CN103135034B - Extract method of high-impedance-grounded fault waveform distortion features - Google Patents
Extract method of high-impedance-grounded fault waveform distortion features Download PDFInfo
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- CN103135034B CN103135034B CN201310043404.4A CN201310043404A CN103135034B CN 103135034 B CN103135034 B CN 103135034B CN 201310043404 A CN201310043404 A CN 201310043404A CN 103135034 B CN103135034 B CN 103135034B
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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
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, based on cubic B-spline function, for detecting the distribution line high resistance earthing fault of system with effectively earthed neutral.
Technical background
Neutral point effectively can overcome distribution system single phase earthing fault transient superpotential through effective grounding modes such as small resistors and exceed standard and the problem such as failure line selection is insensitive, obtains gradually and apply in urban distribution network, large-scale industrial enterprise electrical network; But the single-phase high-impedance often occurred under this method of operation through the imperfectly conduting metal such as branch, sandstone.High resistance earthing fault electric current is subject to the restriction of Fault loop impedance, is less than overcurrent protection action threshold value, and fault is difficult to cut and long-term existence, easily causes the serious consequence such as fire, electric shock, and therefore 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 high resistance earthing fault detection is the feeble signal identification problem under very noisy (electric current and voltage during normal work) background in essence.High resistance earthing fault is usually with arcing events, simultaneous faults impedance loop is non-linear, the harmonic distortion of causing trouble electric current, therefore the multiple fault detection algorithm based on harmonic wave is had to be suggested, mainly comprise: the method based on secondary and third harmonic phase place that A.E.Emanuel etc. propose, the method based on spectrum analysis (patent No. US.5578931) that Texas A & MUniversity proposes for representative with D.B.Russell etc., based on the method (patent No. US.5659453) that harmonic current and fundamental voltage compare, D.I.Jeerings proposes the criterion of phase place change as fault detect of employing third harmonic relative system voltage in nineteen ninety.
But the above method based on harmonic wave have ignored the temporal signatures of electric parameters completely, the sensitivity of therefore fault detect is not high.High resistance earthing fault is the most significantly characterised in that the extinguishing of fault electric arc near current zero-crossing point and characteristic of restriking, this feature shows as zero cross distortion on zero-sequence current, and high resistance earthing fault wave form distortion feature will be effectively utilized, first need the extraction problem solving fault distortion characteristics.
Summary of the invention
In order to overcome the defect 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, that effectively can improve high resistance earthing fault is detected as power, reduces 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 one, the zero-sequence current of monitored feeder line to be sampled, obtain sampled value sequence f (n) of a power frequency cycle, carry out circular convolution with discrete three subcenters B-spline function h (k) and f (n), obtain sequential value F (n), n=1,2,40, wherein h (k)=[0.125,0.375,0.375,0.125];
Step 2, judge the positive going zeror crossing moment t of F (n)
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) of discrete three subcenter B-spline functions and F (n), obtain sequential value F
2(n), n=1,2 ... 40, wherein g (k)=[4 ,-8,4];
Step 4, calculating zero-sequence current zero cross distortion COEFFICIENT K, computing method are: to F
2n () takes absolute value, be denoted as | F
2(n) |, and compare the size of absolute value, obtain maximum absolute value and be denoted as | F
2(max) |, definition K=|F
2(t
pzero) |/| F
2(max) |;
Step 5, can judge the generation of doubtful high resistance earthing fault further according to zero-sequence current zero cross distortion COEFFICIENT K, determination methods is, if K > is K
set, then judge to there occurs high resistance earthing fault, wherein K
setfor setting valve, the sensitivity according to detecting is arranged, and interval is in [0.5,0.9].
Feature of the present invention and effect:
The inventive method pays close attention to the local feature of zero-sequence current at zero crossing, reach the effect of amplifying zero-sequence current zero cross distortion, high resistance earthing fault based on the inventive method detects higher than the detection method sensitivity based on harmonic wave, physical significance is clearer and more definite, that effectively can improve high resistance earthing fault is detected as power, reduces the harm that high resistance earthing fault causes.
Accompanying drawing explanation
Accompanying drawing is through the filtered zero-sequence current waveform of discrete three 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 described in detail.
A kind of high resistance earthing fault wave form distortion Feature Extraction Method, comprises the following steps:
Step one, sample to the zero-sequence current of monitored feeder line, sample frequency 2kHz, obtains sampled value sequence f (n) totally 40 points of a cycle:
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]
Circular convolution is carried out with discrete three subcenter B-spline functions and sampled value sequence, obtain filtered 40 point sequences 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 F (k)=0.125 × f (k-2)+0.375 × f (k-1)+0.375 × f (k)+0.125 × f (k+1) successively, 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 filtered zero-sequence current waveform of discrete three subcenter B-spline function F (n);
Step 2, judge the positive going zeror crossing moment t of F (n)
pzero, observe F (n) and find: F (19) <0 and F (20) >0, therefore judge t
pzero=20;
Step 3, carry out circular convolution with second order derived function g (k) of discrete three subcenter B-spline functions and F (n), obtain sequential value F
2(n), n=1,2 ... 40:
Calculate F successively
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 cross distortion COEFFICIENT K: to F
2n () takes absolute value, be denoted as | F
2(n) |, and compare the size of 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, judge the generation of doubtful high resistance earthing fault further according to zero-sequence current zero cross distortion COEFFICIENT K, setting K
set=0.7, K > K
set, so judge to there occurs high resistance earthing fault.
Claims (2)
1. a high resistance earthing fault wave form distortion Feature Extraction Method, is characterized in that, comprises the following steps:
Step one, the zero-sequence current of monitored feeder line to be sampled, obtain sampled value sequence f (n) of a power frequency cycle, carry out circular convolution with discrete three subcenters B-spline function h (k) and f (n), obtain sequential value F (n), n=1,2,40, wherein h (k)=[0.125,0.375,0.375,0.125];
Step 2, judge the positive going zeror crossing moment t of F (n)
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) of discrete three subcenter B-spline functions and F (n), obtain sequential value F
2(n), n=1,2 ... 40, wherein g (k)=[4 ,-8,4];
Step 4, calculating zero-sequence current zero cross distortion COEFFICIENT K, computing method are: to F
2n () takes absolute value, be denoted as | F
2(n) |, and compare the size of absolute value, obtain maximum absolute value and be denoted as | F
2(max) |, definition K=|F
2(t
pzero) |/| F
2(max) |;
Step 5, can judge the generation of high resistance earthing fault further according to zero-sequence current zero cross distortion COEFFICIENT K, determination methods is, if K>K
set, then judge to there occurs high resistance earthing fault, wherein K
setfor 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
setsensitivity according to detecting is arranged, and interval is in [0.5,0.9].
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| CN103310109B (en) * | 2013-06-24 | 2016-08-10 | 北京工业大学 | A kind of follow-up of patients reminds periodic time self-adapting method of adjustment |
| CN104062555B (en) * | 2014-07-16 | 2016-11-16 | 哈尔滨理工大学 | The discrimination method of distribution line high resistance earthing fault characteristic harmonics |
| 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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