A method and system for preventing malfunction of an active intervention arc extinguishing device in parallel with an arc extinguishing coil

Abstract

The present invention discloses a method and system for preventing false operation of an active intervention type arc extinguishing device in parallel with an arc extinguishing coil, and belongs to the field of energy management / power supply and distribution technology. The present invention uses an acquisition module to collect the three-phase voltage and zero-sequence voltage of the system in real time. After the data is collected, the three-phase voltage, zero-sequence voltage and negative-sequence voltage after the system filtering are obtained through band-pass filtering and voltage synthesis. When the three-phase voltage and zero-sequence voltage suddenly change, the subsequent judgment criteria are started. The instantaneous negative-sequence voltage value at the moment of voltage sudden change is calculated; if the negative-sequence voltage value is greater than the threshold value for a period of time, it is determined that the system is grounded, and the corresponding fault phase switch is controlled to close. Otherwise, it is determined that the system has arc extinguishing coil series resonance, and the locking device performs grounding judgment to prevent resonance false operation. The present invention avoids the misjudgment of the resonance fault as a single-phase grounding fault, and ensures the safety and reliability of the fault phase judgment when the active intervention type arc extinguishing device and the arc extinguishing coil are operated in parallel.

Description

Technical Field

[0001] The present invention relates to the field of energy management / power supply and distribution technology, and more specifically, to a method and system for preventing false operation of an active intervention arc extinguishing device in parallel with an arc extinguishing coil. Background Art

[0002] When a 6-35kV system with its neutral point grounded via an arc suppression coil is grounded, the arc suppression coil compensation current will try to reduce the grounding current at the grounding point, so that the current flowing through the arc suppression coil is close to the total grounding capacitance of the system. Therefore, the inductive reactance of the arc suppression coil and the capacitive reactance of the total grounding capacitance of the system are always close to equal at the fundamental frequency. When the grounding fault disappears, the sudden change in zero-sequence voltage causes the stray capacitance of the system and the inductance of the arc suppression coil to release energy, which will inevitably cause series resonance of the system. Since the inductive reactance of the arc suppression coil is close to the capacitive reactance of the system grounding, the resonance point will be between 40 and 60 Hz. This resonance caused by the arc suppression coil will cause the three-phase voltage and zero-sequence voltage of the system to fluctuate, such as Figure 1 shown.

[0003] Active intervention arc suppression devices are used in medium-voltage distribution networks. When a ground fault occurs in the system, the device will determine the phase of the ground fault as quickly as possible and close the grounding switch corresponding to the fault, thereby quickly converting the unstable ground fault in the system into a stable metal ground in the cabinet, transferring the grounding current at the fault point into the cabinet, limiting the fault phase voltage to zero potential, and eliminating the system overvoltage caused by the ground fault.

[0004] After the grounding switch of the active intervention arc suppression device is actuated, it is necessary to determine whether the system grounding fault is a transient fault or a permanent fault. Therefore, after the grounding switch is actuated, it is necessary to open the switch again after a period of time to re-determine whether the fault still exists. The following two situations may occur at the moment the switch is opened:

[0005] In the first case, the system grounding has disappeared, e.g. Figure 1 As shown, the system will experience neutral point series resonance, and the system three-phase voltage and zero-sequence voltage will be in a resonant state. In this case, the device needs to quickly determine whether the system is in a grounded state or a resonant state.

[0006] In the second case, the system grounding still exists, and the system three-phase voltage and zero-sequence voltage show grounding characteristics. The fault phase voltage decreases, the non-fault phase voltage increases, and the zero-sequence voltage still exists. When high-resistance grounding occurs in the system, the grounding voltage characteristics and the resonant voltage characteristics are very similar in a short time.

[0007] Active-intervention arc suppression devices must be able to quickly distinguish between neutral-point series resonance and ground faults. In the event of a transient ground fault, they must quickly determine that the fault has resolved, preventing the device from malfunctioning. In the event of a permanent fault, when the grounding switch is open, they must be able to quickly determine whether the system is experiencing a ground fault or neutral-point resonance based on the characteristics of the three-phase voltage and zero-sequence voltage, thereby controlling the rapid closing of the switch in the corresponding faulted phase.

[0008] Related patents have been published for parallel operation of arc suppression coils and active intervention arc suppression devices. For example, patent publication number CN108879645A, titled "A device and method for parallel operation of arc suppression coils and active intervention arc suppression devices"; patent publication number CN112103935A, titled "Active intervention arc suppression device with resonant grounding characteristics"; and patent publication number CN113054638A, titled "A method for handling dynamic parallel grounding faults of arc suppression coils and active intervention arc suppression devices."

[0009] Regarding the existing solutions in the prior art, I would like to first explain that the technology of parallel operation of arc suppression coils and active intervention type arc suppression devices is not a mature technology. It is currently only being cautiously promoted and explored, and related technical difficulties need to be continuously resolved. In addition, the above-mentioned patent solutions specifically describe how to realize the method of parallel operation of arc suppression coils and active intervention type arc suppression devices, such as CN108879645A, which includes a primary device and a secondary device. In the primary device, the 10kV bus is connected to the grounding transformer, and the arc suppression coil is connected to the common point of the grounding transformer; in the substation, the 10kV bus ABC three phases are grounded through a phase switch respectively using an active intervention arc suppression device; by running the arc suppression coil in parallel with the active arc suppression device, the advantages of the two devices are combined to provide protection for the operation of the distribution network. CN113054638A solves the problem of differentiated judgment of grounding line selection and fault nature when the arc suppression coil and the active intervention arc suppression device are dynamically connected in parallel through the dynamic switching of the arc suppression branch and the resistance branch of the arc suppression coil device and the dynamic transformation of the compensation damping branch resistance of the active intervention arc suppression device. That is, the above patents involve methods and means for realizing the parallel operation of arc suppression coils and active intervention type arc suppression devices, as well as issues such as primary and secondary design. The issue of preventing misjudgment when the arc suppression coils and active intervention type arc suppression devices are operated in parallel is not addressed. Summary of the Invention

[0010] 1. Technical problem to be solved by the invention

[0011] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method and system for preventing false operation of an active intervention arc extinguishing device in parallel with an arc extinguishing coil; the present invention collects three-phase voltages, quickly calculates the negative sequence voltage of the system, and uses the negative sequence voltage to determine whether a system grounding fault exists when the system voltage fluctuates, thereby solving the problem of false operation of the active intervention arc extinguishing device when the arc extinguishing coil causes neutral point resonance.

[0012] 2. Technical solution

[0013] In order to achieve the above object, the technical solution provided by the present invention is:

[0014] The present invention provides a method for preventing malfunction of an active intervention arc extinguishing device in parallel operation with an arc extinguishing coil, the steps of which are as follows:

[0015] Step S1, obtaining the three-phase voltage and zero-sequence voltage of the system;

[0016] Step S2, performing digital bandpass filtering on the voltage signal collected in step S1;

[0017] Step S3: Using the filtered voltage signal to synthesize a negative sequence voltage signal;

[0018] Step S4, quickly calculating the three-phase voltage and zero-sequence voltage by the derivative method, and starting the subsequent judgment step S5 when the three-phase voltage and zero-sequence voltage suddenly change;

[0019] Step S5: Calculate the instantaneous negative-sequence voltage value at the moment when the voltage suddenly changes based on the sampling of step S3; if the negative-sequence voltage value is greater than the threshold value for a period of time, it is determined that the system is grounded, and the corresponding fault phase switch is controlled to close; otherwise, it is determined that the arc suppression coil series resonance occurs in the system, and the locking device performs a grounding judgment to prevent false operation due to resonance.

[0020] Furthermore, step S1 obtains the three-phase voltage and zero-sequence voltage of the system through a data acquisition module of an active intervention type arc extinguishing device, and the active intervention type arc extinguishing device is installed at the bus position of the system whose neutral point is grounded through an arc extinguishing coil.

[0021] Furthermore, step S2 uses Chebyshev II type to construct the transfer function, and the obtained transfer function is as follows:

[0022] y(0)b(0)+y(1)*b(1)+y(2)*b(2)+y(3)*b(3)=x(0)*a(0)+x(1)*a(1)+x(2)*a(2)+x(3)*a(3)

[0023] In the above formula, [b(0), b(1), b(2), b(3)], [a(0), a(1), a(2), a(3)] are two sets of constant vectors, x(0), x(1), x(2), x(3) are the four sampling values of the input function x, and y(0), y(1), y(2), y(3) are the four corresponding values of the output function y.

[0024] Furthermore, in step S2, vector a[4]=[0.099,-0.396,0.594,-0.396,0.099] and vector b[4]=[1,-3.980,5.943,-3.945,0.982] are specifically set. Through this filtering transfer function, the fundamental signal of 40-100 Hz is retained, and the voltage signal below 2 division and above 3 times the frequency is filtered out.

[0025] Furthermore, step S3 synthesizes the negative sequence voltage signal using the following formula:

[0026] U f =U a +U b *j(∠120°)+U c *j(∠-120°)

[0027] Among them, U f Indicates the resultant negative sequence voltage, U a Indicates the voltage of phase A, U b Indicates the B phase voltage, U c Indicates the C-phase voltage.

[0028] Furthermore, the voltage mutation calculation method in step S4 is as follows:

[0029] U=sqrt(u1*u1+u2*u2-2*u1*u2*cosDT)*cosDT / √2

[0030] Wherein, cosDT is the fundamental voltage constant, u1 is the voltage sampling value at time 1, u2 is the voltage sampling value at time 2, and Sqrt represents the root mean square operation.

[0031] Furthermore, in step S5 , if the negative sequence voltage is continuously greater than the threshold for 5 ms, it is determined that a ground fault occurs in the system.

[0032] The present invention provides an anti-malfunction system for an active intervention arc extinguishing device in parallel with an arc extinguishing coil, comprising a data acquisition module, a bandpass filter module, a negative sequence voltage synthesis module, a mutation detection module, and a fast calculation module; wherein:

[0033] Data acquisition module: obtain the three-phase voltage and zero-sequence voltage of the system;

[0034] Bandpass filter module: performs digital bandpass filtering on the collected voltage signal;

[0035] Negative sequence voltage synthesis module: synthesizes negative sequence voltage signal from filtered voltage signal;

[0036] Sudden change detection module: quickly calculates three-phase voltage and zero-sequence voltage through the derivative method, and detects sudden changes in three-phase voltage and zero-sequence voltage;

[0037] Fast calculation module: calculates the instantaneous negative sequence voltage value when the voltage suddenly changes;

[0038] If the negative sequence voltage value is greater than the threshold value for a period of time, it is determined that the system is grounded and the corresponding fault phase switch is controlled to close. Otherwise, it is determined that the arc suppression coil series resonance has occurred in the system and the locking device performs grounding judgment to prevent false operation due to resonance.

[0039] Furthermore, the data acquisition module is a data acquisition module of an active intervention type arc extinguishing device, and the active intervention type arc extinguishing device is installed at the bus position of a system whose neutral point is grounded through an arc extinguishing coil.

[0040] 3. Beneficial effects

[0041] Compared with the existing known technologies, the technical solution provided by the present invention has the following significant effects:

[0042] The present invention is not intended to realize the function of parallel operation of the active intervention type arc extinguishing device and the arc extinguishing coil, but focuses on solving the problem of malfunction of the active intervention type arc extinguishing device when the arc extinguishing coil causes neutral point resonance. The present invention identifies the resonant state of the active intervention type arc extinguishing device and the arc extinguishing coil during parallel operation through sampling and algorithm, thereby avoiding the misjudgment of the resonance fault as a single-phase grounding fault, and ensuring the safety and reliability of the fault phase discrimination when the active intervention type arc extinguishing device and the arc extinguishing coil are operated in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of recording the neutral point resonance system;

[0044] Figure 2 This is a schematic diagram of the process of the active intervention arc suppression device and the arc suppression coil operating in parallel to prevent resonance malfunction;

[0045] Figure 3 This is a typical application diagram of the present invention. DETAILED DESCRIPTION

[0046] In order to further understand the content of the present invention, the present invention is described in detail with reference to the accompanying drawings and embodiments.

[0047] Example 1

[0048] For systems where the neutral point is grounded via an arc suppression coil, the active intervention arc suppression device needs to quickly distinguish whether the unbalanced voltage in the system is caused by the neutral point resonance caused by the arc suppression coil or by the system grounding. This embodiment provides a method for preventing false operation of an active intervention arc suppression device in parallel with an arc suppression coil. This embodiment quickly distinguishes between the series resonance of the neutral point of the arc suppression coil and the system grounding based on the three-phase voltage characteristics of the system. Figure 2 , the specific steps of this embodiment are as follows:

[0049] S1. The active intervention arc extinguishing device obtains the three-phase voltage and zero-sequence voltage of the system through the data acquisition module.

[0050] S2. Perform digital bandpass filtering on the voltage signal collected in step S1. Considering the attenuation balance of the upper and lower cutoff frequencies of the bandpass filter, a Chebyshev II type transfer function is used to construct the transfer function. The obtained transfer function is as follows:

[0051] y(0)b(0)+y(1)*b(1)+y(2)*b(2)+y(3)*b(3)=x(0)*a(0)+x(1)*a(1)+x(2)*a(2)+x(3)*a(3)

[0052] Where: y represents the system output function; x represents the system input function; [b(0), b(1), b(2), b(3)], [a(0), a(1), a(2), a(3)] are two sets of constant vectors; vector a[4] = [0.099, -0.396, 0.594, -0.396, 0.099]; vector b[4] = [1, -3.980, 5.943, -3.945, 0.982]; x(0), x(1), x(2), x(3) are the 4th sampling values of the input function x, and y(0), y(1), y(2), y(3) are the 4th corresponding values of the output function y. Through this filtering function, the fundamental signal of 40-100 Hz can be retained, and the voltage signal with a frequency below 2 and a frequency above 3 times can be filtered out.

[0053] S3. Use the filtered voltage signal to synthesize the negative sequence voltage signal:

[0054] U f =U a +U b *j(∠120°)+U c *j(∠-120°)

[0055] U f Indicates negative sequence voltage; U a Indicates the voltage of phase A; U b Indicates the B phase voltage; U c Indicates the C-phase voltage.

[0056] S4. Use the derivative method to quickly calculate the three-phase voltage and zero-sequence voltage. When the three-phase voltage and zero-sequence voltage suddenly change, start the subsequent judgment S5. The voltage sudden change calculation method is as follows:

[0057] U=sqrt(u1*u1+u2*u2-2*u1*u2*cosDT)*cosDT / √2

[0058] Here, cosDT is the fundamental voltage constant. This method is simple to calculate and fast. It can effectively reduce calculation errors based on bandpass filtering. Combined with DSP's fast floating-point operations, it can perform voltage calculations in real time. U1 is the voltage sampled value at time 1; U2 is the voltage sampled value at time 2; and Sqrt is the root square operation.

[0059] S5, calculate the instantaneous negative sequence voltage value at the moment when the voltage suddenly changes, that is, according to the sampling in step S3 and the formula U f =U a +U b *j(∠120°)+U c *j(∠-120°) is the calculated negative sequence voltage value.

[0060] If the negative sequence voltage is continuously greater than the threshold for 5ms, it is determined that the system is grounded and the corresponding fault phase switch is controlled to close. Otherwise, it is determined that the arc suppression coil series resonance has occurred in the system and the locking device performs a grounding judgment to prevent false operation due to resonance.

[0061] This embodiment uses sampling and algorithms to identify the resonant state during the parallel operation of the active intervention arc extinguishing device and the arc extinguishing coil, thereby avoiding the misjudgment of the resonant fault as a single-phase grounding fault, and ensuring the safety and reliability of the fault phase identification when the active intervention arc extinguishing device and the arc extinguishing coil are operated in parallel.

[0062] Example 2

[0063] In this embodiment, an active intervention arc suppression device and an arc suppression coil are connected in parallel to prevent malfunction, including a data acquisition module, a bandpass filter module, a negative sequence voltage synthesis module, a sudden change detection module and a fast calculation module; wherein:

[0064] Data acquisition module: obtain the three-phase voltage and zero-sequence voltage of the system;

[0065] Bandpass filter module: performs digital bandpass filtering on the collected voltage signal;

[0066] Negative sequence voltage synthesis module: synthesizes negative sequence voltage signal from filtered voltage signal;

[0067] Sudden change detection module: quickly calculates three-phase voltage and zero-sequence voltage through the derivative method, and detects sudden changes in three-phase voltage and zero-sequence voltage;

[0068] Fast calculation module: Calculate the instantaneous negative-sequence voltage value at the moment when the voltage suddenly changes.

[0069] If the negative-sequence voltage value is greater than the threshold for a period of time, it is determined that the system has a ground fault, and the corresponding fault-phase switch is controlled to close. Otherwise, it is determined that the system has an arc suppression coil series resonance, and the device locks the ground fault judgment to prevent misoperation of the resonance.

[0070] Reference Figure 3 , The active intervention type arc suppression device is installed at the bus position of the system with the neutral point grounded through an arc suppression coil. The acquisition module is used to collect the three-phase voltage and zero-sequence voltage of the system in real time. After the data is collected, through band-pass filtering and voltage synthesis, the three-phase voltage, zero-sequence voltage, and negative-sequence voltage after filtering of the system are obtained, and the effective value of the system voltage is quickly calculated by the derivative method.

[0071] Taking the A-phase instantaneous fault as an example, when the A-phase ground fault occurs in the system, the system becomes unbalanced, the three-phase voltage and zero-sequence voltage suddenly change, and the arc suppression coil starts to compensate the ground current of the system, further increasing the system imbalance. The negative-sequence voltage also starts to change suddenly. The device determines that the A-phase has a ground fault and quickly closes the A-phase voltage, actively transferring the unstable ground fault that occurs in the system to the cabinet. After the switch is closed for △t time, the grounding switch is opened. Since it is an A-phase instantaneous ground fault, the ground fault in the system has disappeared at this time, and a neutral point resonance occurs, and the zero-sequence voltage decays continuously, and the three-phase voltage fluctuates. The system calculates the negative-sequence voltage. If the negative-sequence voltage does not exceed the threshold, it is determined that the system ground fault has been eliminated, and the ground fault judgment is locked for t1 seconds. After t2 (<t1) seconds, the system resonance ends, and the device解除闭锁状态.

[0072] By this method, the problem of misoperation of the neutral point series resonance caused by connecting an arc suppression coil to the neutral point can be effectively solved, ensuring the safety and reliability of the parallel operation of the active intervention type arc suppression device and the arc suppression coil.

[0073] The above schematically describes the present invention and its implementation manners. This description is not restrictive, and only one of the implementation manners of the present invention is shown in the drawings. The actual structure is not limited to this. Therefore, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments without creative efforts without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preventing malfunction of an active intervention arc extinguishing device in parallel with an arc extinguishing coil, characterized in that: The steps are: Step S1, obtaining the three-phase voltage and zero-sequence voltage of the system; Step S2, performing digital bandpass filtering on the voltage signal collected in step S1; Step S3: Using the filtered voltage signal to synthesize a negative sequence voltage signal; Step S4, quickly calculating the three-phase voltage and zero-sequence voltage by the derivative method, and starting the subsequent judgment step S5 when the three-phase voltage and zero-sequence voltage suddenly change; Step S5: Calculate the instantaneous negative-sequence voltage value at the moment when the voltage suddenly changes based on the sampling of step S3; if the negative-sequence voltage value is greater than the threshold value for a period of time, it is determined that the system is grounded, and the corresponding fault phase switch is controlled to close; otherwise, it is determined that the arc suppression coil series resonance occurs in the system, and the locking device performs a grounding judgment to prevent false operation due to resonance.

2. The method for preventing malfunction of an active intervention arc extinguishing device in parallel operation with an arc extinguishing coil according to claim 1, characterized in that: Step S1 obtains the three-phase voltage and zero-sequence voltage of the system through the data acquisition module of the active intervention type arc suppression device, and the active intervention type arc suppression device is installed at the bus position of the system whose neutral point is grounded through the arc suppression coil.

3. The method for preventing malfunction of an active intervention arc extinguishing device in parallel operation with an arc extinguishing coil according to claim 1, characterized in that: Step S2 uses Chebyshev II type to construct the transfer function, and the obtained transfer function is as follows: y(0)b(0)+y(1)*b(1)+y(2)*b(2)+y(3)*b(3)=x(0)*a(0)+x(1)*a(1)+x(2)*a(2)+x(3)*a(3) In the above formula, [b(0), b(1), b(2), b(3)], [a(0), a(1), a(2), a(3)] are two sets of constant vectors, x(0), x(1), x(2), x(3) are the four sampling values of the input function x, and y(0), y(1), y(2), y(3) are the four corresponding values of the output function y.

4. The method for preventing malfunction of an active intervention arc extinguishing device in parallel operation with an arc extinguishing coil according to claim 3, characterized in that: In step S2, vector a[4]=[0.099,-0.396,0.594,-0.396,0.099] and vector b[4]=[1,-3.980,5.943,-3.945,0.982] are specifically set. Through this filtering transfer function, the fundamental signal of 40-100 Hz is retained, and the voltage signal below 2-division and above 3-fold frequency is filtered out.

5. A method for preventing malfunction of an active intervention arc extinguishing device in parallel operation with an arc extinguishing coil according to claim 3 or 4, characterized in that: Step S3 synthesizes the negative sequence voltage signal using the following formula: IN f =U a +U b *j(∠120°)+U c *j(∠-120°) Among them, U f Indicates the resultant negative sequence voltage, U a Indicates the voltage of phase A, U b Indicates the B phase voltage, U c Indicates the C-phase voltage.

6. The method for preventing malfunction of an active intervention arc extinguishing device in parallel operation with an arc extinguishing coil according to claim 5, characterized in that: The voltage mutation calculation method in step S4 is as follows: U=sqrt(u1*u1+u2*u2-2*u1*u2*cosDT)*cosDT / √2 Wherein, cosDT is the fundamental voltage constant, u1 is the voltage sampling value at time 1, u2 is the voltage sampling value at time 2, and Sqrt represents the root mean square operation.

7. The method for preventing malfunction of an active intervention arc extinguishing device in parallel operation with an arc extinguishing coil according to claim 6, characterized in that: In step S5 , if the negative sequence voltage is continuously greater than the threshold for 5 ms, it is determined that a ground fault has occurred in the system.

8. An active intervention arc extinguishing device and an arc extinguishing coil are connected in parallel to prevent malfunction, characterized by: It includes data acquisition module, bandpass filter module, negative sequence voltage synthesis module, mutation detection module and fast calculation module; among which: Data acquisition module: obtain the three-phase voltage and zero-sequence voltage of the system; Bandpass filter module: performs digital bandpass filtering on the collected voltage signal; Negative sequence voltage synthesis module: synthesizes negative sequence voltage signal from filtered voltage signal; Sudden change detection module: quickly calculates three-phase voltage and zero-sequence voltage through the derivative method, and detects sudden changes in three-phase voltage and zero-sequence voltage; Fast calculation module: calculates the instantaneous negative sequence voltage value when the voltage suddenly changes; If the negative sequence voltage value is greater than the threshold value for a period of time, it is determined that the system is grounded and the corresponding fault phase switch is controlled to close. Otherwise, it is determined that the arc suppression coil series resonance has occurred in the system and the locking device performs grounding judgment to prevent false operation due to resonance.

9. The anti-malfunction system of the active intervention arc extinguishing device and the arc extinguishing coil in parallel operation according to claim 8, characterized in that: The data acquisition module is a data acquisition module of an active intervention type arc extinguishing device, and the active intervention type arc extinguishing device is installed at the bus position of a system whose neutral point is grounded through an arc extinguishing coil.

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