Fault current time-to-zero fast recognition and controllable damping opening system and method

Abstract

The application discloses a kind of fault current delay over-zero fast identification and controllable damping opening system and method, it is related to electrical fault opening technical field.The system includes three-phase linkage main break, damping module, current acquisition unit and controller.Current acquisition unit is used to acquire three-phase current signal;Controller is used to construct target interphase loop current under native two-phase interphase short-circuit condition, and construct residual interphase loop current according to remaining two phases after first phase natural arc extinguishing under three-phase short-circuit condition;In local estimation time window, according to target interphase loop current, local periodic component amplitude and local non-periodic component are reconstructed, and whether target interphase loop has natural over-zero condition is judged.Damping module can realize the input, keep and exit of damping.The application can quickly identify fault current delay over-zero risk, and only controllable damping is implemented to target interphase loop existing delay over-zero risk, which is beneficial to improve the rapidity and reliability of fault current opening control.

Description

Technical Field

[0001] This invention relates to the field of electrical fault interruption technology, and in particular to a fault current delay zero-crossing rapid identification and controllable damping interruption system and method. Background Technology

[0002] Generator fault currents often contain strong aperiodic components and high current asymmetry under three-phase or two-phase short-circuit conditions. When the absolute value of the aperiodic component exceeds the amplitude of the periodic component, the current loses its natural zero-crossing point, resulting in a delayed zero-crossing phenomenon. Since the current zero point is an important condition for the reliable arc-extinguishing and breaking of AC circuit breakers, delayed zero-crossing will cause the fault to arc for a long time, making it difficult to quickly and reliably break the fault current.

[0003] To quickly restore the natural zero-crossing condition of the delayed zero-crossing fault current, damping can be applied to accelerate the decay of the aperiodic component. However, whether damping needs to be applied, which loop it should be applied to, and when it should be deactivated all depend on the degree of fault current asymmetry and the availability of its corresponding zero point. Therefore, the ability to accurately identify the degree of asymmetry of the target fault current in a short time is crucial for achieving on-demand damped interruption control.

[0004] Existing methods for identifying fault current asymmetry and determining delayed zero crossing often rely on waveform simulation over long time windows, making it difficult to quickly determine whether the current meets the conditions for natural zero crossing within a short period during fault interruption. Furthermore, existing damping control approaches often directly determine damping requirements based on the degree of asymmetry in single-phase currents during the initial stage of a three-phase short circuit, failing to adequately consider the residual interphase loop formed after the first phase's arc extinguishing following three-phase linkage tripping. This can easily lead to inaccurate damping targeting or unnecessary damping action.

[0005] In summary, the industry currently lacks a fault current interruption technology that can quickly identify the risk of zero-crossing delay, accurately switch damping, and balance equipment safety and interruption efficiency. Summary of the Invention

[0006] The purpose of this invention is to propose a system and method for rapid identification and controllable damping interruption of fault current with delayed zero crossing. Addressing issues such as difficulty in timely assessment of generator source fault current with delayed zero crossing risk, inaccurate damping targeting, and increased device load due to continuous damping, this invention constructs a target phase-to-phase loop current, rapidly identifies the relationship between its periodic and aperiodic components within a local estimation time window, and adjusts damping as needed based on zero-point availability, thereby improving the accuracy and speed of fault current interruption control with delayed zero crossing.

[0007] To achieve the above objectives, this invention proposes a fault current delay zero-crossing rapid identification and controllable damping interruption system, comprising: a three-phase linkage main interruptor, a damping module, a current acquisition unit, and a controller. The three-phase linkage main circuit includes a three-phase vacuum circuit in the three-phase circuit, which is used to synchronously receive the tripping command and execute the three-phase linkage tripping after a fault occurs. The damping module is installed in the circuit where the vacuum break is located in each phase, and is used to engage or disengage damping as needed in the corresponding phase circuit; The current acquisition unit is used to acquire three-phase current signals; The controller is used for: Under the condition of a native two-phase phase-to-phase short circuit, the target phase-to-phase loop current is directly constructed. Alternatively, under three-phase short-circuit conditions, after the first phase naturally extinguishes its arc, the residual interphase loop current is constructed based on the remaining two phases, and this residual interphase loop current is used as the target interphase loop current. ; Within the local estimation time window, based on the target phase-to-phase loop current... The local current information is used to reconstruct the local periodic component amplitude and local aperiodic component of the target phase-to-phase loop; Based on the amplitude of the local periodic component and the local non-periodic component, it is determined whether the target phase-to-phase loop has the natural zero-crossing condition; when the determination result is that it does not have the natural zero-crossing condition, the damping module corresponding to the target phase-to-phase loop is controlled to engage damping to accelerate the decay of the non-periodic component of the target phase-to-phase loop; when the damping holding time reaches the preset value, the zero-point condition is restored, and the damping module is controlled to exit.

[0008] Preferably, the target phase-to-phase loop current The calculation formula is as follows: ; in, , These are the phase currents of the two phases corresponding to the target phase-to-phase loop, respectively. m and n It refers to the two faulty phases under the original two-phase phase-to-phase short circuit condition, or the two phases that continue to conduct after the first phase naturally extinguishes its arc under the three-phase short circuit condition.

[0009] Preferably, the damping module of each phase is connected in series in the circuit where the vacuum break of the corresponding phase is located, and each phase damping module includes three parallel branches: a main current-carrying branch, a damping branch, and a deactivation branch; wherein, during normal operation and the fault-free undamped stage, the current flows through the main current-carrying branch; during the damping activation stage, the current is transferred from the main current-carrying branch to the damping branch; during the damping deactivation stage, the current is transferred from the damping branch to the deactivation branch.

[0010] Preferably, the main current-carrying branch is connected in series with an air circuit breaker (ACB), the damping branch is connected in series with a metal oxide varistor (MOV), and the exit branch is connected in series with a thyristor (SCR). When damping is required, the ACB in the corresponding two-phase damping module of the target phase-to-phase circuit is tripped, and the arc voltage driving current of the ACB tripping circuit is transferred from the main current-carrying branch to the MOV damping branch. When damping needs to be deactivated, the controller triggers the SCR of the corresponding two phases in the target phase-to-phase circuit to conduct, so that the current is transferred from the MOV damping branch to the deactivation branch.

[0011] Preferably, the clamping voltage of the MOV in each phase damping module is The arc voltage generated when the corresponding phase air circuit breaker ACB is tripped is And satisfy < This ensures that the current can be quickly switched from the ACB main current-carrying branch to the MOV damping branch when the damping is applied.

[0012] Preferably, the controller estimates the target phase-to-phase loop current within a local estimation time window. It can be represented as a superposition of local periodic components and local aperiodic components, as shown in the following formula: ; in, For the amplitude of the local periodic component, It is the power frequency angular frequency. It is a local aperiodic component. It is a local phase; The controller at the current determination time t 0. Obtain the target phase-to-phase loop current. The current value, first derivative, and second derivative are obtained, and the local aperiodic components are reconstructed according to the following formula. and local periodic component amplitude : ; ; The controller uses the following criteria to determine whether the target phase-to-phase loop has a natural zero-crossing condition: When satisfied At that time, it is determined that the target phase-to-phase loop has the natural zero-crossing condition; When satisfied When the target phase-to-phase circuit does not meet the natural zero-crossing condition, a damping activation command is issued.

[0013] Preferably, when the controller determines that the target phase-to-phase loop does not meet the natural zero-crossing condition, it controls the two-phase damping module corresponding to the target phase-to-phase loop to engage damping, so that the target phase-to-phase loop is effectively introduced with total constant voltage damping. The preset value for the damping hold time is... , The offline tuning is based on the condition that the aperiodic component of the target phase-to-phase loop reaches the target attenuation ratio when the damping is released, so that the aperiodic component of the target phase-to-phase loop attenuates to the preset ratio during the damping holding time. The formula is as follows: ; in, The natural decay time constant of the target phase-to-phase loop is... The equivalent resistance of the target phase-to-phase circuit. The amplitude of the aperiodic component of the target phase-to-phase loop at the moment of damping activation. The target attenuation ratio, and 0 < <1.

[0014] Preferably, the total constant pressure damping It is formed by the equivalent MOV clamping voltage of the two-phase damping module corresponding to the target phase-to-phase circuit; When the MOV clamping voltage of the two-phase damping module corresponding to the target phase-to-phase circuit is both At that time, the total constant pressure damping satisfy =2 ; Among them, after the two phase damping modules corresponding to the target phase-to-phase loop are simultaneously put into operation, the total constant voltage damping... The polarity of the target phase-to-phase loop is opposite to that of the aperiodic component, so as to accelerate the decay of the aperiodic component of the target phase-to-phase loop.

[0015] This invention also provides a method for rapid identification and controllable damping interruption of fault current with zero-crossing delay, applied to the aforementioned system for rapid identification and controllable damping interruption of fault current with zero-crossing delay. The specific steps are as follows: Step S1: Detect the fault and control the three-phase linkage main circuit breaker to trip synchronously; Step S2: Construct the target phase-to-phase loop current according to the fault type. Under the condition of a primary two-phase phase-to-phase short circuit, the target phase-to-phase loop current is directly constructed from the faulty two-phase current; under the condition of a three-phase short circuit, the natural arc extinction of the first phase is detected, and the residual phase-to-phase loop current is constructed from the continuing conduction current of the two phases after the natural arc extinction of the first phase, and the residual phase-to-phase loop current is used as the target phase-to-phase loop current. Step S3: Sample the target phase-to-phase loop current within the local estimation time window and calculate the current determination time. t The current value at 0, the first derivative, and the second derivative; Step S4: Reconstruct the amplitude of the local periodic component of the target phase-to-phase loop based on the current value, the first derivative, and the second derivative. and local aperiodic components ; Step S5, based on and The magnitude relationship is used to determine whether the target phase-to-phase loop meets the natural zero-crossing condition; when ≤ When the target phase-to-phase loop is determined to have the natural zero-crossing condition, damping is not engaged or the already engaged damping is disengaged; when > When it is determined that the target phase-to-phase loop does not meet the natural zero-crossing condition, damping is applied only to the two phases corresponding to the target phase-to-phase loop; Step S6: After the corresponding two-phase damping module is activated, the target phase-to-phase circuit is effectively introduced with total constant voltage damping. Accelerates the decay of the non-periodic components of the target phase-to-phase loop; Step S7: When the damping duration reaches the preset value, the zero-point condition is restored, and the corresponding two phases are controlled to exit damping, so that the target phase-to-phase circuit resumes natural decay and completes the opening at the subsequent natural zero point.

[0016] Therefore, this invention proposes a fault current delay zero-crossing rapid identification and controllable damping interruption system and method, the beneficial effects of which are as follows: (1) This invention uses a local short time window combined with the higher-order derivative of the current to analyze the current component, abandoning the traditional long time window waveform fitting algorithm. It can complete the fault current delay zero-crossing risk judgment in milliseconds, which meets the timing requirements of rapid fault interruption and greatly improves the control response speed.

[0017] (2) This invention addresses the different operating conditions of two-phase short circuit and three-phase short circuit after the first phase arc is extinguished and a residual circuit is formed. It constructs the target phase-to-phase circuit current differently and applies damping only to the two-phase circuit with the risk of delay crossing zero. This effectively avoids the problems of incorrect damping switching and ineffective action in traditional schemes.

[0018] (3) By introducing reverse constant voltage damping to rapidly attenuate the non-periodic component of the current, the present invention forces the fault current to return to the natural zero crossing point, which completely solves the problem of long-term arcing of the circuit breaker outlet caused by delayed zero crossing, ensuring stable arc extinguishing and reliable fault clearing of the switching equipment, and maintaining the safe operation of the power system.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the generator source fault current delay zero crossing in an embodiment of the present invention; Figure 2 This is a schematic diagram of the controllable damping module structure and its installation position in an embodiment of the present invention; Figure 3This is a schematic diagram of the interruption result under the condition of three-phase short circuit fault where the remaining phase needs to be damped after the first phase is extinguished; wherein, (a) is a schematic diagram of the interruption result under the condition of three-phase short circuit fault without damping, and (b) is a schematic diagram of the interruption result under the condition of three-phase short circuit fault with damping. Figure 4 The diagram shows the breaking results under the condition of damping required under the original two-phase phase-to-phase short-circuit fault in the embodiment of the present invention; wherein, (a) is a schematic diagram of the breaking results under the condition of no damping under the original two-phase phase-to-phase short-circuit fault, and (b) is a schematic diagram of the breaking results under the condition of damping under the original two-phase phase-to-phase short-circuit fault. Figure 5 This is a flowchart of the fault current delay zero-crossing rapid identification and controllable damping interruption method in an embodiment of the present invention. Detailed Implementation

[0021] To make the technical solutions, advantages, and objectives of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0023] Example 1 like Figure 1 As shown, generator fault currents under three-phase or two-phase short-circuit conditions may contain strong aperiodic components. When the absolute value of the aperiodic component exceeds the amplitude of the periodic component, the fault current loses its natural zero-crossing point, resulting in a delayed zero-crossing phenomenon. Since the natural zero-crossing point of the current is an important condition for AC circuit breakers to achieve arc-extinguishing interruption, it is necessary to quickly identify the degree of asymmetry of the target fault current during the interruption process and determine whether to engage damping based on its zero-crossing availability.

[0024] This invention proposes a fault current delay zero-crossing rapid identification and controllable damping interruption system, comprising: a three-phase linkage main break, a damping module, a current acquisition unit, and a controller; The three-phase linkage main circuit includes a three-phase vacuum circuit set in the three-phase circuit, which is used to synchronously receive the tripping command and execute the three-phase linkage tripping after a fault occurs. The damping module is installed in the circuit where the vacuum break is located in each phase, and is used to engage or disengage the damping in the corresponding phase circuit as needed; The current acquisition unit is used to acquire three-phase current signals; The controller is used to directly construct the target phase-to-phase loop current under the condition of a native two-phase phase-to-phase short circuit. Alternatively, under three-phase short-circuit conditions, after the first phase naturally extinguishes its arc, the residual interphase loop current is constructed based on the remaining two phases, and this residual interphase loop current is used as the target interphase loop current. ; Within the local estimation time window, based on the target phase-to-phase loop current... The local current information is used to reconstruct the local periodic component amplitude and local aperiodic component of the target phase-to-phase loop; The system determines whether the target phase-to-phase loop has the natural zero-crossing condition based on the amplitude of the local periodic component and the local non-periodic component. When the determination result is that the natural zero-crossing condition is not met, the damping module corresponding to the target phase-to-phase loop is controlled to engage damping to accelerate the decay of the non-periodic component of the target phase-to-phase loop. When the damping holding time reaches the preset value, the zero-point condition is restored, and the damping module is controlled to exit.

[0025] In this embodiment, the target phase-to-phase loop current The calculation formula is as follows: ; in, , These are the phase currents of the two phases corresponding to the target phase-to-phase loop, respectively. m and n It refers to the two faulty phases under the original two-phase phase-to-phase short circuit condition, or the two phases that continue to conduct after the first phase naturally extinguishes its arc under the three-phase short circuit condition.

[0026] like Figure 2 As shown, the damping module of each phase is connected in series in the circuit where the vacuum break of the corresponding phase is located, and each phase damping module includes three parallel branches: the main current-carrying branch, the damping branch, and the deactivation branch. During normal operation and the non-damped fault stage, the current flows through the main current-carrying branch; during the damping activation stage, the current is transferred from the main current-carrying branch to the damping branch; during the damping deactivation stage, the current is transferred from the damping branch to the deactivation branch.

[0027] In this embodiment, an air circuit breaker ACB is connected in series in the main current-carrying branch, a metal oxide varistor MOV is connected in series in the damping branch, and a thyristor SCR is connected in series in the outgoing branch. When damping is required, the ACB in the corresponding two-phase damping module of the target phase-to-phase circuit is tripped, and the arc voltage driving current of the ACB tripping circuit is transferred from the main current-carrying branch to the MOV damping branch. When damping needs to be deactivated, the controller triggers the SCR of the corresponding two phases in the target phase-to-phase circuit to conduct, so that the current is transferred from the MOV damping branch to the deactivation branch.

[0028] In this embodiment, the clamping voltage of the MOV in each phase damping module is The arc voltage generated when the corresponding phase air circuit breaker ACB is tripped is And satisfy < This ensures that the current can be quickly switched from the ACB main current-carrying branch to the MOV damping branch when the damping is applied.

[0029] In this embodiment of the invention, the controller estimates the target phase-to-phase loop current within a local estimation time window. It can be represented as a superposition of local periodic components and local aperiodic components, as shown in the following formula: ; in, For the amplitude of the local periodic component, It is the power frequency angular frequency. It is a local aperiodic component. It is a local phase; The controller at the current decision moment t 0. Obtain the target phase-to-phase loop current The current value, first derivative, and second derivative are obtained, and the local aperiodic components are reconstructed according to the following formula. and local periodic component amplitude : ; ; The controller uses the following criteria to determine whether the target phase-to-phase loop has the natural zero-crossing condition: When satisfied At that time, it is determined that the target phase-to-phase loop has the natural zero-crossing condition; When satisfied When the target phase-to-phase circuit does not meet the natural zero-crossing condition, a damping activation command is issued.

[0030] In this embodiment, when the controller determines that the target phase-to-phase loop does not meet the natural zero-crossing condition, it controls the two-phase damping module corresponding to the target phase-to-phase loop to engage damping, so that the target phase-to-phase loop is effectively introduced with total constant voltage damping. The preset value for the damping hold time is... , The offline tuning is based on the condition that the aperiodic component of the target phase-to-phase loop reaches the target attenuation ratio when the damping is released, so that the aperiodic component of the target phase-to-phase loop attenuates to the preset ratio during the damping holding time. The formula is as follows: ; in, The natural decay time constant of the target phase-to-phase loop is... The equivalent resistance of the target phase-to-phase circuit. The amplitude of the aperiodic component of the target phase-to-phase loop at the moment of damping activation. The target attenuation ratio, and 0 < <1.

[0031] In this embodiment, the total constant pressure damping It is formed by the equivalent MOV clamping voltage of the two-phase damping module corresponding to the target phase-to-phase circuit; When the MOV clamping voltage of the two-phase damping module corresponding to the target phase-to-phase circuit is both At that time, total constant pressure damping satisfy =2 ; Among them, after the two-phase damping modules corresponding to the target phase-to-phase circuit are simultaneously put into operation, the total constant voltage damping... The polarity of the target phase-to-phase loop is opposite to that of the aperiodic component, so as to accelerate the decay of the aperiodic component of the target phase-to-phase loop.

[0032] Example 2 like Figure 5 As shown, the present invention also provides a method for rapid identification and controllable damping interruption of fault current with delayed zero crossing, applied to the aforementioned system for rapid identification and controllable damping interruption of fault current with delayed zero crossing. The specific steps are as follows: Step S1: Detect the fault and control the three-phase linkage main circuit breaker to trip synchronously; Step S2: Construct the target phase-to-phase loop current according to the fault type. Under the condition of a primary two-phase phase-to-phase short circuit, the target phase-to-phase loop current is directly constructed from the faulty two-phase current; under the condition of a three-phase short circuit, the natural arc extinction of the first phase is detected, and the residual phase-to-phase loop current is constructed from the continuing conduction current of the two phases after the natural arc extinction of the first phase, and the residual phase-to-phase loop current is used as the target phase-to-phase loop current. Step S3: Sample the target phase-to-phase loop current within the local estimation time window and calculate the current determination time. t The current value at 0, the first derivative, and the second derivative; Step S4: Reconstruct the amplitude of the local periodic component of the target phase-to-phase loop based on the current value, first derivative, and second derivative. and local aperiodic components ; Step S5, based on and The magnitude relationship is used to determine whether the target phase-to-phase loop meets the natural zero-crossing condition; when ≤ When the target phase-to-phase loop is determined to have the natural zero-crossing condition, damping is not engaged or the already engaged damping is disengaged; when > When it is determined that the target phase-to-phase loop does not meet the natural zero-crossing condition, damping is only applied to the two phases corresponding to the target phase-to-phase loop. Step S6: After the corresponding two-phase damping module is activated, the target phase-to-phase circuit is effectively introduced with total constant voltage damping. Accelerates the decay of the non-periodic components of the target phase-to-phase loop; Step S7: When the damping duration reaches the preset value, the zero-point condition is restored, and the corresponding two phases are controlled to exit damping, so that the target phase-to-phase circuit resumes natural decay and completes the opening at the subsequent natural zero point.

[0033] Example 3 To verify the effectiveness of the above system and method, this embodiment establishes a generator source fault current interruption simulation model. This model includes a synchronous generator, a three-phase linked vacuum main circuit breaker, each phase damping module, a fault branch, a current acquisition unit, and a controller. The three-phase linked vacuum main circuit breaker is used to simulate the three-phase synchronous tripping process after a fault; each phase damping module adopts the following... Figure 2 The diagram shows the structure of the main current-carrying branch, damping branch, and disconnection branch; the controller continuously collects the three-phase current after the main circuit breaker is tripped, and constructs the target phase-to-phase loop current according to the fault type. Then, the asymmetry is quickly identified within the local estimation time window, and a decision is made on whether to apply damping based on this.

[0034] In this embodiment, the generator has a rated power of 200MW and a rated voltage of 13.8kV. The single-phase MOV clamping voltage is taken as... =2.0 kV, target attenuation ratio is taken as =2 / 3, the most unfavorable target phase-to-phase loop natural decay time constant is taken as... =0.8s. Damping hold time obtained from offline tuning. =3.64ms, rounded to the nearest integer in actual control. =4ms. The three-phase current sampling interval is set to 0.50ms, and the local estimation time window length is set to 5.00ms. For the three-phase short-circuit switching condition, after the arc extinction of the first phase is detected, a short protection delay of 5.00ms is set to reduce the impact of the instantaneous disturbance during the switching on the local derivative estimation.

[0035] like Figure 3 As shown, this embodiment first verifies the operating condition where damping is required after a three-phase short circuit transition. In this condition, after a three-phase short circuit occurs, the three-phase linkage main circuit breaks synchronously open. Phase A extinguishes its arc naturally first, while phases B and C continue to conduct, forming a residual interphase loop. Without damping, the residual interphase loop after the first phase extinguishes its arc still exhibits a significant time delay before zero crossing, making it difficult for the remaining two phases to extinguish their arcs naturally within the expected time. Using the method of this invention, after the controller detects the arc extinguishing of the first phase and after a preset short protection delay, the target interphase loop current is constructed from the currents of phases B and C. The asymmetry is rapidly identified within the local estimation time window. Since the target phase-to-phase loop lacks a natural zero-crossing condition, the controller issues damping activation commands to the damping modules corresponding to phases B and C. After the damping modules are activated, the target phase-to-phase loop is effectively introduced with total constant-pressure damping. The non-periodic component decays rapidly; after the damping is maintained for a preset time, the controller triggers the corresponding two-phase SCR to turn on, causing the MOV damping branch to stop working. Figure 3 The results show that, by using the method of the present invention, the zero-crossing time of the residual phase-to-phase circuit is significantly shortened, and the fault current can recover to its natural zero point and complete the interruption.

[0036] like Figure 4 As shown, this embodiment also verifies the operating condition where damping is required for a native two-phase phase-to-phase short circuit. In this condition, the target phase-to-phase circuit is composed of the two faulty phases from the moment the fault occurs. After the controller detects the fault and controls the three-phase linkage main circuit to open synchronously, the target phase-to-phase circuit current is directly constructed from the current of the two faulty phases. Within the local estimation time window, asymmetry is rapidly identified. When the target phase-to-phase loop does not meet the natural zero-crossing condition, the controller issues a damping activation command to the damping modules corresponding to the two faults. After damping activation, the MOV damping branch introduces total constant-voltage damping into the target phase-to-phase loop. This accelerates the decay of aperiodic components; after the damping is maintained for a preset time, the SCR exits the conduction of the branch, causing the MOV damping branch to exit operation. Figure 4 The results show that, for native two-phase short circuits, the present invention can also accurately identify the time-delay zero-crossing risk of the target phase-to-phase circuit and restore the natural zero point of the fault current by controlling the input and output of damping.

[0037] Depend on Figure 3 and Figure 4 It is understood that the present invention can cover three typical operating conditions: damping required after a three-phase short circuit transition and damping required for a primary two-phase interphase short circuit. Compared with the method of directly determining the damping requirement based on the single-phase asymmetry at the initial stage of a three-phase short circuit, the present invention uses whether the target interphase circuit has a natural zero-crossing condition as the criterion, which can more accurately determine the damping target and timing. At the same time, by preset the damping holding time and the SCR bypass exit method, the MOV can be prevented from absorbing energy continuously for a long time, thus improving the speed and economy of damping interruption control.

[0038] It is worth noting that all contents not described in detail in this invention are existing technologies and are well known to those skilled in the art.

[0039] Therefore, this invention provides a system and method for rapid identification and controllable damping interruption of fault current with delayed zero crossing. By constructing the target phase-to-phase loop current, the local periodic component amplitude and local aperiodic component of the target phase-to-phase loop are reconstructed within a local estimation time window. The relationship between these two components is used to determine whether the target phase-to-phase loop possesses the natural zero-crossing condition. When the target phase-to-phase loop does not possess the natural zero-crossing condition, damping is applied only to the corresponding two phases for a short time, and the damping is deactivated after the damping duration reaches a preset value. This invention enables rapid identification of fault current asymmetry and on-demand control of damping interruption, improving the accuracy and reliability of generator-source delayed zero-crossing fault current interruption control.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A fault current delay-zero-crossing rapid identification and controllable damping interruption system, characterized in that, include: Three-phase linkage main break, damping module, current acquisition unit and controller; The three-phase linkage main circuit includes a three-phase vacuum circuit in the three-phase circuit, which is used to synchronously receive the tripping command and execute the three-phase linkage tripping after a fault occurs. The damping module is installed in the circuit where the vacuum break is located in each phase, and is used to engage or disengage damping as needed in the corresponding phase circuit; The current acquisition unit is used to acquire three-phase current signals; The controller is used for: Under the condition of a native two-phase phase-to-phase short circuit, the target phase-to-phase loop current is directly constructed. Alternatively, under three-phase short-circuit conditions, after the first phase naturally extinguishes its arc, the residual interphase loop current is constructed based on the remaining two phases, and this residual interphase loop current is used as the target interphase loop current. ; Within the local estimation time window, based on the target phase-to-phase loop current... The local current information is used to reconstruct the local periodic component amplitude and local aperiodic component of the target phase-to-phase loop; Based on the amplitude of the local periodic component and the local non-periodic component, it is determined whether the target phase-to-phase loop has the natural zero-crossing condition; when the determination result is that it does not have the natural zero-crossing condition, the damping module corresponding to the target phase-to-phase loop is controlled to engage damping to accelerate the decay of the non-periodic component of the target phase-to-phase loop; when the damping holding time reaches the preset value, the zero-point condition is restored, and the damping module is controlled to exit.

2. The fault current delay zero-crossing rapid identification and controllable damping interruption system according to claim 1, characterized in that, Target interphase loop current The calculation formula is as follows: ； in, , These are the phase currents of the two phases corresponding to the target phase-to-phase loop, respectively. m and n It refers to the two faulty phases under the original two-phase phase-to-phase short circuit condition, or the two phases that continue to conduct after the first phase naturally extinguishes its arc under the three-phase short circuit condition.

3. The fault current delay zero-crossing rapid identification and controllable damping interruption system according to claim 2, characterized in that, The damping module of each phase is connected in series in the circuit where the vacuum break of the corresponding phase is located, and each phase damping module includes three parallel branches: a main current-carrying branch, a damping branch, and a deactivation branch. During normal operation and the non-damped fault stage, the current flows through the main current-carrying branch; during the damping activation stage, the current is transferred from the main current-carrying branch to the damping branch; during the damping deactivation stage, the current is transferred from the damping branch to the deactivation branch.

4. The fault current delay zero-crossing rapid identification and controllable damping interruption system according to claim 3, characterized in that, The main current-carrying branch is connected in series with an air circuit breaker (ACB), the damping branch is connected in series with a metal oxide varistor (MOV), and the exit branch is connected in series with a thyristor (SCR). When damping is required, the ACB in the corresponding two-phase damping module of the target phase-to-phase circuit is tripped, and the arc voltage driving current of the ACB tripping circuit is transferred from the main current-carrying branch to the MOV damping branch. When damping needs to be deactivated, the controller triggers the SCR of the corresponding two phases in the target phase-to-phase circuit to conduct, so that the current is transferred from the MOV damping branch to the deactivation branch.

5. The fault current delay zero-crossing rapid identification and controllable damping interruption system according to claim 4, characterized in that, The clamping voltage of the MOV in each phase damping module is The arc voltage generated when the corresponding phase air circuit breaker ACB is tripped is And satisfy < This ensures that the current can be quickly switched from the ACB main current-carrying branch to the MOV damping branch when the damping is applied.

6. The fault current delay zero-crossing rapid identification and controllable damping interruption system according to claim 5, characterized in that, The controller will estimate the target phase-to-phase loop current within a local estimation time window. It can be represented as a superposition of local periodic components and local aperiodic components, as shown in the following formula: ； in, For the amplitude of the local periodic component, It is the power frequency angular frequency. It is a local aperiodic component. It is a local phase; The controller at the current determination time t 0. Obtain the target phase-to-phase loop current. The current value, first derivative, and second derivative are obtained, and the local aperiodic components are reconstructed according to the following formula. and local periodic component amplitude : ； ； The controller uses the following criteria to determine whether the target phase-to-phase loop has a natural zero-crossing condition: When satisfied At that time, it is determined that the target phase-to-phase loop has the natural zero-crossing condition; When satisfied When the target phase-to-phase circuit does not meet the natural zero-crossing condition, a damping activation command is issued.

7. The fault current delay zero-crossing rapid identification and controllable damping interruption system according to claim 6, characterized in that, When the controller determines that the target phase-to-phase loop does not meet the natural zero-crossing condition, it controls the two-phase damping module corresponding to the target phase-to-phase loop to engage damping, so that the target phase-to-phase loop is effectively introduced with total constant voltage damping. The preset value for the damping hold time is... , The offline tuning is based on the condition that the aperiodic component of the target phase-to-phase loop reaches the target attenuation ratio when the damping is released, so that the aperiodic component of the target phase-to-phase loop attenuates to the preset ratio during the damping holding time. The formula is as follows: ； in, The natural decay time constant of the target phase-to-phase loop is... The equivalent resistance of the target phase-to-phase circuit. The amplitude of the aperiodic component of the target phase-to-phase loop at the moment of damping activation. The target attenuation ratio, and 0 < <1.

8. The fault current delay zero-crossing rapid identification and controllable damping interruption system according to claim 7, characterized in that, The total constant pressure damping It is formed by the equivalent MOV clamping voltage of the two-phase damping module corresponding to the target phase-to-phase circuit; When the MOV clamping voltage of the two-phase damping module corresponding to the target phase-to-phase circuit is both At that time, the total constant pressure damping satisfy =2 ; Among them, after the two phase damping modules corresponding to the target phase-to-phase loop are simultaneously put into operation, the total constant voltage damping... The polarity of the target phase-to-phase loop is opposite to that of the aperiodic component, so as to accelerate the decay of the aperiodic component of the target phase-to-phase loop.

9. A method for rapid identification and controllable damping interruption of fault current with delayed zero crossing, applied to the rapid identification and controllable damping interruption system for fault current with delayed zero crossing as described in any one of claims 1 to 8, characterized in that, The specific steps are as follows: Step S1: Detect the fault and control the three-phase linkage main circuit breaker to trip synchronously; Step S2: Construct the target phase-to-phase loop current according to the fault type. Under the condition of a primary two-phase phase-to-phase short circuit, the target phase-to-phase loop current is directly constructed from the faulty two-phase current; under the condition of a three-phase short circuit, the natural arc extinction of the first phase is detected, and the residual phase-to-phase loop current is constructed from the continuing conduction current of the two phases after the natural arc extinction of the first phase, and the residual phase-to-phase loop current is used as the target phase-to-phase loop current. Step S3: Sample the target phase-to-phase loop current within the local estimation time window and calculate the current determination time. t The current value at 0, the first derivative, and the second derivative; Step S4: Reconstruct the amplitude of the local periodic component of the target phase-to-phase loop based on the current value, the first derivative, and the second derivative. and local aperiodic components ; Step S5, based on and The magnitude relationship is used to determine whether the target phase-to-phase loop meets the natural zero-crossing condition; when ≤ When the target phase-to-phase loop is determined to have the natural zero-crossing condition, damping is not engaged or the already engaged damping is disengaged; when > When it is determined that the target phase-to-phase loop does not meet the natural zero-crossing condition, damping is applied only to the two phases corresponding to the target phase-to-phase loop; Step S6: After the corresponding two-phase damping module is activated, the target phase-to-phase circuit is effectively introduced with total constant voltage damping. Accelerates the decay of the non-periodic components of the target phase-to-phase loop; Step S7: When the damping duration reaches the preset value, the zero-point condition is restored, and the corresponding two phases are controlled to exit damping, so that the target phase-to-phase circuit resumes natural decay and completes the opening at the subsequent natural zero point.

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