Arc extinguishing effectiveness identification method and system for arc extinguishing device of rapid fault transfer point

Abstract

The invention discloses a method for identifying the arc extinguishing effectiveness of a quick transfer fault point arc extinguishing device, which includes obtaining fault information and judging the fault type, fault phase and fault line; in the case of single-phase arc grounding fault, putting into the quick transfer fault point arc extinguishing device; and identifying whether the original fault point is eliminated during the grounding of the fault phase bus according to whether the amplitude and phase offset of the grounding point current of the bus and the zero-sequence current of the fault line before and after putting into the quick transfer fault point arc extinguishing device exceed the set threshold values. The invention realizes the online identification of the state of the original fault point during the first action of the arc extinguishing device, avoids the impact on the original fault point caused by the sudden change of the fault phase voltage due to the repeated opening and closing of the bus grounding switch, enhances the quick disposal ability of the single-phase grounding fault of the distribution network, and improves the safety of the distribution network.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and particularly to the fault state identification in an ungrounded neutral system configured with a fast fault point transfer and arc extinguishing device. Background Art

[0002] In recent years, in the systems with ungrounded neutral mode at 3 - 35 kV in China, the voltage arc extinguishing method represented by the fast fault point transfer and arc extinguishing method has been widely applied on site. Its basic idea is that after a single-phase grounding fault occurs, the metal of the fault-phase bus is quickly grounded to limit the voltage of the fault phase, so that the arc is difficult to reignite after extinguishing at the zero crossing of the arc path current.

[0003] At present, the operation process of the fast fault point transfer and arc extinguishing device is as follows: after the fault-phase bus is grounded for a period of time, the grounding switch automatically disconnects. If the fault disappears, the system resumes normal operation. If the fault still exists, the fault-phase bus is grounded again and the grounding switch remains closed waiting for fault handling. When the original fault does not disappear, the sudden change of the fault-phase voltage caused by the repeated opening and closing of the bus grounding switch impacts the original fault point. In addition, the delay caused by the secondary grounding of the fault-phase bus may also cause the fault to expand further, increasing the difficulty of fault handling and being unfavorable to the system safety.

[0004] At present, the research on single-phase grounding faults in medium and low voltage distribution networks mostly focuses on fault line selection and location ranging. Judging whether the original fault is eliminated under the condition of single-phase grounding of the bus is a derivative problem of the fast fault point transfer and arc extinguishing technology, and there is currently a lack of corresponding identification methods.

[0005] In summary, the existing device and operation process cannot judge the state of the original fault point during the grounding of the fault-phase bus. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method and system for identifying the arc extinguishing effectiveness of a fast fault point transfer and arc extinguishing device. The present invention improves the existing arc extinguishing device, requires fewer measuring devices, does not need to increase the investment in primary equipment, avoids the impact of the sudden change of the fault-phase voltage caused by the repeated opening and closing of the bus grounding switch on the original fault point, enhances the fast disposal ability of single-phase grounding faults in the distribution network, and improves the safety of the distribution network.

[0007] In the first aspect, an embodiment of the present invention provides an online identification method for the state of the original fault point based on a fast fault point transfer and arc extinguishing device, including:

[0008] Obtaining fault information, and judging the fault type, fault phase, and fault line according to the fault information;

[0009] When the fault type is a single-phase arc grounding fault, putting into the fast fault point transfer and arc extinguishing device;

[0010] Calculate the amplitude and phase deviation according to the bus grounding point current before and after the arc extinguishing device of the rapid fault transfer point is put into operation and the zero-sequence current of the fault line;

[0011] Whether the original fault point is eliminated during the period when the fault phase bus is grounded is identified according to whether the amplitude and phase deviation exceed the set threshold value.

[0012] In combination with the first aspect, an embodiment of the present invention provides a first possible implementation manner of the first aspect, wherein the busbar grounding point current includes:

[0013] When the original fault point is successfully extinguished, the current flowing through the busbar grounding point is the sum of all line non-fault phase capacitance currents;

[0014] When the original fault point fails to extinguish the arc successfully, the current flowing through the busbar grounding point will Includes capacitive current component and load current component.

[0015] In combination with the first aspect, an embodiment of the present invention provides a second possible implementation method of the first aspect, wherein the zero-sequence current of the fault line includes: when the original fault point successfully extinguishes the arc, the grounding point and the line-to-ground capacitance constitute a zero-sequence path, and the zero-sequence current of the fault line is mainly capacitive current; when the original fault point fails to extinguish the arc successfully, the system has two points of grounding in the same phase, the two grounding points and the line-to-ground capacitance constitute a zero-sequence path, and the zero-sequence current of the fault line is the shunt of the capacitive current between the two grounding points.

[0016] In combination with the first aspect, the embodiment of the present invention provides a third possible implementation of the first aspect, wherein the identifying whether the original fault point is eliminated during the period when the fault phase bus is grounded includes: calculating Relative to the system zero sequence voltage The phase difference, and relative to When the amplitude deviation is greater than 20% or Hysteresis When it is greater than 100°, it is considered that the original fault has not been eliminated; when the load current is small and the bus grounding current criterion fails, the zero-sequence current amplitude of the fault line is calculated. When it is lower than 90% of the zero-sequence current of the fault line when the original fault point is eliminated, it is judged that the fault at the original fault point has not been eliminated.

[0017] In a second aspect, an embodiment of the present invention provides an online identification system for the original fault point state based on a fast-transfer fault point arc extinguishing device, comprising:

[0018] A fault information judgment unit, used to obtain fault information and judge the fault type, fault phase and fault line according to the fault information;

[0019] An arc extinguishing device input unit, used to input an arc extinguishing device for rapidly transferring the fault point when the fault type is a single-phase arc grounding fault;

[0020] A signal recording unit, used to record the busbar grounding point current signal and the fault line zero-sequence current signal before and after the arc extinguishing device is put into use;

[0021] An identification unit is used to identify whether the original fault point is eliminated by combining the bus grounding point current and the fault line zero-sequence current amplitude phase deviation to determine whether it exceeds a set threshold value;

[0022] The decision unit is used to combine the identified original fault point state, reset the rapid transfer fault point arc extinguishing device when the original fault point is eliminated, and send out an alarm signal when the original fault point is not eliminated to notify the on-duty personnel to handle the fault.

[0023] The present invention provides a method and system for identifying the effectiveness of arc extinguishing of a fast-transfer fault point arc extinguishing device, including obtaining fault information, determining the fault type, fault phase and fault line; in the case of a single-phase arc grounding fault, putting into operation the fast-transfer fault point arc extinguishing device; and identifying whether the original fault point is eliminated during the bus grounding of the fault phase according to whether the bus grounding current before and after the fast-transfer fault point arc extinguishing device is put into operation and the zero-sequence current amplitude and phase deviation of the fault line exceed a set threshold value. The present invention realizes the online identification of the original fault point state during the first action of the arc extinguishing device, avoids the impact of the fault phase voltage mutation caused by the repeated opening and closing of the bus grounding switch on the original fault point, enhances the rapid handling capability of the distribution network for single-phase grounding faults, and improves the safety of the distribution network.

[0024] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1A flow chart of a method for online identification of the original fault point state based on a fast-transfer fault point arc extinguishing device provided by an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of the principle of rapid fault point transfer is provided for an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of a 10kV distribution network provided in an embodiment of the present invention;

[0030] Figure 4 A schematic diagram of an online identification system for the original fault point state based on a fast-transfer fault point arc extinguishing device provided by an embodiment of the present invention;

[0031] Figure 5 A circuit diagram of an arc extinguishing device for rapid fault transfer provided by an embodiment of the present invention;

[0032] Figure 6 A busbar grounding point current simulation waveform diagram provided by an embodiment of the present invention;

[0033] Figure 7 This is a simulated waveform diagram of zero-sequence current of a fault line provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The existing device and action flow cannot determine the state of the original fault point during the period when the fault phase bus is grounded. Based on this, the arc extinguishing effectiveness identification method and system of the arc extinguishing device for rapid fault transfer provided by the embodiment of the present invention improves the existing arc extinguishing device, requires fewer measuring devices, does not require additional primary equipment investment, avoids the impact of the fault phase voltage mutation caused by the repeated opening and closing of the bus grounding switch on the original fault point, enhances the rapid handling capability of the distribution network single-phase grounding fault, and improves the safety of the distribution network.

[0036] To facilitate understanding of this embodiment, firstly, the online identification method of the original fault point state based on the rapid transfer fault point arc extinguishing device disclosed in the embodiment of the present invention is introduced in detail.

[0037] Embodiment 1:

[0038] Reference Figure 1 , an online identification method of the original fault point state based on the rapid transfer fault point arc extinguishing device, comprising:

[0039] Obtaining fault information, and determining the fault type and the fault phase and fault line according to the fault information;

[0040] In the case where the fault type is a single-phase arc grounding fault, an arc extinguishing device for rapid fault transfer is put into operation;

[0041] Calculate the amplitude and phase deviation according to the bus grounding point current before and after the arc extinguishing device of the rapid fault transfer point is put into operation and the zero-sequence current of the fault line;

[0042] Whether the original fault point is eliminated during the period when the fault phase bus is grounded is identified according to whether the amplitude and phase deviation exceed the set threshold value.

[0043] Furthermore, the busbar grounding current includes:

[0044] When the original fault point is successfully extinguished, the current flowing through the busbar grounding point is the sum of all line non-fault phase capacitance currents;

[0045] When the original fault point fails to extinguish the arc successfully, the current flowing through the busbar grounding point will Includes capacitive current component and load current component.

[0046] Specifically, Figure 2 The figure shows a 10kV distribution network with an ungrounded neutral point. The basic principle of the fast fault point transfer arc extinguishing technology is: when a C-phase arc grounding fault occurs at point k of the line, the C-phase fast grounding switch at the substation busbar is quickly closed, and the open circuit voltage at point m of the line is The system equivalent internal impedance is 1 / j3ωC. When the fault is eliminated, the transition resistance R tr is infinite, the line impedance Z L And busbar grounding resistance R B Relative to the system capacitive reactance, which can be ignored, the system zero-sequence voltage is The busbar grounding current for:

[0047]

[0048] If the original fault point is not eliminated after the fault phase bus is grounded or the insulation of the original fault point has been damaged, the fault phase bus grounding point and the original fault point will have two grounding points of the same phase coexisting in the system. At this time, the system capacitance current path and load current path will change, both passing through R B and R tr Diversion.

[0049]

[0050] Furthermore, the zero-sequence current of the fault line includes:

[0051] When the original fault point is successfully extinguished, the grounding point and the line-to-ground capacitance form a zero-sequence path, and the zero-sequence current of the fault line is mainly capacitive current;

[0052] When the original fault point fails to extinguish the arc successfully, two points of the same phase are grounded in the system. The two grounding points and the line-to-ground capacitance form a zero-sequence path, and the zero-sequence current of the fault line is the shunt of the capacitive current between the two grounding points.

[0053] Specifically, according to the symmetrical component method, the zero-sequence current of the fault line when the original fault is successfully extinguished during the period when the fault phase bus is grounded is calculated as:

[0054]

[0055] When the original fault point fails to extinguish the arc successfully, the zero-sequence current of the fault line is:

[0056]

[0057] Furthermore, the step of identifying whether the original fault point is eliminated during the period when the fault phase bus is grounded includes:

[0058] calculate Relative to the system zero sequence voltage The phase difference, and relative to When the amplitude deviation is greater than 20% or Hysteresis When it is greater than 100°, it is considered that the original fault has not been eliminated;

[0059] When the load current is small and the bus grounding current criterion fails, the zero-sequence current amplitude of the fault line is calculated. When it is lower than 90% of the zero-sequence current of the fault line when the original fault point is eliminated, it is determined that the fault at the original fault point has not been eliminated.

[0060] Specifically, Figure 3 In the distribution network shown, all lines are single-circuit outgoing lines, with a length set to 15km. The fault point k is 5km away from the busbar outlet, and the fault type is C phase grounding through arc. The load current of line L4 is set to 182A, the line current phase lags the electromotive force by 32°, the original fault point transition resistance is 20Ω, the busbar grounding point grounding resistance is equivalent to 4Ω, the fault occurs at 0.1s, and the busbar grounding switch is closed at 0.145s. The current waveforms of the busbar grounding point in the two cases of fault not being eliminated and fault elimination are recorded respectively, as shown in Figure 6As shown in the figure. When the fault is eliminated, the current at the bus grounding point lags behind the bus zero-sequence voltage by 89.61°. When the fault is not eliminated, the current phase at the bus grounding point lags behind the bus zero-sequence voltage by 118.21°, and the amplitude exceeds the current amplitude when the fault is eliminated by 56.31%. According to the offset, it can be judged that the fault at the original fault point has not been eliminated.

[0061] When the load current is set to 75A and the transition resistance of the original fault point is 4Ω, the current phase of the busbar grounding point lags the zero-sequence voltage by 103.5° when the fault is not eliminated, and the amplitude exceeds the current amplitude when the fault is eliminated by 6.41%. At this time, the amplitude deviation is less than 20%, and further judgment is required based on the zero-sequence current of the fault line. At this time, the zero-sequence current waveform of the fault line in the two cases of fault not eliminated and fault eliminated is as follows Figure 7 As shown in the figure, in both cases, the current amplitude when the fault is not eliminated is 52.07% of the current amplitude when the fault is eliminated. According to the offset, the fault status of the original fault point can be determined.

[0062] At present, the arc extinguishing device and action flow of the rapid fault transfer point cannot determine the state of the original fault point during the period when the fault phase bus is grounded. The embodiment of the present invention proposes to use the bus grounding point current and the zero-sequence current of the fault line to identify the state of the original fault point during the period when the fault phase bus is grounded, which has the following advantages: (1) There is no need to increase the primary equipment investment, and the identification can be completed using the existing arc extinguishing device and measurement device; (2) The impact of the fault phase voltage mutation caused by the repeated opening and closing of the bus grounding switch on the original fault point is avoided; (3) The ability to quickly handle single-phase grounding faults in the distribution network is enhanced, and the safety of the distribution network is improved. Theoretical analysis and simulation experiments have proved the accuracy and effectiveness of the original fault point state identification proposed in this article.

[0063] Embodiment 2:

[0064] like Figure 4 The original fault point state online identification system based on the rapid transfer fault point arc extinguishing device shown includes:

[0065] The fault information judging unit 100 is used to obtain fault information and judge the fault type, fault phase and fault line according to the fault information;

[0066] The arc extinguishing device input unit 200 is used to input the arc extinguishing device for rapid fault transfer when the fault type is a single-phase arc grounding fault;

[0067] A signal recording unit 300, used to record the busbar grounding point current signal and the fault line zero-sequence current signal before and after the arc extinguishing device is put into use;

[0068] An identification unit 400 is used to identify whether the original fault point is eliminated by combining the bus grounding point current and the fault line zero-sequence current amplitude phase deviation to determine whether it exceeds a set threshold value;

[0069] The decision unit 500 is used to reset the arc extinguishing device of the rapid fault transfer point when the original fault point is eliminated in combination with the identified original fault point state, and to send out an alarm signal to notify the on-duty personnel to handle the fault when the original fault point is not eliminated.

[0070] like Figure 5 As shown, the fast transfer fault point arc extinguishing device includes phase-splitting electronic switches (thyristors) KA, KB, KC, fuses FU, control units, voltage transformers PT, and current transformers CT; one end of the phase-splitting electronic switches KA, KB, and KC is connected to the busbar through a fuse FU, and the other end is grounded; the voltage transformer PT and the current transformer CT are connected to the busbar, and the voltage transformer is grounded. The control unit is respectively connected to the phase-splitting electronic switches KA, KB, and KC, the voltage transformer PT, and the current transformer CT. The control unit is used to collect PT and CT information and calculate the effective grounding time, and is also used to send the closing signal to the phase-splitting electronic switch. By taking advantage of the rapid action and short delay of the electronic switch, it is ensured that the fault phase busbar is reliably short-circuited when the current passes through the zero point.

[0071] The online identification system for the original fault point state based on the rapid transfer fault point arc extinguishing device provided in the embodiment of the present invention has the same technical features as the online identification method for the original fault point state based on the rapid transfer fault point arc extinguishing device provided in the above embodiment, so it can also solve the same technical problems and achieve the same technical effects.

[0072] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0073] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0074] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0075] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An online identification method for the original fault point state based on a fast transfer fault point arc extinguishing device, It is characterized in that The steps include: Obtaining fault information, and determining the fault type and the fault phase and fault line according to the fault information; In the case where the fault type is a single-phase arc grounding fault, an arc extinguishing device for rapid fault transfer is put into operation; Calculate the busbar grounding current when the original fault point fails to extinguish the arc according to the busbar grounding current before and after the arc extinguishing device is put into use. Relative to the system zero sequence voltage The phase difference and the busbar grounding current when the original fault point fails to extinguish the arc Busbar grounding current when arc is successfully extinguished relative to the original fault point Amplitude deviation; when the amplitude deviation is greater than 20% or Hysteresis When it is greater than 100°, it is judged that the fault at the original fault point has not been eliminated; Otherwise, make a judgment based on the zero-sequence current of the fault line; The busbar grounding point current includes: when the original fault point successfully extinguishes the arc, the current flowing through the busbar grounding point It is the sum of the capacitance currents of all non-fault phases of all lines. When the original fault point fails to extinguish the arc successfully, the current flowing through the bus grounding point is Including capacitive current component and load current component; When the load current is small and the busbar grounding current criterion fails, the zero-sequence current amplitude of the fault line is calculated. When it is lower than 90% of the zero-sequence current of the fault line when the original fault point is eliminated, it is judged that the fault of the original fault point has not been eliminated; otherwise, it is judged that the fault of the original fault point has been eliminated. The zero-sequence current of the fault line includes: when the original fault point successfully extinguishes the arc, the grounding point and the line-to-ground capacitance form a zero-sequence path, and the zero-sequence current of the fault line is mainly capacitive current; when the original fault point fails to extinguish the arc, the system has two points of grounding in the same phase, the two grounding points and the line-to-ground capacitance form a zero-sequence path, and the zero-sequence current of the fault line is the shunting of the capacitive current between the two grounding points.

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