Non-full-phase protection method for circuit breaker on high-voltage side of main transformer in three-second wiring mode

Abstract

The invention provides a main transformer high-voltage side circuit breaker non-full-phase protection method in a three-second wiring mode, and the method comprises the steps: setting the three-phase inconsistent contact input of a circuit breaker to 1 when the three-phase contact positions of a middle circuit breaker or a side circuit breaker connected with the high-voltage side of a main transformer are inconsistent; configuring non-full-phase negative-sequence and zero-sequence current protection criteria by taking the transformer as a unit; recording the main transformer high-voltage side voltage and the bus voltage, making a difference between the main transformer high-voltage side voltage and the bus voltage, and calculating positive sequence and negative sequence voltage difference effective values of the main transformer high-voltage side voltage and the bus voltage; the positive sequence voltage difference is used as a protection starting criterion, meanwhile, a ratio criterion which takes the negative sequence voltage difference as an action quantity and takes the positive sequence voltage difference as a braking quantity is supplemented and proposed, and the ratio criterion and the starting criterion are subjected to AND logic to form non-full-phase voltage quantity protection; non-full-phase negative-sequence and zero-sequence current protection and non-full-phase voltage protection are used as' OR 'logic outlets; and when the switching value and the electrical quantity of the non-full-phase protection are set to be 1, the non-full-phase protection action of the main transformer high-voltage side circuit breaker is carried out, the tripping of the circuit breaker is delayed, and the failure protection is started.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection of electric power systems, and more specifically relates to a non-full-phase protection method for a circuit breaker on a high-voltage side of a main transformer in a two-thirds wiring mode. Background Art

[0002] Voltage levels of 220 kV and above usually use a switch phase-splitting mechanism to enable the circuit breaker to have phase-splitting operation capabilities (for large power plants, it is generally the circuit breaker on the high-voltage side of the main transformer), but mechanical problems such as circuit breaker mechanism failure or electrical problems such as operating circuit failure will cause the circuit breaker to have an abnormal operating state with inconsistent three-phase switches. For the circuit breaker on the high-voltage side of the main transformer, the asymmetry of non-full-phase abnormal operation is equivalent to adding negative-sequence and zero-sequence fault sources on the high-voltage side of the main transformer, generating significant negative-sequence and zero-sequence current components, and generating a negative-sequence current component with a larger amplitude on the low-voltage side, which will not only threaten the safe operation of the generator, but may also cause the zero-sequence current protection of the power grid to trip. It is a more serious grid-related fault and requires the configuration of a dedicated circuit breaker non-full-phase protection.

[0003] In existing research results and engineering applications, the circuit breaker non-full-phase protection has been relatively complete, but there are still some problems to be solved in the special application scenario of the two-thirds wiring method: the high-voltage side of the main transformer of a large power station is connected to a 500kV two-thirds wiring substation. According to the countermeasure requirements, the failure protection needs to be activated when the three-phase inconsistency of the circuit breaker on the high-voltage side of the main transformer is required. However, for the two-thirds wiring method, when either the circuit breaker on the high-voltage side of the main transformer or the circuit breaker is operating normally, even if the other circuit breaker has a three-phase inconsistency, the generator set is still in normal operation, and the failure protection should not be activated to avoid expanding the scope of the fault.

[0004] In view of the problems existing in the existing methods, an improved method for non-full-phase protection of the circuit breaker on the high-voltage side of the main transformer under the two-thirds wiring mode is proposed. Summary of the invention

[0005] In order to solve the current technical problems, the main purpose of the present invention is to provide a non-full-phase protection method for the circuit breaker on the high-voltage side of the main transformer under the two-thirds wiring mode, which aims to avoid the false start of failure protection caused by the non-full-phase single circuit breaker on the high-voltage side of the main transformer, and will not expand the scope of the fault impact.

[0006] In order to realize the above technical features, the object of the present invention is achieved as follows: a non-full-phase protection method for a main transformer high-voltage side circuit breaker in a two-thirds wiring mode comprises the following steps: S1. When the three-phase contact positions of the circuit breaker or side circuit breaker connected to the high-voltage side of the main transformer are inconsistent, the three-phase inconsistent contact input of the circuit breaker is set to 1, that is, the switch value of non-full-phase protection is set to 1; S2. Configure non-full-phase negative-sequence and zero-sequence current protection criteria based on transformers; S3. Record the voltage on the high-voltage side of the main transformer and the bus voltage, make a difference and calculate the effective value of the positive-sequence and negative-sequence voltage difference between the voltage on the high-voltage side of the main transformer and the bus voltage; use the positive-sequence voltage difference between the voltage on the high-voltage side of the main transformer and the bus voltage as the protection start criterion, and at the same time, propose a ratio criterion with the negative-sequence voltage difference as the action amount and the positive-sequence voltage difference as the braking amount, and make an "AND" logic with the start criterion to form a non-full-phase voltage protection; S4. Make the non-full-phase negative-sequence and zero-sequence current protection and the non-full-phase voltage protection into "OR" logic output, that is, if any protection is activated, the electrical quantity of the non-full-phase protection is set to 1; when the switch quantity and electrical quantity of the non-full-phase protection are both set to 1, the non-full-phase protection of the circuit breaker on the high-voltage side of the main transformer is activated, and the circuit breaker is tripped with a delay and the failure protection is started.

[0007] Preferably, S2 includes: S21. The current analyzed by the negative-sequence and zero-sequence current protection is taken from the bushing current on the high-voltage side of the main transformer or the sum current of the two circuit breakers on the high-voltage side.

[0008] Preferably, S3 includes: S31. The starting criterion for the positive sequence voltage difference protection between the main transformer high voltage side voltage and the bus voltage is: ; In the formula, is the effective value of the positive sequence voltage difference between the high voltage side voltage of the main transformer and the bus voltage, is the voltage setting value; considering the transformer ratio k Influence, set the setting value to ; S32. To avoid mis-starting of the protection described in step S31 due to system disturbances, impacts and occasional factors of voltage measurement errors, a ratio criterion with negative sequence voltage difference as the action amount and positive sequence voltage difference as the braking amount is constructed, specifically: ; In the formula, It is the effective value of the negative sequence voltage difference between the high voltage side voltage of the main transformer and the bus voltage.

[0009] On the other hand, the present invention also provides a non-full-phase protection system for a main transformer high-voltage side circuit breaker in a two-thirds wiring mode, comprising: a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium and execute the method according to any one of claims 1 to 3.

[0010] The present invention has the following beneficial effects: 1. The present invention proposes for the first time to use the positive-sequence voltage difference between the high-voltage side voltage of the main transformer and the bus voltage as a protection starting criterion, and at the same time supplements a ratio criterion using the negative-sequence voltage difference as the action amount and the positive-sequence voltage difference as the braking amount, and performs "AND" logic with the starting criterion to form a non-full-phase voltage protection.

[0011] 2. The non-full-phase improved protection method proposed in the present invention has strong reliability, can avoid false start of failure protection caused by non-full-phase single circuit breaker on the high-voltage side of the main transformer, and will not expand the scope of fault impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0013] Figure 1 A protection logic diagram of a non-full-phase protection method for a main transformer high-voltage side circuit breaker under a two-thirds wiring mode provided in an embodiment of the present invention.

[0014] Figure 2 Schematic diagram of the overall simulation model in an embodiment of the present invention.

[0015] Figure 3 The A-phase line of the circuit breaker 12 is broken in the embodiment of the present invention, and the changes of the three-phase current flowing through the high-voltage side of the main transformer, and the effective values ​​of the negative-sequence and zero-sequence currents at various locations before and after the fault.

[0016] Figure 4 It shows the A-phase line break of the circuit breaker 12 in the embodiment of the present invention, the effective value of the positive-sequence and negative-sequence voltage difference between the high-voltage side voltage of the main transformer and the bus voltage, and the action of the voltage protection criterion.

[0017] Figure 5 The A-phase of the circuit breakers 12 and 13 is broken in the embodiment of the present invention, and the changes of the three-phase current flowing through the high-voltage side of the main transformer, and the effective values ​​of the negative-sequence and zero-sequence currents at various locations before and after the fault.

[0018] Figure 6 It shows the A-phase disconnection of the circuit breakers 12 and 13 in the embodiment of the present invention, the effective value of the positive-sequence and negative-sequence voltage difference between the high-voltage side voltage of the main transformer and the bus voltage, and the action of the voltage protection criterion. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0020] Embodiment 1: The present invention provides a non-full-phase protection method for a main transformer high voltage side circuit breaker in a two-thirds wiring mode, such as Figure 1 As shown, the proposed method specifically includes: S1. When the three-phase contact positions of the circuit breaker or side circuit breaker connected to the high-voltage side of the main transformer are inconsistent, the three-phase inconsistent contact input of the circuit breaker is set to 1, that is, the switch value of non-full-phase protection is set to 1; S2. Configure non-full-phase negative-sequence and zero-sequence current protection criteria based on transformers; Specifically, step S2 includes: S21. The current analyzed by the negative-sequence and zero-sequence current protection is taken from the bushing current on the high-voltage side of the main transformer or the sum current of the two circuit breakers on the high-voltage side.

[0021] S3. Record the high-voltage side voltage of the main transformer and the bus voltage, make a difference and calculate the effective value of the positive-sequence and negative-sequence voltage difference between the high-voltage side voltage of the main transformer and the bus voltage. Use the positive-sequence voltage difference between the high-voltage side voltage of the main transformer and the bus voltage as the protection start criterion, and at the same time, propose a ratio criterion with the negative-sequence voltage difference as the action amount and the positive-sequence voltage difference as the braking amount, and make an "AND" logic with the start criterion to form a non-full-phase voltage protection; Specifically, step S3 includes: S31. The starting criterion for the positive sequence voltage difference protection between the main transformer high voltage side voltage and the bus voltage is: ; In the formula, is the effective value of the positive sequence voltage difference between the high voltage side voltage of the main transformer and the bus voltage, is the voltage setting value. Consider the transformer ratio k Influence, set the setting value to .

[0022] S32. In order to avoid mis-starting of the protection shown in S31 due to incidental factors such as system disturbance, impact, voltage measurement error, etc., a ratio criterion with negative sequence voltage difference as the action amount and positive sequence voltage difference as the braking amount is constructed, specifically: ; In the formula, It is the effective value of the negative sequence voltage difference between the high voltage side voltage of the main transformer and the bus voltage.

[0023] S4. Make the non-full-phase negative-sequence and zero-sequence current protection and the non-full-phase voltage protection into an "OR" logic output, that is, if any protection is activated, the electrical quantity of the non-full-phase protection is set to 1; when the switch quantity and electrical quantity of the non-full-phase protection are both set to 1, the non-full-phase protection of the circuit breaker on the high-voltage side of the main transformer is activated, and the circuit breaker is tripped with a delay and the failure protection is started.

[0024] The effectiveness of the proposed protection and positioning method is verified through simulation below.

[0025] Built using PSCAD / EMTDC software Figure 2The simulation model of the substation with two-thirds connection mode is shown. Among them, the rated capacity of generators 1 and 2 is 300 MVA, the rated voltage of the generators is 18 kV, and the rated current is 9.62 kA. The connection mode of the main transformer is Yn / d11, and the transformation ratio is 525 / 18 kV. The positive sequence voltage difference setting value between the high-voltage side voltage of the main transformer and the bus voltage is 87.5 V.

[0026] Set the A phase of circuit breaker 12 to be disconnected, the fault time is 0.4s, record the three-phase current flowing through the high-voltage side of the main transformer before and after the fault, and calculate the changes in the effective values ​​of the negative-sequence and zero-sequence currents at various locations before and after the fault, such as Figure 3 As shown. It can be found that the negative sequence and zero sequence current judgment criteria on the high voltage side of the main transformer do not work. Considering that the system is still in normal operation at this time, the circuit breaker non-full-phase protection should not work, so the correctness of the following conclusion is verified: the non-full-phase protection of the circuit breaker on the high voltage side of the main transformer under the two-thirds wiring mode should be configured with the transformer as a unit. Record the voltage on the high voltage side of the main transformer and the bus voltage, make a difference and calculate the effective value of the positive sequence and negative sequence voltage difference between the voltage on the high voltage side of the main transformer and the bus voltage, and obtain the action of the voltage protection judgment criteria as shown in Figure 4 It can be found that the difference between the high-voltage side voltage of the main transformer and the bus voltage is less than 0.5V, and the action value of the voltage protection criterion is much smaller than the set value, that is, the proposed voltage protection criterion will not malfunction.

[0027] Set the A phase of circuit breakers 12 and 13 to be disconnected, the fault time is 0.4s, record the three-phase current flowing through the high-voltage side of the main transformer before and after the fault, and calculate the changes in the effective values ​​of the negative-sequence and zero-sequence currents at various locations before and after the fault, such as Figure 5 Record the high-voltage side voltage of the main transformer and the bus voltage, make a difference and calculate the positive and negative sequence voltage difference effective value between the high-voltage side voltage of the main transformer and the bus voltage, and obtain the action of the voltage protection criterion as shown in Figure 6 It can be found that the voltage difference amplitude corresponding to the fault increases rapidly, and the effective value of the positive sequence voltage difference can reach tens of kV, which is much larger than the set value of 87.5V; in addition, the negative sequence voltage difference also increases significantly after the fault, and its effective value is greater than 0.67 times of the positive sequence voltage difference, so the voltage protection criterion can operate correctly.

Claims

1. A non-full-phase protection method for a main transformer high-voltage side circuit breaker under a two-thirds wiring mode, characterized in that: The following steps are involved: S1. When the three-phase contact positions of the circuit breaker or side circuit breaker connected to the high-voltage side of the main transformer are inconsistent, the three-phase inconsistent contact input of the circuit breaker is set to 1, that is, the switch value of non-full-phase protection is set to 1; S2. Configure non-full-phase negative-sequence and zero-sequence current protection criteria based on transformers; S3. Record the voltage on the high-voltage side of the main transformer and the bus voltage, make a difference and calculate the effective value of the positive-sequence and negative-sequence voltage difference between the voltage on the high-voltage side of the main transformer and the bus voltage; use the positive-sequence voltage difference between the voltage on the high-voltage side of the main transformer and the bus voltage as the protection start criterion, and at the same time, propose a ratio criterion with the negative-sequence voltage difference as the action amount and the positive-sequence voltage difference as the braking amount, and make an "AND" logic with the start criterion to form a non-full-phase voltage protection; S4. Make the non-full-phase negative-sequence and zero-sequence current protection and the non-full-phase voltage protection into an "OR" logic output, that is, if any protection is activated, the electrical quantity of the non-full-phase protection is set to 1; When the switch quantity and electrical quantity of the non-full-phase protection are both set to 1, the non-full-phase protection of the circuit breaker on the high-voltage side of the main transformer will be activated, and the circuit breaker will be tripped with a delay and the failure protection will be started.

2. According to the non-full-phase protection method of the main transformer high-voltage side circuit breaker in the two-thirds wiring mode as described in claim 1, it is characterized in that: The S2 includes: S21. The current analyzed by the negative-sequence and zero-sequence current protection is taken from the bushing current on the high-voltage side of the main transformer or the sum current of the two circuit breakers on the high-voltage side.

3. According to the non-full-phase protection method of the main transformer high-voltage side circuit breaker in the two-thirds wiring mode as described in claim 1, it is characterized in that: The S3 includes: S31. The starting criterion for the positive sequence voltage difference protection between the main transformer high voltage side voltage and the bus voltage is: ； In the formula, is the effective value of the positive sequence voltage difference between the high voltage side voltage of the main transformer and the bus voltage, is the voltage setting value; considering the transformer ratio k Influence, set the setting value to ; S32. To avoid mis-starting of the protection described in step S31 due to system disturbances, impacts and occasional factors of voltage measurement errors, a ratio criterion with negative sequence voltage difference as the action amount and positive sequence voltage difference as the braking amount is constructed, specifically: ； In the formula, It is the effective value of the negative sequence voltage difference between the high voltage side voltage of the main transformer and the bus voltage.

4. The non-full-phase protection system of the circuit breaker on the high-voltage side of the main transformer under the two-thirds wiring mode is characterized by: include: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium and execute the method according to any one of claims 1 to 3.

Images