A relay protection method for bypass circuit breaker failure in bypass transformer mode

Abstract

The present invention discloses a relay protection method for bypass circuit breaker failure in bypass transformer mode, which solves the technical problem of bypass circuit breaker protection failure in a 220kV substation with double busbars and bypass busbar connection when the bypass circuit breaker replaces the transformer circuit breaker. The present invention connects the No. 1 or No. 2 transformer protection opening signal, the bypass circuit breaker protection opening signal and the bypass circuit breaker CT secondary current to the vacant transformer branch in the six unified busbar protection to form bypass circuit breaker failure protection in bypass transformer mode. It prevents the bypass circuit breaker from operating without failure protection in the bypass transformer mode, can quickly cut off the fault, ensure the safe and stable operation of the power grid, and improve the power supply reliability of the power grid. Through the input and output pressure plate, the bypass circuit breaker failure protection is also applicable to bypass circuit breaker failure protection in the bypass circuit breaker empty charging 220kV bypass bus mode and the bypass No. 1 or No. 2 transformer mode.

Description

Technical Field

[0001] The invention relates to a relay protection method for bypass circuit breaker failure in a bypass transformer mode, and belongs to the technical field of protection and control equipment of power transmission and distribution networks. Background Art

[0002] Currently, the 220kV side of a 220kV substation features a dual busbar with a bypass busbar. When 220kV busbar protection utilizes six standardized devices, circuit breaker failure protection is generally integrated into the busbar protection. This busbar protection includes each branch current circuit, auxiliary contacts for the busbar disconnectors on each branch's sections I and II, an input circuit for the protection trip contact to initiate failure protection, a busbar differential logic circuit, a failure initiation logic circuit, and a trip circuit. The interconnecting circuits between external protection devices and the busbar protection include: each branch current circuit, the input circuit for the protection trip contact to initiate failure protection, the input circuit for the auxiliary contacts for the disconnector position on each branch's busbars I and II, and the input circuit and trip circuit for the busbar protection. The failure initiation logic circuit includes logic for both the line branch and the transformer branch, all implemented within the busbar protection. The line branch failure initiation logic circuitry combines single-phase and three-phase tripping modes. The transformer branch failure initiation logic circuitry combines three-phase tripping modes. Current discrimination in the failure protection initiation logic is also implemented in the busbar protection, sharing the same current transformer secondary winding current as the busbar differential protection. The current discrimination and protection tripping contacts of each branch together constitute the failure protection initiation circuitry for that branch.

[0003] The failure protection logic of a 220kV bypass circuit breaker is generally designed based on the operation mode of using a 220kV bypass circuit breaker instead of a 220kV line circuit breaker. This logic has the following problems when the bypass circuit breaker replaces the 220kV transformer circuit breaker (hereinafter referred to as the bypass transformer breaker mode): 1. The bypass circuit breaker failure protection logic is the same as the line branch circuit breaker failure protection logic and cannot adapt to the bypass transformer breaker operation mode; 2. The transformer protection trip contact is not connected to the 220kV bypass circuit breaker failure circuit, so the 220kV bypass circuit breaker failure protection cannot be activated when the transformer protection is activated; 3. In the bypass transformer breaker mode, since the transformer protection changes from tripping the transformer's own circuit breaker to tripping the bypass circuit breaker, the bypass circuit breaker's own protection needs to be disabled. Therefore, in the bypass transformer breaker mode, the bypass circuit breaker failure protection is not adapted to the bypass transformer operation mode because the protection logic cannot adapt to the bypass transformer operation mode.

[0004] To sum up, the protection adopted by the six unified designs does not take into account the implementation method of the bypass circuit breaker failure protection under the bypass transformer circuit breaker mode. Therefore, the bypass circuit breaker failure protection needs to be disabled. If the transformer fails at this time and the bypass circuit breaker fails, the fault cannot be cleared by the bypass circuit breaker failure protection and can only be cleared by the backup protection of other equipment in the power grid. First, the fault clearing time is long, affecting the safe and stable operation of the power grid. Second, it violates the relevant provisions of DL / T 559 "Operation and Setting Procedures for Relay Protection Devices of 220kV~750kV Power Grids" and "Eighteen Major Anti-Accident Measures for Power Grids of State Grid Corporation of China": No electrical equipment is allowed to operate without protection. Summary of the Invention

[0005] The purpose of the present invention is to provide a relay protection method for bypass circuit breaker failure in bypass transformer mode, so as to solve the technical problem of bypass circuit breaker protection failure in a 220kV substation with double busbars and bypass busbar connection when the bypass circuit breaker replaces the transformer circuit breaker operation mode.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A relay protection method for bypass circuit breaker failure in a bypass transformer mode, comprising:

[0008] 1) Use the unused transformer branch in the 220kV busbar protection to form the corresponding circuits for busbar protection and failure protection of the bypass circuit breaker;

[0009] 2) Access to the bypass disconnector position contacts:

[0010] The position contacts 1G and 2G of the bypass disconnectors for sections I and II are connected to the 220kV busbar protection, forming a circuit for the bypass breaker branch current to participate in the current calculation of section I or section II busbar protection. When the bypass breaker operates in the transformer breaker replacement mode, the bypass current is connected to the vacant transformer branch in the busbar protection. The inputs of the auxiliary contacts 1G and 2G, which reflect the busbar information on which the bypass breaker is operating, are also synchronously connected to the corresponding transformer branch in the busbar protection, realizing busbar operation mode identification and busbar differential protection section I and section II busbar small differential current calculation.

[0011] 3) Technical solution for connecting the bypass circuit breaker secondary current to the busbar protection current loop:

[0012] The bypass circuit breaker CT secondary current I A , I B , I C , I NThe current branch of the idle transformer connected to the 220kV busbar protection constitutes the current of the bypass circuit breaker in the busbar protection for differential protection to calculate the differential current; on the other hand, it completes the current conversion in the busbar protection and converts the bypass circuit breaker CT secondary current I A , I B , I C , I N Converted into negative sequence current I2 and zero sequence current 3I0, phase current I φ , I2 and 3I0 are in a logical OR relationship, forming a current discrimination circuit for bypass circuit breaker failure protection;

[0013] 4) Technical solution for digital input access to busbar protection:

[0014] Inputs connected to busbar protection include: the electrical quantity protection tripping relay operating contacts for the No. 1 or No. 2 transformer tripping on the 220kV side, and the bypass circuit breaker protection operating contacts. 1TJ1 and 1TJ2 are the two pairs of operating contacts for the No. 1 main transformer electrical quantity protection output relay, and 2TJ1 and 2TJ2 are the two pairs of operating contacts for the No. 2 main transformer electrical quantity protection output relay. 1TJ1 or 2TJ1 contacts are used to release the re-pressure locking element of the busbar differential protection, while 1TJ2 or 2TJ2 contacts are used to start the circuit for the unoccupied transformer branch failure discrimination logic in the 220kV busbar protection. The bypass circuit breaker protection tripping relay operating contacts are connected to the unoccupied transformer branch failure discrimination logic in the 220kV busbar protection.

[0015] When the 220kV bypass circuit breaker replaces the 220kV circuit breaker of No. 1 transformer, if No. 1 transformer fails, the No. 1 transformer protection action output signal enters the busbar protection unoccupied transformer branch failure judgment logic through the pressure plate 1LP, and at the same time, the output signal enters the busbar protection release re-pressure locking element through the pressure plate 4LP; when the 220kV bypass circuit breaker replaces the 220kV circuit breaker of No. 2 transformer, if No. 2 transformer fails, the No. 2 transformer protection action output signal enters the busbar protection unoccupied transformer branch failure judgment logic through the pressure plate 1LP, and at the same time, the output signal enters the busbar protection release re-pressure locking element through the pressure plate 4LP; Board 2LP enters the busbar protection bypass circuit breaker failure judgment logic, and at the same time, the output signal enters the busbar protection release re-pressure locking element through the 5LP pressure board; when the 220kV bypass circuit breaker is empty charging the 220kV bypass bus or impacting the No. 1 and No. 2 transformers, the bypass circuit breaker itself needs to be enabled for protection. If the 220kV bypass bus or 220kV transformer fails at this time, the bypass circuit breaker protection output signal passes through the pressure board 3LP and enters the busbar protection bypass circuit breaker failure judgment logic;

[0016] The logic judgment and delay circuit of bypass circuit breaker failure protection are completed by the internal logic of busbar protection, and by the logic corresponding to the corresponding transformer branch when bypassing the transformer;

[0017] 5) Technical solution for transformer circuit breaker failure protection tripping output:

[0018] (1) Connect the output trip relay contact of the vacant transformer branch in the 220kV busbar protection in series with the throw-in / out pressure plate 1CLP to the trip circuit of the bypass circuit breaker protection panel to achieve failure protection tripping of the bypass circuit breaker;

[0019] (2) Connect the failure output contact of the vacant transformer branch in the 220kV busbar protection to the failure tripping input circuit of the No. 1 transformer protection panel in series with the throw-in / out pressure plate 2CLP and the switching pressure plate 3CLP. If any of the phase current, negative sequence current and zero sequence current is greater than the set value, the No. 1 transformer protection main output will be activated after a 50ms delay to realize the failure protection tripping of the circuit breakers on both sides of the No. 1 transformer; or connect the failure output contact of the vacant transformer branch in the 220kV busbar protection to the throw-in / out pressure plate 2CLP and the switching pressure plate 3CLP in series to realize the failure tripping input circuit of the No. 1 transformer protection panel. Pressure plate 2CLP and switching pressure plate 4CLP are connected to the failure tripping circuit of the protection panel of transformer No. 2. If any of the phase current, negative sequence current and zero sequence current is greater than the set value, the main protection outlet of transformer No. 2 is started after a 50ms delay, and the circuit breakers on both sides of transformer No. 2 are tripped for failure protection. When the bypass circuit breaker fails, the 220kV busbar protection will trip the busbar circuit breaker after a delay of t1 time after failure judgment, and will trip all circuit breakers on the bus where the bypass circuit breaker is located after a delay of t2 time.

[0020] The purpose of the present invention can be further achieved by the following technical measures:

[0021] The relay protection method for bypass circuit breaker failure in the bypass transformer mode mentioned above is as follows:

[0022] The method for judging whether there is current in the bypass circuit breaker 2DL is to collect the secondary winding current I of the current transformer of the bypass circuit breaker 2DL respectively. A , I B , I C , I N , and converted into phase current I φ , negative sequence current I2 and zero sequence current 3I0, whether there is a fault current is determined by the phase current, negative sequence current and zero sequence current. The current setting principles are as follows:

[0023] Phase current setting value: Set the current value to ensure sufficient sensitivity to two-phase short-circuit faults under the minimum operating mode of the transformer low-voltage side, with a sensitivity coefficient of ≥1.5;

[0024] Negative sequence current setting value: It is set based on the sufficient sensitivity of the asymmetric short-circuit fault of the low-voltage side busbar of the transformer in the minimum operating mode, with a sensitivity coefficient of ≥2.0;

[0025] Zero-sequence current setting value: It is set with sufficient sensitivity to the minimum grounding fault of the 110kV side busbar of the transformer in the minimum operating mode, and the sensitivity coefficient is ≥2.0.

[0026] The relay protection method for bypass circuit breaker failure in the bypass transformer mode mentioned above is as follows:

[0027] The calculation formula of negative sequence current I2 is: A2 =1 / 3(I A +α 2 I B +αI C ), I B2 =1 / 3(I B +α 2 I C +αI A ),

[0028] I C2 =1 / 3(I C +α 2 I A +αI B );

[0029] The calculation formula of zero sequence current 3I0 is: 3I0=1 / 3(I A +I B +I C ).

[0030] The relay protection method for bypass circuit breaker failure under the bypass transformer mode mentioned above is as follows: after determining that the bypass circuit breaker has failed, the 220kV bus tie circuit breaker is tripped after a delay of t1, where t1 is 50 milliseconds; and all circuit breakers of the faulty bus are tripped after a delay of t2, where t2 is 200 milliseconds.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention is a method for relay protection of bypass circuit breaker failure in a 220kV substation double busbar with bypass busbar connection, in which a bypass circuit breaker replaces a transformer circuit breaker in operation mode, and has the following advantages:

[0033] 1. This invention connects the No. 1 or No. 2 transformer protection trip signal, the bypass breaker protection trip signal, and the bypass breaker CT secondary current to the unused transformer branch of the six-unified busbar protection system, creating bypass breaker failure protection in bypass transformer mode. This prevents the bypass breaker from operating without failure protection in bypass transformer mode, enabling rapid fault removal, ensuring safe and stable grid operation, and improving grid power supply reliability.

[0034] 2. Through the switching on and off of the pressure plate, this bypass circuit breaker failure protection is also applicable to the bypass circuit breaker failure protection in the bypass circuit breaker no-charge 220kV bypass bus mode and the bypass circuit breaker No. 1 or No. 2 transformer mode.

[0035] 3. The solution of the present invention is simple, practical, easy to implement, and utilizes existing protection devices. There is no need to reconfigure the protection devices, no increase in equipment investment, no additional costs, and good economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the primary main wiring diagram of transformer No. 1 or No. 2 in a 220kV substation;

[0037] Figure 2 This is the bypass circuit breaker failure protection principle diagram in bypass transformer or bypass circuit breaker no-charge mode;

[0038] Figure 3 This is the schematic diagram of the transformer circuit breaker failure protection trip output;

[0039] Figure 4 This is the main transformer failure interlocking circuit diagram. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown, the power transmission and distribution network applied by the present invention is a 220kV substation double busbar with bypass primary main connection system network. The primary main connection of the 220kV system of the transmission and distribution network includes: 220kV busbar section I and busbar section II connected to the 220kV circuit breaker bay of transformer No. 1 or transformer No. 2, the 220kV bypass circuit breaker bay and the 220kV busbar section I and busbar section II voltage transformers (hereinafter referred to as PTs); the transformer 220kV circuit breaker bay is connected to the busbar side disconnector, 220kV side circuit breaker 1DL, current transformer 1LH, transformer side disconnector and bypass busbar side disconnector; the 220kV bypass circuit breaker bay is equipped with the busbar side disconnector, 220kV bypass circuit breaker 2DL, current transformer 2LH, bypass busbar side disconnector, and the 220kV bypass circuit breaker bay is connected to the 220kV bypass busbar; the 220kV bypass busbar is connected to transformer No. 1 or No. 2 through the 220kV bypass disconnector of transformer No. 1 or No. 2.

[0042] When bypass breaker 2DL replaces transformer breaker 1DL, bypass breaker failure protection is disabled because it was not initially designed. This relay protection method is proposed for bypass breaker failure protection in 220kV substations with dual busbars and bypass busbars in transmission and distribution networks. This method can be used to replace the transformer breaker with a bypass breaker.

[0043] 1. Bypass circuit breaker failure protection configuration scheme:

[0044] Circuit breaker failure protection generally consists of three parts: starting circuit, logic judgment and delay circuit and tripping output circuit.

[0045] 1.1 Selection of busbar protection circuit breaker branches

[0046] Busbar protection designed according to the six unified standards typically includes 24 branches: one bus tie breaker branch, 17 line breaker branches, four transformer breaker branches, and two backup branches. Currently, 220kV substations are typically equipped with only two or three transformers, utilizing two or three 220kV transformer branches. Unused transformer branches (such as those for transformers 3 or 4) in the 220kV busbar protection can be utilized to form bypass breaker busbar protection and failure protection circuits.

[0047] 1.2 Access to the bypass disconnector position contacts

[0048] The bypass disconnector position contacts 1G and 2G for busbar sections I and II are connected to the 220kV busbar protection, forming a loop for the bypass breaker branch current to participate in the current calculation for busbar section I or II protection. When the bypass breaker operates in transformer breaker replacement mode, the bypass current is connected to the vacant transformer branch No. 3 or No. 4 in the busbar protection. The inputs of the auxiliary contacts 1G and 2G, which reflect the busbar on which the bypass breaker is operating, must also be connected to the corresponding transformer branch in the busbar protection to identify the busbar operating mode and calculate the small differential current for busbar sections I and II of the busbar differential protection.

[0049] 1.3 Solution for connecting the bypass circuit breaker secondary current to the busbar protection current loop

[0050] The bypass circuit breaker CT secondary current I A , I B , I C , I N The current branch of the No. 3 or No. 4 transformer connected to the 220kV busbar protection, on the one hand, constitutes the current of the bypass circuit breaker in the busbar protection, which is used for differential protection to calculate the differential current; on the other hand, it completes the current conversion in the busbar protection and converts the secondary current I A , I B , I C , I N Converted into negative sequence current I2 and zero sequence current 3I0, phase current I φ (Including the phase current I of phases A, B, and C A , I B , I C ), I2 and 3I0 are in an "OR gate" relationship, forming a current discrimination circuit for bypass circuit breaker failure protection. Figure 2 .

[0051] 1.4 Digital input access busbar protection scheme

[0052] The inputs connected to busbar protection include: the electrical quantity protection trip relay operating contacts for the 220kV side of transformer No. 1 or No. 2, and the bypass circuit breaker protection operating contacts. 1TJ1 and 1TJ2 are the two pairs of operating contacts for the No. 1 main transformer electrical quantity protection output relay, while 2TJ1 and 2TJ2 are the two pairs of operating contacts for the No. 2 main transformer electrical quantity protection output relay. 1TJ1 or 2TJ1 contacts are used to release the re-pressure blocking element of the busbar differential protection, while 1TJ2 or 2TJ2 contacts are used to initiate the failure discrimination logic for the vacant No. 3 or No. 4 transformer branch in the 220kV busbar protection. Furthermore, the bypass circuit breaker protection trip relay operating contacts are connected to the failure discrimination logic for the vacant No. 3 or No. 4 transformer branch in the 220kV busbar protection.

[0053] When the 220kV bypass circuit breaker replaces the No. 1 transformer 220kV circuit breaker and is in operation, if the No. 1 transformer fails, the No. 1 transformer protection action output signal enters the busbar protection vacant No. 3 transformer or No. 4 transformer branch failure judgment logic through the pressure plate 1LP (since the vacant branch is used for the bypass circuit breaker branch, it is collectively referred to as the bypass circuit breaker failure judgment logic below). At the same time, the output signal enters the busbar protection release re-pressure locking element through the 4LP pressure plate; when the 220kV bypass circuit breaker replaces the No. 2 transformer 220kV circuit breaker and is in operation, if the No. 2 transformer fails, the No. 1 transformer protection action output signal enters the busbar protection vacant No. 3 transformer or No. 4 transformer branch failure judgment logic through the pressure plate 1LP (since the vacant branch is used for the bypass circuit breaker branch, it is collectively referred to as the bypass circuit breaker failure judgment logic below). If the transformer fails, the protection action of transformer No. 2 will trigger the output signal to enter the busbar protection bypass circuit breaker failure judgment logic through the pressure plate 2LP. At the same time, the output signal will enter the busbar protection release re-pressure locking element through the 5LP pressure plate. In addition, when the 220kV bypass circuit breaker is empty charging the 220kV bypass bus or impacting transformers No. 1 and No. 2, the bypass circuit breaker itself needs to be enabled. If the 220kV bypass bus or 220kV transformer fails at this time, the bypass circuit breaker protection output signal will enter the busbar protection bypass circuit breaker failure judgment logic through the pressure plate 3LP.

[0054] 1.5 Start-up judgment circuit of bypass circuit breaker failure protection

[0055] The protection trip relay action contacts and current discrimination in 1.3 and 1.4 together constitute the start-up discrimination circuit for bypass circuit breaker failure protection.

[0056] 1.6 Logical judgment and delay circuit of bypass circuit breaker failure protection

[0057] The logic judgment and delay circuit of bypass circuit breaker failure protection are completed by the internal logic of busbar protection, such as Figure 2 When the bypass transformer mode is used, the logic corresponding to the corresponding transformer branch is used to complete the operation.

[0058] 1.7 Transformer circuit breaker failure protection tripping output scheme

[0059] The “six unified” standard protection stipulates that busbar protection and circuit breaker failure protection share one output relay.

[0060] 1) Connect the trip relay contacts of the vacant No. 3 or No. 4 transformer branch in the 220kV busbar protection in series with the throw-in / out pressure plate 1CLP to the trip circuit of the bypass circuit breaker protection panel to achieve failure protection and trip the bypass circuit breaker. Figure 3 ;

[0061] 2) Connect the failure output contact of the vacant No. 3 or No. 4 transformer branch in the 220kV busbar protection in series with the throw-in / out pressure plate 2CLP and the switching pressure plate 3CLP to the failure inter-tripping circuit of the No. 1 transformer protection panel. According to the current judgment (any current among the phase current, negative sequence current and zero sequence current is greater than the set value), the No. 1 transformer protection main output is started after a 50ms delay to achieve failure protection tripping of the circuit breakers on both sides of the No. 1 transformer; or connect the failure output contact of the vacant No. 3 or No. 4 transformer branch in the 220kV busbar protection in series with the throw-in / out pressure plate 2CLP and the switching pressure plate 4CLP to the failure inter-tripping circuit of the No. 2 transformer protection panel. According to the current judgment (any current among the phase current, negative sequence current and zero sequence current is greater than the set value), the No. 2 transformer protection main output is started after a 50ms delay to achieve failure protection tripping of the circuit breakers on both sides of the No. 2 transformer, see Figure 3 When the bypass circuit breaker fails, after failure identification, the 220kV busbar protection will trip the bus tie circuit breaker after a delay of t1, and will trip all circuit breakers on the bus where the bypass circuit breaker is located after a delay of t2.

[0062] 2. Setting of current setting value and time setting value of bypass circuit breaker

[0063] In the above-mentioned relay protection method for bypass circuit breaker failure protection in the bypass circuit breaker replacement transformer circuit breaker operation mode, the method for judging whether there is current in the bypass circuit breaker 2DL is to respectively collect the secondary winding current I of the current transformer of the bypass circuit breaker 2DL. A , I B , I C , I N , and converted into phase current I φ , negative sequence current I2 and zero sequence current 3I0, the phase current, negative sequence current and zero sequence current are used to determine whether there is a fault current. The setting principles of the above currents are as follows:

[0064] Phase current setting value: Set the current value to ensure sufficient sensitivity to two-phase short-circuit faults under the minimum operating mode of the transformer low-voltage side, with a sensitivity coefficient of ≥1.5;

[0065] Negative sequence current setting value: It is set based on the sufficient sensitivity of the asymmetric short-circuit fault of the low-voltage side busbar of the transformer in the minimum operating mode, with a sensitivity coefficient of ≥2.0;

[0066] Zero-sequence current setting value: It is set with sufficient sensitivity to the minimum grounding fault of the 110kV side busbar of the transformer in the minimum operating mode, and the sensitivity coefficient is ≥2.0.

[0067] The calculation formula of negative sequence current I2 is: A2 =1 / 3(I A +α 2 I B +αI C ), I B2 =1 / 3(I B +α 2 I C +αI A ), I C2 =1 / 3(I C +α 2 I A +αI B ).

[0068] The calculation formula of zero sequence current 3I0 is: 3I0=1 / 3(I A +I B +I C ).

[0069] The above bypass circuit breaker failure protection method trips the 220kV bus tie circuit breaker after determining that the bypass circuit breaker has failed, with a delay of t1 being 50 milliseconds; and trips all circuit breakers of the faulty busbar after a delay of t2 being 200 milliseconds.

[0070] This solution can also be used for bypass circuit breaker failure protection in bypass operation mode in substations with double busbars and bypass busbars at other voltage levels.

[0071] Provide the specific embodiment of the method of the present invention below:

[0072] 1.1 Implementation of bypass circuit breaker failure protection when the bypass circuit breaker replaces the No. 1 transformer circuit breaker

[0073] When the bypass circuit breaker 2DL replaces the No. 1 transformer circuit breaker 1DL in operation, the bypass circuit breaker 2DL is in operation, the No. 1 transformer circuit breaker 1DL is in cold standby, and the No. 1 transformer bypass disconnector is in operation. The 1LP and 4LP pressure plates are put into operation, and the 2LP, 3LP and 5LP pressure plates are withdrawn. The secondary current of the bypass 2DL circuit breaker CT is connected to the vacant No. 3 or No. 4 transformer branch in the busbar protection. In this operating mode, if the No. 1 transformer fails and the bypass circuit breaker 2DL fails. The No. 1 transformer protection output signal 1TJ2 enters the No. 3 or No. 4 transformer failure judgment logic in the busbar protection through the pressure plate 1LP, and the output signal 1TJ1 enters the busbar protection release re-pressure locking element through the 4LP pressure plate. In addition, since the fault does not disappear after the No. 1 transformer protection is activated, there is current in the bypass circuit breaker branch, and the bypass circuit breaker CT secondary current I A , I B , I C , I N Entering the No. 3 or No. 4 transformer branch in busbar protection, the phase current I φ The presence of current is determined by either negative-sequence current I2 or zero-sequence current 3I0. The No. 1 transformer protection output relay operates and outputs a signal, the bypass circuit breaker presence criteria, and the "composite voltage element" form an "AND gate" relationship. When all of these conditions are met, the 220kV bus tie circuit breaker trips after a delay of t1, and all circuit breakers on the faulty bus (including the bypass circuit breaker) trip after a delay of t2.

[0074] 1.2 Implementation of bypass circuit breaker failure protection when the bypass circuit breaker replaces the No. 2 transformer circuit breaker

[0075] When bypass circuit breaker 2DL replaces the No. 2 transformer circuit breaker, the bypass circuit breaker failure protection is implemented in the same way as when the bypass circuit breaker replaces the No. 1 transformer circuit breaker, and will not be repeated here.

[0076] 1.3 Implementation of Bypass Breaker Failure Protection in Bypass Breaker No-Charge 220kV Bypass Busbar Mode

[0077] When the bypass breaker 2DL is in no-charge operation on the 220kV bypass bus, the bypass breaker 2DL is in operation, the bypass breaker's own protection is enabled, the 3LP pressure plate is put into operation, and the 1LP, 2LP, 4LP and 5LP pressure plates are withdrawn. In this operating mode, if the 220kV bypass bus fails and the bypass breaker 2DL fails, the bypass breaker protection output signal CKJ enters the No. 3 or No. 4 transformer failure judgment logic in the bus protection through the pressure plate 3LP. In addition, since the fault does not disappear after the bypass breaker protection is activated, there is current in the bypass breaker, and the bypass breaker CT secondary current I A , I B , I C , I NEnters the No. 3 or No. 4 transformer failure judgment logic in the busbar protection and is converted into phase current I φ , negative sequence current I2 and zero sequence current 3I0, where I φ , I2, and 3I0 form an OR relationship. Since the fault point is located on the 220kV bypass busbar and is electrically close, the composite voltage element must meet the requirements. The bypass breaker protection trip signal, the bypass breaker current criterion, and the composite voltage element form an AND relationship. When all these conditions are met, the 220kV bus tie breaker trips after a delay of t1, and all circuit breakers on the faulty busbar trip after a delay of t2.

[0078] 1.4 Implementation of bypass circuit breaker failure protection in bypass circuit breaker empty charge (no load) mode of No. 1 transformer

[0079] When the bypass breaker 2DL is in no-charge operation and the No. 1 transformer is in operation, the bypass breaker 2DL is in operation, the No. 1 transformer protection is enabled, the bypass breaker's own protection is enabled, the 1LP, 3LP and 4LP pressure plates are put into operation, and the 2LP and 5LP pressure plates are withdrawn. In this operating mode, if the 220kV transformer fails and the bypass breaker 2DL fails, the No. 1 transformer protection output signal 1TJ2 and the bypass breaker protection output signal CKJ enter the No. 3 or No. 4 transformer failure judgment logic in the busbar protection through the pressure plates 1LP and 3LP respectively. At the same time, the No. 1 transformer protection action output signal 1TJ1 enters the busbar protection release re-pressure locking element through the 4LP pressure plate. In addition, since the fault has not disappeared after the No. 1 transformer protection and the bypass breaker protection are activated, there is current in the bypass breaker, and the bypass breaker CT secondary current I A , I B , I C , I N Enters the No. 3 or No. 4 transformer failure judgment logic in the busbar protection and is converted into phase current I φ , negative sequence current I2 and zero sequence current 3I0, where I φ , I2, and 3I0 form an OR relationship. Transformer No. 1 protection trip signal, the bypass breaker protection trip signal, the bypass breaker current criterion, and the composite voltage element form an AND relationship. When all of these conditions are met, the 220kV bus tie breaker trips after a delay of t1, and all circuit breakers on the faulty busbar trip after a delay of t2.

[0080] 1.5 Implementation of bypass circuit breaker failure protection under bypass circuit breaker no-load (no load) mode of No. 2 transformer

[0081] The implementation of bypass breaker failure protection in the bypass breaker no-charge mode for transformer No. 2 is the same as the implementation of bypass breaker failure protection in the bypass breaker no-charge mode for transformer No. 1, and will not be repeated here.

[0082] In addition to the above embodiments, the present invention may also have other implementation methods. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A relay protection method for bypass circuit breaker failure in a bypass transformer mode, characterized in that: include: 1) Use the unused transformer branch in the 220kV busbar protection to form the corresponding circuits for busbar protection and failure protection of the bypass circuit breaker; 2) Access to the bypass disconnector position contacts: The position contacts 1G of the busbar bypass disconnector for section I and 2G of the busbar bypass disconnector for section II are connected to the 220kV busbar protection, forming a circuit for calculating the current of the bypass breaker branch and participating in the current calculation of the busbar protection for section I or section II. When the bypass breaker is operating in the transformer breaker replacement mode, the bypass current is connected to the vacant transformer branch in the busbar protection. The position contacts 1G of the busbar bypass disconnector for section I and 2G of the busbar bypass disconnector for section II, which reflect the busbar on which the bypass breaker is operating, are also synchronously connected to the corresponding transformer branch in the busbar protection, realizing busbar operation mode identification and calculation of the small differential current of busbar sections I and II in the busbar differential protection. 3) The secondary current of the bypass circuit breaker is connected to the busbar protection current circuit: The bypass circuit breaker CT secondary current I A , I B , I C , I N The current branch of the idle transformer connected to the 220kV busbar protection constitutes the current of the bypass circuit breaker in the busbar protection for differential protection to calculate the differential current; on the other hand, it completes the current conversion in the busbar protection and converts the bypass circuit breaker CT secondary current I A , I B , I C , I N Converted into negative sequence current I2 and zero sequence current 3I0, phase current I φ , I2 and 3I0 are in a logical OR relationship, forming a current discrimination circuit for bypass circuit breaker failure protection; 4) Digital input access to busbar protection: Inputs connected to busbar protection include: the electrical quantity protection tripping relay operating contacts for the No. 1 or No. 2 transformer tripping on the 220kV side, and the bypass circuit breaker protection operating contacts. 1TJ1 and 1TJ2 are the two pairs of operating contacts for the No. 1 main transformer electrical quantity protection output relay, and 2TJ1 and 2TJ2 are the two pairs of operating contacts for the No. 2 main transformer electrical quantity protection output relay. 1TJ1 or 2TJ1 contacts are used to release the re-pressure locking element of the busbar differential protection, while 1TJ2 or 2TJ2 contacts are used to start the circuit for the unoccupied transformer branch failure discrimination logic in the 220kV busbar protection. The bypass circuit breaker protection tripping relay operating contacts are connected to the unoccupied transformer branch failure discrimination logic in the 220kV busbar protection. When the 220kV bypass circuit breaker replaces the 220kV circuit breaker of No. 1 transformer, if No. 1 transformer fails, the No. 1 transformer protection action output signal passes through the pressure plate 1LP and enters the busbar protection unused transformer branch failure judgment logic. At the same time, the output signal passes through the 4LP pressure plate and enters the busbar protection release re-pressure locking element; when the 220kV bypass circuit breaker replaces the 220kV circuit breaker of No. 2 transformer, if No. 2 transformer fails, the No. 2 transformer protection action output signal passes through the 4LP pressure plate and enters the busbar protection release re-pressure locking element. The 2LP pressure plate enters the busbar protection bypass circuit breaker failure judgment logic, and at the same time, the output signal enters the busbar protection release re-pressure locking element through the 5LP pressure plate; when the 220kV bypass circuit breaker is empty charging the 220kV bypass bus or impacting the No. 1 and No. 2 transformers, the bypass circuit breaker itself needs to be enabled for protection. If the 220kV bypass bus or 220kV transformer fails at this time, the bypass circuit breaker protection output signal passes through the 3LP pressure plate and enters the busbar protection bypass circuit breaker failure judgment logic; The logic judgment and delay circuit of bypass circuit breaker failure protection are completed by the internal logic of busbar protection, and by the logic corresponding to the corresponding transformer branch when bypassing the transformer; 5) Transformer circuit breaker failure protection trip output: (1) Connect the output trip relay contact of the vacant transformer branch in the 220kV busbar protection in series with the throw-in / out pressure plate 1CLP, and connect it to the trip circuit of the bypass circuit breaker protection panel to achieve failure protection tripping of the bypass circuit breaker; (2) Connect the failure output contact of the unoccupied transformer branch in the 220kV busbar protection to the throw-in / out pressure plate 2CLP and the switching pressure plate 3CLP in series, and connect it to the failure tripping input circuit of the No. 1 transformer protection panel. If any of the phase current, negative sequence current and zero sequence current is greater than the set value, the No. 1 transformer protection main output will be activated after a 50ms delay, and the failure protection will trip the circuit breakers on both sides of the No. 1 transformer. Alternatively, connect the failure output contact of the unoccupied transformer branch in the 220kV busbar protection to the throw-in / out pressure plate 2CLP and the switching pressure plate 3CLP in series, and connect it to the failure tripping input circuit of the No. 1 transformer protection panel. If any of the phase current, negative sequence current and zero sequence current is greater than the set value, the No. 1 transformer protection main output will be activated after a 50ms delay, and the circuit breakers on both sides of the No. 1 transformer will be tripped due to failure protection. Pressure plate 2CLP and switching pressure plate 4CLP are connected to the failure tripping circuit of the protection panel of transformer No.

2. If any of the phase current, negative sequence current and zero sequence current is greater than the set value, the main protection outlet of transformer No. 2 will be activated after a 50ms delay, and the circuit breakers on both sides of transformer No. 2 will be tripped for failure protection. When the bypass circuit breaker fails, the 220kV busbar protection will trip the busbar circuit breaker after a delay of t1 after failure judgment, and all circuit breakers on the bus where the bypass circuit breaker is located will trip after a delay of t2.

2. The relay protection method for bypass circuit breaker failure in bypass transformer mode according to claim 1, characterized in that: The method for judging whether there is current in the bypass circuit breaker 2DL is to collect the secondary winding current I of the current transformer of the bypass circuit breaker 2DL respectively. A , I B , I C , I N , and converted into phase current I φ , negative sequence current I2 and zero sequence current 3I0, whether there is a fault current is determined by the phase current, negative sequence current and zero sequence current. The current setting principles are as follows: Phase current setting value: Set the current value to ensure sufficient sensitivity to two-phase short-circuit faults under the minimum operating mode of the transformer low-voltage side, with a sensitivity coefficient of ≥1.5; Negative sequence current setting value: It is set based on the sufficient sensitivity of the asymmetric short-circuit fault of the low-voltage side busbar of the transformer in the minimum operating mode, with a sensitivity coefficient of ≥2.0; Zero-sequence current setting value: It is set with sufficient sensitivity to the minimum grounding fault of the 110kV side busbar of the transformer in the minimum operating mode, and the sensitivity coefficient is ≥2.

0.

3. The relay protection method for bypass circuit breaker failure in bypass transformer mode according to claim 1, characterized in that: The bypass circuit breaker failure protection method is to trip the 220kV bus tie circuit breaker after determining that the bypass circuit breaker has failed, after a delay of t1, t1 is 50 milliseconds; and to trip all circuit breakers of the faulty bus after a delay of t2, t2 is 200 milliseconds.

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