CN104198888B - One-phase grounding fault judgment method - Google Patents
One-phase grounding fault judgment method Download PDFInfo
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- CN104198888B CN104198888B CN201410440208.5A CN201410440208A CN104198888B CN 104198888 B CN104198888 B CN 104198888B CN 201410440208 A CN201410440208 A CN 201410440208A CN 104198888 B CN104198888 B CN 104198888B
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Abstract
The invention relates to a one-phase grounding fault judgment method which includes the steps: firstly, setting an asymmetric current source for transmitting characteristic signals when a one-phase grounding fault happens; secondly, acquiring current signals on a circuit by a fault indicator, performing primary discrete Fourier transform for the current signals acquired by each cyclic wave, and obtaining fundamental wave current values of the current signals on the circuit; thirdly, taking fundamental wave current values I1 of n2 cyclic waves to form sequences a, performing primary discrete Fourier transform for the sequences a by each n2 cyclic wave, and obtaining fundamental wave current values I2 of the sequences a; fourthly, sequentially taking the fundamental wave current values I2 of n3 sequences a to form sequences b, and updating the sequences b every time T in a first-in first-out mode; fifthly, judging one-phase grounding faults of the fundamental wave current values in the sequences b. According to the technical scheme, the one-phase grounding fault judgment method can overcome the shortcomings of the prior art, and selectivity, reliability and accuracy of single-phase grounding fault detection are ensured.
Description
Technical field
The present invention relates to Single-phase Earth Fault of Power System detection technique field, and in particular to a kind of singlephase earth fault is sentenced
Determine method.
Background technology
In small current neutral grounding system, the detection of singlephase earth fault and positioning always ensure what power distribution network normally ran
Technological difficulties.The section of singlephase earth fault is accurately found out, the unnecessary grid switching operation to non-faulting region can be avoided, protected
Hold the continuity of power supply.As fault detector can indicate and report single-phase earthing and short trouble, therefore, it can by seeing
Examine fault detector state change to search fault section.At present, the phase-to-ground fault detection based on fault detector is main
Depend on the change of electrical network parameter.But due to the own characteristic of small current neutral grounding system, when there is singlephase earth fault, which is produced
Raw fault-signal itself is weaker, and is polluted by electromagnetic interference harmonic.This does not only result in the distorted signals of acquisition, also straight
Connect selectivity when affecting phase-to-ground fault detection, reliability and accuracy.
The content of the invention
It is an object of the invention to provide a kind of singlephase earth fault decision method, the earth fault judging method can gram
Take prior art not enough, it is ensured that the selectivity, reliability and accuracy during phase-to-ground fault detection.
For achieving the above object, present invention employs technical scheme below：A kind of singlephase earth fault decision method, the party
Method is comprised the following steps：
(1) asymmetric current source is set, for sending characteristic signal, described feature letter when there is singlephase earth fault
Number be square-wave signal.
(2) fault detector is with sample frequency f1, per cycle sampling number n1, the current signal on Real-time Collection circuit.
Discrete Fourier transform DFT1 is carried out to the current signal for collecting per cycle, and according to discrete Fourier transform DFT1's
As a result obtain fundamental current value I1 of current signal on circuit.
(3) the fundamental current value I1 composition sequence a of n2 cycle is taken, discrete Fu is carried out once to sequence a per n2 cycle
In leaf transformation DFT2, and obtain fundamental current value I2 of sequence a according to the result of discrete Fourier transform DFT2.
(4) the fundamental current value I2 composition sequence b of n3 sequence a is taken successively, according to the mode of first in first out, every the time
T is updated to sequence b.
(5) threshold range of fundamental current value I2 of sequence a is set, according to the threshold value model of fundamental current value I2 of sequence a
Enclose, singlephase earth fault judgement is carried out to the fundamental current value in sequence b every time T.
Further, described asymmetric current source includes that microcontroller, Earth Fault Detection module, characteristic signal occur
Module, high-pressure vacuum contactor and current-limiting resistance.
Earth Fault Detection module is used for real-time detection singlephase earth fault, and in singlephase earth fault to microcontroller
Send ground signalling.Microcontroller is used for receiving the ground signalling of Earth Fault Detection module transmission, and sends control command control
There is module work in characteristic signal processed.There is module for, after the control command for receiving microcontroller, producing in characteristic signal
Square-wave characteristic signal, and drive high-pressure vacuum contactor to work.High-pressure vacuum contactor is used for will by current-limiting resistance and the earth
Square-wave characteristic Signal averaging is on the normal duty electric current of ground path.
There is module and be set to send 8 square-wave signals in described characteristic signal, its cycle is 1s, and its dutycycle is
50%.
The resistance of described current-limiting resistance is 100 Ω.
Further, sample frequency f1 described in step (2) is 800Hz, is 16 per cycle sampling number n1.It is described
Circuit on current signal be sine wave signal, its frequency be 50Hz, its cycle be 20ms.Described discrete Fourier transform
The fundamental frequency of DFT1 is 50Hz.
Further, in step (3), the value of n2 is 50.The fundamental frequency of described discrete Fourier transform DFT2 is
1Hz。
When asymmetric current source does not send square-wave characteristic signal, fundamental current value I2 of sequence a be on circuit just
Normal load current.When asymmetric current source sends square-wave characteristic signal, fundamental current value I2 of sequence a is normal on circuit
Load current and square-wave characteristic signal code and.
Further, in step (4), the value of n3 is 8；Time T described in step (4) and step (5) is 1s.
Further, the threshold range of fundamental current value I2 of setting sequence a described in step (5), according to sequence a
Fundamental current value I2 threshold range, singlephase earth fault judgement is carried out to the fundamental current value in sequence b every time T
Detailed process is：
If in fundamental current value I2 of n3 sequence a of sequence b, fundamental current value I2 of at least n4 sequence a is in threshold
In the range of value, then can determine whether as singlephase earth fault.
As shown from the above technical solution, the present invention is by electric in normal duty when distribution line occurs singlephase earth fault
Power current is superimposed on stream, realizes judging the accurate, reliable of singlephase earth fault.First, in the present invention, be not only given
The sending method and the parameter information of characteristic signal of asymmetric current source characteristic signal, gives fault detector extraction
The method of characteristic signal, therefore, the present invention is complete singlephase earth fault determination methods, with reliability and accurately
Property.Secondly, characteristic signal of the present invention is the square-wave signal that 8 cycles are 1s, by being used as using the square-wave signal
Singlephase earth fault basis for estimation, it is easy to which fault detector extracts characteristic signal using conventional discrete Fourier transformation, makes single-phase
Earth fault judge take into account metallic earthing and high resistance ground connection, can with rejection frequency as 1Hz beyond load fluctuation signal,
Improve the accuracy of singlephase earth fault judgement.Again, when the Rule of judgment of singlephase earth fault is set to 8s by the present invention
Interior at least 6 characteristic signals meet threshold range, greatly reduce the possibility of singlephase earth fault malfunction.
Description of the drawings
Fig. 1 is the flow chart of earth fault judging method of the present invention.
Specific embodiment
The present invention will be further described below in conjunction with the accompanying drawings：
As shown in figure 1, a kind of singlephase earth fault decision method, by there is single-phase earthing event in distribution line in the method
Power current is superimposed on normal duty electric current during barrier, realizes judging the accurate, reliable of singlephase earth fault.The method bag
Include following steps：
(1) asymmetric current source is set, for sending characteristic signal, described feature letter when there is singlephase earth fault
Number be square-wave signal.Described asymmetric current source is arranged in transformer station or switching station.
Described asymmetric current source includes that microcontroller, Earth Fault Detection module, characteristic signal occur module, high pressure
Vacuum contactor and current-limiting resistance.Earth Fault Detection module is used for real-time detection singlephase earth fault, and in single-phase earthing event
Ground signalling is sent to microcontroller during barrier.Microcontroller is used for receiving the ground signalling of Earth Fault Detection module transmission, and
Send the work of control command controlling feature signal generating module.There is module for receiving the control of microcontroller in characteristic signal
After system order, square-wave characteristic signal is produced, and drives high-pressure vacuum contactor to work.High-pressure vacuum contactor is used for by current limliting
Resistance and the earth are by the normal duty electric current of square-wave characteristic Signal averaging to ground path.
There is module and be set to send 8 square-wave signals in described characteristic signal, its cycle is 1s, and its dutycycle is
50%.
The resistance of described current-limiting resistance is 100 Ω.
(2) fault detector is with sample frequency f1, per cycle sampling number n1, the current signal on Real-time Collection circuit.
Discrete Fourier transform DFT1 is carried out to the current signal for collecting per cycle, and according to discrete Fourier transform DFT1's
As a result obtain fundamental current value I1 of current signal on circuit.
Wherein, sample frequency f1 is 800Hz, is 16 per cycle sampling number n1.Current signal on described circuit
For sine wave signal, its frequency is 50Hz, and its cycle is 20ms.The fundamental frequency of described discrete Fourier transform DFT1 is
50Hz。
(3) the fundamental current value I1 composition sequence a of n2 cycle is taken, discrete Fu is carried out once to sequence a per n2 cycle
In leaf transformation DFT2, and obtain fundamental current value I2 of sequence a according to the result of discrete Fourier transform DFT2.Wherein, n2
Value is 50.The fundamental frequency of described discrete Fourier transform DFT2 is 1Hz.
When asymmetric current source does not send square-wave characteristic signal, fundamental current value I2 of sequence a be on circuit just
Normal load current.When asymmetric current source sends square-wave characteristic signal, fundamental current value I2 of sequence a is normal on circuit
Load current and square-wave characteristic signal code and.
(4) the fundamental current value I2 composition sequence b of n3 sequence a is taken successively, according to the mode of first in first out, every the time
T is updated to sequence b.After the quantity of the fundamental current value in sequence b reaches n3, fundamental current value I2 in sequence b
Quantity remain at n3.Wherein, n3 values are 8, and time T value is 1s.
(5) threshold range of fundamental current value I2 of sequence a is set, according to the threshold value model of fundamental current value I2 of sequence a
Enclose, singlephase earth fault judgement is carried out to the fundamental current value in sequence b every time T.If the base of n3 sequence a of sequence b
In ripple current value I2, fundamental current value I2 of at least n4 sequence a is can determine whether as single-phase earthing event in threshold range, then
Barrier.Wherein, n4 values are 6, and time T value is 1s.
The threshold range of fundamental current value I2 of sequence a, by the installation site of asymmetric current source, current-limiting resistance
Impedance ground when size and line-to-ground is determined.May be metallic earthing in view of single-phase earthing, it is also possible to for high resistant
Property ground connection；When asymmetric current source is arranged in transformer station, when high-pressure vacuum contactor is arranged on grounding transformer neutral point, threshold
Value scope is set to 8～60A.
Specifically, when asymmetric current source is arranged in transformer station, if the fundamental current of 8 sequences a in sequence b
Value I2 is respectively 3A, 1A, 23A, 40A, 42A, 39A, 41A, 42A, then understand have 6 fundamental current values I2 to fall in 8～60A scopes
It is interior, therefore, can determine whether as singlephase earth fault.If fundamental current value I2 of 8 sequences a in sequence b be respectively 2A, 3A,
12A, 3A, 5A, 2A, 2A, 1A, then understand that only 1 fundamental current value I2 falls in the range of 8～60A, therefore, can determine whether to be yes
The current value caused by load fluctuation, is not judged as singlephase earth fault.
As when there is singlephase earth fault, only the fault detector between trouble point and asymmetric current source can be sent out
It is lively to make.Therefore, when judging to exist singlephase earth fault, it can be determined that be out of order circuit and specific trouble point.Because
Action in the fault detector on non-fault line, the fault detector generation action on faulty line there is no；So, in failure
On circuit, trouble point is located at the fault detector of adjacent generation action and no between the fault detector of generation action.
Embodiment described above is only that the preferred embodiment of the present invention is described, not the model to the present invention
Enclose and be defined, on the premise of without departing from design spirit of the present invention, technical side of the those of ordinary skill in the art to the present invention
Various modifications and improvement that case is made, all should fall in the protection domain of claims of the present invention determination.
Claims (6)
1. a kind of singlephase earth fault decision method, it is characterised in that：The method is comprised the following steps：
（1）Asymmetric current source is set, and for sending characteristic signal when there is singlephase earth fault, described characteristic signal is
Square-wave signal；
（2）Fault detector is with sample frequency f1, per cycle sampling number n1, the current signal on Real-time Collection circuit；Weekly
Ripple carries out a discrete Fourier transform DFT1 to the current signal for collecting, and according to the result of discrete Fourier transform DFT1
Obtain fundamental current value I1 of current signal on circuit；
（3）The fundamental current value I1 composition sequence a of n2 cycle is taken, and a discrete fourier is carried out to sequence a per n2 cycle
Conversion DFT2, and fundamental current value I2 of sequence a is obtained according to the result of discrete Fourier transform DFT2；
（4）The fundamental current value I2 composition sequence b of n3 sequence a is taken successively, according to the mode of first in first out, every time T pair
Sequence b is updated；
（5）The threshold range of fundamental current value I2 of setting sequence a, according to the threshold range of fundamental current value I2 of sequence a, often
Singlephase earth fault judgement is carried out to the fundamental current value in sequence b every time T.
2. a kind of singlephase earth fault decision method according to claim 1, it is characterised in that：Described asymmetric electric current
Source includes that microcontroller, Earth Fault Detection module, characteristic signal occur module, high-pressure vacuum contactor and current-limiting resistance；
Earth Fault Detection module is used for real-time detection singlephase earth fault, and sends to microcontroller in singlephase earth fault
Ground signalling；Microcontroller is used for receiving the ground signalling of Earth Fault Detection module transmission, and it is special to send control command control
Levy signal generating module work；There is module for, after the control command for receiving microcontroller, producing square wave in characteristic signal
Characteristic signal, and drive high-pressure vacuum contactor to work；High-pressure vacuum contactor is used for by current-limiting resistance and greatly by square wave
Characteristic signal is added on the normal duty electric current of ground path；
There is module and be set to send 8 square-wave signals in described characteristic signal, its cycle is 1s, and its dutycycle is 50%；
The resistance of described current-limiting resistance is 100 Ω.
3. a kind of singlephase earth fault decision method according to claim 1, it is characterised in that：Step（2）Described in
Sample frequency f1 is 800Hz, is 16 per cycle sampling number n1；Current signal on described circuit is sine wave signal,
Its frequency is 50Hz, and its cycle is 20ms；The fundamental frequency of described discrete Fourier transform DFT1 is 50Hz.
4. a kind of singlephase earth fault decision method according to claim 1, it is characterised in that：Step（3）Middle n2's takes
It is worth for 50；The fundamental frequency of described discrete Fourier transform DFT2 is 1Hz；
When asymmetric current source does not send square-wave characteristic signal, fundamental current value I2 of sequence a is normal negative on circuit
Charged current；When asymmetric current source sends square-wave characteristic signal, fundamental current value I2 of sequence a is the normal duty on circuit
Electric current and square-wave characteristic signal code and.
5. a kind of singlephase earth fault decision method according to claim 1, it is characterised in that：Step（4）Middle n3's takes
It is worth for 8；Step（4）And step（5）Described in time T be 1s.
6. a kind of singlephase earth fault decision method according to claim 1, it is characterised in that：Step（5）Described in
The threshold range of fundamental current value I2 of setting sequence a, according to the threshold range of fundamental current value I2 of sequence a, every time T
To the detailed process that the fundamental current value in sequence b carries out singlephase earth fault judgement it is：
If in fundamental current value I2 of n3 sequence a of sequence b, fundamental current value I2 of at least n4 sequence a is in threshold value model
In enclosing, then can determine whether as singlephase earth fault.
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| CN105425182B (en) * | 2015-11-10 | 2018-07-27 | 科大智能电气技术有限公司 | A kind of current precision calibration method for fault detector production link |
| CN106908686A (en) * | 2017-04-21 | 2017-06-30 | 国网安徽省电力公司淮北供电公司 | Single-phase grounded malfunction in grounded system of low current reliability judgment means based on asymmetric method |
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| JP2609793B2 (en) * | 1993-03-25 | 1997-05-14 | 財団法人 関西電気保安協会 | Ground fault monitoring equipment for electrical equipment |
| CN101187687A (en) * | 2007-12-21 | 2008-05-28 | 清华大学 | High resistance earthing fault detection method based on transient traveling wave |
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|---|---|---|---|---|
| JPH11178200A (en) * | 1997-12-10 | 1999-07-02 | Yaskawa Electric Corp | Power distribution system |
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| JP2609793B2 (en) * | 1993-03-25 | 1997-05-14 | 財団法人 関西電気保安協会 | Ground fault monitoring equipment for electrical equipment |
| CN101452038A (en) * | 2007-11-29 | 2009-06-10 | 上海蓝瑞软件技术有限公司 | Low current neutral grounding electric network single-phase earth fault diagnostic method |
| CN101187687A (en) * | 2007-12-21 | 2008-05-28 | 清华大学 | High resistance earthing fault detection method based on transient traveling wave |
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