CN103018632B - Small current grounding system single-phase ground fault line selection method based on fisher information - Google Patents

Small current grounding system single-phase ground fault line selection method based on fisher information Download PDF

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CN103018632B
CN103018632B CN201210527999.6A CN201210527999A CN103018632B CN 103018632 B CN103018632 B CN 103018632B CN 201210527999 A CN201210527999 A CN 201210527999A CN 103018632 B CN103018632 B CN 103018632B
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information
fault
window
rest
state
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CN103018632A (en
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蔡舒平
刘国海
董雪
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Jiangsu University
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Jiangsu University
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Abstract

The invention discloses a small current grounding system single-phase ground fault line selection method based on fisher information. The method includes: S1, a discrete wavelet coefficient is divided into a series of time windows; S2, data points in each time window are packaged into a state; S3, a probability density function pi based on possibility of observing a system state is established in each time window; S4, the fisher information is calculated from the probability density function for each time window; and S5, a line with the minimum fisher information value is selected to be a fault line. By means of the method, under different grounding methods, fault lines and non-fault lines can be distinguished effectively, effects of voltage initial phase angles, ground resistance and fault location are avoided, and fault moments can be located accurately. Under the adverse conditions of short data, small amplitudes and disturbance existence and the like, feature information hidden in a signal sequence can be effectively extracted, simultaneously a complex degree of each signal sequence can be expressed quantitatively, and an effective means for analyzing a non-stable signal sequence is provided.

Description

The single-phase ground fault line selecting method of small-electric current grounding system of information of having a rest based on expense
Technical field
The present invention relates to Relay Protection Technology in Power System field, particularly relate to a kind of single-phase ground fault line selecting method of small-electric current grounding system of information of having a rest based on expense.
Background technology
Its neutral point major part of China's low and medium voltage distribution network system adopts non_direct ground mode and small current neutral grounding mode, and its fault overwhelming majority is singlephase earth fault.If do not excise faulty line at the appointed time when there is singlephase earth fault, or multipoint earthing short circuit can be expanded at 2 by causing trouble, thus formation phase fault even causes system overvoltage, and then damage equipment, destroy system safety operation, so faulty line and trouble spot must be found as early as possible and excised; And failure line selection is accurately located and gets rid of the important prerequisite of one-phase earthing failure in electric distribution network.
Recent domestic scientific research personnel has done a large amount of work to this, investigated various fault-line selecting method, is mainly divided into two large classes: the selection method based on steady-state component and the selection method based on transient state component.
The former is as zero-sequence current amplitude com parison method, zero-sequence current direction method, zero-sequence current real component method, negative-sequence current method, zero sequence admittance method, Harmonic Method etc.The advantage of this type of selection method is that steady-state component exists always in the process of operating with failure, and has the advantages that easily extract; Shortcoming is that steady-state current amplitude is little, and be vulnerable to the impact of stake resistance, electric arc summation current transformer out-of-balance current, its sensitivity is low, so the result of route selection is not as utilizing transient state component route selection accuracy rate high.Patent " based on the earthing wire-selecting method of zero-sequence current real component, device and the application system " (patent No.: 200910238392.4) be namely a kind of selection method based on steady-state quantity, its principle there is conductance and arc suppression coil over the ground according to circuit to there is ohmic loss, containing real component in fault current, and faulty line real component is larger and direction this feature contrary selects faulty line than non-fault line.Its advantage is not by the impact of arc suppression coil; But because real component in fault current is very little and affect by circuit triphase parameter is unbalanced, detection sensitivity is low, and the reliability of route selection is not high.Injecting signal is limited to trouble spot continuous earth because of it, and therefore the applications that signal is more stable also belongs to the one of stable state route selection method.Patent " universal small current grounding system single-phase grounding selecting and locating device " (patent No.: 93111309.1) and patent " a kind of small grounding current system single-phase grounding selecting method " (patent No. 200410024015.8) all belong to these class methods, the advantage of the method is not by the impact of arc suppression coil, do not require installing zero sequence current mutual inductor (CT), and the position of overhead transmission line trouble spot can also be determined along faulty line detection with detector; Its shortcoming needs to install signal injection equipment, and signal injection energy is by the restriction of PT in addition, can not be too high; When stake resistance is larger, non-fault line distributed capacitance can be shunted Injection Signal, disturbs correct route selection.Concerning intermittent ground connection, the signal intensity of injection is discontinuous, affects correct route selection.Contrast with the above-mentioned selection method based on steady-state quantity, low current grounding transient current amplitude is several times of stable state capacitive earth current to tens times, and numerical value between tens of A to hundreds of A, and is not subject to the impact of arc suppression coil.
Utilize transient state component to carry out earthing wire-selecting can overcome stable state route selection method to there is sensitivity low, by the shortcoming that arc suppression coil affects.200910081958.7) and the patent (patent No.: 200810058173.3) be all a kind of earthing wire-selecting method based on transient state component that " utilizes the low current neutral grounding system fault route selecting method of zero mould electric current Simulation after test " patent " a kind of method and apparatus of the grounding and selecting lines of low-current grounding system " (patent No.:.But the transient state component rate of decay is fast, extracts difficulty large, if only utilize transient state component to carry out failure line selection, route selection result will be made when transient state component is little inaccurate.Obtain based on the fault-line selecting method of modern signal processing in recent years and develop faster.Patent " self-adaption route selection method for single-phase ground fault of power distribution network based on the transient zero-sequence current " (patent No.: 200710059830.1) be a kind of selection method based on wavelet transformation, its principle utilizes wavelet analysis earth fault transient signal, and according to the phase place of harmonic wave in transient state process, the relation such as contrary and amplitude maximum makes route selection.The advantage of these class methods make use of wavelet analysis to make this type of selection method sensitivity higher to unusual very sensitive characteristic; Shortcoming is the impact that the result of route selection is subject to undesired signal.
Above method is all the results providing route selection based on the various parameters (size, phase place, power etc. of current amplitude) of current zero sequence component, but when there is singlephase earth fault, fault-signal general very faint, fault signature is not obvious, this makes only to utilize traditional current amplitude size to be difficult to achieve satisfactory results with the conventional method of the information such as phase place is contrary.More crucially after low current grounding occurs, in the 1 ~ 2h operated with failure, fault-signal is not unalterable, some period signal reflects fault signature and is suitable for route selection, some period signal is interfered and is unfavorable for route selection, and this also makes to need to observe based on the practical application effect of the fault-line selecting method of modern signal processing technology in recent years.So never obtain satisfactory solution about the faulty line reliable recognition problem of small current neutral grounding system generation singlephase earth fault.
From information-theoretical angle, contain a large amount of failure messages in its fault-signal during small current neutral grounding system generation singlephase earth fault, and faulty line information is far away than non-fault line abundant information.Therefore the key of problem how to make good use of these failure messages better, for low current neutral grounding system fault route selecting problem finds some blanket characteristic variables to characterize faulty line.Expense has a rest information usually as a kind of index of measuring Ecosystem sustainability, it sharply can catch the severe degree that also describing system is undergone mutation, by its inspiration, it is applied to failure line selection, select faulty line according to the difference of regular link during generation singlephase earth fault and faulty line mutation content, solve the route selection problem of single-phase grounded malfunction in grounded system of low current with a kind of brand-new thinking.
In view of this, the single-phase ground fault line selecting method of small-electric current grounding system that a kind of information of having a rest based on expense is provided is necessary.
Summary of the invention
The present invention proposes a kind of single-phase ground fault line selecting method of small-electric current grounding system of information of having a rest based on expense, it solves the route selection problem of single-phase grounded malfunction in grounded system of low current effectively.
To achieve these goals, the technical scheme that provides of the invention process case is as follows:
A single-phase ground fault line selecting method of small-electric current grounding system for information of having a rest based on expense, described method comprises:
S1, discrete wavelet coefficient is divided into a series of time window;
S2, in each time window, data point is packaged into state;
S3, in each time window, construct one based on the probability density function p of possibility observing this system state i;
S4, information that each time window calculating expense from probability density function had a rest;
S5, the sorting charge minimum circuit of the value of information of having a rest is faulty line.
As a further improvement on the present invention, also comprise before described step S1:
Signal Pretreatment, carries out wavelet decomposition to remove noise and Isolate Problem feature each circuit zero sequence current signal obtained through real-time sampling.
As a further improvement on the present invention, described zero sequence current signal is after wavelet transformation, and under jth decomposition scale, the high fdrequency component coefficient in k moment is cD jk (), low frequency component coefficient is cA j(k), the component of signal D obtained after carrying out single reconstruct j(k), A j(k) comprise information frequency bandwidth range be then
D j(k):[2 -jf s,2 -(j-1)f s],A j(k):[0,2 -jf s],j=1,2,…,J,
Wherein f sfor the sample frequency of signal, J is maximum decomposition scale.
As a further improvement on the present invention, described step S1 is specially:
Be located on jth layer, the discrete wavelet coefficient of multiresolution analysis be D=d (k), k=1 ..., N }, the wavelet coefficient of this layer defines a sliding window, and window width is w ∈ N, and slippage factor is δ ∈ N, and sliding window is:
W(m,w,δ)={d(k),k=1+m*δ,…,w+m*δ},
Wherein m=1,2 ..., M, M are window number and meet M=(N-w)/δ.
As a further improvement on the present invention, described step S2 is specially:
All elements in sliding window is divided into L state, then in window, total number of element equals element number sum in each state, namely wherein, Z l={ Z l: | Z l(i)-Z l(j) |≤2* σ, i, j=1,2 ... w; I ≠ j}, σ be circuit normal time the standard deviation of wavelet coefficient D.
As a further improvement on the present invention, from probability density function, calculating the formula taking information of having a rest in described step S4 is: I ≈ 4 ∑ [q i-q i+1] 2, q i, q i+1for the square root of the probability density at i and i+1 place, I is that expense is had a rest information.
The present invention achieves the route selection problem of single-phase grounded malfunction in grounded system of low current as single criterion with the positive number of a nondimensional non-negative.There is following beneficial effect:
Under different earthing modes, all can effectively distinguish faulty line and non-fault line, and not by voltage initial angle, stake resistance, the impact of abort situation, can accurate localizing faults moment;
Under the adverse condition such as short data, small magnitude, existence interference, effectively can extract the characteristic information be hidden in burst, simultaneously the complexity of each burst of energy quantitatively characterizing, for the analysis of non-stationary signal sequence provides effective means.
Accompanying drawing explanation
Fig. 1 is that the expense of the present invention is based on is had a rest the schematic flow sheet of single-phase ground fault line selecting method of small-electric current grounding system of information;
Fig. 2 is that in the embodiment of the present invention one, circuit L1, at distance bus 10km place, singlephase earth fault occurs, and the moment occurs fault is 0.02s, stake resistance 200 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 schematic diagram of each bar circuit when voltage initial angle is 0 °;
Fig. 3 is the FI value schematic diagram of faulty line L1 and regular link L2 ﹑ L3 in Fig. 2;
Fig. 4 is that in the embodiment of the present invention one, circuit L1, at distance bus 20km place, singlephase earth fault occurs, and the moment occurs fault is 0.02s, fault resstance 20 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 schematic diagram of each bar circuit when voltage initial angle is 180 °;
Fig. 5 is the FI value schematic diagram of faulty line L1 and regular link L2 ﹑ L3 in Fig. 4.
Embodiment
Describe the present invention below with reference to each embodiment shown in the drawings.But these embodiments do not limit the present invention, the structure that those of ordinary skill in the art makes according to these embodiments, method or conversion functionally are all included in protection scope of the present invention.
Shown in ginseng Fig. 1, one of the present invention is had a rest based on expense the single-phase ground fault line selecting method of small-electric current grounding system of (fisher) information, comprising:
S1, discrete wavelet coefficient is divided into a series of time window;
S2, in each time window, data point is packaged into state;
S3, in each time window, construct one based on the probability density function p of possibility observing this system state i;
S4, information that each time window calculating expense from probability density function had a rest;
S5, the sorting charge minimum circuit of the value of information of having a rest is faulty line.
Further, before step S1, also comprise Signal Pretreatment, each circuit zero sequence current signal obtained through real-time sampling is carried out wavelet decomposition to remove noise and Isolate Problem feature.
If zero sequence current signal x (n) is after wavelet transformation, under jth decomposition scale, the high fdrequency component coefficient in k moment is cD jk (), low frequency component coefficient is cA j(k), the component of signal D obtained after carrying out single reconstruct j(k), A j(k) comprise information frequency bandwidth range be then
D j(k):[2 -jf s,2 -(j-1)f s],A j(k):[0,2 -jf s],j=1,2,…,J,
Wherein f sfor the sample frequency of signal, J is maximum decomposition scale.F in present embodiment sget 20kHz, select db5 mother wavelet, carry out 5 layers of wavelet decomposition to data, namely J gets 5.
Step S1 is specially:
Be located on jth layer, the discrete wavelet coefficient of multiresolution analysis be D=d (k), k=1 ..., N }, the wavelet coefficient of this layer defines a sliding window, and window width is w ∈ N, and slippage factor is δ ∈ N, obtains sliding window as follows:
W(m,w,δ)={d(k),k=1+m*δ,…,w+m*δ},
Wherein m=1,2 ..., M, M are window number and meet M=(N-w)/δ.
Step S2 is specially:
Suppose that in sliding window, all elements can be divided into L state, then
Length ( w ) = Σ l = 1 L Length ( Z l ) ,
Wherein, Z l={ Z l: | Z l(i)-Z l(j) |≤2* σ, i, j=1,2 ... w; I ≠ j}.
Above formula shows that in window, total number of element equals element number sum in each state.Wherein σ be circuit normal time the standard deviation of wavelet coefficient D, according to Chebyshev (Chebyshev) theorem, the principle of above-mentioned division can ensure that the data point of 89 ﹪ in this window is in same state and no matter its form of probability is how.
From probability density function, calculate the formula taking information of having a rest in step s 4 which is: I ≈ 4 ∑ [q i-q i+1] 2, q i, q i+1for the square root of the probability density at i and i+1 place, I is that expense is had a rest information.
Take information computing formula of having a rest to be drawn by following steps:
The expense of the variable single measurement information I that has a rest is calculated as follows:
I = ∫ ds P ( s ) ( dP ( s ) ds ) 2 ,
Wherein, P (s) is probability density function (PDF), and s is a state variable;
Make q 2(s)=P (s), so above formula becomes:
I = 4 ∫ ds [ dq ( s ) ds ] 2 ;
Replace the differential in above formula by difference, replace the integration in above formula can obtain expense with summation and to have a rest the approximate formula of information:
I≈4∑[q i-q i+1] 2
Below in conjunction with embodiment, the invention will be further described.
Example one: isolated neutral system single-phase earth fault line selection example.
If 3 of 35kv/10kv isolated neutral system outlet is L1 ﹑ L2 and L3, the positive order parameter of circuit is R 1=0.484 Ω/km, L 1=0.3454mH/km, C 1=0.0345 μ F/km, Zero sequence parameter R 0=1.16 Ω/km, L 0=1.10362mH/km, C 0=0.0219 μ F/km, other parameter is the same.
Figure 2 shows that circuit L1, at distance bus 10km place, singlephase earth fault occurs, the moment occurs fault is 0.02s, stake resistance 200 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 of each bar circuit when voltage initial angle is 0 °; Figure 3 shows that the FI value (namely taking the value of information of having a rest) that each circuit zero sequence current signal is calculated as stated above.
Figure 4 shows that circuit L1 singlephase earth fault occurs, fault resstance 20 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 of three-line when voltage initial angle is 180 ° at distance bus 20km place; Fig. 5 is the FI value that three-line calculates.
Example two: neutral by arc extinction coil grounding system single-phase earth fault route selecting example.
Table 1 lists the route selection result under neutral by arc extinction coil grounding system different faults condition, and when grounding through arc, adopt over-compensation mode, compensativity is 8%, and other parameter is the same.
Table 1: neutral by arc extinction coil grounding system route selection result
As can be seen from above embodiment, the present invention achieves the route selection problem of single-phase grounded malfunction in grounded system of low current as single criterion with the positive number of a nondimensional non-negative.Compared with prior art, have the following advantages:
Under different earthing modes, all can effectively distinguish faulty line and non-fault line, and not by voltage initial angle, stake resistance, the impact of abort situation, can accurate localizing faults moment;
Under the adverse condition such as short data, small magnitude, existence interference, effectively can extract the characteristic information be hidden in burst, simultaneously the complexity of each burst of energy quantitatively characterizing, for the analysis of non-stationary signal sequence provides effective means.
Be to be understood that, although this instructions is described according to embodiment, but not each embodiment only comprises an independently technical scheme, this narrating mode of instructions is only for clarity sake, those skilled in the art should by instructions integrally, technical scheme in each embodiment also through appropriately combined, can form other embodiments that it will be appreciated by those skilled in the art that.
A series of detailed description listed is above only illustrating for feasibility embodiment of the present invention; they are also not used to limit the scope of the invention, all do not depart from the skill of the present invention equivalent implementations done of spirit or change all should be included within protection scope of the present invention.

Claims (6)

1. a single-phase ground fault line selecting method of small-electric current grounding system for information of having a rest based on expense, it is characterized in that, described method comprises:
S1, discrete wavelet coefficient is divided into a series of time window;
S2, in each time window, data point is packaged into state;
S3, in each time window, construct one based on the probability density function pi of possibility observing this system state;
S4, information that each time window calculating expense from probability density function had a rest;
S5, the sorting charge minimum circuit of the value of information of having a rest is faulty line.
2. method according to claim 1, is characterized in that, also comprises before described step S1:
Signal Pretreatment, carries out wavelet decomposition to remove noise and Isolate Problem feature each circuit zero sequence current signal obtained through real-time sampling.
3. method according to claim 2, is characterized in that, described zero sequence current signal is after wavelet decomposition, and under jth decomposition scale, the high fdrequency component coefficient in k moment is cD jk (), low frequency component coefficient is cA j(k), the component of signal D obtained after carrying out single reconstruct j(k), A j(k) comprise information frequency bandwidth range be then
D j(k):[2 -jf s,2 -(j-1)f s],A j(k):[0,2 -jf s],j=1,2,...,J,
Wherein f sfor the sample frequency of signal, J is maximum decomposition scale.
4. method according to claim 3, is characterized in that, described step S1 is specially:
Be located on jth layer, the discrete wavelet coefficient of multiresolution analysis is D={d (k), k=1 ..., N}, the wavelet coefficient of this layer defines a sliding window, and window width is w ∈ N, and slippage factor is δ ∈ N, and sliding window is:
W(m,w,δ)={d(k),k=1+m*δ,…,w+m*δ},
Wherein m=1,2 ..., M, M are window number and meet M=(N-w)/δ.
5. method according to claim 4, is characterized in that, described step S2 is specially:
All elements in sliding window is divided into L state, then in window, total number of element equals element number sum in each state, namely wherein, Z l={ Z l: | Z l(x)-Z l(y) |≤2* σ, x, y=1,2 ... w; X ≠ y}, σ be circuit normal time the standard deviation of wavelet coefficient D.
6. method according to claim 1, is characterized in that, calculates the formula taking information of having a rest to be in described step S4 from probability density function: I ≈ 4 Σ [q i-q i+1] 2, q i, q i+1for the probability density square root at i and i+1 place, I is that expense is had a rest information.
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CN103592574B (en) * 2013-11-20 2016-06-22 国家电网公司 A kind of method and system of small current line selection
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