CN109782115B - Method for judging disappearance of full-compensation ground fault of controllable voltage source - Google Patents
Method for judging disappearance of full-compensation ground fault of controllable voltage source Download PDFInfo
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- CN109782115B CN109782115B CN201910246915.3A CN201910246915A CN109782115B CN 109782115 B CN109782115 B CN 109782115B CN 201910246915 A CN201910246915 A CN 201910246915A CN 109782115 B CN109782115 B CN 109782115B
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Abstract
The embodiment of the application discloses a method for judging the disappearance of the full compensation ground fault of a controllable voltage source. And (3) keeping the amplitude of the output voltage of the controllable voltage source unchanged, changing the phase angle of the output voltage of the controllable voltage source, and if the phase angles of the zero-sequence currents of all the lines are changed along with the phase angle of the output voltage of the controllable voltage source before and after the phase angle of the output voltage of the controllable voltage source is changed, the ground fault disappears at the moment, and the controllable voltage source stops compensation output. The method is simple, accurate in calculation and strong in applicability, and a controllable voltage source independent full compensation structure or a controllable voltage source parallel arc suppression coil full compensation structure can be used, so that the method for judging the disappearance of the ground fault in the state of controllable voltage source ground current full compensation is simple, convenient and effective.
Description
Technical Field
The application relates to the technical field of single-phase grounding current full compensation of a power grid, in particular to a method for judging disappearance of a full-compensation grounding fault of a controllable voltage source.
Background
In a power grid system, particularly in a medium-low voltage power distribution network system, single-phase earth faults account for the absolute majority of the total number of faults. The neutral point grounding mode of the medium and low voltage distribution network mainly comprises a neutral point ungrounded mode, a neutral point grounded mode through an arc suppression coil or a neutral point grounded mode through a low-value resistor. Under the mode that the neutral point is not grounded, grounding current is not compensated and operates with faults, and personal electric shock risks exist. Under the mode that the neutral point is grounded through the arc suppression coil, the arc suppression coil compensates grounding capacity flow after single-phase grounding, grounding electric arcs can be extinguished, a system can operate with faults, but certain grounding residual flow still exists in the grounding point, and personal electric shock risks still exist. Under the mode that the neutral point is grounded through a low-value resistor, the grounding circuit is tripped through the zero sequence protection of the circuit of the relay protection device, and the power supply reliability cannot be guaranteed.
Therefore, how to quickly and accurately judge whether the ground fault disappears becomes a problem to be solved urgently by those skilled in the art.
Disclosure of Invention
The application provides a method for judging whether a controllable voltage source full-compensation ground fault disappears, which aims to solve the problem that whether the ground fault disappears can not be judged quickly and accurately in the prior art.
The application provides a method for judging disappearance of a full-compensation ground fault of a controllable voltage source, which comprises the following steps:
after the single-phase grounding of the system, the controllable voltage source outputs compensation voltage to perform grounding current compensation;
keeping the amplitude of the output voltage of the controllable voltage source unchanged, and changing the phase angle of the output voltage of the controllable voltage source to obtain the phase angle change quantity of the output voltage of the controllable voltage source;
calculating the absolute value of the variation of the phase angle of the zero-sequence current of each line before and after the phase angle of the voltage output by the controllable voltage source is changed;
calculating the absolute value of the difference between the phase angle change of the output voltage of the controllable voltage source and the absolute value of the change of each line;
determining that a ground fault is disappeared if the absolute value of the difference for each line is less than or equal to a difference absolute value threshold.
Further, the direction of change of the phase angle of the voltage output by the controllable voltage source comprises clockwise or counterclockwise.
Further, the phase angle change amount of the output voltage of the controllable voltage source is 0.3-0.5 degrees.
Further, the absolute value threshold of the difference is 15% -20% of the phase angle change of the output voltage of the controllable voltage source.
According to the above embodiments, the present application provides a method for determining that a full-compensation ground fault of a controllable voltage source disappears. And (3) keeping the amplitude of the output voltage of the controllable voltage source unchanged, changing the phase angle of the output voltage of the controllable voltage source, and if the phase angles of the zero-sequence currents of all the lines are changed along with the phase angle of the output voltage of the controllable voltage source before and after the phase angle of the output voltage of the controllable voltage source is changed, the ground fault disappears at the moment, and the controllable voltage source stops compensation output. The method is simple, accurate in calculation and strong in applicability, and a controllable voltage source independent full compensation structure or a controllable voltage source parallel arc suppression coil full compensation structure can be used, so that the method for judging the disappearance of the ground fault in the state of controllable voltage source ground current full compensation is simple, convenient and effective.
Drawings
In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without any creative effort.
Fig. 1 is a flowchart of a method for determining disappearance of a full-compensation ground fault of a controllable voltage source according to the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.
The grounding current of the power grid system is fully compensated, the grounding point current can be compensated to a minimum value when single-phase grounding is carried out, the system can still operate with faults, the personal electric shock hazard of the grounding point is eliminated, and the method is an advanced grounding current compensation mode.
The ground current full compensation based on the controllable voltage source outputs compensation voltage with adjustable phase and amplitude through the controllable voltage source to generate compensation current, and the ground current full compensation is realized. The full compensation of the controllable voltage source can be compensated independently or can be used in parallel with the arc suppression coil. After the controllable voltage source performs grounding current full compensation, no matter whether a single-phase grounding fault disappears or not, the amplitude and the phase relation of each phase voltage and zero sequence voltage of the system are the same as the single-phase metallic grounding phenomenon, and whether the grounding fault disappears or not cannot be judged through the amplitude and the phase relation of the phase voltage and the zero sequence voltage of the system.
According to the method for judging the disappearance of the ground fault of the full compensation of the controllable voltage source, the fault state can be judged quickly and accurately under various topological structures of the full compensation of the ground current of the controllable voltage source, and a quick, effective and simple method for judging the disappearance of the ground fault is provided for realizing the full compensation of the ground current of the controllable voltage source.
Referring to fig. 1, the present application provides a method for determining disappearance of a full-compensation ground fault of a controllable voltage source, where the method includes:
s101, after the system is grounded in a single phase, a controllable voltage source outputs compensation voltage to perform grounding current compensation;
s102, keeping the amplitude of the output voltage of the controllable voltage source unchanged, and changing the phase angle of the output voltage of the controllable voltage source to obtain the phase angle change amount of the output voltage of the controllable voltage source;
step S103, calculating the absolute value of the variation of the phase angle of the zero-sequence current of each line before and after the phase angle of the output voltage of the controllable voltage source is changed;
step S104, calculating the absolute value of the difference between the phase angle change of the output voltage of the controllable voltage source and the absolute value of the change of each line;
and step S105, if the absolute value of the difference value of each line is less than or equal to the absolute value threshold of the difference value, determining that the ground fault disappears.
Further, the direction of change of the phase angle of the voltage output by the controllable voltage source comprises clockwise or counterclockwise.
Further, the phase angle change amount of the output voltage of the controllable voltage source is 0.3-0.5 degrees.
Further, the absolute value threshold of the difference is 15% -20% of the phase angle change of the output voltage of the controllable voltage source.
According to the embodiment, the method is simple, accurate in calculation and high in applicability, the controllable voltage source independent full compensation structure or the controllable voltage source parallel arc suppression coil full compensation structure can be used, and the simple, convenient and effective method for judging the disappearance of the grounding fault in the state of full compensation of the grounding current of the controllable voltage source is provided.
Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It will be understood that the present application is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (4)
1. A method for determining disappearance of a fully compensated ground fault of a controllable voltage source, the method comprising:
after the single-phase grounding of the system, the controllable voltage source outputs compensation voltage to perform grounding current compensation;
keeping the amplitude of the output voltage of the controllable voltage source unchanged, and changing the phase angle of the output voltage of the controllable voltage source to obtain the phase angle change quantity of the output voltage of the controllable voltage source;
calculating the absolute value of the variation of the phase angle of the zero-sequence current of each line before and after the phase angle of the voltage output by the controllable voltage source is changed;
calculating the absolute value of the difference between the phase angle change of the output voltage of the controllable voltage source and the absolute value of the change of each line;
determining that a ground fault is disappeared if the absolute value of the difference for each line is less than or equal to a difference absolute value threshold.
2. The method as claimed in claim 1, wherein the direction of change of the phase angle of the voltage outputted from the controllable voltage source includes clockwise or counterclockwise.
3. The method for determining disappearance of ground fault of full compensation of controllable voltage source according to claim 1, wherein the phase angle change of the output voltage of the controllable voltage source is 0.3 ° -0.5 °.
4. The method for determining disappearance of ground fault of full compensation of controllable voltage source according to claim 1, wherein the threshold of absolute difference value is 15% -20% of the absolute value of the phase angle change of the output voltage of the controllable voltage source.
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| US9759759B2 (en) * | 2015-07-15 | 2017-09-12 | Vale S.A. | Apparatus and method for sensing a leakage current between first and second locations in a single wire earth return circuit |
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