CN104198888A - Fault indicator grounding fault judgment method - Google Patents
Fault indicator grounding fault judgment method Download PDFInfo
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- CN104198888A CN104198888A CN201410440208.5A CN201410440208A CN104198888A CN 104198888 A CN104198888 A CN 104198888A CN 201410440208 A CN201410440208 A CN 201410440208A CN 104198888 A CN104198888 A CN 104198888A
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Abstract
The invention relates to a fault indicator grounding fault judgment method which includes the steps: firstly, setting an asymmetric current source for transmitting characteristic signals when a 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 grounding faults of the fundamental wave current values in the sequences b. According to the technical scheme, the fault indicator 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, be specifically related to a kind of fault detector earth fault judging method.
Background technology
In small current neutral grounding system, the detection of singlephase earth fault is the technological difficulties that ensure the normal operation of power distribution network with location always.Accurately find out the section of singlephase earth fault, can avoid the unnecessary grid switching operation to non-fault zone, keep the continuity of power supply.Because single-phase earthing and short trouble can be indicated and report to fault detector, therefore, can carry out looking up the fault section by observing fault detector state variation.At present, the phase-to-ground fault detection based on fault detector mainly depends on the variation of electrical network parameter.But due to the own characteristic of small current neutral grounding system, occur when singlephase earth fault, its fault-signal producing itself a little less than, and be subject to electromagnetic interference (EMI) and harmonic pollution.This not only causes the distorted signals obtaining, selectivity, reliability and accuracy while also directly affecting phase-to-ground fault detection.
Summary of the invention
The object of the present invention is to provide a kind of fault detector earth fault judging method, this earth fault judging method can overcome prior art deficiency, selectivity, reliability and accuracy while ensureing phase-to-ground fault detection.
For achieving the above object, the present invention has adopted following technical scheme: a kind of fault detector earth fault judging method, and the method comprises the following steps:
(1) asymmetric current source is set, for send characteristic signal in the time there is earth fault, described characteristic signal is square-wave signal.
(2) fault detector is with sample frequency f1, every cycle sampling number n1, the current signal on Real-time Collection circuit.Every cycle carries out discrete Fourier transformation DFT1 one time to the current signal collecting, and obtains the fundamental current value I1 of current signal on circuit according to the result of discrete Fourier transformation DFT1.
(3) get the fundamental current value I1 composition sequence a of n2 cycle, every n2 cycle carries out discrete Fourier transformation DFT2 one time to sequence a, and obtains the fundamental current value I2 of sequence a according to the result of discrete Fourier transformation DFT2.
(4) get successively the fundamental current value I2 composition sequence b of n3 sequence a, according to the mode of first in first out, every time T, sequence b is upgraded.
(5) threshold range of the fundamental current value I2 of setting sequence a, according to the threshold range of the fundamental current value I2 of sequence a, carries out earth fault judgement every time T to the fundamental current value in sequence b.
Further, described asymmetric current source comprises microcontroller, Earth Fault Detection module, characteristic signal generation module, high-pressure vacuum contactor and current-limiting resistance.
Earth Fault Detection module is used for real-time detection of ground faults, and sends ground signalling to microcontroller in the time of earth fault.The ground signalling that microcontroller sends for receiving Earth Fault Detection module, and send the work of control command controlling feature signal generating module.Characteristic signal generation module, for receiving after the control command of microcontroller, produces square wave characteristic signal, and drives high-pressure vacuum contactor work.High-pressure vacuum contactor for by current-limiting resistance and the earth by the be added to normal load electric current of ground path of square wave characteristic signal.
Described characteristic signal generation module is set to send 8 square-wave signals, and its cycle is 1s, and its dutycycle is 50%.
The resistance of described current-limiting resistance is 100 Ω.
Further, the sample frequency f1 described in step (2) is 800Hz, and every cycle sampling number n1 is 16.Current signal on described circuit is sine wave signal, and its frequency is 50Hz, and its cycle is 20ms.The fundamental frequency of described discrete Fourier transformation DFT1 is 50Hz.
Further, in step (3), the value of n2 is 50.The fundamental frequency of described discrete Fourier transformation DFT2 is 1Hz.
In the time that asymmetric current source does not have sender's wave characteristic signal, the fundamental current value I2 of sequence a is the normal load electric current on circuit.In the time of asymmetric current source sender wave characteristic signal, the fundamental current value I2 of sequence a be normal load electric current on circuit and square wave characteristic signal electric current 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 the fundamental current value I2 of the setting sequence a described in step (5), according to the threshold range of the fundamental current value I2 of sequence a, carries out to the fundamental current value in sequence b the detailed process that earth fault judges every time T and is:
If in the fundamental current value I2 of the n3 of sequence b sequence a, have the fundamental current value I2 of n4 sequence a at least in threshold range, can be judged as earth fault.
As shown from the above technical solution, the present invention is by the power current that superposes on normal load electric current when the distribution line generation singlephase earth fault, realize to singlephase earth fault accurately, reliably judgement.First, in the present invention, the sending method of asymmetric current source characteristic signal and the parameter information of characteristic signal are not only provided, give the method that fault detector extracts characteristic signal, therefore, the present invention is a complete singlephase earth fault determination methods, has reliability and accuracy.Secondly, characteristic signal of the present invention is 8 cycles square-wave signals that are 1s, by adopting this square-wave signal as singlephase earth fault basis for estimation, being easy to fault detector uses conventional discrete Fourier transformation to extract characteristic signal, make earth fault judgement take into account metallic earthing and high resistive ground connection, can also rejection frequency be the load fluctuation signal beyond 1Hz, improve the accuracy of singlephase earth fault judgement.Again, the Rule of judgment of the present invention's earth fault is set at least 6 characteristic signals in the 8s time and meets threshold range, greatly reduces the possibility of singlephase earth fault malfunction.
Brief description of the drawings
Fig. 1 is the process flow diagram of earth fault judging method of the present invention.
Embodiment
Below in conjunction with accompanying drawing, the present invention will be further described:
As shown in Figure 1, a kind of fault detector earth fault judging method, the method is by the power current that superposes on normal load electric current when the distribution line generation singlephase earth fault, realize to singlephase earth fault accurately, reliably judgement.The method comprises the following steps:
(1) asymmetric current source is set, for send characteristic signal in the time there is earth fault, described characteristic signal is square-wave signal.Described asymmetric current source is arranged in transformer station or switching station.
Described asymmetric current source comprises microcontroller, Earth Fault Detection module, characteristic signal generation module, high-pressure vacuum contactor and current-limiting resistance.Earth Fault Detection module is used for real-time detection of ground faults, and sends ground signalling to microcontroller in the time of earth fault.The ground signalling that microcontroller sends for receiving Earth Fault Detection module, and send the work of control command controlling feature signal generating module.Characteristic signal generation module, for receiving after the control command of microcontroller, produces square wave characteristic signal, and drives high-pressure vacuum contactor work.High-pressure vacuum contactor for by current-limiting resistance and the earth by the be added to normal load electric current of ground path of square wave characteristic signal.
Described characteristic signal generation module is set to send 8 square-wave signals, and 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, every cycle sampling number n1, the current signal on Real-time Collection circuit.Every cycle carries out discrete Fourier transformation DFT1 one time to the current signal collecting, and obtains the fundamental current value I1 of current signal on circuit according to the result of discrete Fourier transformation DFT1.
Wherein, sample frequency f1 is 800Hz, and every cycle sampling number n1 is 16.Current signal on described circuit is sine wave signal, and its frequency is 50Hz, and its cycle is 20ms.The fundamental frequency of described discrete Fourier transformation DFT1 is 50Hz.
(3) get the fundamental current value I1 composition sequence a of n2 cycle, every n2 cycle carries out discrete Fourier transformation DFT2 one time to sequence a, and obtains the fundamental current value I2 of sequence a according to the result of discrete Fourier transformation DFT2.Wherein, the value of n2 is 50.The fundamental frequency of described discrete Fourier transformation DFT2 is 1Hz.
In the time that asymmetric current source does not have sender's wave characteristic signal, the fundamental current value I2 of sequence a is the normal load electric current on circuit.In the time of asymmetric current source sender wave characteristic signal, the fundamental current value I2 of sequence a be normal load electric current on circuit and square wave characteristic signal electric current and.
(4) get successively the fundamental current value I2 composition sequence b of n3 sequence a, according to the mode of first in first out, every time T, sequence b is upgraded.When the quantity of the fundamental current value in sequence b reaches after n3, the quantity of the fundamental current value I2 in sequence b remains at n3.Wherein, n3 value is 8, and time T value is 1s.
(5) threshold range of the fundamental current value I2 of setting sequence a, according to the threshold range of the fundamental current value I2 of sequence a, carries out earth fault judgement every time T to the fundamental current value in sequence b.If in the fundamental current value I2 of the n3 of sequence b sequence a, have the fundamental current value I2 of n4 sequence a at least in threshold range, can be judged as earth fault.Wherein, n4 value is 6, and time T value is 1s.
The threshold range of the fundamental current value I2 of described sequence a, the impedance ground during by the size of the installation site of asymmetric current source, current-limiting resistance and line-to-ground determines.Considering that single-phase earthing may be metallic earthing, may be also high resistive ground connection; When asymmetric current source is arranged in transformer station, when high-pressure vacuum contactor is arranged on grounding transformer neutral point, threshold range is set to 8 ~ 60A.
Specifically, in the time that asymmetric current source is arranged in transformer station, if the fundamental current value I2 of 8 sequence a in sequence b is respectively 3A, 1A, 23A, 40A, 42A, 39A, 41A, 42A, known have 6 fundamental current value I2 to drop within the scope of 8 ~ 60A, therefore, can be judged as earth fault.If the fundamental current value I2 of 8 sequence a in sequence b is respectively 2A, 3A, 12A, 3A, 5A, 2A, 2A, 1A, known only have 1 fundamental current value I2 to drop within the scope of 8 ~ 60A, therefore, can be judged as YES the current value being caused by load fluctuation, not be judged as earth fault.
Due in the time there is singlephase earth fault, only have the fault detector between trouble spot and asymmetric current source to move.Therefore,, when judging while there is earth fault, can judge faulty line and concrete trouble spot.Because the fault detector on non-fault line does not move, the fault detector on faulty line moves; So on faulty line, trouble spot is between the fault detector of adjacent generation action and the fault detector of no generation action.
Above-described embodiment is described the preferred embodiment of the present invention; not scope of the present invention is limited; design under the prerequisite of spirit not departing from the present invention; various distortion and improvement that those of ordinary skill in the art make technical scheme of the present invention, all should fall in the definite protection domain of the claims in the present invention book.
Claims (6)
1. a fault detector earth fault judging method, is characterized in that: the method comprises the following steps:
(1) asymmetric current source is set, for send characteristic signal in the time there is earth fault, described characteristic signal is square-wave signal;
(2) fault detector is with sample frequency f1, every cycle sampling number n1, the current signal on Real-time Collection circuit; Every cycle carries out discrete Fourier transformation DFT1 one time to the current signal collecting, and obtains the fundamental current value I1 of current signal on circuit according to the result of discrete Fourier transformation DFT1;
(3) get the fundamental current value I1 composition sequence a of n2 cycle, every n2 cycle carries out discrete Fourier transformation DFT2 one time to sequence a, and obtains the fundamental current value I2 of sequence a according to the result of discrete Fourier transformation DFT2;
(4) get successively the fundamental current value I2 composition sequence b of n3 sequence a, according to the mode of first in first out, every time T, sequence b is upgraded;
(5) threshold range of the fundamental current value I2 of setting sequence a, according to the threshold range of the fundamental current value I2 of sequence a, carries out earth fault judgement every time T to the fundamental current value in sequence b.
2. a kind of fault detector earth fault judging method according to claim 1, is characterized in that: described asymmetric current source comprises microcontroller, Earth Fault Detection module, characteristic signal generation module, high-pressure vacuum contactor and current-limiting resistance;
Earth Fault Detection module is used for real-time detection of ground faults, and sends ground signalling to microcontroller in the time of earth fault; The ground signalling that microcontroller sends for receiving Earth Fault Detection module, and send the work of control command controlling feature signal generating module; Characteristic signal generation module, for receiving after the control command of microcontroller, produces square wave characteristic signal, and drives high-pressure vacuum contactor work; High-pressure vacuum contactor for by current-limiting resistance and the earth by the be added to normal load electric current of ground path of square wave characteristic signal;
Described characteristic signal generation module is set to send 8 square-wave signals, and its cycle is 1s, and its dutycycle is 50%;
The resistance of described current-limiting resistance is 100 Ω.
3. a kind of fault detector earth fault judging method according to claim 1, is characterized in that: the sample frequency f1 described in step (2) is 800Hz, every cycle sampling number n1 is 16; Current signal on described circuit is sine wave signal, and its frequency is 50Hz, and its cycle is 20ms; The fundamental frequency of described discrete Fourier transformation DFT1 is 50Hz.
4. a kind of fault detector earth fault judging method according to claim 1, is characterized in that: in step (3), the value of n2 is 50; The fundamental frequency of described discrete Fourier transformation DFT2 is 1Hz;
In the time that asymmetric current source does not have sender's wave characteristic signal, the fundamental current value I2 of sequence a is the normal load electric current on circuit; In the time of asymmetric current source sender wave characteristic signal, the fundamental current value I2 of sequence a be normal load electric current on circuit and square wave characteristic signal electric current and.
5. a kind of fault detector earth fault judging method according to claim 1, is characterized in that: in step (4), the value of n3 is 8; Time T described in step (4) and step (5) is 1s.
6. a kind of fault detector earth fault judging method according to claim 1, it is characterized in that: the threshold range of the fundamental current value I2 of the setting sequence a described in step (5), according to the threshold range of the fundamental current value I2 of sequence a, every time T, the fundamental current value in sequence b is carried out to the detailed process that earth fault judges and is:
If in the fundamental current value I2 of the n3 of sequence b sequence a, have the fundamental current value I2 of n4 sequence a at least in threshold range, can be judged as earth fault.
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| CN105425182A (en) * | 2015-11-10 | 2016-03-23 | 科大智能电气技术有限公司 | Current accuracy calibration method for fail indicator 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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| CN105425182A (en) * | 2015-11-10 | 2016-03-23 | 科大智能电气技术有限公司 | Current accuracy calibration method for fail indicator production link |
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| 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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