CN112909902B - Control method for flexible tripping of power distribution network, fault feeder line identification method and system - Google Patents
Control method for flexible tripping of power distribution network, fault feeder line identification method and system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
- H02J13/00007—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using the power network as support for the transmission
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/20—Systems supporting electrical power generation, transmission or distribution using protection elements, arrangements or systems
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
- Y04S40/121—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using the power network as support for the transmission
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Abstract
The invention discloses a control method for flexible tripping of a power distribution network, a fault feeder line identification method and a system, wherein the method is characterized in that a flexible zero sequence voltage source with continuously adjustable amplitude and phase angle is integrated to a neutral point of the power distribution network, the voltage flexibility of a fault phase is restrained to be zero, flexible tripping is realized, the power supply of a fault grounding branch is cut off, the effect of isolating faults similar to the traditional tripping is achieved, and the power supply of a load is not interrupted; the zero sequence voltage source amplitude is used for carrying out moderate flexible callback, the fault phase voltage of the power distribution network is regulated and controlled to be gradually increased from 0, flexible reclosing is realized, meanwhile, whether faults disappear is detected, the effect is the same as that of the traditional reclosing, and the whole process does not need complete power failure.
Description
Technical Field
The invention belongs to the field of fault identification of power distribution networks, and particularly relates to a control method for flexible tripping of a power distribution network, a fault feeder line identification method and a system.
Background
The distribution network goes deep into the user side, various random faults are easy to occur in the operation process, and the proportion of single-phase earth faults of the distribution network is up to more than 70% among the faults. If the single-phase grounding fault can not be handled in time, personal electric shock accidents and burning of power equipment are easy to occur, and the single-phase grounding fault is easy to generate interphase faults and three-phase short circuit faults, so that large-area malignant power failure accidents are caused, and the power supply reliability of the region is affected. The main relay protection means adopted by the current 6-66kV medium-low voltage distribution network is three-section current protection, which is current protection with a short time limit or no time limit action, and mainly comprises instantaneous current quick-break protection, time-limited current quick-break protection and time-limited overcurrent protection. However, although the current quick-break protection with a short time limit is adopted, a certain time is required to effectively cut off the short-circuit fault and control the accident spreading. In the whole process, normal operation is recovered or fault isolation is carried out, and due to tripping and reclosing, a short-time outage phenomenon can occur, so that the continuous power supply reliability and the power supply quality of the power distribution network are affected. Therefore, the principle research and the device operation of the uninterrupted reliable protection technology are urgently needed.
In the prior art, once a power distribution network fault occurs, a traditional tripping-reclosing processing method detects that a ground fault occurs when the ground fault occurs, and then a breaker trips to cut off the fault (three-phase tripping, downstream power failure). After a period of time (for example, 5 seconds), the circuit breaker recloses and detects whether the fault is eliminated, if the fault is eliminated, normal power supply is restored, if the fault is not eliminated, the circuit breaker is permanently tripped again, and the personnel wait to arrive at the site to handle the fault. The whole process requires at least several hours, and the power distribution voltage in the reclosing process is hard abrupt change, which is very easy to damage the power grid.
Disclosure of Invention
The invention aims to provide a flexible tripping control method of a power distribution network, a fault feeder line identification method and a system, wherein the flexible tripping control of flexible reclosing is achieved by combining a flexible zero sequence voltage source with continuously adjustable amplitude and phase angle into a neutral point of the power distribution network, so that the purpose of flexibly inhibiting single-phase grounding faults of the power distribution network is achieved, meanwhile, fault lines are selected, and the problems that when the power distribution network has grounding faults in the prior art, the power distribution network cannot continuously supply power reliably and simultaneously perform fault line selection are solved.
A control method for flexible tripping of a power distribution network comprises the following steps:
step 1: continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network, entering a step 2 when a single-phase earth fault occurs in the power distribution network, otherwise, repeating the step 1 to continuously monitor;
step 2: the zero sequence voltage source with continuously adjustable amplitude and phase angle is merged into the neutral point, the fault phase voltage is regulated to 0, and the fault phase voltage is enabled to be kept for a time T of 0, so that flexible tripping is realized;
step 3: when the fault phase is completely extinguished, the zero sequence voltage is appliedIs flexibly adjusted back to a magnitude lower than the magnitude of the fault phase supply voltage,/or%>And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, and realizing flexible reclosing;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the neutral point voltage in the first section of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0, 1.
A fault feeder line identification method for flexible tripping of a power distribution network comprises the following steps:
step 1: continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network, entering a step 2 when a single-phase earth fault occurs in the power distribution network, otherwise, repeating the step 1 to continuously monitor;
step 2: the zero sequence voltage source with continuously adjustable amplitude and phase angle is integrated to the neutral point, the fault phase voltage is regulated to 0, the fault phase voltage is enabled to be kept at 0 for a time T, flexible tripping is realized, and the zero sequence to ground parameters of the detection points at the head ends of all feeder lines are measured in the time T;
regulating to 0, and completely reducing the voltage of a fault point to zero to realize complete arc extinction;
the amplitude of the zero sequence voltage source is the same as the voltage amplitude of the fault phase, and the phase angle of the zero sequence voltage source is opposite to the phase angle of the fault phase;
the voltage of the fault phase is reduced to zero, the non-fault phase rises to line voltage, normal user power supply is not affected, and the arc extinction process is not powered off;
the zero-sequence voltage source of the neutral point is a zero-sequence adjustable voltage source based on PWM closed-loop adjustment, and the zero-sequence voltage of the neutral point is continuously adjusted by combining a zero-sequence voltage source with continuously adjustable amplitude and phase angle at the neutral point of the power distribution network; thereby indirectly and continuously suppressing the voltage of the fault point of the fault feeder lineContinuously regulating the voltage of the fault point>To 0, the condition of arc re-burning is destroyed, so as to achieve the purpose of flexible arc extinction;
when the fault point is completely extinguished, measuring the zero sequence to ground parameters at the detection point of each feeder line at the moment, and recording the measured value at the moment;
step 3: when the fault phase is completely extinguished, the zero sequence voltage is appliedIs flexibly adjusted back to below the amplitude of the fault phase supply,/>And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, performing flexible reclosing, and measuring zero sequence earth parameters of the detection points at the head ends of the feeder lines again in the time T;
callback is used for slightly rising the voltage of a fault phase, is a tentative process for judging whether a line is in transient or permanent fault, and is uninterrupted;
wherein,representing the electromotive force of the j phase of the fault phase, namely the value range of the j phase line first section to the neutral point voltage is as follows{ A, B, C }; k represents a callback coefficient, and the value is 0 and 1;
the larger the grounding resistance is, the smaller the callback coefficient k is, the smaller the grounding resistance is, and the larger the callback coefficient k is;
step 4: judging and selecting a fault line by comparing the zero sequence earth parameter measured values of the front and rear two times of the detection point of the head end of each feeder line;
and judging the difference value of the zero sequence ground parameter measurement values of the front and rear two times of the detection point of the head end of each feeder line in sequence, if the difference value exceeds a set threshold value, permanent faults exist in the corresponding feeder line, otherwise, transient faults exist in the corresponding feeder line or no faults exist in the corresponding feeder line.
The scheme starts from the basic requirement of continuous and reliable power supply of the power distribution network, and provides a control method for flexible tripping of the power distribution network and a new fault feeder line identification method. The voltage type flexible tripping compensation device is high in arc extinguishing speed and has an auxiliary function of concomitantly carrying out dynamic identification on fault feeder lines. The dynamic identification technology of the ground fault feeder line based on the zero sequence to ground parameter measurement value front-back comparison is organically combined together. And (3) finishing the measurement of the zero sequence parameter to the ground once in a complete arc extinction state, and carrying out the measurement of the zero sequence parameter to the ground once again by flexibly calling back the neutral point zero sequence voltage for the first time. And (3) comparing the zero sequence to ground parameter measurement module values of the front and rear two times of each feeder line, judging the transient and permanent fault threshold values, and recovering the normal operation of the power distribution network or sensitively identifying the permanent ground fault feeder line. The distribution network works in a working state of continuous power supply in the whole process of arc extinction of flexible tripping and feeder line identification, so that the most basic power consumption requirement of a user is ensured. The dynamic identification technology of the fault feeder is not influenced by factors such as transition resistance, fault closing angle, fault distance and the like, and is also applicable to high-resistance grounding faults.
Further, the failed phase is identified by:
and if the neutral point voltage exceeds 15% of the rated phase voltage or the neutral point voltage variation exceeds 3% of the rated phase voltage, judging that the ground fault occurs.
Further, the faulty wire is identified by the following method:
firstly, setting a grounding branch circuit for uniformly adjusting the winding access quantity at a transformer winding tap;
secondly, continuously measuring the neutral point voltage and the neutral point voltage variation of the grounding transformer, if the neutral point voltage exceeds 15% of rated phase voltage or the neutral point voltage variation exceeds 3% of rated phase voltage, then a grounding fault possibly exists, closing a grounding branch which is arranged at a transformer winding tap and uniformly adjusts the winding access, namely closing a switch of the grounding branch of a fault phase, otherwise, judging that the grounding fault does not exist currently;
and finally, gradually increasing the access gear of the tapping tap of the winding of the lowest voltage phase in the grounding transformer, measuring the zero sequence current of the three-phase line of the system, if the zero sequence current is linearly increased along with the increase of the access gear, no fault occurs, and if the zero sequence current of a certain line is in nonlinear change, judging that the corresponding line has faults.
Further, the fact that the zero sequence current increases or decreases linearly along with the change of the access gear means that when the correlation coefficient r between the size of the access gear of the tapping tap of the grounding transformer winding and the size of the zero sequence current is greater than or equal to 0.98, the zero sequence current increases linearly along with the increase of the access gear, and the zero sequence current decreases linearly along with the decrease of the access gear.
Further, the correlation coefficient r between the gear position and the zero sequence current is calculated by the following formula:
wherein: i is the size of an access gear where a tapping tap of a grounding transformer winding is positioned, I 0i And n represents the total gear of the grounding transformer winding for the zero sequence current of the line in the ith gear.
Further, the transformer winding tap connected with the grounding support for uniformly adjusting the winding access quantity is provided with n access gears, and the value of n is an integer greater than or equal to 2.
A fault feeder identification system for flexible tripping of a power distribution network, comprising:
the single-phase fault monitoring unit of the power distribution network is used for continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network and detecting single-phase earth faults of the power distribution network;
the complete arc extinguishing unit is used for adjusting the fault phase voltage to 0 by combining a zero sequence voltage source with continuously adjustable amplitude and phase angle into a neutral point, enabling the fault phase voltage to be kept at 0 for a time T, performing flexible tripping, and measuring zero sequence grounding parameters of detection points at the head end of each feeder line in the time T;
the amplitude of the zero sequence voltage source is the same as the voltage amplitude of the fault phase, and the phase angle of the zero sequence voltage source is opposite to the phase angle of the fault phase;
fault discrimination flexible test unit for zero sequence voltageIs flexibly adjusted back to a magnitude lower than the magnitude of the fault phase supply voltage,/or%>And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, performing flexible reclosing, and measuring zero sequence earth parameters of the detection points at the head ends of the feeder lines again in the time T;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the central point voltage at the head end of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0 and 1;
the feeder fault determining unit is used for determining and selecting a fault line by comparing the zero sequence to ground parameter measured values of the front and rear two times of the detection point of the first section of each feeder obtained by the fault determining probe unit;
and judging the difference value of the zero sequence ground parameter measurement values of the front and rear two times of the detection point of the head end of each feeder line in sequence, if the difference value exceeds a set threshold value, permanent faults exist in the corresponding feeder line, otherwise, transient faults exist in the corresponding feeder line or no faults exist in the corresponding feeder line.
Advantageous effects
The invention provides a control method of flexible tripping of a power distribution network, a fault feeder line identification method and a system, wherein the method creatively designs a flexible tripping and reclosing concept, and a flexible zero-sequence voltage source with continuously adjustable amplitude and phase angle is integrated to a neutral point of the power distribution network to flexibly inhibit fault phase voltage to zero, so that flexible tripping is realized, and power supply of a fault grounding branch is cut off (the same effect as that of traditional tripping is achieved); the fault phase voltage of the power distribution network is regulated and controlled to be gradually increased from 0 through moderate flexible callback of the amplitude of the zero sequence voltage source, flexible reclosing is realized, meanwhile, whether the fault disappears or not is detected (the same effect as that of the traditional reclosing is achieved), and the whole process does not need to be completely powered off; compared with the prior art, the method has the following advantages:
(1) The method can quickly restrain the voltage of the fault point to 0, destroy the reignition condition of the fault arc of the grounding point, solve the problem of intermittent arc grounding fault and reduce the potential safety hazard of equipment;
(2) The method provides an advanced concept of flexible tripping-reclosing, does not need to perform power failure in the whole fault treatment process, and can reliably operate for a period of time with faults; the fault voltage of the power distribution network is flexible and gradually changed in the whole process, and the fault voltage is not similar to rigid tripping-reclosing, so that abrupt impact damage is easily caused to the system; the power distribution network can be ensured to work under a continuous power supply state in the whole process, and the power failure during fault removal is avoided.
(3) The active arc extinction technology, the fault line selection technology and the zero sequence voltage source flexible regulation and control technology of the power distribution network with faults are organically combined together, and in the process of rapidly processing the ground faults, the flexible callback of the zero sequence voltage source concomitantly selects fault lines of the power distribution network.
Drawings
FIG. 1 is a flow chart of a method according to an example of the invention;
fig. 2 is a schematic diagram of a voltage-type flexible tripping device of a power distribution network in complete arc extinction;
FIG. 3 is a schematic diagram of a zero sequence to ground parameter measurement model for a metallic ground fault;
FIG. 4 is a schematic diagram of a zero sequence ground parameter measurement model for a 200Ω ground fault;
fig. 5 is a schematic diagram of a zero sequence of 1kΩ ground fault versus ground parameter measurement model.
Detailed Description
The invention will be further described with reference to examples and figures.
A control method for flexible tripping of a power distribution network comprises the following steps:
step 1: continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network, entering a step 2 when a single-phase earth fault occurs in the power distribution network, otherwise, repeating the step 1 to continuously monitor;
step 2: the zero sequence voltage source with continuously adjustable amplitude and phase angle is merged into the neutral point, the fault phase voltage is regulated to 0, and the fault phase voltage is enabled to be kept for a time T of 0, so that flexible tripping is realized;
step 3: when the fault phase is completely extinguished, the zero sequence voltage is appliedIs flexibly adjusted back to a magnitude lower than the magnitude of the fault phase supply voltage,/or%>And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, and realizing flexible reclosing;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the neutral point voltage in the first section of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0, 1.
As shown in fig. 1, a fault feeder line identification method for flexible tripping of a power distribution network comprises the following steps:
step 1: continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network, entering a step 2 when a single-phase earth fault occurs in the power distribution network, otherwise, repeating the step 1 to continuously monitor;
step 2: the zero sequence voltage source with continuously adjustable amplitude and phase angle is integrated to the neutral point, the fault phase voltage is regulated to 0, the fault phase voltage is enabled to be kept at 0 for a time T, flexible tripping is realized, and the zero sequence to ground parameters of the detection points at the head ends of all feeder lines are measured in the time T;
regulating to 0, and completely reducing the voltage of a fault point to zero to realize complete arc extinction;
the amplitude of the zero sequence voltage source is the same as the voltage amplitude of the fault phase, and the phase angle of the zero sequence voltage source is opposite to the phase angle of the fault phase;
the voltage of the fault phase is reduced to zero, the non-fault phase rises to line voltage, normal user power supply is not affected, and the arc extinction process is not powered off;
the zero-sequence voltage source of the neutral point is a zero-sequence adjustable voltage source based on PWM closed-loop adjustment, and the zero-sequence voltage of the neutral point is continuously adjusted by injecting a zero-sequence voltage source with continuously adjustable amplitude and phase angle into the neutral point of the power distribution network; thereby indirectly and continuously suppressing the voltage of the fault point of the fault feeder lineContinuously regulating the voltage of the fault point>To 0, the condition of arc re-burning is destroyed, so as to achieve the purpose of flexible arc extinction;
when the fault point is completely extinguished, measuring the zero sequence to ground parameters at the detection point of each feeder line at the moment, and recording the measured value at the moment;
step 3: flexibly adjusting the amplitude of the zero sequence voltage source to a value lower than the amplitude of the fault phase power supply after the fault phase is completely extinguished And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, performing flexible reclosing, and measuring zero sequence earth parameters of the first section detection points of all feeder lines again in the time T;
callback is used for slightly rising the voltage of a fault phase, is a tentative process for judging whether a line is in transient or permanent fault, and is uninterrupted;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the neutral point voltage in the first section of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0 and 1;
the larger the grounding resistance is, the smaller the callback coefficient k is, the smaller the grounding resistance is, and the larger the callback coefficient k is;
step 4: judging and selecting a fault line by comparing the zero sequence earth parameter measured values of the front and rear two times of the detection point of the head end of each feeder line;
and judging the difference value of the zero sequence to ground parameter measurement values of the front and rear two times of detection points of the first section of each feeder line in sequence, if the difference value exceeds a set threshold value, permanent faults exist in the corresponding feeder line, otherwise, transient faults exist in the corresponding feeder line or no faults exist in the corresponding feeder line.
The scheme starts from the basic requirement of continuous and reliable power supply of the power distribution network, and provides a control method for flexible tripping of the power distribution network and a new fault feeder line identification method. The voltage type flexible tripping and reclosing system has the advantages of high arc extinguishing speed and auxiliary function of concomitantly carrying out dynamic identification on fault feeder lines. The method organically combines the ground fault feeder dynamic identification technology based on zero sequence to ground parameter measurement value front-back comparison with the power distribution network tripping control, fault arc extinction, continuous power supply and uninterrupted operation. And (3) finishing the measurement of the zero sequence parameter to the ground once in a complete arc extinction state, and carrying out the measurement of the zero sequence parameter to the ground once again by flexibly calling back the zero sequence voltage of the neutral point once. And (3) comparing the zero sequence to ground parameter measurement module values of the front and rear two times of each feeder line, judging the transient and permanent fault threshold values, and recovering the normal operation of the power distribution network or sensitively completing the identification of the permanent ground fault feeder line. The distribution network works in a working state of continuous power supply in the whole process of flexible tripping, reclosing arc extinction and feeder line identification, so that the most basic power consumption requirement of a user is ensured. The dynamic identification technology of the fault feeder is not influenced by factors such as transition resistance, fault closing angle, fault distance and the like, and is also applicable to high-resistance grounding faults.
The faulty phase is identified by the following method:
and if the neutral point voltage exceeds 15% of the rated phase voltage or the neutral point voltage variation exceeds 3% of the rated phase voltage, judging that the ground fault occurs.
The fault line is identified by the following method:
firstly, setting a grounding branch circuit for uniformly adjusting the winding access quantity at a transformer winding tap;
secondly, continuously measuring the neutral point voltage and the neutral point voltage variation of the grounding transformer, if the neutral point voltage exceeds 15% of rated phase voltage or the neutral point voltage variation exceeds 3% of rated phase voltage, then a grounding fault possibly exists, closing a grounding branch which is arranged at a transformer winding tap and uniformly adjusts the winding access, namely closing a switch of the grounding branch of a fault phase, otherwise, judging that the grounding fault does not exist currently;
and finally, gradually increasing the access gear of the tapping tap of the winding of the lowest voltage phase in the grounding transformer, measuring the zero sequence current of the three-phase line of the system, if the zero sequence current is linearly increased along with the increase of the access gear, no fault occurs, and if the zero sequence current of a certain line is in nonlinear change, judging that the corresponding line has faults.
The fact that the zero sequence current is increased or decreased linearly along with the change of the access gear means that when the correlation coefficient r between the size of the access gear of the tapping tap of the grounding transformer winding and the size of the zero sequence current is greater than or equal to 0.98, the zero sequence current is increased linearly along with the increase of the access gear, and the zero sequence current is decreased linearly along with the decrease of the access gear.
The correlation coefficient r of the gear position and the zero sequence current is calculated by adopting the following formula:
wherein: i is the size of an access gear where a tapping tap of a grounding transformer winding is positioned, I 0i And n represents the total gear of the grounding transformer winding for the zero sequence current of the line in the ith gear.
The transformer winding tap connected with the grounding circuit for uniformly adjusting the winding access quantity is provided with n access gears, and the value of n is an integer greater than or equal to 2.
A fault feeder identification system for flexible tripping of a power distribution network, comprising:
the single-phase fault monitoring unit of the power distribution network is used for continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network and detecting single-phase earth faults of the power distribution network;
the complete arc extinguishing unit is used for adjusting the fault phase voltage to 0 by combining a zero sequence voltage source with continuously adjustable amplitude and phase angle into a neutral point, enabling the fault phase voltage to be kept at 0 for a time T, realizing flexible tripping, and measuring zero sequence parameters of a first section detection point of each feeder line in the time T;
the amplitude of the zero sequence voltage source is the same as the voltage amplitude of the fault phase, and the phase angle of the zero sequence voltage source is opposite to the phase angle of the fault phase;
the fault discrimination flexible probing unit flexibly calls back the amplitude of the zero sequence voltage source to a value lower than the amplitude of the fault phase power supply after the fault phase is completely extinguished And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, performing flexible reclosing, and measuring zero sequence earth parameters of the detection points at the head ends of the feeder lines again in the time T;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the neutral point voltage in the first section of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0 and 1;
the fault feeder line determining unit is used for determining and selecting a fault line by comparing the zero sequence to ground parameter measured values of the front and rear two times of the detection point of the first section of each feeder line, which are obtained by the fault determining probe unit;
and judging the difference value of the two zero sequence ground parameter measurement values before and after the detection point of the head end of each feeder line in sequence, if the difference value exceeds a set threshold value, permanent faults exist in the corresponding feeder line, and otherwise, transient faults exist or no faults exist in the corresponding feeder line.
By adopting the method, the line selection is carried out according to whether the ground parameters of the fault line and the non-fault line are changed before and after flexible callback; the principle of fault feeder line identification before and after flexible callback based on the voltage type flexible tripping and reclosing full arc extinction technology is as follows: the distribution network has a plurality of feeder lines, the fault feeder line is assumed to be Lm and the non-fault feeder line is assumed to be Ln, and a principle formula description is carried out, wherein the zero sequence voltage of a neutral point isFlexible callback back->The zero sequence current of the fault feeder line and the zero sequence current of the non-fault feeder line are respectively +.>Principle of fault feeder line Lm zero sequence to ground parameterThe formulas are (1) - (2) as follows:
when the power distribution network is completely extinguished to the ground after the flexible tripping device of the power distribution network is put into operation, the fault feeder line is measured to the ground parameter z0m at the moment, whereinAfter flexible callback, the fault feeder line measures z0m' to the ground parameter: wherein->(0≤k＜1)/>z01 is the single relative ground impedance of the faulty feeder under normal conditions, z 01 ＝r 01 //(1/jωc 01 ) R01 and c01 are the single relative ground leakage resistance and the ground capacitance, respectively, of the faulty line under normal conditions. Related formulas such as (3) - (4):
conclusion 1: 1) If z0m=z0m', then it is indicated that the feeder Lm is experiencing an instantaneous fault. 2) If z0m+.z0m', then it is indicated that feeder Lm is permanently faulty.
The principle formulas of the zero sequence of the non-fault feeder Ln to the ground parameters are as follows (5) - (7):
when the voltage type flexible tripping device is put into operation and the distribution network is completely extinguished to the ground as shown in fig. 2, the zero sequence of the non-fault feeder line Ln is measured to be z0n, whereinAfter flexible callback, measuring the non-fault feeder line to ground parameter z0n': wherein->z02 is the single phase to ground impedance of the normal non-faulty feeder, z 02 ＝r 02 //(1/jωc 02 ) R02 and c02 are the non-faulty line single-phase to ground leakage resistance and single-phase to ground capacitance, respectively.
Conclusion 2: the zero sequence parameters of the non-fault line Ln before and after flexible callback are constant z0n=z0n' =z 02 ＝r 02 //(1/jωc 02 )。
Combining conclusion 1 with conclusion 2 can draw the following conclusion: 1) And comparing the zero sequence to ground parameter measurement values of any feeder line before and after two times, if the two zero sequence to ground parameter measurement values are unequal, judging that the line is a fault line, and meanwhile, judging that the line is permanently faulty. 2) And comparing the zero sequence to ground parameter measurement values of the front and back two times of any feeder line, and if the zero sequence to ground parameter measurement values of the front and back two times are equal, indicating that the line is a normal feeder line or a fault feeder line with transient ground fault.
If a first condition occurs in one feeder line, the full compensation voltage of the flexible tripping device is gradually and flexibly restored, manual maintenance or fault isolation is further carried out, and then the normal power supply state is restored.
If all the feeder lines are in the second condition, the input voltage of the flexible reclosure is gradually reduced, and finally the operation is stopped, so that the normal power supply state is restored.
The method of the invention is used for identifying the fault feeder line, and a schematic diagram of the voltage-type flexible tripping device of the power distribution network is shown in figure 2. In the example, in a 10kV power distribution network system, the line length of a fault feeder Lm is 10km, and the line capacitance to ground is c0am=c0bm=c0cm=c0m=0.28 uf; line-to-ground resistance r0am=r0bm=r0cm=r0m=380 kΩ; the line length of the non-fault feeder Ln is 75km, and the line capacitance to ground is C0an=C0Bn=C0Cn=C0n=2.1 uf; line-to-ground resistance r0an=r0bn=r0cn=r0n=50kΩ; arc suppression coil inductance value lp=1200 mH.
A simulation model is built by adopting PSCAD for analysis, corresponding relevant data of the voltage type flexible tripping device after flexible callback when the voltage type flexible tripping device performs complete arc extinction compensation are respectively measured and recorded aiming at different grounding fault types, and corresponding zero sequence to ground parameter values are respectively calculated; when the 10kV power distribution network respectively generates a metallic ground fault, a low-resistance ground fault and a high-resistance ground fault, the simulation measurement waveforms of the zero-sequence to-ground parameters are shown in the following figures 3-5.
As can be seen from fig. 3 to 5, the fault occurs at 0.5s, 20ms after the fault occurs, the voltage type flexible tripping device of the power distribution network acts at 0.52s, the fault phase voltage is suppressed to 0, and the voltage type flexible tripping device of the power distribution network acts again with flexible callback when the current passing through the fault transition resistor Rf is 0,1s, and at this time, the flexible callback coefficient takes k=0.8; the upper graph shows that the zero sequence parameter measurement module value of the non-fault feeder line to the ground is basically unchanged after the flexible callback and the zero sequence parameter measurement values of the front and back two times; however, when the fault line is completely extinguished, the zero sequence to ground parameter measurement module value which is twice after flexible callback is obviously changed, the characteristic quantity is obvious, and the fault feeder line identification is easy to carry out.
When the ground transition resistance is larger, k=0.8 is not easy to identify, and the callback value needs to be reduced. If k=0.2 is taken, the fault feeder line identification can be performed with high sensitivity for the ground fault resistance of tens of kiloohms.
The above description is illustrative of the invention and is not intended to be limiting, and the invention may be modified in any form without departing from the spirit of the invention.
Claims (8)
1. The control method for flexible tripping of the power distribution network is characterized by comprising the following steps of:
step 1: continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network, entering a step 2 when a single-phase earth fault occurs in the power distribution network, otherwise, repeating the step 1 to continuously monitor;
step 2: the zero sequence voltage source with continuously adjustable amplitude and phase angle is merged into the neutral point, the fault phase voltage is regulated to 0, and the fault phase voltage is enabled to be kept for a time T of 0, so that flexible tripping is realized;
step 3: when the fault phase is completely extinguished, the zero sequence voltage is appliedIs flexibly adjusted back to a magnitude lower than the magnitude of the fault phase supply voltage,/or%>And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, and realizing flexible reclosing;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the neutral point voltage in the first section of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0, 1.
2. The fault feeder line identification method for flexible tripping of the power distribution network is characterized by comprising the following steps of:
step 1: continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network, entering a step 2 when a single-phase earth fault occurs in the power distribution network, otherwise, repeating the step 1 to continuously monitor;
step 2: the zero sequence voltage source with continuously adjustable amplitude and phase angle is integrated to the neutral point, the fault phase voltage is regulated to 0, the fault phase voltage is enabled to be kept at 0 for a time T, flexible tripping is realized, and the zero sequence to ground parameters of the detection points at the head ends of all feeder lines are measured in the time T;
the amplitude of the zero sequence voltage source is the same as the voltage amplitude of the fault phase, and the phase angle of the zero sequence voltage source is opposite to the phase angle of the fault phase;
step 3: when the fault phase is completely extinguished, the zero sequence voltage is appliedIs flexibly adjusted back to a magnitude lower than the magnitude of the fault phase supply voltage,/or%>And the amplitude of the zero sequence voltage source is made to be +.>Keeping the time T, performing flexible reclosing, and measuring zero sequence earth parameters of the detection points at the head ends of the feeder lines again in the time T;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the neutral point voltage in the first section of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0 and 1;
step 4: judging and selecting a fault line by comparing the zero sequence earth parameter measured values of the front and rear two times of the detection point of the head end of each feeder line;
and judging the difference value of the zero sequence ground parameter measurement values of the front and rear two times of the detection point of the head end of each feeder line in sequence, if the difference value exceeds a set threshold value, permanent faults exist in the corresponding feeder line, otherwise, transient faults exist in the corresponding feeder line or no faults exist in the corresponding feeder line.
3. The method of claim 2, wherein the failed phase is identified by:
if the neutral point voltage exceeds 15% of rated phase voltage or the neutral point voltage variation exceeds 3% of rated phase voltage, judging that the ground fault occurs; the lowest voltage phase is determined to be the failed phase.
4. The method of claim 2, wherein the faulty line is identified by:
firstly, setting a grounding branch circuit for uniformly adjusting the winding access quantity at a transformer winding tap;
secondly, continuously measuring the neutral point voltage and the neutral point voltage variation of the grounding transformer, if the neutral point voltage exceeds 15% of rated phase voltage or the neutral point voltage variation exceeds 3% of rated phase voltage, then a grounding fault possibly exists, closing a grounding branch which is arranged at a transformer winding tap and uniformly adjusts the winding access, namely closing a switch of the grounding branch of a fault phase, otherwise, judging that the grounding fault does not exist currently;
and finally, gradually increasing the access gear of the tapping tap of the winding of the lowest voltage phase in the grounding transformer, measuring the zero sequence current of the system line, if the zero sequence current is linearly increased along with the increase of the access gear, no fault occurs, and if the zero sequence current of a certain line is in nonlinear change, judging that the corresponding line has faults.
5. The method according to claim 4, wherein the linear increase or decrease of the zero sequence current along with the change of the access gear is that the zero sequence current increases along with the increase of the access gear and the linear decrease of the zero sequence current along with the decrease of the access gear when the correlation coefficient r of the magnitude of the access gear of the tapping tap of the grounding transformer winding and the magnitude of the zero sequence current is larger than or equal to 0.98.
6. The method according to claim 5, wherein the correlation coefficient r between the gear position magnitude and the zero sequence current magnitude is calculated by the following formula:
wherein: i is the size of an access gear where a tapping tap of a grounding transformer winding is positioned, I 0i And n represents the total gear of the grounding transformer winding for the zero sequence current of the line in the ith gear.
7. The method according to any one of claims 4-6, wherein the transformer winding tap connected to the ground connection for uniformly adjusting the winding access is provided with n access gear steps, n being an integer greater than or equal to 2.
8. A fault feeder identification system for flexible tripping of a power distribution network, comprising:
the single-phase fault monitoring unit of the power distribution network is used for continuously monitoring three-phase voltage and zero-sequence voltage of the power distribution network and detecting single-phase earth faults of the power distribution network;
the full arc extinguishing unit is used for merging a zero sequence voltage source with continuously adjustable amplitude and phase angle to a neutral point through a flexible tripping device, adjusting the fault phase voltage to 0, enabling the fault phase voltage to be kept at 0, realizing flexible tripping, and measuring zero sequence to ground parameters of first section detection points of all feeder lines in the time T;
the amplitude of the zero sequence voltage source is the same as the voltage amplitude of the fault phase, and the phase angle of the zero sequence voltage source is opposite to the phase angle of the fault phase;
the fault discrimination flexible test unit is used for detecting zero sequence voltage after the fault phase is completely extinguishedIs flexibly adjusted back to a magnitude lower than the magnitude of the fault phase supply voltage,/or%>And make the amplitude of zero sequence voltage sourceThe value is +.>Keeping the time T, performing flexible reclosing, and measuring zero sequence earth parameters of the first section detection points of all feeder lines again in the time T;
wherein,the electromotive force of the j phase of the fault phase is represented, namely the value range of j to the neutral point voltage in the first section of the j phase line is { A, B, C }; k represents a callback coefficient, and the value is 0 and 1;
the feeder fault determining unit is used for determining and selecting a fault line by comparing the zero sequence to ground parameter measured values of the front and rear two times of the detection point of the first section of each feeder obtained by the fault determining probe unit;
and judging the difference value of the zero sequence ground parameter measurement values of the front and rear two times of the detection point of the head end of each feeder line in sequence, if the difference value exceeds a set threshold value, permanent faults exist in the corresponding feeder line, otherwise, transient faults exist in the corresponding feeder line or no faults exist in the corresponding feeder line.
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