illustrating another fault location and busbar protection method provided in an embodiment of the present invention;

[0049] Figure 4 This is a flowchart illustrating another fault location and busbar protection method provided in an embodiment of the present invention;

[0050] Figure 5 This is a flowchart illustrating another fault location and busbar protection method provided in an embodiment of the present invention. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0052] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0053] Figure 1 This is a flowchart illustrating a fault location and busbar protection method provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of a fault location and busbar protection system provided in an embodiment of the present invention. The fault location and busbar method is applied to the fault location and busbar protection system, as shown below. Figure 2The fault location and busbar protection system includes at least a main transformer and busbars. The main transformers include a first main transformer Z1 and a second main transformer Z2. The busbars include a first busbar M1 and a second busbar M2. The first busbar M1 is connected to the secondary side of the first main transformer Z1, and the second busbar M2 is connected to the secondary side of the second main transformer Z2. A tie switch DL1 is installed between the first busbar M1 and the second busbar M2. Multiple feeders and a grounding transformer are connected to each busbar, and the grounding transformer is grounded through a small resistor. A switch is installed between each busbar and the main transformer, the grounding transformer, and the feeders.

[0054] Reference Figure 1 The fault location and busbar method includes:

[0055] S110. Collect simulation information and switch information of the fault location and bus protection system;

[0056] Specifically, analog and switching information from the secondary side of the first main transformer Z1 and the secondary side of the second main transformer Z2 are collected.

[0057] S120. Based on the simulation information, determine the area where the fault point is located;

[0058] Specifically, the fault location is determined based on the simulated information collected from the secondary side of the first main transformer Z1 and the secondary side of the second main transformer Z2.

[0059] S130. Based on the area where the fault point is located and the switch information, control the switch in the area where the fault point is located to disconnect.

[0060] Specifically, based on the faulty area and the collected switch information from the secondary side of the first main transformer Z1 and the secondary side of the second main transformer Z2, the switch in the faulty area is controlled to be turned off.

[0061] The fault location and busbar protection method provided in this invention determines the faulty area of ​​the fault location and busbar protection system by collecting analog information from the secondary side of the first main transformer Z1 and the secondary side of the second main transformer Z2; and disconnects the switches in the faulty area of ​​the fault location and busbar protection system by collecting switch information from the secondary side of the first main transformer Z1 and the secondary side of the second main transformer Z2. Therefore, this invention can achieve accurate determination and precise isolation of the faulty area of ​​the fault location and busbar protection system.

[0062] Figure 3 This is a flowchart illustrating another fault location and busbar protection method provided in an embodiment of the present invention. (Refer to...) Figure 3 The collection of simulation information and switch information from the fault location and bus protection system includes:

[0063] S310. The simulation information of the fault location and bus protection system is collected through the zero-sequence current transformer; wherein, the secondary side of the main transformer of the fault location and bus protection system is connected in a delta connection; the simulation information includes the three-phase current and zero-sequence current of the secondary side of the main transformer, the three-phase current and zero-sequence current of each feeder, the three-phase current of the primary side of the grounding transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, as well as the capacitive current of each bay.

[0064] Specifically, the analog information collected by the zero-sequence current transformer includes: the magnitude and direction of the three-phase current and the zero-sequence current on the secondary side of the first main transformer Z1 and the secondary side of the second main transformer Z2; the magnitude and direction of the three-phase current and the zero-sequence current on each feeder; the magnitude and direction of the three-phase current on the primary side of the grounding transformer; the magnitude and direction of the zero-sequence current of the small resistor on the secondary side of the grounding transformer; and the magnitude and direction of the capacitive current in each bay.

[0065] S320. Collect fault location and bus protection system switch information; the switch information includes the switch position of the secondary side of the main transformer, the position of the tie switch, the switch position of each feeder, and the switch position of the grounding transformer.

[0066] Specifically, the collected switch information includes the switch positions on the secondary side of the main transformer, the positions of tie switches, the switch positions of each feeder, and the switch positions of the grounding transformer. Switch positions include the location of the switch within the fault location and busbar protection system, as well as the position of the disconnector.

[0067] This invention collects switch information of the fault location and bus protection system, and collects simulation information of the fault location and bus protection system through a zero-sequence current transformer, so as to achieve accurate identification of the operating status of the fault location and bus protection system.

[0068] Figure 4 This is a flowchart illustrating another fault location and busbar protection method provided in an embodiment of the present invention. Based on simulation information, referring to... Figure 4 The area where the fault is located includes:

[0069] S410. Determine the fault of the zero-sequence current transformer of the grounding transformer based on the three-phase current on the primary side of the grounding transformer and the zero-sequence current on the secondary side of the grounding transformer.

[0070] Specifically, zero-sequence current is the current generated when the vector sum of the three-phase currents is not zero. This means that the sum of the three-phase currents is consistent with the zero-sequence current. When the vector sum of the three-phase currents on the primary side of the grounding transformer is inconsistent with the zero-sequence current on the secondary side of the grounding transformer, a fault in the zero-sequence current transformer of the grounding transformer can be determined.

[0071] S420. Based on the fault location and the vector sum of the total zero-sequence current of the bus protection system and the threshold value of the zero-sequence vector sum, determine the bus area fault; among which, the bus area fault includes bus short-circuit fault, dead zone short-circuit fault near the tie switch, short-circuit fault of each feeder near the bus side, and short-circuit fault of the secondary side switch of the main transformer near the bus side.

[0072] Specifically, in the fault location and busbar protection system, the zero-sequence current transformer in the feeder containing the grounding transformer induces a large zero-sequence current, while the zero-sequence current transformers in other feeders in the same system induce smaller zero-sequence currents. The vector sum of the total zero-sequence current in the fault location and busbar protection system is calculated based on the magnitude of the zero-sequence current induced by the zero-sequence current transformers. At this point, the majority of the zero-sequence current in the fault location and busbar protection system flows from the fault point through the small resistance on the secondary side of the grounding transformer, returns to the fault point via the earth, forming the main zero-sequence path; a very small portion forms a secondary zero-sequence path through the capacitive effect between each feeder and the earth, creating capacitive currents. The vector sum of the total zero-sequence current in the fault location and busbar protection system is determined by the zero-sequence current flowing through the small resistance on the secondary side of the grounding transformer and the capacitive current in each bay. The direction of the zero-sequence current flowing through the small resistance on the secondary side of the grounding transformer and the direction of the capacitive current in each bay are the same. Therefore, the vector sum of the total zero-sequence current in the fault location and busbar protection system is very large. Whether a fault occurs in the bus region can be determined by comparing the vector sum of the total zero-sequence currents in the fault location and bus protection system with the zero-sequence vector sum threshold value. The zero-sequence vector sum threshold value is a set value used for fault identification in the fault location and bus protection system. If the vector sum of the total zero-sequence currents in the fault location and bus protection system is greater than the zero-sequence vector sum threshold value, then the fault area of ​​the fault location and bus protection system is the bus region; otherwise, it is not.

[0073] Reference Figure 2 In the fault location and bus protection system, bus short-circuit faults include faults at points D12 and D22 on the bus; dead-zone short-circuit faults near the tie switch in the fault location and bus protection system refer to faults near point D0 of the bus tie switch; short-circuit faults near the bus on each feeder in the fault location and bus protection system include faults at points D17 and D27 on the feeder; and short-circuit faults near the bus on the secondary side of the main transformer in the fault location and bus protection system include faults near points DZ11 and DZ21 of the secondary side of the main transformer.

[0074] S430. Based on the magnitude and direction of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, determine that a high-resistance grounding fault has occurred in the area between the secondary coil of the main transformer and the switch on the secondary side of the main transformer.

[0075] Specifically, in the fault location and busbar protection system, the zero-sequence current induced by the zero-sequence current transformers on the low-voltage side of the main transformer and the busbar increases. The zero-sequence current transformers in the feeders where the grounding transformer is located in the fault location and busbar protection system induce a large zero-sequence current, while the zero-sequence current transformers in other feeders in the fault location and busbar protection system induce a smaller zero-sequence current. At this time, most of the zero-sequence current on the low-voltage side of the transformer in the system returns to the fault point through the ground via the small resistance on the secondary side of the grounding transformer, forming the main zero-sequence path. In this main zero-sequence path, the zero-sequence current flowing through the small resistance on the secondary side of the grounding transformer is in the opposite direction to the zero-sequence current on the low-voltage side of the main transformer. Therefore, the vector sum of the currents cancels each other out, and the calculated result is close to zero. This indicates that a high-resistance grounding fault has occurred in the area between the secondary winding of the main transformer and the secondary switch of the main transformer.

[0076] Reference Figure 2 In the fault location and bus protection system, a high-resistance grounding fault occurs in the area between the secondary coil of the main transformer and the secondary switch of the main transformer, referring to the faults at points DZ11 and DZ21 between the secondary coil of the main transformer and the secondary switch of the main transformer.

[0077] S440. Based on the magnitude and direction of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, determine that a single-phase grounding fault has occurred on the feeder; or, determine that at least two feeders in the external ring network have experienced single-phase grounding faults.

[0078] Specifically, when the zero-sequence current induced by the zero-sequence current transformers in the feeders and busbars of the fault location and busbar protection system increases, and the zero-sequence current transformer in the feeder where the grounding transformer of the fault location and busbar protection system is located induces a larger zero-sequence current, while the zero-sequence current transformer on the low-voltage side of the main transformer in the fault location and busbar protection system induces a smaller zero-sequence current, the zero-sequence current in the system flows from the fault point through the feeder zero-sequence current transformer into the busbar. Most of the zero-sequence current flows out of the busbar through the small resistance on the secondary side of the grounding transformer and returns to the fault point through the earth, forming the main zero-sequence path. In this main zero-sequence path, the direction of the zero-sequence current flowing through the feeder is opposite to that of the zero-sequence current flowing through the small resistance on the secondary side of the grounding transformer. Therefore, the vector sum of the currents cancels out, and the calculation result is close to zero. This allows us to determine that the fault occurred on the feeder, and based on logical calculations, to determine whether a single-phase ground fault occurred on the feeder or whether at least two feeders in the external ring network experienced a single-phase ground fault.

[0079] Reference Figure 2 In the fault location and bus protection system, at least two feeders in the external ring network and a single-phase grounding fault occurs, which refers to the fault at point D18 outside the station.

[0080] The fault location and bus protection system of this invention monitors the magnitude and direction of the zero-sequence current at each location by using zero-sequence current transformers distributed throughout the system. The monitoring results are then logically calculated, and based on the location of the zero-sequence current and the logical calculation results, the fault area of ​​the fault location and bus protection system is determined, thereby achieving accurate identification and location of the fault area of ​​the fault location and bus protection system.

[0081] Figure 5 This is a flowchart illustrating another fault location and busbar protection method provided in an embodiment of the present invention. (Refer to...) Figure 5 Based on the three-phase current on the primary side of the grounding transformer and the zero-sequence current on the secondary side of the grounding transformer, the fault of the zero-sequence current transformer of the grounding transformer is determined, including:

[0082] S510. Calculate the sum of the three-phase currents on the primary side of the grounding transformer based on the three-phase currents on the primary side of the grounding transformer.

[0083] Specifically, the vector sum of the three-phase currents is calculated based on the three-phase currents on the primary side of the grounding transformer, and this vector sum is defined as I. jd .

[0084] S520. Compare the sum of the three-phase currents on the primary side of the grounding transformer with the zero-sequence current on the secondary side of the grounding transformer. Based on the comparison result, determine the fault status of the current transformer on the primary side of the grounding transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the internal fault status of the grounding transformer.

[0085] Specifically, the zero-sequence current on the secondary side of the grounding transformer is defined as I. j0 And the three-phase current vector on the primary side of the grounding transformer and I jd Zero-sequence current I on the secondary side of the grounding transformer j0 Comparison. Based on the comparison results, determine the fault status of the primary current transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the internal components of the grounding transformer.

[0086] In this embodiment of the invention, the three-phase current vector on the primary side of the grounding transformer and I jd Zero-sequence current I on the secondary side of the grounding transformer j0 By comparing the faults, the fault status of the primary current transformer, the secondary zero-sequence current transformer, and the internal fault status of the grounding transformer can be determined based on the comparison results, thereby achieving accurate identification and location of fault areas in the bus protection system.

[0087] Optionally, compare the sum of the three-phase currents on the primary side of the grounding transformer with the zero-sequence current on the secondary side of the grounding transformer, and based on the comparison result, determine the fault states of the current transformer on the primary side of the grounding transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the interior of the grounding transformer, including: when |I jd - I j0 | > I z1 ), determine the zero-sequence current transformer on the secondary side of the grounding transformer and an internal fault of the grounding transformer; where I z1 is a setting value, I jd is the sum of the three-phase currents on the primary side of the grounding transformer, and I j0 is the zero-sequence current on the secondary side of the grounding transformer.

[0088] Specifically, the zero-sequence current is the current generated when the vector sum of the three-phase currents is not zero. That is to say, the sum of the three-phase currents is consistent with the zero-sequence current. It should be noted that I z1 is a setting value used to determine whether I jd and I j0 are consistent. When |I jd - I j0 | > I z1 ), it indicates that the sum of the three-phase currents on the primary side of the grounding transformer is inconsistent with the zero-sequence current on the secondary side of the grounding transformer.

[0089] In an embodiment of the present invention, by comparing the logical operation result of the sum of the three-phase currents on the primary side of the grounding transformer and the zero-sequence current on the secondary side of the grounding transformer with I z1 , it is determined whether the sum of the three-phase currents on the primary side of the grounding transformer is consistent with the zero-sequence current on the secondary side of the grounding transformer. In this way, the fault states of the current transformer on the primary side of the grounding transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the interior of the grounding transformer are judged.

[0090] Optionally, determine a bus zone fault according to the vector sum of the total zero-sequence current of the fault location and bus protection system and the zero-sequence vector sum threshold value, including:

[0091] Compare the vector sum of the total zero-sequence current of the fault location and bus protection system with the zero-sequence vector sum threshold value to generate a comparison result;

[0092] Determine a bus zone fault according to the comparison result.

[0093] Specifically, in the fault location and busbar protection system, the zero-sequence current transformer in the feeder containing the grounding transformer induces a large zero-sequence current, while the zero-sequence current transformers in other feeders in the same system induce smaller zero-sequence currents. The total zero-sequence current vector sum of the fault location and busbar protection system is calculated based on the magnitude of the zero-sequence current induced by the zero-sequence current transformers. At this point, the majority of the zero-sequence current in the fault location and busbar protection system flows from the fault point through the small resistance on the secondary side of the grounding transformer, returns to the fault point via the earth, forming the main zero-sequence path; a very small portion forms a secondary zero-sequence path through the capacitive effect between each feeder and the earth, creating capacitive currents. The total zero-sequence current vector sum of the fault location and busbar protection system is determined by the zero-sequence current flowing through the small resistance on the secondary side of the grounding transformer and the capacitive current in each bay. The zero-sequence current flowing through the small resistance on the secondary side of the grounding transformer and the capacitive current in each bay have the same direction. Therefore, the total zero-sequence current vector sum of the fault location and busbar protection system is very large. The vector sum of the total zero-sequence currents in the fault location and busbar protection system is defined as I0. Whether a fault occurs in the busbar region can be determined by comparing the vector sum of the total zero-sequence currents in the fault location and busbar protection system with a zero-sequence vector sum threshold value. When I0 > I... z3 When the fault location and busbar protection system fails, the fault occurs in the busbar area; otherwise, it occurs elsewhere. Wherein, I z3 The zero-sequence vector sum and threshold value are setpoints. This invention determines whether a fault exists in the bus region of the fault location and bus protection system by comparing the vector sum of the total zero-sequence current in the fault location and bus protection system with the zero-sequence vector sum and threshold value. If the vector sum of the total zero-sequence current in the fault location and bus protection system is greater than the zero-sequence vector sum and threshold value, then the fault area of ​​the fault location and bus protection system is the bus region; otherwise, it is less than the threshold value. This achieves accurate identification and location of the fault area in the fault location and bus protection system.

[0094] Optionally, based on the magnitude and direction of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, a high-resistance grounding fault in the area between the secondary coil of the main transformer and the secondary switch of the main transformer is determined, including: comparing the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer; when the directions of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer are opposite, and the vector sum of the opposite directions of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer is zero, a high-resistance grounding fault in the area between the secondary coil of the main transformer and the secondary switch of the main transformer is determined.

[0095] Specifically, the zero-sequence current sensed by the zero-sequence current transformers on the low-voltage side of the main transformer and the busbar in the fault location and busbar protection system increases. A relatively large zero-sequence current is sensed by the zero-sequence current transformer in the feeder where the earthing transformer of the fault location and busbar protection system is located, and relatively small zero-sequence currents are sensed by the zero-sequence current transformers in other feeders of the fault location and busbar protection system. At this time, most of the zero-sequence current on the low-voltage side of the transformer in the system returns to the fault point through the small resistor on the secondary side of the earthing transformer via the earth, forming the main zero-sequence path; a very small part forms a capacitive current through the capacitive effect between each feeder and the earth to form a secondary zero-sequence path. In the main zero-sequence path at this time, the direction of the zero-sequence current flowing through the small resistor on the secondary side of the earthing transformer is opposite to that of the zero-sequence current on the low-voltage side of the main transformer. Therefore, the vector sum of the current addition cancels out, and the calculation result is close to zero. Define the zero-sequence current on the secondary side of the main transformer as I 10 , define the vector sum of the zero-sequence currents of each interval on the busbar as I0. Since the vector sum of the zero-sequence current on the low-voltage side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the earthing transformer cancels out, the value of I0 at this time is the vector sum of the zero-sequence currents on other feeders connected to the busbar. The vector sum of this zero-sequence current is small and the direction is out of the busbar. When I0 < I z3 , and |I 10 | > I z3 , where I0 is the vector sum of the zero-sequence currents of each interval on the busbar, I 10 is the value of the zero-sequence current on the low-voltage side of the main transformer, I z3 is the zero-sequence vector sum threshold value, and when the direction of the zero-sequence current on the low-voltage side of the transformer is into the busbar, it is determined that a high-resistance grounding fault occurs in the area from the delta side coil of the main transformer to the low-voltage switch area, that is, in the area between the secondary side coil of the main transformer and the switch on the secondary side of the main transformer.

[0096] Through the monitoring of the magnitudes and directions of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the earthing transformer, and the comparison of the zero-sequence current on the secondary side of the main transformer, the vector sum of the zero-sequence currents of each interval on the busbar with I z3 , this embodiment of the present invention determines whether a fault occurs in the area from the delta side coil of the main transformer to the low-voltage switch area, and realizes the accurate identification and location of the fault area in the fault location and busbar protection system.

[0097] Optionally, determine that a single-phase grounding fault has occurred in the feeder according to the magnitude and direction of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer; or, determine that at least two feeders form a loop network outside the substation and a single-phase grounding fault has occurred, including: comparing the zero-sequence current of the feeder with the zero-sequence current of the small resistor on the secondary side of the grounding transformer; when the direction of the zero-sequence current of the feeder is opposite to the zero-sequence current of the small resistor on the secondary side of the grounding transformer, the vector sum of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer is zero, and the maximum value of the zero-sequence current of the feeder is greater than X% * I j0 When this occurs, it is determined that a single-phase grounding fault has occurred in the feeder, or at least two feeders form a loop network outside the substation and a single-phase grounding fault has occurred; where X% is a percentage. When there is no loop network outside the substation in the fault location and bus protection system, set X% = 80%; when there are at most two feeders on the same bus forming a loop network outside the substation, set X% = 40%; when there are at most three feeders on the same bus forming a loop network outside the substation, set X% = 30%.

[0098] Specifically, when the zero-sequence current sensed by the zero-sequence current transformers of the feeder and the bus in the fault location and bus protection system increases, the zero-sequence current transformer in the feeder where the grounding transformer of the fault location and bus protection system is located senses a larger zero-sequence current, and the zero-sequence current transformer on the low-voltage side of the main transformer in the fault location and bus protection system senses a smaller zero-sequence current. At this time, the zero-sequence current in the system enters the bus through the zero-sequence current transformer of the feeder from the fault point. Most of the zero-sequence current flows out of the bus through the small resistor on the secondary side of the grounding transformer and returns to the fault point through the earth, forming the main zero-sequence path; a very small part forms a capacitive current through the capacitive effect between each feeder and the earth to form a secondary zero-sequence path. In the main zero-sequence path at this time, the direction of the zero-sequence current flowing through the feeder is opposite to the zero-sequence current flowing through the small resistor on the secondary side of the grounding transformer. Therefore, the vector sum of the currents cancels each other out, and the calculation result is close to zero. Since the vector sum of the zero-sequence current flowing through the feeder and the zero-sequence current flowing through the small resistor on the secondary side of the grounding transformer cancels each other out, the value of I0 at this time is the vector sum of the zero-sequence current on the low-voltage side of the main transformer and the zero-sequence current on the unfaulted feeder, and this vector sum is smaller. And because there is no fault on the low-voltage side of the main transformer, the zero-sequence current value on the low-voltage side of the main transformer is smaller at this time. Since there may be a situation where two feeders form a loop network outside the substation and a single-phase grounding fault occurs, therefore, through the vector sum of the total zero-sequence current of the fault location and bus protection system, the zero-sequence current value on the low-voltage side of the main transformer, and whether the maximum value of the zero-sequence current of the feeder is greater than X% * I j0 Judge the fault situation of the feeder. Refer to Figure 2 , taking the Z1 side of the first main transformer as an example, that is, when I0 < I z3 , |I 10 | < I z3 and max{I12 I 33 I 14}>X%*I j0 At that time, a fault occurs in the feeder of the fault location and busbar protection system. Here, I0 is the vector sum of the total zero-sequence currents in the fault location and busbar protection system, I... 10 The zero-sequence current value on the low-voltage side of the main transformer, I z3 Given the zero-order vector and threshold value, I 12 I 33 I 14 These refer to the zero-sequence currents induced by zero-sequence current transformers T12, T13, and T14 on the Z1 side of the first main transformer. When the fault location and busbar protection system does not have an external ring network, X% is set to 80%; when two feeders on the same busbar are in the external ring network, the zero-sequence current generated at the fault point is diverted through the two feeders of the ring network, so X% is set to 40%; when three feeders on the same busbar are in the external ring network, the zero-sequence current generated at the fault point is diverted through the three feeders of the ring network, so X% is set to 30%.

[0099] In this embodiment of the invention, is the maximum value of the zero-sequence current through the feeder greater than X%*I? j0 Determine the fault status of the feeder and set the value of X% based on the fault location and whether there is an external ring network in the bus protection system. Avoid the feeder's own zero-sequence protection setting value not being reached due to the diversion of the external ring network. This enables the determination of single-phase grounding faults of feeders and single-phase grounding faults caused by at least two feeders forming an external ring network.

[0100] Optionally, based on the area where the fault point is located and the switch information, the switch in the area where the fault point is located is controlled to open, including: when the zero-sequence current transformer of the grounding transformer fails, the primary side switch of the grounding transformer is controlled to open and the protection is blocked; when the busbar area fails, the switch in the busbar area is controlled to open after one level difference and the standby automatic transfer device is blocked; when a high-resistance grounding fault occurs in the area between the secondary coil of the main transformer and the secondary side switch of the main transformer, the secondary side switch of the main transformer is controlled to open after one level difference; when a single-phase grounding fault occurs on a feeder, or at least two feeders in the external ring network experience a single-phase grounding fault, the switch of the feeder with the fault occurs is controlled to open after one level difference and the feeder reclosing is blocked.

[0101] This embodiment of the invention identifies the fault area based on the above embodiments and disconnects the switches in the fault area. When the zero-sequence current transformer of the grounding transformer fails, the primary side switch of the grounding transformer is disconnected; when the busbar area fails, the busbar area switch is disconnected, and the standby automatic transfer device is locked to reduce further impact on the busbar; when a high-resistance grounding fault occurs in the area between the secondary winding of the main transformer and the secondary side switch of the main transformer, the secondary side switch of the main transformer is disconnected. This embodiment achieves precise isolation of the fault area, reducing the scope of the fault's impact.

[0102] Reference Figure 2 The fault location and busbar protection system includes: a main transformer and busbars. The main transformers include a first main transformer Z1 and a second main transformer Z2. The busbars include a first busbar M1 and a second busbar M2. The first busbar M1 is connected to the secondary side of the first main transformer Z1, and the second busbar M2 is connected to the secondary side of the second main transformer Z2. A tie switch DL1 is provided between the first busbar M1 and the second busbar M2. Multiple feeders and a grounding transformer are connected to each busbar, and the grounding transformer is grounded through a small resistor. A switch is provided between each busbar and the main transformer, the grounding transformer, and the feeders. A zero-sequence current transformer is used to collect simulation information and switch information of the fault location and busbar protection system. A fault location module is used to determine the area where the fault point is located based on the simulation information. A control module is used to control the switch located in the area where the fault point is located to open based on the area where the fault point is located and the switch information. The fault location and busbar protection system provided in this embodiment is used to execute the above-described fault location and busbar protection method and has the beneficial effects of the fault location and busbar protection method provided in any of the above embodiments, which will not be elaborated further here.

[0103] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0104] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fault location and busbar protection method, characterized in that, The method is applied to a fault location and busbar protection system, which includes at least a main transformer and busbars. The main transformers include a first main transformer and a second main transformer, and the busbars include a first busbar and a second busbar. The first busbar is connected to the secondary side of the first main transformer, and the second busbar is connected to the secondary side of the second main transformer. A tie switch is provided between the first busbar and the second busbar. Multiple feeders and a grounding transformer are connected to each busbar, and the grounding transformer is grounded through a small resistor. A switch is provided between each busbar and the main transformer, the grounding transformer, and the feeders. The method includes: Collect simulation and switch information from the fault location and busbar protection system; Based on the simulation information, the area where the fault point is located is determined; Based on the area where the fault point is located and the switch information, control the switch located in the area where the fault point is located to be disconnected; The step of controlling the switch located in the area where the fault point is located to disconnect based on the area where the fault point is located and the switch information includes: When the zero-sequence current transformer of the grounding transformer fails, the switch on the primary side of the grounding transformer is opened, and this protection is locked. When a fault occurs in the busbar area, the switch of the busbar area is disconnected after one step and the standby automatic switching device is locked. When a high-resistance ground fault occurs in the area between the secondary winding of the main transformer and the secondary switch of the main transformer, the secondary switch of the main transformer is disconnected after one step. When a single-phase ground fault occurs on the feeder, or when at least two feeders in the external ring network experience a single-phase ground fault, the switch of the faulty feeder is disconnected after one level of differential control, and the feeder reclosing is blocked.

2. The fault location and busbar protection method according to claim 1, characterized in that, The acquisition of the simulation information and switch information of the fault location and bus protection system includes: Simulation information of the fault location and bus protection system is collected through a zero-sequence current transformer; wherein, the secondary side of the main transformer of the fault location and bus protection system is connected in a delta configuration; the simulation information includes the three-phase current and zero-sequence current of the secondary side of the main transformer, the three-phase current and zero-sequence current of each feeder, the three-phase current of the primary side of the grounding transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, as well as the capacitive current of each bay. Collect the switch information of the fault location and bus protection system; wherein, the switch information includes the switch position of the secondary side of the main transformer, the position of the tie switch, the switch position of each feeder, and the switch position of the grounding transformer.

3. The fault location and busbar protection method according to claim 2, characterized in that, Determining the area where the fault point is located based on the simulation information includes: The fault of the zero-sequence current transformer of the grounding transformer is determined based on the three-phase current on the primary side and the zero-sequence current on the secondary side of the grounding transformer. Based on the fault location and the vector sum of the total zero-sequence current of the bus protection system and the threshold value of the zero-sequence vector sum, the bus area fault is determined; wherein, the bus area fault includes bus short-circuit fault, dead zone short-circuit fault near the tie switch, short-circuit fault of each feeder near the bus side, and short-circuit fault of the secondary side switch of the main transformer near the bus side. Based on the magnitude and direction of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, it is determined that a high-resistance grounding fault occurs in the area between the secondary coil of the main transformer and the switch on the secondary side of the main transformer. Based on the magnitude and direction of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer, it is determined that a single-phase grounding fault has occurred on the feeder; or, it is determined that at least two feeders in the external ring network have experienced single-phase grounding faults.

4. The fault location and busbar protection method according to claim 3, characterized in that, The method of determining a fault in the zero-sequence current transformer of a grounding transformer based on the three-phase current on the primary side and the zero-sequence current on the secondary side includes: Calculate the sum of the three-phase currents on the primary side of the grounding transformer based on the three-phase currents on the primary side of the grounding transformer. The sum of the three-phase currents on the primary side of the grounding transformer is compared with the zero-sequence current on the secondary side of the grounding transformer. Based on the comparison result, the fault status of the current transformer on the primary side of the grounding transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the internal fault status of the grounding transformer are determined.

5. The fault location and busbar protection method according to claim 4, characterized in that, The step of comparing the sum of the three-phase currents on the primary side of the grounding transformer with the zero-sequence current on the secondary side of the grounding transformer, and determining the fault status of the primary current transformer, the zero-sequence current transformer on the secondary side of the grounding transformer, and the internal fault status of the grounding transformer based on the comparison result, includes: When |I jd - I j0 | > I z1 , determine the zero - sequence current transformer on the secondary side of the grounding transformer and the internal fault of the grounding transformer; where I z1 is the setting value, I jd is the sum of the three - phase currents on the primary side of the grounding transformer, and I j0 is the zero - sequence current on the secondary side of the grounding transformer.

6. The fault location and busbar protection method according to claim 3, characterized in that, The determination of busbar area faults based on fault location and the vector sum of the total zero-sequence current of the busbar protection system, along with the zero-sequence vector sum threshold value, includes: The vector sum of the total zero-sequence current in the fault location and bus protection system is compared with the zero-sequence vector sum threshold value to generate a comparison result. Based on the comparison results, a fault in the busbar area is determined.

7. The fault location and busbar protection method according to claim 3, characterized in that, The method of determining the high-resistance grounding fault in the area between the secondary coil of the main transformer and the secondary switch of the main transformer based on the magnitude and direction of the zero-sequence current of the secondary side of the main transformer and the small resistance of the grounding transformer includes: The zero-sequence current on the secondary side of the main transformer is compared with the zero-sequence current of the small resistor on the secondary side of the grounding transformer. When the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer are in opposite directions, and the vector sum of the zero-sequence current on the secondary side of the main transformer and the zero-sequence current of the small resistor on the secondary side of the grounding transformer are in opposite directions, a high-resistance grounding fault is determined in the area between the secondary coil of the main transformer and the switch on the secondary side of the main transformer.

8. The fault location and busbar protection method according to claim 3, characterized in that, The method determines that a single-phase ground fault has occurred in the feeder based on the magnitude and direction of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer. Alternatively, it can be determined that at least two feeders form a loop outside the station and experience a single-phase ground fault, including: The zero-sequence current of the feeder is compared with the zero-sequence current of the small resistor on the secondary side of the grounding transformer; When the zero-sequence current of the feeder is in the opposite direction to the zero-sequence current of the small resistor on the secondary side of the grounding transformer, the vector sum of the zero-sequence current of the feeder and the zero-sequence current of the small resistor on the secondary side of the grounding transformer is zero, and the maximum value of the zero-sequence current of the feeder is greater than X%*I. j0 When a single-phase ground fault occurs in the feeder, or at least two feeders form a ring network outside the station and a single-phase ground fault occurs; where X% is a percentage, X% is set to 80% when the fault location and bus protection system does not have an external ring network; X% is set to 40% when two feeders on the same busbar are in an external ring network; and X% is set to 30% when three feeders on the same busbar are in an external ring network.

9. A fault location and busbar protection system, used to perform the fault location and busbar protection method as described in any one of claims 1-8, characterized in that, include: Main transformer and busbar, The main transformer includes a first main transformer and a second main transformer, and the busbars include a first busbar and a second busbar; the first busbar is connected to the secondary side of the first main transformer, and the second busbar is connected to the secondary side of the second main transformer; a tie switch is provided between the first busbar and the second busbar; multiple feeders and a grounding transformer are connected to each busbar, and the grounding transformer is grounded through a small resistor; a switch is provided between each busbar and the main transformer, the grounding transformer, and the feeders; Zero-sequence current transformers are used to collect analog and switching information from fault location and bus protection systems. The fault location module is used to determine the area where the fault point is located based on the simulation information. The control module is used to control the switch located in the area where the fault point is located to disconnect based on the area where the fault point is located and the switch information.

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