CN103135034A - Extract method of high-impedance-grounded fault waveform distortion features - Google Patents

Extract method of high-impedance-grounded fault waveform distortion features Download PDF

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CN103135034A
CN103135034A CN2013100434044A CN201310043404A CN103135034A CN 103135034 A CN103135034 A CN 103135034A CN 2013100434044 A CN2013100434044 A CN 2013100434044A CN 201310043404 A CN201310043404 A CN 201310043404A CN 103135034 A CN103135034 A CN 103135034A
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impedance
sequence current
high resistance
zero
resistance earthing
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CN103135034B (en
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王宾
耿建昭
董新洲
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Tsinghua University
Yangtze Delta Region Institute of Tsinghua University Zhejiang
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Tsinghua University
Yangtze Delta Region Institute of Tsinghua University Zhejiang
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Abstract

The invention discloses an extract method of high-impedance-grounded fault waveform distortion features, and belongs to the field of power system default detecting and protecting. According to the method, firstly, lowpass filtering is conducted on zero sequence current momentary value by a disperse three-time center B-spline function aiming at the zero sequence current momentary value of a to-be-detected feeder line, and then filtering is conducted on the sequence again after the lowpass filtering by a second derivative function of the disperse three-time center B-spline function, and finally, a coefficient of efficient characterization high-impedance-grounded fault features, namely, a zero sequence current zero crossing point distortion coefficient is obtained through calculation, and therefore whether a high-impedance-grounded fault is generated or not is judged through comparison of the zero sequence current zero crossing point distortion coefficient and threshold value. The extraction method is capable of improving detecting success rate of a high-impedance-grounded fault effectively, and damages caused by the high-impedance-grounded fault can be reduced.

Description

A kind of high resistance earthing fault wave form distortion Feature Extraction Method
Technical field
The invention belongs to Power System Faults Detection and protection field, particularly a kind of high resistance earthing fault wave form distortion Feature Extraction Method is based on cubic B-spline function, for detection of the distribution line high resistance earthing fault of system with effectively earthed neutral.
Technical background
Neutral point can overcome effectively that distribution system single phase earthing fault transient superpotential exceeds standard and the problem such as failure line selection is insensitive through effective grounding modes such as small resistors, has obtained applying gradually in urban distribution network, large-scale industrial enterprise electrical network; But the single-phase high resistance earthing fault through imperfect conductors such as branch, sandstones often occurs under this method of operation.The high resistance earthing fault electric current is subject to the restriction of fault loop impedance, and less than overcurrent protection action threshold value, fault is difficult to cut and long-term existence, easily causes the serious consequences such as fire, electric shock, so high resistance earthing fault detects very important.
During circuit generation high resistance earthing fault, voltage, failure of the current component are all very faint, and the high resistance earthing fault detection is the feeble signal identification problem under very noisy (electric current and voltage during normal operation) background in essence.High resistance earthing fault is followed the arc discharge phenomenon usually, the simultaneous faults impedance loop is non-linear, cause the harmonic distortion of fault current, therefore there is multiple fault detection algorithm based on harmonic wave to be suggested, mainly comprise: the method based on secondary and third harmonic phase place that A.E.Emanuel etc. propose, Texas A﹠amp; The method based on spectrum analysis (patent No. US.5578931) that M University proposes take D.B.Russell etc. as representative, based on harmonic current and fundamental voltage method (patent No. US.5659453) relatively, D.I.Jeerings has proposed to adopt the phase place of third harmonic relative system voltage to change criterion as fault detect in nineteen ninety.
But, the above temporal signatures of having ignored electric parameters based on the method for harmonic wave fully, so the sensitivity of fault detect is not high.High resistance earthing fault the most significantly is characterised in that near fault electric arc extinguishing and the characteristic of restriking current zero-crossing point, this feature shows as the zero crossing distortion on zero-sequence current, and to effectively utilize high resistance earthing fault wave form distortion feature, at first need to solve the extraction problem of fault distortion characteristics.
Summary of the invention
In order to overcome the defective of above-mentioned prior art, the object of the present invention is to provide a kind of high resistance earthing fault wave form distortion Feature Extraction Method, the present invention is based on cubic B-spline function, can effectively improve the power that is detected as of high resistance earthing fault, reduce the harm that high resistance earthing fault causes.
In order to achieve the above object, technical scheme of the present invention is:
A kind of high resistance earthing fault wave form distortion Feature Extraction Method comprises the following steps:
Step 1, the zero-sequence current of monitored feeder line is sampled, obtain the sampled value sequence f (n) of a power frequency cycle, carry out circular convolution with discrete three subcenter B-spline function h (k) and f (n), obtain sequential value F (n), n=1,2,40, h (k)=[0.125,0.375 wherein, 0.375,0.125];
The positive going zeror crossing of step 2, judgement F (n) is t constantly Pzero, determination methods is: if F (n-1)＜0 and F (n)＞0 t Pzero=n, n=1,2 ... 40, and make F (0)=F (40);
Step 3, carry out circular convolution with second order derived function g (k) and the F (n) of discrete three subcenter B-spline functions, obtain sequential value F 2(n), n=1,2 ... 40, g (k)=[4 ,-8,4] wherein;
Step 4, calculating zero-sequence current zero crossing distortion factor K, computing method are: to F 2(n) take absolute value, be denoted as | F 2(n) |, and the size of comparison absolute value, obtain maximum absolute value and be denoted as | F 2(max) |, definition K=|F 2(t Pzero) |/| F 2(max) |;
Step 5, further can judge the generation of doubtful high resistance earthing fault according to zero-sequence current zero crossing distortion factor K, determination methods is, if K＞K set, high resistance earthing fault, wherein K have occured in judgement setBe setting valve, arrange according to the sensitivity that detects, interval is in [0.5,0.9].
Characteristics of the present invention and effect:
The inventive method is paid close attention to zero-sequence current at the local feature of zero crossing, reached the effect of amplifying the distortion of zero-sequence current zero crossing, high resistance earthing fault based on the inventive method detects than higher based on the detection method sensitivity of harmonic wave, physical significance is clearer and more definite, can effectively improve the power that is detected as of high resistance earthing fault, reduce the harm that high resistance earthing fault causes.
Description of drawings
Accompanying drawing is through the discrete three filtered zero-sequence current waveforms of subcenter B-spline function f (n), and through the second order derived function F of discrete three subcenter B-spline functions 2(n) filtered waveform.
Embodiment
Below in conjunction with accompanying drawing, the present invention is done and be described in detail.
A kind of high resistance earthing fault wave form distortion Feature Extraction Method comprises the following steps:
Step 1, the zero-sequence current of monitored feeder line is sampled, sample frequency 2kHz, the sampled value sequence f (n) that obtains a cycle is totally 40 points:
f(n)=
[-1.75,-3,-4.75,-6.75,-8.5,-10,-11.25,-12,-12.25,-12.25,-12,-12,-11.25,-10,-8.75,-7,-5,-2.5,-0.5,1,2,3.25,5.25,7.25,9,10.5,11.75,12.75,12.75,12.75,12.5,12.25,11.50,10,8.5,6.25,4.5,2.25,0.25,-1]
carry out circular convolution with discrete three subcenter B-spline functions and sampled value sequence, obtain filtered 40 point sequence F (n): F (1)=0.125 * f (2)+0.375 * f (1)+0.375 * f (40)+0.125 * f (39), F (2)=0.125 * f (3)+0.375 * f (2)+0.375 * f (1)+0.125 * f (40), F (40)=0.125 * f (38)+0.375 * f (39)+0.375 * f (40)+0.125 * f (1), calculate successively F (k)=0.125 * f (k-2)+0.375 * f (k-1)+0.375 * f (k)+0.125 * f (k+1), k=3,4, ... 39, obtain:
F(n)=
[1.375 ,-2.500 ,-3.969 ,-5.750 ,-7.562 ,-9.188 ,-10.53,-11.50 ,-12.03 ,-12.19 ,-12.12 ,-11.94 ,-11.47 ,-10.56,-9.312 ,-7.781 ,-5.906 ,-3.750 ,-1.625,0.125,1.469,2.750,4.344,6.219,8.062,9.688,11.06,12.09,12.62,12.72,12.59,12.31,11.72,10.66,9.156,7.344,5.375,3.344,1.375 ,-0.2188]; With reference to accompanying drawing, for through the discrete three filtered zero-sequence current waveforms of subcenter B-spline function F (n);
The positive going zeror crossing of step 2, judgement F (n) is t constantly Pzero, observe F (n) and find: F (19)＜0 and F (20)〉and 0, therefore judge t Pzero=20;
Step 3, carry out circular convolution with second order derived function g (k) and the F (n) of discrete three subcenter B-spline functions, obtain sequential value F 2(n), n=1,2 ... 40:
Calculate successively F 2(1)=4 * f (2)-8 * f (1)+4 * f (40), F 2(40)=4 * f (39)-8 * f (40)+4 * f (1), F 2(k)=4 * f (k-1)-8 * f (k)+4 * f (k+1), k=2,4 ... 39; Obtain:
F 2(n)=
[0.1250 ,-1.375 ,-1.25 ,-0.125,0.75,1.125,1.5,1.75,1.500,0.8750,0.5,1.125,1.75,1.375,1.125,1.375,1.125 ,-0.125 ,-1.5 ,-1.625 ,-0.25,1.25,1.125 ,-0.125 ,-0.875 ,-1 ,-1.375 ,-2,-1.75 ,-0.875 ,-0.625 ,-1.25 ,-1.875 ,-1.75,-1.25 ,-0.625 ,-0.25,0.25,1.5,1.75]; With reference to accompanying drawing, through the second order derived function F of discrete three subcenter B-spline functions 2(n) filtered waveform;
Step 4, calculating zero-sequence current zero crossing distortion factor K: to F 2(n) take absolute value, be denoted as | F 2(n) |, and the size of comparison absolute value, obtain maximum absolute value | F 2(max) |=| F 2(28) |=2, K=|F 2(20) |/| F 2(28) |=1.625/2=0.81;
Step 5, further according to the generation of the doubtful high resistance earthing fault of zero-sequence current zero crossing distortion factor K judgement, set K set=0.7, K＞K setSo high resistance earthing fault has occured in judgement.

Claims (2)

1. a high resistance earthing fault wave form distortion Feature Extraction Method, is characterized in that, comprises the following steps:
Step 1, the zero-sequence current of monitored feeder line is sampled, obtain the sampled value sequence f (n) of a power frequency cycle, carry out circular convolution with discrete three subcenter B-spline function h (k) and f (n), obtain sequential value F (n), n=1,2, ... 40, h (k)=[0.125,0.375 wherein, 0.375,0.125];
The positive going zeror crossing of step 2, judgement F (n) is t constantly Pzero, determination methods is: if F (n-1)＜0 and F (n)＞0 t Pzero=n, n=1,2 ... 40, and make F (0)=F (40);
Step 3, carry out circular convolution with second order derived function g (k) and the F (n) of discrete three subcenter B-spline functions, obtain sequential value F 2(n), n=1,2 ... 40, g (k)=[4 ,-8,4] wherein;
Step 4, calculating zero-sequence current zero crossing distortion factor K, computing method are: to F 2(n) take absolute value, be denoted as | F 2(n) |, and the size of comparison absolute value, obtain maximum absolute value and be denoted as | F 2(max) |, definition K=|F 2(t Pzero) |/| F 2(max) |;
Step 5, further can judge the generation of doubtful high resistance earthing fault according to zero-sequence current zero crossing distortion factor K, determination methods is, if K〉K set, high resistance earthing fault, wherein K have occured in judgement setBe setting valve.
2. a kind of high resistance earthing fault wave form distortion Feature Extraction Method according to claim 1, is characterized in that K setArrange according to the sensitivity that detects, interval is in [0.5,0.9].
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CN104062555A (en) * 2014-07-16 2014-09-24 哈尔滨理工大学 Identification method for distributing line high-resistance ground fault feature harmonic waves
CN112666421A (en) * 2019-10-16 2021-04-16 李景禄 Fault area isolation method based on compensation damping type active intervention arc suppression device

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Publication number Priority date Publication date Assignee Title
CN103310109A (en) * 2013-06-24 2013-09-18 北京工业大学 Patient follow-up visit reminding cycle self-adaptive adjustment method
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CN104062555A (en) * 2014-07-16 2014-09-24 哈尔滨理工大学 Identification method for distributing line high-resistance ground fault feature harmonic waves
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CN112666421A (en) * 2019-10-16 2021-04-16 李景禄 Fault area isolation method based on compensation damping type active intervention arc suppression device

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