Generator source current short arcing breaking device and method based on environment-friendly GCB

Abstract

The invention discloses a generator source current short arcing breaking device and method based on an environment-friendly generator circuit breaker GCB, and belongs to the technical field of electrical equipment. The device comprises the environment-friendly generator circuit breaker GCB, a first open phase selection unit, a current zero-crossing prediction module and a split-phase operation execution mechanism; wherein the first open phase selection unit divides intervals according to a fault phase angle, screens a phase with medium asymmetry degree as a first open phase, and prevents arc energy surge caused by extreme asymmetry degree; the current zero-crossing prediction module processes fault current sampling data and accurately identifies an ideal zero-crossing point at the tail end of a small half wave; and the phase-splitting operation execution mechanism reserves mechanical operation time and controls each phase to be switched off near an ideal zero crossing point so as to complete short arcing switching-on and switching-off of fault current. Through split-phase operation, first open-phase optimization selection and ideal current zero crossing point prediction, short arcing on-off of high-asymmetry fault current can be realized, arc energy can be controlled and reduced, and rapidity, environmental protection and reliability of fault on-off are considered.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical equipment, and in particular to a generator source current short arc breaking device and method based on an environmentally friendly GCB. Background Art

[0002] In power systems, the safe operation of large-capacity generators (such as 1000MW and above units) is highly dependent on the rapid and reliable interruption of fault currents. Generator circuit breakers (GCBs) are the core equipment to ensure the rapid isolation of generator source short-circuit faults.

[0003] Currently, fault current interruption at the outlet of large-capacity generators faces multiple technical bottlenecks. While traditional SF6-based GCBs can interrupt high-amplitude, long-delay zero-crossing fault currents, SF6 gas has a strong greenhouse effect (with a global warming potential 23,500 times that of carbon dioxide), making it unsuitable for environmental protection. Furthermore, arc voltages can reach over 1500V, with arc energies reaching 1500kJ, leading to severe contact erosion and reduced current interruption reliability. Existing vacuum-type GCBs, while environmentally friendly and offering rapid post-arc dielectric strength recovery, often employ a three-phase random tripping operation, lacking a single-phase independent operation strategy and inability to actively control tripping timing. When a three-phase symmetrical fault occurs, the high asymmetry of the fault current (>100%) results in a delayed zero-crossing, resulting in an extremely long and uncontrollable arcing time, making it difficult to quickly and reliably interrupt the fault current. While some solutions reduce arc energy by adding external damping devices, this significantly increases equipment cost and mechanical complexity, making it unsuitable for the efficient protection required of large-capacity generators. Summary of the Invention

[0004] The purpose of the present invention is to provide a generator source current short arc interruption device and method based on an environmentally friendly GCB, which can achieve short arc interruption of highly asymmetric fault currents, control and reduce arc energy, extend equipment life, have excellent environmental protection, do not require additional damping devices, have a simple structure and good economy.

[0005] To achieve the above-mentioned object, the present invention provides a generator source current short arc breaking device based on an environmentally friendly GCB, comprising an environmentally friendly generator circuit breaker GCB for realizing three-phase independent opening operation;

[0006] The first-to-break phase selection unit is used to calculate the asymmetry of the fault phase and select the phase with medium asymmetry as the first-to-break phase;

[0007] Current zero-crossing prediction module, used to fit the fault current waveform and predict the ideal zero-crossing point;

[0008] The phase-splitting operation actuator is used to control the opening action of the three-phase contacts of the environmentally friendly generator circuit breaker GCB.

[0009] Preferably, the environmentally friendly generator circuit breaker GCB adopts a vacuum interrupter configuration.

[0010] Preferably, the screening logic of the first-opening phase selection unit is: dividing intervals based on the fault phase angle θ0, where θ0 = θ U0 +δ0, θ U0 is the voltage phase angle at the fault moment, and δ0 is the power angle; the phase with medium asymmetry within the corresponding interval is matched as the first-opening phase.

[0011] Preferably, the current zero-crossing prediction module combines the fault current sampling data to predict the subsequent cycle current value, and identifies the zero-crossing point with an interval < T0 / 2 from the previous zero-crossing point as the ideal zero-crossing point, where T0 is the power frequency cycle, that is, the zero-crossing point at the end of the small half-wave is selected as the ideal zero-crossing point.

[0012] Preferably, the phase-separated operation actuator responds to the opening commands of the first-opening phase and the remaining phases respectively.

[0013] The present invention also provides a method for short-duration arc interruption of generator source current based on an environmentally friendly GCB, including the following steps:

[0014] S1. After detecting a three-phase short circuit fault, the first-opening phase selection unit first calculates the fault phase angle θ0, divides several intervals according to θ0, and then combines the three-phase asymmetry characteristics corresponding to each interval to screen the phase with medium asymmetry as the first-opening phase;

[0015] S2. The current zero-crossing prediction module performs waveform fitting on the fault current of the first-opening phase, and predicts the time t1 of its ideal zero-crossing point at the end of the small half-wave;

[0016] S3. Reserve the mechanical opening operation and fault tolerance time t op , control the first-opening phase contact to start opening at an interval t op before the ideal zero-crossing point time (that is, start opening at the time t1 - t op ), ensure that the first-opening phase contact has been fully opened when the ideal zero-crossing point time t1 arrives, so as to achieve arc interruption of the first-opening phase current at the ideal zero-crossing point t1;

[0017] S4. After the first-opening phase is opened, the remaining two phases are converted into an inter-phase fault, and the remaining phase current is interrupted according to the inter-phase fault current interruption method. The common ideal zero-crossing point time t2 of the remaining two phases is predicted through the current zero-crossing prediction module, reserve the mechanical opening operation and fault tolerance time t op , control the two-phase contacts to start opening simultaneously at the time t2 - t op , until the arc interruption of all currents is completed at the time t2.

[0018] Preferably, in S1, for the screening of the medium asymmetry phase, it is necessary to avoid selecting the phase with the highest asymmetry and the phase with the lowest asymmetry.

[0019] Preferably, in S2, the prediction process of the ideal zero crossing includes the following steps:

[0020] S21. Determine the fault time t by monitoring the sudden change of terminal voltage f ;

[0021] S22. Select the corresponding current model according to the fault type;

[0022] S23. Combine the fault phase angle θ0 and the current sampling data, and use an algorithm to fit the subsequent current waveform;

[0023] S24. Identify the zero crossing by the sign change of adjacent predicted values of the current, and screen the zero crossing with an interval < T0 / 2 from the previous zero crossing as the ideal zero crossing.

[0024] Preferably, in S4, the magnitudes of the remaining two-phase currents are equal, the directions are opposite, and the zero crossings are consistent.

[0025] Therefore, the present invention adopts the above-mentioned generator source current short arc interruption device and method based on an environmentally friendly GCB. Through phase-separated operation, optimal selection of the first-opening phase, and prediction of the ideal current zero crossing, it is possible to achieve short arc interruption of high asymmetry fault current, control and reduce the arc energy, and balance the fastness, environmental friendliness, and reliability of fault interruption.

[0026] Next, through the drawings and embodiments, the technical solution of the present invention will be further described in detail. Description of the Drawings

[0027] Figure 1 is a schematic diagram of the generator source current short arc interruption device based on an environmentally friendly GCB according to an embodiment of the present invention;

[0028] Figure 2 is a diagram of the division of the first-opening phase selection interval based on θ0 and the matching of the corresponding medium asymmetry phase according to an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of the ideal zero point according to an embodiment of the present invention;

[0030] Figure 4 is a step diagram of the generator source current short arc interruption method based on an environmentally friendly GCB according to an embodiment of the present invention;

[0031] Figure 5Schematic diagram of current waveform when an inappropriate asymmetry phase is selected as the first opening phase in an embodiment of the present invention; wherein (a) is a schematic diagram of current waveform when the highest asymmetry phase is mistakenly selected as the first opening phase, and (b) is a schematic diagram of current waveform when the lowest asymmetry phase is mistakenly selected as the first opening phase;

[0032] Figure 6 This is a diagram of the ideal zero point prediction steps of an embodiment of the present invention;

[0033] Figure 7 Schematic diagram of the current waveforms and arc energy of the first-open phase and the remaining phases in an embodiment of the present invention; wherein (a) is the phase A current in the remaining phase, (b) is the phase B current in the remaining phase, and (c) is the phase C current in the first-open phase. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0035] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0036] Example 1

[0037] like Figure 1 As shown, the present invention provides a generator source current short arc breaking device based on an environmentally friendly GCB, including an environmentally friendly generator circuit breaker GCB, a first-opening phase selection unit, a current zero-crossing prediction module and a phase-splitting operation actuator.

[0038] Among them, the environmentally friendly generator circuit breaker GCB adopts a vacuum interrupter configuration to realize three-phase independent opening operation; the first-opening phase selection unit is used to calculate the asymmetry of the fault phase and select the medium-asymmetry phase as the first-opening phase; the current zero-crossing prediction module is used to fit the fault current waveform and predict the ideal zero-crossing point; the phase-splitting operation actuator is used to control the three-phase contact opening action of the environmentally friendly generator circuit breaker GCB, and can respond to the opening instructions of the first-opening phase and the remaining phases respectively.

[0039] The screening logic of the first-opening phase selection unit is as follows: divide the interval based on the fault phase angle θ0, where θ0 = θ U0 +δ0, θ U0 is the voltage phase angle at the fault moment, and δ0 is the power angle. Divide [0, 2π] into 12 intervals, as Figure 2 shown, and select the phase with medium asymmetry (neither the highest nor the lowest) within the corresponding interval as the first-opening phase.

[0040] The current zero-crossing prediction module combines the fault current sampling data to predict the subsequent cycle current value, and identifies the zero-crossing point with an interval < T0 / 2 from the previous zero-crossing point as the ideal zero-crossing point, where T0 is the power frequency cycle, that is, select the zero-crossing point at the end of the small half-wave as the ideal zero-crossing point, as Figure 3 shown.

[0041] In this embodiment, an opening method applied to a generator source current short arcing interruption device based on an environmentally friendly GCB is provided, as Figure 4 shown, including the following steps:

[0042] S1. After detecting a three-phase short circuit fault, the first-opening phase selection unit first calculates the fault phase angle θ0, divides several intervals according to θ0, and then combines the three-phase asymmetry characteristics corresponding to each interval to screen the phase with medium asymmetry as the first-opening phase.

[0043] Among them, for the screening of the phase with medium asymmetry, two extreme cases need to be avoided: avoid selecting the phase with the highest asymmetry, because its current delay zero-crossing will cause the arcing time to extend and the arc energy to surge, as Figure 5 shown in (a) of; avoid selecting the phase with the lowest asymmetry, because the asymmetry of the remaining two phases will climb to ~100% after tripping, which is likely to generate large arc energy, as Figure 5 shown in (b) of

[0044] S2. The current zero-crossing prediction module performs waveform fitting on the fault current of the first-opening phase to predict the moment t1 of its ideal zero-crossing point at the end of the small half-wave.

[0045] As Figure 6 shown, the prediction process of the ideal zero-crossing point includes the following steps:

[0046] S21. Determine the fault moment t f ;

[0047] S22. Select the corresponding current model according to the fault type;

[0048] S23. Combine the fault phase angle θ0 and the current sampling data, and use the algorithm to fit the subsequent current waveform;

[0049] S24. Identify the zero crossing point by the sign change of the adjacent predicted value of the current, and screen the zero crossing point with an interval < T0 / 2 from the previous zero crossing point as the ideal zero crossing point.

[0050] S3. Reserve the mechanical opening operation and fault tolerance time t op , and control the first-opening phase contact to start opening at an interval of t op before the ideal zero crossing point moment (i.e., start opening at the moment of t1 - t op ), ensuring that the first-opening phase contact has been fully opened when the ideal zero crossing point moment t1 arrives, so as to achieve the arc-extinguishing interruption of the first-opening phase current at the ideal zero crossing point t1.

[0051] S4. After the first-opening phase is opened, the remaining two phases turn into an inter-phase fault. Among them, the magnitudes of the currents of the remaining two phases are equal, the directions are opposite, and the zero crossing points are consistent.

[0052] Interrupt the currents of the remaining phases according to the inter-phase fault current interruption method. Predict the common ideal zero crossing point moment t2 of the remaining two phases through the current zero crossing prediction module, and reserve the mechanical opening operation and fault tolerance time t op , and control the two-phase contacts to start opening simultaneously at the moment of t2 - t op , until the arc-extinguishing interruption of all currents is completed at the moment of t2.

[0053] In this embodiment, taking the three-phase symmetrical fault interruption of a 1200MW steam turbine generator as a simulation example, each phase of the phase-separated operation type vacuum GCB is independently equipped with a vacuum interrupter; the sampling frequency of the first-opening phase selection unit is 10kHz, which can detect and calculate the fault phase angle θ0 in real time and match the interval; the current zero crossing prediction module adopts the Levenberg-Marquardt nonlinear fitting algorithm, and the sampling interval is 0.1ms.

[0054] Interrupt the three-phase currents step by step:

[0055] (1) When a fault occurs, determine the fault moment as t f = 15s by monitoring the sudden change of the generator terminal voltage (voltage change rate > 1E+7V / s); the first-opening phase selection unit calls the voltage data of the previous 2 power frequency cycles (2·T0 = 40ms) before the fault, and obtains the voltage phase angle array [θ U(t) [[ID=|32]]] through the phase-locked loop (PLL), and substitutes it into t f to obtain θ U0 = 0; because the generator is no-load and the power angle δ0 = 0, the fault phase angle θ0 = θ U0 + δ0 = 0; according to the interval [0, π / 6] where θ0 = 0 is located, match the three-phase asymmetry characteristics (as Figure 2 shown), determine that phase C is the phase with medium asymmetry, and select it as the first-opening phase.

[0056] (2)Collect the C-phase current data within 10 ms after the fault (at an interval of 0.1 ms), substitute it into the three-phase fault current model, and obtain the current waveform through non-linear fitting by the Levenberg-Marquardt algorithm; predict that the subsequent zero points of the C-phase are 20 ms, 26 ms, and 40 ms respectively. Calculate that the interval between the zero point at 26 ms and the previous zero point (20 ms) is 6 ms < T0 / 2 = 10 ms, determine that the zero point at 26 ms is at the end of the small half-wave, and select 26 ms as the ideal zero crossing point of the first-opening phase current.

[0057] (3)Reserve 7 ms for mechanical operation and fault tolerance time, issue a tripping command at 19 ms, the C-phase contact trips and arcs near 26 ms, and the current actually crosses zero at 28 ms, and the arc extinguishes, completing the interruption of the first-opening phase.

[0058] (4)After the C-phase is interrupted, the fault turns into a short-circuit fault between the A and B phases. The currents of the two phases are equal in magnitude and opposite in direction, and the zero crossing points are the same; collect the A-phase current data from 30 - 40 ms, and fit to obtain the subsequent zero points: 40 ms, 56 ms, 60 ms, and select 60 ms (the end of the small half-wave) as the ideal zero point of the remaining phase current; reserve 7 ms for mechanical operation and fault tolerance time, issue a tripping command at 53 ms, the A and B-phase contacts act synchronously, and the current actually crosses zero at 59 ms and completes the interruption.

[0059] The three-phase current waveforms during the interruption process are as Figure 7 shown. The zero crossing prediction error of the current is ≤2 ms. During the interruption process, the arc energy of the first-opening phase C is only about 35 kJ, and the arc energies of the remaining phases A and B are only about 22 kJ. The arc energies of the three phases are all < 50 kJ, verifying the controllable short-arc interruption effect of this embodiment.

[0060] Therefore, the present invention adopts the above-mentioned generator source current short-arc interruption device and method based on an environmentally friendly GCB, without an additional damping device, can reduce the arc energy to below 50 kJ, effectively solves the problems of the traditional SF6 type GCB being non-environmentally friendly, having a large arc energy, and the existing vacuum type GCB having no single-pole operation ability resulting in uncontrollable arc time, has both environmental friendliness and reliability, and is applicable to the large-capacity generator source fault current interruption scenario.

[0061] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. The generator source current short arc interrupter device based on the environmentally friendly GCB is characterized by: It includes an environmentally friendly generator circuit breaker GCB for implementing three-phase independent opening operations; A first-opening phase selection unit for calculating the fault phase asymmetry degree and screening the phase with medium asymmetry degree as the first-opening phase; A current zero-crossing prediction module for fitting the fault current waveform and predicting the ideal zero-crossing point; A phase-separated operation actuator for controlling the opening actions of the three-phase contacts of the environmentally friendly generator circuit breaker GCB.

2. The generator source current short arc interrupting device based on the environmentally friendly GCB according to claim 1 is characterized by: The environmentally friendly generator circuit breaker GCB adopts a vacuum interrupter configuration.

3. The generator source current short arc interrupting device based on the environmentally friendly GCB according to claim 1 is characterized by: The screening logic of the first-open phase selection unit is: divide the interval based on the fault phase angle θ0, where θ0=θ U0 +δ0,θ U0 is the voltage phase angle at the moment of fault, δ0 is the power angle; the phase with medium asymmetry in the corresponding interval is matched as the first phase to be opened.

4. The generator source current short arc interrupting device based on the environmentally friendly GCB according to claim 1 is characterized by: The current zero-crossing prediction module combines the fault current sampling data to predict the subsequent cycle current value, and identifies the zero-crossing point with an interval <T0 / 2 from the previous zero-crossing point as the ideal zero-crossing point, where T0 is the power frequency cycle, that is, the zero-crossing point located at the end of the small half-wave is selected as the ideal zero-crossing point.

5. The generator source current short arc interrupting device based on the environmentally friendly GCB according to claim 1 is characterized by: The phase-separated operation actuator responds to the opening commands of the first-opening phase and the remaining phases respectively.

6. The generator source current short arc breaking method based on the environmentally friendly GCB is characterized by: It includes the following steps: S1. After detecting a three-phase short-circuit fault, the first-opening phase selection unit first calculates the fault phase angle θ0, divides several intervals according to θ0, and then combines the three-phase asymmetry degree characteristics corresponding to each interval to screen the phase with medium asymmetry degree as the first-opening phase; S2. The current zero-crossing prediction module fits the waveform of the fault current of the first-opening phase and predicts the moment t1 of its ideal zero-crossing point at the end of the small half-wave; S3, reserve mechanical opening operation and fault tolerance time t op , control the first phase contact to open before the ideal zero crossing time interval t op Start opening the circuit breaker to ensure that the first phase contact is completely opened when the ideal zero crossing time t1 arrives, so as to achieve arc extinguishing and interruption of the first phase current at the ideal zero crossing time t1; S4. After the first phase is opened, the remaining two phases are converted to interphase faults. The remaining phase currents are interrupted according to the interphase fault current interruption method. The current zero-crossing prediction module predicts the common ideal zero-crossing time t2 of the remaining two phases, and reserves the mechanical opening operation and fault tolerance time t op , control the two-phase contacts at the same time at t2-t op The circuit breaker starts to open at time t2 until the arc is extinguished and the entire current is interrupted at time t3.

7. The generator source current short arc interruption method based on the environmentally friendly GCB according to claim 6 is characterized in that: In S1, for the screening of the phase with medium asymmetry degree, it is necessary to avoid selecting the phase with the highest asymmetry degree and avoid selecting the phase with the lowest asymmetry degree.

8. The generator source current short arc interruption method based on the environmentally friendly GCB according to claim 6 is characterized in that: In S2, the prediction process of the ideal zero-crossing point includes the following steps: S21, determine the fault time t by monitoring the voltage mutation at the terminal f ; S22. Select the corresponding current model according to the fault type; S23. Combine the fault phase angle θ0 and the current sampling data, and use an algorithm to fit the subsequent current waveform; S24. Identify the zero-crossing point by the sign change of the adjacent predicted current values, and screen the zero-crossing point with an interval <T0 / 2 from the previous zero-crossing point as the ideal zero-crossing point.

9. The generator source current short arc interruption method based on the environmentally friendly GCB according to claim 6 is characterized in that: In S4, the magnitudes of the currents of the remaining two phases are equal, the directions are opposite, and the zero-crossing points are the same.

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