Generator source current short arc interruption device and method based on environment-friendly GCB

Abstract

This invention discloses a generator current short-arc interruption device and method based on an environmentally friendly generator circuit breaker (GCB), belonging to the field of electrical equipment technology. The device includes an environmentally friendly generator circuit breaker (GCB), a first-phase selection unit, a current zero-crossing prediction module, and a phase-by-phase operation actuator. The first-phase selection unit divides the fault phase angle into intervals and selects phases with moderate asymmetry as the first-phase to avoid a surge in arc energy caused by extreme asymmetry. The current zero-crossing prediction module processes fault current sampling data and accurately identifies the ideal zero-crossing point at the end of the small half-wave. The phase-by-phase operation actuator reserves mechanical operation time to control each phase to trip near the ideal zero-crossing point, completing the short-arc interruption of the fault current. This invention, through phase-by-phase operation, optimized first-phase selection, and ideal current zero-crossing point prediction, can achieve short-arc interruption of fault currents with high asymmetry, control and reduce arc energy, and balance the speed, environmental friendliness, and reliability of fault interruption.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment technology, and in particular to a generator source current short-circuit interruption device and method based on an environmentally friendly GCB. Background Technology

[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, the interruption of fault current at the outlet of large-capacity generators faces multiple technical bottlenecks. While traditional SF6-type GCBs can interrupt high-amplitude, long-delay zero-crossing fault currents, SF6 gas has a strong greenhouse effect (its global warming potential is 23,500 times that of carbon dioxide), failing to meet environmental protection requirements. Furthermore, its arc voltage can reach over 1500V, and its arc energy can reach 1500kJ, resulting in severe contact erosion and reducing the reliability of current interruption. Existing vacuum-type GCBs, while possessing advantages such as environmental friendliness and rapid post-arc dielectric strength recovery, mostly employ a three-phase simultaneous random tripping operation, lacking a single-phase independent operation strategy and unable to actively control the tripping time. When a three-phase symmetrical fault occurs, the high asymmetry of the fault current (>100%) leads to a delay in the current zero-crossing point, resulting in an extremely long and uncontrollable arcing time, making it difficult to quickly and reliably interrupt the fault current. Although some solutions reduce arc energy by adding external damping devices, this significantly increases equipment costs and mechanical complexity, failing to meet the high-efficiency protection requirements of large-capacity units. Summary of the Invention

[0004] The purpose of this invention is to provide a generator source current short-arc interruption device and method based on environmentally friendly GCB, which can realize short-arc interruption of fault current with high asymmetry, control and reduce arc energy, extend equipment life, has excellent environmental protection, does not require additional damping device, and has a simple structure and good economy.

[0005] To achieve the above objectives, the present invention provides a generator source current short-circuit interruption device based on an environmentally friendly GCB, including an environmentally friendly generator circuit breaker (GCB) for realizing three-phase independent tripping operation.

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

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

[0008] The phase-separation operation actuator is used to control the tripping 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 as follows: divide 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; match the phase with medium asymmetry within the corresponding interval 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, select the zero-crossing point at the end of the small half-wave 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 arc interruption of generator source current based on the 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 moment 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 moment (that is, start opening at the moment t1 - t op ), ensure that the first-opening phase contact has been fully opened when the ideal zero-crossing point moment 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. Predict the common ideal zero-crossing point moment t2 of the remaining two phases 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 moment t2 - t op , until the arc interruption of all currents is completed at the moment t2.

[0018] Preferably, in S1, for the screening of medium asymmetry phases, 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 moment 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-breaking device and method based on an environmentally friendly GCB. Through phase-separated operation, optimal selection of the first-breaking phase, and prediction of the ideal current zero crossing, short arc-breaking of high asymmetry fault current can be achieved, the arc energy can be controlled and reduced, and the rapidity, environmental friendliness, and reliability of fault breaking are taken into account.

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

[0027] Figure 1 is a schematic diagram of the generator source current short arc-breaking 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-breaking phase selection interval based on θ0 and the matching of corresponding medium asymmetry phases 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-breaking method based on an environmentally friendly GCB according to an embodiment of the present invention;

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

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

[0033] Figure 7 This is a 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 A phase current in the remaining phase, (b) is the B phase current in the remaining phase, and (c) is the C phase current in the first open phase. Detailed Implementation

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

[0035] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object 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 interruption device based on an environmentally friendly GCB, including an environmentally friendly generator circuit breaker GCB, a first-phase selection unit, a current zero-crossing prediction module, and a phase-splitting operation actuator.

[0038] The environmentally friendly generator circuit breaker (GCB) is equipped with a vacuum interrupter to enable independent tripping of three phases. The first-phase selection unit calculates the asymmetry of the fault phase and selects the phase with moderate asymmetry as the first-phase tripping phase. The current zero-crossing prediction module fits the fault current waveform and predicts the ideal zero-crossing point. The phase-splitting operation actuator controls the tripping action of the three-phase contacts of the environmentally friendly generator circuit breaker (GCB), and can respond to the tripping commands of the first-phase tripping phase and the remaining phases respectively.

[0039] The screening logic of the first-opening phase selection unit is as follows: intervals are divided based on the fault phase angle θ0, where θ0 = θ U0 +δ0, and θ U0 is the voltage phase angle at the fault moment, and δ0 is the power angle. [0, 2π] is divided into 12 intervals. As Figure 2 shown, the phase with medium asymmetry (neither the highest nor the lowest) within the corresponding interval is selected 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, the zero-crossing point at the end of the small half-wave is selected as the ideal zero-crossing point. As Figure 3 shown.

[0041] In this embodiment, an opening method applied to the generator source current short arc interruption device based on an environmentally friendly GCB is provided. As Figure 4 shown, it includes 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 in zero-crossing will lead to an extended arcing time and a sharp increase in arc energy, as Figure 5 (a) shown; avoid selecting the phase with the lowest asymmetry, because after tripping, the asymmetry of the remaining two phases will climb to ~100%, which is likely to generate a large arc energy, as Figure 5 (b) shown.

[0044] S2. The current zero-crossing prediction module performs waveform fitting on 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.

[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 an 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 filter out the zero crossing point whose interval from the previous zero crossing point is < T0 / 2 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 in the remaining two phases are equal, the directions are opposite, and the zero crossing points are the same.

[0052] Interrupt the currents in 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 arc extinguishing chamber; 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) through the phase-locked loop (PLL), and substitutes t f to obtain θ U0 = 0; because the generator is no-load and the power angle δ0 = 0, then 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), and 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 contactor trips and arcs near 26 ms, and the current actually crosses zero at 28 ms, and the arc extinguishes, and the opening of the first-opening phase is completed.

[0058] (4)After the C-phase is opened, the fault turns into a short-circuit fault between the A and B phases. The magnitudes of the two-phase currents are equal and the directions are opposite, and the zero crossing points are the same; collect the A-phase current data from 30 to 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 contactors act synchronously, and the current actually crosses zero at 59 ms and the opening is completed.

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

[0060] Therefore, the present invention adopts the above-mentioned generator source current short-arc opening 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 opening 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. A generator source current short-circuit interruption device based on environmentally friendly GCB, characterized in that: This includes the environmentally friendly generator circuit breaker (GCB), used to achieve independent three-phase tripping operation; The first-phase selection unit is used to calculate the asymmetry of the faulty phase and select the phase with moderate asymmetry as the first-phase; The filtering logic of the first-phase selection unit is as follows: based on the fault phase angle. θ 0 divides the interval, where, θ 0= θ U0 + δ 0, θ U0 The voltage phase angle at the time of the fault. δ 0 represents the power angle; the phase with moderate asymmetry within the corresponding interval is selected 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-separation operation actuator is used to control the tripping action of the three-phase contacts of the environmentally friendly generator circuit breaker (GCB).

2. The generator source current short-circuit interruption device based on environmentally friendly GCB according to claim 1, characterized in that: The environmentally friendly generator circuit breaker (GCB) is equipped with a vacuum interrupter.

3. The generator source current short-circuit interruption device based on environmentally friendly GCB according to claim 1, characterized in that: The current zero-crossing prediction module combines fault current sampling data to predict the current value of subsequent cycles and identifies the interval between the previous zero-crossing point and the previous zero-crossing point. T The zero-crossing point of 0 / 2 is taken as the ideal zero-crossing point, where T 0 represents the power frequency period, meaning the zero-crossing point located at the end of the small half-wave is selected as the ideal zero-crossing point.

4. The generator source current short-circuit interruption device based on environmentally friendly GCB according to claim 1, characterized in that: The phase-by-phase operation actuators respond to the tripping commands for the first phase and the remaining phases, respectively.

5. A generator source current short-circuit interruption method based on environmentally friendly GCB, characterized in that, Includes the following steps: S1. After detecting a three-phase short-circuit fault, the first phase selection unit first calculates the fault phase angle. θ 0, and according to θ Divide the phase into several intervals, and then combine the three-phase asymmetry characteristics of each interval to select the phase with medium asymmetry as the first phase to open. S2. The current zero-crossing prediction module performs waveform fitting on the fault current of the first open phase and predicts the time when it is at the ideal zero-crossing point at the end of the small half-wave. t 1; S3, Reserved time for mechanical tripping operation and fault tolerance. t op Control the first phase contact to be spaced before the ideal zero-crossing point. t op Start tripping to ensure it occurs at the ideal zero-crossing point. t When phase 1 arrives, the first phase contact has already fully opened, thus achieving the ideal zero-crossing point. t 1. Achieve arc-extinguishing interruption of the first-phase current; S4. After the first phase trips, the remaining two phases become inter-phase faults. The remaining phase currents are interrupted according to the inter-phase fault current interruption method. The common ideal zero-crossing time of the remaining two phases is predicted by the current zero-crossing prediction module. t 2. Reserve time for mechanical tripping operation and fault tolerance. t op Control the two phase contacts simultaneously t 2- t op The circuit breaker will start tripping at any time, until... t The arc is extinguished and interrupted at time 2.

6. The generator source current short-circuit interruption method based on environmentally friendly GCB according to claim 5, characterized in that: In S1, for screening phases with moderate asymmetry, it is necessary to avoid selecting the phase with the highest asymmetry and the phase with the lowest asymmetry.

7. The generator source current short-arc interruption method based on environmentally friendly GCB according to claim 5, characterized in that: In S2, the prediction process for the ideal zero-crossing point includes the following steps: S21. Determine the fault time by monitoring sudden changes in terminal voltage. t f ; S22. Select the corresponding current model according to the fault type; S23, combined with fault phase angle θ 0 and current sampling data, and then use an algorithm to fit the subsequent current waveform; S24. Identify zero-crossing points by observing the sign change of adjacent current prediction values, and filter points with intervals between the previous zero-crossing point and the previous zero-crossing point. T The zero-crossing point of 0 / 2 is taken as the ideal zero-crossing point.

8. The generator source current short-circuit interruption method based on environmentally friendly GCB according to claim 5, characterized in that: In S4, the currents of the remaining two phases are equal in magnitude, opposite in direction, and have the same zero-crossing point.

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