CN103018632A - 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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CN103018632A
CN103018632A CN2012105279996A CN201210527999A CN103018632A CN 103018632 A CN103018632 A CN 103018632A CN 2012105279996 A CN2012105279996 A CN 2012105279996A CN 201210527999 A CN201210527999 A CN 201210527999A CN 103018632 A CN103018632 A CN 103018632A
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information
fault
window
rest
state
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CN103018632B (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

Based on the have a rest single-phase ground fault line selecting method of small-electric current grounding system of information of expense
Technical field
The present invention relates to the Relay Protection Technology in Power System field, relate in particular to a kind of based on the have a rest single-phase ground fault line selecting method of small-electric current grounding system of information of expense.
Background technology
The most of employing of its neutral point of China low and medium voltage distribution network system non_direct ground mode is the small current neutral grounding mode, and its fault overwhelming majority is singlephase earth fault.Then can not cause fault to be expanded into or multipoint earthing short circuit at 2 if excise at the appointed time faulty line when singlephase earth fault occurs, thereby form phase fault even cause 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 the important prerequisite of accurately locating and get rid of one-phase earthing failure in electric distribution network.
The recent domestic scientific research personnel has done a large amount of work to this, worked out various fault-line selecting methods, mainly is divided into two large classes: based on the selection method of steady-state component with based on the selection method of transient state component.
The former is such as zero-sequence current amplitude relative method, zero-sequence current direction method, zero-sequence current real component method, negative-sequence current method, zero sequence node-pair 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 characteristics of easy extraction; Shortcoming is that the steady-state current amplitude is little, is vulnerable to the impact of stake resistance, electric arc summation current transformer out-of-balance current, and its sensitivity is low, so the result of route selection is high not as utilizing transient state component route selection accuracy rate.Patent " based on earthing wire-selecting method, device and the application system of zero-sequence current the real component " (patent No.: 200910238392.4) namely be a kind of selection method based on steady-state quantity, its principle is to exist over the ground electricity to lead and there is ohmic loss in arc suppression coil according to circuit, contain real component in the fault current, and the faulty line real component than non-fault line large and these characteristics of opposite direction select faulty line.Its advantage is the impact that is not subjected to arc suppression coil; But because real component is very little and be subjected to that the circuit triphase parameter is unbalanced to be affected in the fault current, detection sensitivity is low, and the reliability of route selection is not high.Injecting signal is limited to the trouble spot continuous earth because of it, and therefore the applications that signal is more stable also belongs to a kind of 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 the impact that is not subjected to arc suppression coil, do not require installing zero sequence current mutual inductor (CT), and survey the position that to determine the overhead transmission line trouble spot along faulty line with detector; Its shortcoming is to need signal injection equipment is installed, and the signal injection energy is subjected to the restriction of PT in addition, can not be too high; When stake resistance was larger, the non-fault line distributed capacitance can be shunted Injection Signal, disturbed correct route selection.Concerning intermittent ground connection, the signal intensity of injection is discontinuous, affects correct route selection.Contrast with above-mentioned selection method based on steady-state quantity, low current grounding transient current amplitude is several times to tens times of stable state capacitive earth current, and numerical value arrives between hundreds of A at tens of A, and is not subjected to the impact of arc suppression coil.
Utilizing transient state component to carry out earthing wire-selecting can overcome stable state route selection method and exist sensitivity low, the shortcoming that affected by arc suppression coil.200910081958.7) and patent " low current neutral grounding system fault route selecting method of simulation after utilizing zero mould electric current the to survey " (patent No.: 200810058173.3) all be based on a kind of earthing wire-selecting method of transient state component patent " a kind of method and apparatus of the grounding and selecting lines of low-current grounding system " (patent No.:.Yet the transient state component rate of decay is fast, and it is large to extract difficulty, if only utilize transient state component to carry out failure line selection, and will be so that the route selection result be inaccurate in transient state component situation seldom.Fault-line selecting method based on modern signal processing has obtained faster development in recent years.Patent " based on the self-adaption route selection method for single-phase ground fault of power distribution network of the transient zero-sequence current " (patent No.: 200710059830.1) be a kind of selection method based on wavelet transformation, its principle is to utilize wavelet analysis earth fault transient signal, makes route selection according to relations such as the single spin-echo of harmonic wave in the transient state process and amplitude are maximum.The advantage of these class methods is to have utilized wavelet analysis to unusual very sensitive characteristic and so that this type of selection method sensitivity is higher; Shortcoming is the impact that the result of route selection is subject to undesired signal.
The various parameters (size of current amplitude, phase place, power etc.) that above method all is based on the current zero sequence component provide the result of route selection, yet when singlephase earth fault occurs, fault-signal generally very faint, fault signature is not obvious, this is so that only utilize the conventional method of the information such as traditional current amplitude size and single spin-echo to be difficult to achieve satisfactory results.More crucial is after low current grounding occurs, in the 1~2h that operates with failure, fault-signal is not unalterable, some the time segment signal reflected that fault signature is suitable for route selection, some the time segment signal be interfered and be unfavorable for route selection, this is also so that be still waiting to observe based on the practical application effect of the fault-line selecting method of modern signal processing technology in recent years.So the faulty line reliable recognition problem of relevant small current neutral grounding system generation singlephase earth fault never obtains satisfactory solution.
From information-theoretical angle, comprised 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 is how to make good use of better these failure messages, seeks some blanket characteristic variables for the low current neutral grounding system fault route selecting problem and characterizes faulty line.Expense is had a rest information usually as a kind of index of measuring Ecosystem sustainability, the severe degree that it can sharply catch and describing system is undergone mutation, be subjected to its inspiration that it is applied to failure line selection, the difference of regular link and faulty line sudden change degree selects faulty line during according to the generation singlephase earth fault, solves 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, be necessary to provide a kind of based on the have a rest single-phase ground fault line selecting method of small-electric current grounding system of information of expense.
Summary of the invention
The present invention proposes a kind ofly based on the have a rest single-phase ground fault line selecting method of small-electric current grounding system of information of 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 kind of based on the have a rest single-phase ground fault line selecting method of small-electric current grounding system of information of expense, described method comprises:
S1, the 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 probability density function p based on the possibility of observing this system state of structure i
S4, each time window is calculated the expense information of having a rest from probability density function;
The have a rest circuit of value of information minimum of S5, sorting charge is faulty line.
As a further improvement on the present invention, also comprise before the described step S1:
Signal Pretreatment is carried out wavelet decomposition to each the circuit zero sequence current signal that obtains through real-time sampling in order to remove noise and Isolate Problem feature.
As a further improvement on the present invention, described zero sequence current signal is behind wavelet transformation, and k high fdrequency component coefficient constantly is cD under the j decomposition scale j(k), the low frequency component coefficient is cA j(k), carry out the component of signal D that obtains after single the reconstruct j(k), A j(k) the frequency span scope of institute's inclusion information then is
D j(k):[2 -jf s,2 -(j-1)f s],A j(k):[0,2 -jf s],j=1,2,…,J,
F wherein sBe 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 the j layer, the discrete wavelet coefficient of multiresolution analysis be D=d (k), k=1 ..., N }, at wavelet coefficient definition one sliding window of this layer, 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},
M=1 wherein, 2 ..., M, M are window number and satisfy M=(N-w)/δ.
As a further improvement on the present invention, described step S2 is specially:
All elements in the sliding window is divided into L state, and then total number of element equals element number sum in each state in the window, namely Wherein, Z l={ Z l: | Z l(i)-Z l(j) |≤2* σ, i, j=1,2 ... w; I ≠ j}, σ are the standard deviation of the wavelet coefficient D of circuit when normal.
As a further improvement on the present invention, calculating the formula that takes the information of having a rest among the described step S4 from probability density function is: I ≈ 4 ∑ [q i-q I+1] 2, q i, q I+1Be the square root of the probability density at i and i+1 place, I is the expense information of having a rest.
The present invention has realized the route selection problem of single-phase grounded malfunction in grounded system of low current as single criterion with a nondimensional non-negative positive number.Have following beneficial effect:
Under different earthing modes, all can effectively distinguish faulty line and non-fault line, and not be subjected to the voltage initial phase angle, stake resistance, fault moment can be accurately located in the impact of abort situation;
Under the adverse condition such as short data, small magnitude, existence interference, can effectively extract the characteristic information that is hidden in the burst, complexity that simultaneously can each burst of quantitatively characterizing is for the analysis of non-stationary signal sequence provides effective means.
Description of drawings
Fig. 1 is the have a rest schematic flow sheet of single-phase ground fault line selecting method of small-electric current grounding system of information of the expense of the present invention is based on;
Fig. 2 is that singlephase earth fault occurs at distance bus 10km place circuit L1 in the embodiment of the invention one, and it is 0.02s that fault occurs constantly, stake resistance 200 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 synoptic diagram of each bar circuit when the voltage initial phase angle is 0 °;
Fig. 3 is the FI value synoptic diagram of faulty line L1 and regular link L2 ﹑ L3 among Fig. 2;
Fig. 4 is that singlephase earth fault occurs at distance bus 20km place circuit L1 in the embodiment of the invention one, and it is 0.02s that fault occurs constantly, fault resstance 20 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 synoptic diagram of each bar circuit when the voltage initial phase angle is 180 °;
Fig. 5 is the FI value synoptic diagram of faulty line L1 and regular link L2 ﹑ L3 among 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, and the conversion on the structure that those of ordinary skill in the art makes according to these embodiments, method or the function all is included in protection scope of the present invention.
Join shown in Figure 1ly, of the present invention a kind of based on the have a rest single-phase ground fault line selecting method of small-electric current grounding system of (fisher) information of expense, comprising:
S1, the 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 probability density function p based on the possibility of observing this system state of structure i
S4, each time window is calculated the expense information of having a rest from probability density function;
The have a rest circuit of value of information minimum of S5, sorting charge is faulty line.
Further, also comprise Signal Pretreatment before the step S1, each the circuit zero sequence current signal that obtains through real-time sampling is carried out wavelet decomposition in order to remove noise and Isolate Problem feature.
If zero sequence current signal x (n) is behind wavelet transformation, k high fdrequency component coefficient constantly is cD under the j decomposition scale j(k), the low frequency component coefficient is cA j(k), carry out the component of signal D that obtains after single the reconstruct j(k), A j(k) the frequency span scope of institute's inclusion information then is
D j(k):[2 -jf s,2 -(j-1)f s],A j(k):[0,2 -jf s],j=1,2,…,J,
F wherein sBe the sample frequency of signal, J is maximum decomposition scale.F in the present embodiment sGet 20kHz, select db5 base small echo, data are carried out 5 layers of wavelet decomposition, namely J gets 5.
Step S1 is specially:
Be located on the j layer, the discrete wavelet coefficient of multiresolution analysis be D=d (k), k=1 ..., N }, at wavelet coefficient definition one sliding window of this layer, window width is w ∈ N, and slippage factor is δ ∈ N, and it is as follows to get sliding window:
W(m,w,δ)={d(k),k=1+m*δ,…,w+m*δ},
M=1 wherein, 2 ..., M, M are window number and satisfy M=(N-w)/δ.
Step S2 is specially:
Suppose that all elements can be divided into L state in the sliding window, 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}.
Following formula shows that total number of element equals element number sum in each state in the window.Wherein σ is the standard deviation of the wavelet coefficient D of circuit when normal, according to Chebyshev (Chebyshev) theorem, the principle of above-mentioned division can guarantee that the data point of 89 ﹪ in this window is in same state and no matter its form of probability how.
Calculating the formula that takes the information of having a rest in step S4 from probability density function is: I ≈ 4 ∑ [q i-q I+1] 2, q i, q I+1Be the square root of the probability density at i and i+1 place, I is the expense information of having a rest.
Taking the information calculations formula of having a rest is 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 following formula becomes:
I = 4 ∫ ds [ dq ( s ) ds ] 2 ;
Replace differential in the following formula with difference, replace integration in the following formula can obtain the have a rest approximate formula of information of expense with summation:
I≈4∑[q i-q i+1] 2
The invention will be further described below in conjunction with embodiment.
Example one: isolated neutral system single-phase earth fault line selection example.
If 3 outlets of 35kv/10kv isolated neutral system are 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 singlephase earth fault occurs at distance bus 10km place circuit L1, it is 0.02s that fault occurs constantly, stake resistance 200 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 of each bar circuit when the voltage initial phase 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 singlephase earth fault, fault resstance 20 Ω, the zero-sequence current waveform I01 ﹑ I02 ﹑ I03 of three-line when the voltage initial phase angle is 180 ° occur at distance bus 20km place circuit L1; 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 has been listed the route selection result under the neutral by arc extinction coil grounding system different faults condition, adopts the over-compensation mode when grounding through arc, and compensativity is 8%, and other parameter is the same.
Table 1: the route selection result of neutral by arc extinction coil grounding system
Can be found out that by above embodiment the present invention has realized the route selection problem of single-phase grounded malfunction in grounded system of low current as single criterion with a nondimensional non-negative positive number.Compared with prior art, have the following advantages:
Under different earthing modes, all can effectively distinguish faulty line and non-fault line, and not be subjected to the voltage initial phase angle, stake resistance, fault moment can be accurately located in the impact of abort situation;
Under the adverse condition such as short data, small magnitude, existence interference, can effectively extract the characteristic information that is hidden in the burst, complexity that simultaneously can each burst of quantitatively characterizing is 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 be not that each embodiment only comprises an independently technical scheme, this narrating mode of instructions only is for clarity sake, those skilled in the art should make instructions as a whole, technical scheme in each embodiment also can through appropriate combination, form other embodiments that it will be appreciated by those skilled in the art that.
Above listed a series of detailed description only is specifying for feasibility embodiment of the present invention; they are not to limit protection scope of the present invention, allly do not break away from equivalent embodiment or the change that skill spirit of the present invention does and all should be included within protection scope of the present invention.

Claims (6)

1. one kind based on the have a rest single-phase ground fault line selecting method of small-electric current grounding system of information of expense, it is characterized in that described method comprises:
S1, the 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 probability density function p based on the possibility of observing this system state of structure i
S4, each time window is calculated the expense information of having a rest from probability density function;
The have a rest circuit of value of information minimum of S5, sorting charge is faulty line.
2. method according to claim 1 is characterized in that, also comprises before the described step S1:
Signal Pretreatment is carried out wavelet decomposition to each the circuit zero sequence current signal that obtains through real-time sampling in order to remove noise and Isolate Problem feature.
3. method according to claim 2 is characterized in that, described zero sequence current signal is behind wavelet transformation, and k high fdrequency component coefficient constantly is cD under the j decomposition scale j(k), the low frequency component coefficient is cA j(k), carry out the component of signal D that obtains after single the reconstruct j(k), A j(k) the frequency span scope of institute's inclusion information then is
D j(k):[2 -jf s,2 -(j-1)f s],A j(k):[0,2 -jf s],j=1,2,…,J,
F wherein sBe the sample frequency of signal, J is maximum decomposition scale.
4. method according to claim 1 is characterized in that, described step S1 is specially:
Be located on the j layer, the discrete wavelet coefficient of multiresolution analysis be D=d (k), k=1 ..., N }, at wavelet coefficient definition one sliding window of this layer, 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},
M=1 wherein, 2 ..., M, M are window number and satisfy M=(N-w)/δ.
5. method according to claim 4 is characterized in that, described step S2 is specially:
All elements in the sliding window is divided into L state, and then total number of element equals element number sum in each state in the window, namely Wherein, Z l={ Z l: | Z l(i)-Z l(j) |≤2* σ, i, j=1,2 ... w; I ≠ j}, σ are the standard deviation of the wavelet coefficient D of circuit when normal.
6. method according to claim 1 is characterized in that, calculates the formula that takes the information of having a rest among the described step S4 to be from probability density function: I ≈ 4 ∑ [q i-q I+1] 2, q i, q I+1Be the probability density square root at i and i+1 place, I is for taking the information of having a rest.
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CN103364684A (en) * 2013-07-12 2013-10-23 桐乡市供电局 Fault line selection method based on wavelet analysis
CN103592574A (en) * 2013-11-20 2014-02-19 国家电网公司 Low-current line selection method and system
CN104037728A (en) * 2014-05-05 2014-09-10 珠海许继电气有限公司 Distribution circuit single-phase grounding protection control method based on software frequency measurement and harmonic wave analysis
CN107340449A (en) * 2017-06-16 2017-11-10 国网福建省电力有限公司 A kind of method for locating single-phase ground fault and system of ADAPTIVE MIXED earthing mode
CN108197822A (en) * 2018-01-24 2018-06-22 贵州电网有限责任公司 A kind of distribution network fault line selection adaptability teaching decision-making technique
CN109324241A (en) * 2017-08-01 2019-02-12 国网辽宁省电力有限公司电力科学研究院 A kind of grounding net of transformer substation corrosion diagnosis method for early warning and system
CN110221182A (en) * 2019-07-03 2019-09-10 李晓明 A kind of distribution small current earthing wire-selecting method and wire selection system
CN110554274A (en) * 2019-09-03 2019-12-10 广东电网有限责任公司 adaptive weight grounding line selection method based on wavelet singular information
CN111791720A (en) * 2020-07-16 2020-10-20 东莞市高标软件科技有限公司 Electric vehicle control system

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CN103364684A (en) * 2013-07-12 2013-10-23 桐乡市供电局 Fault line selection method based on wavelet analysis
CN103364684B (en) * 2013-07-12 2015-07-08 国家电网公司 Fault line selection method based on wavelet analysis
CN103592574A (en) * 2013-11-20 2014-02-19 国家电网公司 Low-current line selection method and system
CN104037728A (en) * 2014-05-05 2014-09-10 珠海许继电气有限公司 Distribution circuit single-phase grounding protection control method based on software frequency measurement and harmonic wave analysis
CN104037728B (en) * 2014-05-05 2017-02-15 珠海许继电气有限公司 Distribution circuit single-phase grounding protection control method based on software frequency measurement and harmonic wave analysis
CN107340449A (en) * 2017-06-16 2017-11-10 国网福建省电力有限公司 A kind of method for locating single-phase ground fault and system of ADAPTIVE MIXED earthing mode
CN107340449B (en) * 2017-06-16 2020-05-05 国网福建省电力有限公司 Single-phase earth fault positioning method and system adopting self-adaptive hybrid earth mode
CN109324241A (en) * 2017-08-01 2019-02-12 国网辽宁省电力有限公司电力科学研究院 A kind of grounding net of transformer substation corrosion diagnosis method for early warning and system
CN108197822A (en) * 2018-01-24 2018-06-22 贵州电网有限责任公司 A kind of distribution network fault line selection adaptability teaching decision-making technique
CN110221182A (en) * 2019-07-03 2019-09-10 李晓明 A kind of distribution small current earthing wire-selecting method and wire selection system
CN110221182B (en) * 2019-07-03 2021-04-02 李晓明 Distributed small-current grounding line selection method and line selection system
CN110554274A (en) * 2019-09-03 2019-12-10 广东电网有限责任公司 adaptive weight grounding line selection method based on wavelet singular information
CN110554274B (en) * 2019-09-03 2021-05-28 广东电网有限责任公司 Adaptive weight grounding line selection method based on wavelet singular information
CN111791720A (en) * 2020-07-16 2020-10-20 东莞市高标软件科技有限公司 Electric vehicle control system
CN111791720B (en) * 2020-07-16 2021-05-14 东莞市高标软件科技有限公司 Electric vehicle control system

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