CN105606944A - Single-phase grounding fault line selection method and device for distribution system - Google Patents
Single-phase grounding fault line selection method and device for distribution system Download PDFInfo
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Abstract
The invention proposes a single-phase grounding fault line selection method and device for a distribution system. The method comprises the steps: obtaining the zero mode current traveling waves of all feed lines in the distribution system, and determining a reference line according to the zero mode current traveling waves; carrying out the cross wavelet transform of the zero mode current traveling wave of the reference line and the zero mode current traveling waves of all feed lines except the reference line, obtaining a plurality of time frequency sets, and determining a target time frequency set according to the plurality of time frequency sets; determining a plurality of initial wave heads corresponding to the zero mode current traveling waves of all feed lines in the target time frequency sets, and determining a fault line according to the plurality of initial wave heads. According to the technical scheme of the invention, the method can effectively improve the selection accuracy and reliability of the fault line.
Description
Technical field
The present invention relates to protecting electrical power system and control technology field, in particular to a kind of fault line selection method for single-phase-to-ground fault of distribution system and the single-phase earth fault line selection device of distribution system.
Background technology
At present, along with the fast development of intelligent distribution network, the safe and reliable operation of intelligent distribution network becomes the important prerequisite of intelligent distribution network development. And distribution network failure detects and excision is vital link in intelligent distribution network. Distribution network failure is generally singlephase earth fault. Because singlephase earth fault frequently occurs, for ensureing the continued power to power distribution network load, China's distribution system adopts neutral non-effective grounding distribution system mostly, wherein, neutral non-effective grounding distribution system comprises isolated neutral distribution system and neutral by arc extinction coil grounding distribution system two classes. Neutral non-effective grounding distribution system does not form ground short circuit loop under singlephase earth fault, therefore only produces very faint short circuit current, under singlephase earth fault condition, does not trip, and can effectively ensure the power supply reliability of distribution system.
But the singlephase earth fault of neutral non-effective grounding distribution system will produce many harm, as because neutral non-effective grounding distribution system is perfecting phase voltage and can raise as rated value when singlephase earth fault occursDoubly, easily singlephase earth fault is developed into two-phase, three-phase fault, easily cause trouble point to be burnt, finally cause device damage and personal safety to threaten. Therefore, the detection tool of singlephase earth fault is of great significance.
In order accurately to detect the singlephase earth fault of neutral non-effective grounding distribution system, failure line selection technology is arisen at the historic moment. Its central idea for: utilize the current-voltage information of all feeder lines that connect on same bus, by mutual comparison, select the faulty line of singlephase earth fault occurs.
The key of failure line selection technology is that the fault message of many feeder lines is carried out to Obtaining Accurate and analyzing and processing. On bus in distribution system, be conventionally connected to many feeder lines, once distribution system generation singlephase earth fault, first distribution system need to accurately select the feeder line that singlephase earth fault occurs from many feeder lines. Traditional selection method or utilize power frequency information, or utilize the transient information of mixing to realize failure line selection, wherein, based on the selection method of power frequency information, due to the too small and sensitivity deficiency of power frequency information amplitude, and helpless under intermittent singlephase earth fault, and selection method based on transient information is because the amplitude of transient information is larger, feature is obvious, and has good route selection effect, but the physical significance of transient information own is clear not, is difficult to mathematical description. The new development of route selection technology is row ripple route selection technology, and utilization can be analyzed, row ripple primary wave header mensurable, explicit physical meaning is realized failure line selection. But, the correctness of row ripple route selection depends on the correctness of initial wave head seizure and feature extraction thereof, the initial wave head extracting in wrong time and wrong frequency range will obtain less amplitude, even contrary polarity, thus cause the accuracy rate of failure line selection greatly to reduce.
Therefore, how effectively to extract the initial wave head of row ripple, thereby accuracy and the reliability of raising failure line selection become current problem demanding prompt solution.
Summary of the invention
The present invention, just based on the problems referred to above, has proposed a kind of new technical scheme, can effectively improve accuracy and the reliability of failure line selection.
In view of this, a first aspect of the present invention has proposed a kind of fault line selection method for single-phase-to-ground fault of distribution system, comprising: obtain zero mould current traveling wave of all feeder lines in distribution system, and determine reference line according to described zero mould current traveling wave; Zero mould current traveling wave of other feeder lines except described reference line in zero mould current traveling wave of described reference line and described all feeder lines is intersected respectively to wavelet transformation and calculate multiple time-frequency set, determine the set of target time-frequency according to multiple described time-frequency set; In the set of described target time-frequency, determine the multiple initial wave head of the zero mould current traveling wave that corresponds respectively to every feeder line in described all feeder lines, and determine faulty line according to described multiple initial wave heads.
In this technical scheme, by obtaining zero mould current traveling wave of all feeder lines in distribution system, wherein, zero mould current traveling wave can be in the time that distribution system breaks down before 1ms to zero mould current traveling wave in 2ms after breaking down, then intersect respectively wavelet transformation with reference to zero mould current traveling wave of circuit and zero mould current traveling wave of other feeder lines, can obtain more much higher time-frequency set of zero mould current traveling wave degree of correlation of zero mould current traveling wave He other feeder lines of reference line, then in the target time-frequency set definite according to multiple time-frequency set, determine the multiple initial wave head of zero mould current traveling wave of every feeder line, for example, can first determine the wave head in all wave heads of every feeder line with maximum amplitude, then amplitude is greater thanArbitrary wave head of maximum amplitude is as initial wave head, further, determine faulty line according to multiple initial wave heads, therefore, pass through technique scheme, the multiple initial wave head of zero mould current traveling wave of every feeder line be can determine exactly, thereby accuracy and the reliability of determining faulty line by multiple initial wave heads improved.
In technique scheme, preferably, the described step of determining reference line according to described zero mould current traveling wave, specifically comprise: the energy value that calculates zero mould current traveling wave of described every circuit, and using the circuit corresponding to maximum energy value as described reference line, wherein, calculate each described energy value by following formula:Wherein, EkRepresent described energy value, i0kThe zero mould current traveling wave that represents k article of circuit, n represents sampling sequence number, N represents total number of sample points.
In this technical scheme, can calculate more exactly the energy value of zero mould current traveling wave of every feeder line by above-mentioned formula, using by the feeder line corresponding to maximum energy value as with reference to circuit.
In above-mentioned arbitrary technical scheme, preferably, the described zero mould current traveling wave by other feeder lines except described reference line in zero mould current traveling wave of described reference line and described all feeder lines intersects respectively wavelet transformation and calculates multiple time-frequency set, determine that according to multiple described time-frequency set the set of target time-frequency specifically comprises: zero mould current traveling wave of zero mould current traveling wave of described reference line and each described other feeder lines is intersected respectively to wavelet transformation and calculate, to obtain respectively the multiple intersection small echo power spectral densities between zero mould current traveling wave of described reference line and zero mould current traveling wave of each described other feeder lines, multiple described intersection small echo power spectral densities are normalized, and determine the multiple described time-frequency set between other feeder lines described in described reference line and every according to the multiple intersection small echo power spectral densities after normalization, determine the set of described target time-frequency according to multiple described time-frequency set, wherein, calculate described time-frequency set by following formula:Wherein, A represents described time-frequency set, and s represents scale factor, and τ represents the time shift factor, and x represents described reference line, and k represents described k article of feeder line, Wxk(s, τ) represents the described intersection small echo power spectral density between described reference line x and described k article of feeder line, σxRepresent the zero mould current traveling wave standard deviation of described reference line x, σkThe zero mould current traveling wave standard deviation that represents described k article of feeder line, p is arbitrary numerical value.
In this technical scheme, by multiple intersection small echo power spectral densities of intersecting between the capable ripple of zero moding circuit of reference line and the zero mould current traveling wave of each other feeder lines that wavelet transformation calculates are normalized, wherein, can use the variance of zero mould current traveling wave to be normalized the plurality of intersection small echo power spectral density, then calculate multiple time-frequency set according to the multiple intersection small echo power spectral densities after normalization, therefore, pass through technique scheme, can determine more exactly multiple time-frequency set, thereby determine the set of target time-frequency according to multiple time-frequency set more exactly.
In addition, in the time of p=0.3, the multiple time-frequency set that calculate are best multiple time-frequency set, secondly, and because the initial wave head of zero mould current traveling wave is the strongest signal of correlation in all wave heads of zero mould current traveling wave, therefore, no matter what value p gets, and all initial wave head can be included in multiple time-frequency set, also just explanation, when other numerical value in p gets 0.3 neighborhood, also can determine more exactly multiple time-frequency set.
In above-mentioned arbitrary technical scheme, preferably, the described step of determining the set of described target time-frequency according to multiple described time-frequency set, comprising: using the highest the overlapping region medium frequency of multiple described time-frequency set and time arbitrary time-frequency set the earliest as the set of described target time-frequency.
In this technical scheme, by using the highest the overlapping region medium frequency of multiple time-frequency set and time arbitrary time-frequency set the earliest as the set of target time-frequency, thereby can in the set of target time-frequency, determine exactly the initial wave head of zero mould current traveling wave of every feeder line, wherein, this overlapping region is irregularly shaped, comprises one or disconnected multiple time-frequency set.
In above-mentioned arbitrary technical scheme, preferably, describedly determine that according to described multiple initial wave heads faulty line specifically comprises: select feeder line that amplitude maximum in described multiple initial wave head and polarity is different from other initial wave heads as described faulty line; If or the polarity of described multiple initial wave heads is consistent, using the bus of described distribution system as described faulty line.
In this technical scheme, by selecting feeder line that amplitude maximum in multiple initial wave heads and polarity is different from other initial wave heads as faulty line, can determine more exactly faulty line. In addition, if the polarity of multiple initial wave heads is all consistent, also just illustrating that all feeder lines are perfects circuit, and the bus that can judge distribution system is faulty line.
A second aspect of the present invention has proposed a kind of single-phase earth fault line selection device of distribution system, comprising: acquiring unit, for obtaining zero mould current traveling wave of all feeder lines of distribution system, and determine reference line according to described zero mould current traveling wave; The first computing unit, calculate multiple time-frequency set for zero mould current traveling wave of described reference line and zero mould current traveling wave of other feeder lines of described all feeder lines except described reference line are intersected respectively to wavelet transformation, determine the set of target time-frequency according to multiple described time-frequency set; The first determining unit, in the set of described target time-frequency, determines the multiple initial wave head of the zero mould current traveling wave that corresponds respectively to every feeder line in described all feeder lines, and determines faulty line according to described multiple initial wave heads.
In this technical scheme, by obtaining zero mould current traveling wave of all feeder lines in distribution system, wherein, zero mould current traveling wave can be in the time that distribution system breaks down before 1ms to zero mould current traveling wave in 2ms after breaking down, then intersect respectively wavelet transformation with reference to zero mould current traveling wave of circuit and zero mould current traveling wave of other feeder lines, can obtain more much higher time-frequency set of zero mould current traveling wave degree of correlation of zero mould current traveling wave He other feeder lines of reference line, then in the target time-frequency set definite according to multiple time-frequency set, determine the multiple initial wave head of zero mould current traveling wave of every feeder line, for example, can first determine the wave head in all wave heads of every feeder line with maximum amplitude, then amplitude is greater thanArbitrary wave head of maximum amplitude is as initial wave head, further, determine faulty line according to multiple initial wave heads, therefore, pass through technique scheme, the multiple initial wave head of zero mould current traveling wave of every feeder line be can determine exactly, thereby accuracy and the reliability of determining faulty line by multiple initial wave heads improved.
In technique scheme, preferably, described acquiring unit comprises: the second computing unit, be used for the energy value of the zero mould current traveling wave that calculates described every feeder line, and using the feeder line corresponding to maximum energy value as described reference line, wherein, calculate each described energy value by following formula:Wherein, EkRepresent described energy value, i0kThe zero mould current traveling wave that represents k article of feeder line, n represents sampling sequence number, N represents total number of sample points.
In this technical scheme, can calculate more exactly the energy value of zero mould current traveling wave of every feeder line by above-mentioned formula, using by the feeder line corresponding to maximum energy value as with reference to circuit.
In above-mentioned arbitrary technical scheme, preferably, described the first computing unit specifically for, zero mould current traveling wave of zero mould current traveling wave of described reference line and each described other feeder lines is intersected respectively to wavelet transformation and calculate, to obtain respectively the multiple intersection small echo power spectral densities between zero mould current traveling wave of described reference line and zero mould current traveling wave of each described other feeder lines; Multiple described intersection small echo power spectral densities are normalized, and determine the multiple described time-frequency set between other feeder lines described in described reference line and every according to the multiple intersection small echo power spectral densities after normalization, determine the set of described target time-frequency according to multiple described time-frequency set, wherein, calculate described time-frequency set by following formula:Wherein, A represents described time-frequency set, and s represents scale factor, and τ represents the time shift factor, and x represents described reference line, and k represents described k article of feeder line, Wxk(s, τ) represents the described intersection small echo power spectral density between described reference line x and described k article of feeder line, σxRepresent the zero mould current traveling wave standard deviation of described reference line x, σkThe zero mould current traveling wave standard deviation that represents described k article of feeder line, p is arbitrary numerical value.
In this technical scheme, by multiple intersection small echo power spectral densities of intersecting between the capable ripple of zero moding circuit of reference line and the zero mould current traveling wave of each other feeder lines that wavelet transformation calculates are normalized, wherein, can use the variance of zero mould current traveling wave to be normalized the plurality of intersection small echo power spectral density, then calculate multiple time-frequency set according to the multiple intersection small echo power spectral densities after normalization, therefore, pass through technique scheme, can determine more exactly multiple time-frequency set, thereby determine the set of target time-frequency according to multiple time-frequency set more exactly.
In addition, in the time of p=0.3, the multiple time-frequency set that calculate are best multiple time-frequency set, secondly, and because the initial wave head of zero mould current traveling wave is the strongest signal of correlation in all wave heads of zero mould current traveling wave, therefore, no matter what value p gets, and all initial wave head can be included in multiple time-frequency set, also just explanation, when other numerical value in p gets 0.3 neighborhood, also can determine more exactly multiple time-frequency set.
In above-mentioned arbitrary technical scheme, preferably, described the first computing unit comprises: the second determining unit, and for using the highest the overlapping region medium frequency of multiple described time-frequency set and time arbitrary time-frequency set the earliest as the set of described target time-frequency.
In this technical scheme, by using the highest the overlapping region medium frequency of multiple time-frequency set and time arbitrary time-frequency set the earliest as the set of target time-frequency, thereby can in the set of target time-frequency, determine exactly the initial wave head of zero mould current traveling wave of every circuit, wherein, this overlapping region is irregularly shaped, comprises one or disconnected multiple time-frequency set.
In above-mentioned arbitrary technical scheme, preferably, described the first determining unit specifically for, select feeder line that amplitude maximum in described multiple initial wave head and polarity is different from other initial wave heads as described faulty line; If or the polarity of described multiple initial wave heads is consistent, using the bus of described distribution system as described faulty line.
In this technical scheme, by selecting feeder line that amplitude maximum in multiple initial wave heads and polarity is different from other initial wave heads as faulty line, can determine more exactly faulty line. In addition, if the polarity of multiple initial wave heads is all consistent, also just illustrating that all feeder lines are perfects circuit, and the bus that can judge distribution system is faulty line.
By technical scheme of the present invention, can effectively improve accuracy and the reliability of failure line selection.
Brief description of the drawings
Fig. 1 shows the schematic flow sheet of the fault line selection method for single-phase-to-ground fault of distribution system according to an embodiment of the invention;
Fig. 2 shows the structured flowchart of the single-phase earth fault line selection device of distribution system according to an embodiment of the invention.
Detailed description of the invention
In order more clearly to understand above-mentioned purpose of the present invention, feature and advantage, below in conjunction with the drawings and specific embodiments, the present invention is further described in detail. It should be noted that, in the situation that not conflicting, the feature in the application's embodiment and embodiment can combine mutually.
A lot of details are set forth in the following description so that fully understand the present invention; but; the present invention can also adopt other to be different from other modes described here and implement, and therefore, protection scope of the present invention is not subject to the restriction of following public specific embodiment.
Fig. 1 shows the schematic flow sheet of the fault line selection method for single-phase-to-ground fault of distribution system according to an embodiment of the invention.
As shown in Figure 1, the fault line selection method for single-phase-to-ground fault of distribution system according to an embodiment of the invention, comprising:
Step 102, obtains zero mould current traveling wave of all feeder lines in distribution system, and determines reference line according to described zero mould current traveling wave;
Step 104, zero mould current traveling wave of other feeder lines except described reference line in zero mould current traveling wave of described reference line and described all feeder lines is intersected respectively to wavelet transformation and calculate multiple time-frequency set, determine the set of target time-frequency according to multiple described time-frequency set;
Step 106, in the set of described target time-frequency, determines the multiple initial wave head of the zero mould current traveling wave that corresponds respectively to every feeder line in described all feeder lines, and determines faulty line according to described multiple initial wave heads.
In this technical scheme, by obtaining zero mould current traveling wave of all feeder lines in distribution system, wherein, zero mould current traveling wave can be in the time that distribution system breaks down before 1ms to zero mould current traveling wave in 2ms after breaking down, then intersect respectively wavelet transformation with reference to zero mould current traveling wave of circuit and zero mould current traveling wave of other feeder lines, can obtain more much higher time-frequency set of zero mould current traveling wave degree of correlation of zero mould current traveling wave He other feeder lines of reference line, then in the target time-frequency set definite according to multiple time-frequency set, determine the multiple initial wave head of zero mould current traveling wave of every feeder line, for example, can first determine the wave head in all wave heads of every feeder line with maximum amplitude, then amplitude is greater thanArbitrary wave head of maximum amplitude is as initial wave head, further, determine faulty line according to multiple initial wave heads, therefore, pass through technique scheme, the multiple initial wave head of zero mould current traveling wave of every feeder line be can determine exactly, thereby accuracy and the reliability of determining faulty line by multiple initial wave heads improved.
In addition, before obtaining zero mould current traveling wave of all feeder lines in distribution system, can carry out row ripple and start the zero mould current traveling wave that judges to obtain all feeder lines, simultaneously, carry out power frequency residual voltage every 1ms and start judgement, the electric current of avoiding zero mould current traveling wave is too small and make row ripple start judgement can not to get zero mould current traveling wave of all feeder lines.
Preferably, can determine the wave head in all wave heads of every feeder line with maximum amplitude by dyadic wavelet transform, wherein, because intersection wavelet transformation is the continuous wavelet transform based on multiple wavelet function, therefore, the scale coefficient that the small echo that intersects changes is decimal, so can choose the smallest positive integral of intersecting in the yardstick system scope of the wavelet transformation scale coefficient as dyadic wavelet transform.
In technique scheme, preferably, described step 102 specifically comprises: calculate the energy value of zero mould current traveling wave of described every feeder line, and using the feeder line corresponding to maximum energy value as described reference line, wherein, calculate each described energy value by following formula: Wherein, EkRepresent described energy value, i0kThe zero mould current traveling wave that represents k article of feeder line, n represents sampling sequence number, N represents total number of sample points.
In this technical scheme, can calculate more exactly the energy value of zero mould current traveling wave of every feeder line by above-mentioned formula, using by the circuit corresponding to maximum energy value as with reference to circuit.
In above-mentioned arbitrary technical scheme, preferably, described step 104 specifically comprises: zero mould current traveling wave of zero mould current traveling wave of described reference line and each described other feeder lines is intersected respectively to wavelet transformation and calculate, to obtain respectively the multiple intersection small echo power spectral densities between zero mould current traveling wave of described reference line and zero mould current traveling wave of each described other feeder lines; Multiple described intersection small echo power spectral densities are normalized, and determine the multiple described time-frequency set between other feeder lines described in described reference line and every according to the multiple intersection small echo power spectral densities after normalization, determine the set of described target time-frequency according to multiple described time-frequency set, wherein, calculate described time-frequency set by following formula:Wherein, A represents described time-frequency set, and s represents scale factor, and τ represents the time shift factor, and x represents described reference line, and k represents described k article of feeder line, Wxk(s, τ) represents the described intersection small echo power spectral density between described reference line x and described k article of feeder line, σxRepresent the zero mould current traveling wave standard deviation of described reference line x, σkThe zero mould current traveling wave standard deviation that represents described k article of feeder line, p is arbitrary numerical value.
In this technical scheme, by multiple intersection small echo power spectral densities of intersecting between the capable ripple of zero moding circuit of reference line and the zero mould current traveling wave of each other feeder lines that wavelet transformation calculates are normalized, wherein, can use the variance of zero mould current traveling wave to be normalized the plurality of intersection small echo power spectral density, then calculate multiple time-frequency set according to the multiple intersection small echo power spectral densities after normalization, therefore, pass through technique scheme, can determine more exactly multiple time-frequency set, thereby determine the set of target time-frequency according to multiple time-frequency set more exactly.
In addition, in the time of p=0.3, the multiple time-frequency set that calculate are best multiple time-frequency set, secondly, and because the initial wave head of zero mould current traveling wave is the strongest signal of correlation in all wave heads of zero mould current traveling wave, therefore, no matter what value p gets, and all initial wave head can be included in multiple time-frequency set, also just explanation, when other numerical value in p gets 0.3 neighborhood, also can determine more exactly multiple time-frequency set.
In above-mentioned arbitrary technical scheme, preferably, described step 104 comprises: using the highest the overlapping region medium frequency of multiple described time-frequency set and time arbitrary time-frequency set the earliest as the set of described target time-frequency.
In this technical scheme, by using the highest the overlapping region medium frequency of multiple time-frequency set and time arbitrary time-frequency set the earliest as the set of target time-frequency, thereby can in the set of target time-frequency, determine exactly the initial wave head of zero mould current traveling wave of every circuit, wherein, this overlapping region is irregularly shaped, comprises one or disconnected multiple time-frequency set. For example,, if when overlapping region only comprises a time-frequency set, using this time-frequency set as the set of target time-frequency; If while comprising disconnected multiple time-frequency set in overlapping region, using arbitrary time-frequency set the highest multiple time-frequency set medium frequencys as the set of target time-frequency; If in overlapping region, comprise the frequency of disconnected multiple time-frequency set and multiple time-frequency set be the highest, using the arbitrary time-frequency set the earliest of time in multiple time-frequency set as the set of target time-frequency.
In above-mentioned arbitrary technical scheme, preferably, described step 106 comprises: select feeder line that amplitude maximum in described multiple initial wave head and polarity is different from other initial wave heads as described faulty line; If or the polarity of described multiple initial wave heads is consistent, using the bus of described distribution system as described faulty line.
In this technical scheme, by selecting feeder line that amplitude maximum in multiple initial wave heads and polarity is different from other initial wave heads as faulty line, can determine more exactly faulty line. In addition, if the polarity of multiple initial wave heads is all consistent, also just illustrating that all feeder lines are perfects circuit, and the bus that can judge distribution system is faulty line.
Fig. 2 shows the structured flowchart of the single-phase earth fault line selection device of distribution system according to an embodiment of the invention.
As shown in Figure 2, the single-phase earth fault line selection device 200 of distribution system according to an embodiment of the invention, comprise: acquiring unit 202, the first computing unit 204 and the first determining unit 206, wherein, described acquiring unit 202, for obtaining zero mould current traveling wave of all feeder lines of distribution system, and determines reference line according to described zero mould current traveling wave; Described the first computing unit 204, calculate multiple time-frequency set for zero mould current traveling wave of described reference line and zero mould current traveling wave of other feeder lines of described all feeder lines except described reference line are intersected respectively to wavelet transformation, determine the set of target time-frequency according to multiple described time-frequency set; Described the first determining unit 206, in the set of described target time-frequency, determines the multiple initial wave head of the zero mould current traveling wave that corresponds respectively to every feeder line in described all feeder lines, and determines faulty line according to described multiple initial wave heads.
In this technical scheme, by obtaining zero mould current traveling wave of all feeder lines in distribution system, wherein, zero mould current traveling wave can be in the time that distribution system breaks down before 1ms to zero mould current traveling wave in 2ms after breaking down, then intersect respectively wavelet transformation with reference to zero mould current traveling wave of circuit and zero mould current traveling wave of other feeder lines, can obtain more much higher time-frequency set of zero mould current traveling wave degree of correlation of zero mould current traveling wave He other feeder lines of reference line, then in the target time-frequency set definite according to multiple time-frequency set, determine the multiple initial wave head of zero mould current traveling wave of every feeder line, for example, can first determine the wave head in all wave heads of every feeder line with maximum amplitude, then amplitude is greater thanArbitrary wave head of maximum amplitude is as initial wave head, further, determine faulty line according to multiple initial wave heads, therefore, pass through technique scheme, the multiple initial wave head of zero mould current traveling wave of every feeder line be can determine exactly, thereby accuracy and the reliability of determining faulty line by multiple initial wave heads improved.
In addition, before obtaining zero mould current traveling wave of all feeder lines in distribution system, can carry out row ripple and start the zero mould current traveling wave that judges to obtain all feeder lines, simultaneously, carry out power frequency residual voltage every 1ms and start judgement, the electric current of avoiding zero mould current traveling wave is too small and make row ripple start judgement can not to get zero mould current traveling wave of all feeder lines.
Preferably, can determine the wave head in all wave heads of every feeder line with maximum amplitude by dyadic wavelet transform, wherein, because intersection wavelet transformation is the continuous wavelet transform based on multiple wavelet function, therefore, the scale coefficient that the small echo that intersects changes is decimal, so can choose the smallest positive integral of intersecting in the yardstick system scope of the wavelet transformation scale coefficient as dyadic wavelet transform.
In technique scheme, preferably, described acquiring unit 202 comprises: the second computing unit 2022, be used for the energy value of the zero mould current traveling wave that calculates described every feeder line, and using the feeder line corresponding to maximum energy value as described reference line, wherein, calculate each described energy value by following formula:Wherein, EkRepresent described energy value, i0kThe zero mould current traveling wave that represents k article of feeder line, n represents sampling sequence number, N represents total number of sample points.
In this technical scheme, can calculate more exactly the energy value of zero mould current traveling wave of every feeder line by above-mentioned formula, using by the feeder line corresponding to maximum energy value as with reference to circuit.
In above-mentioned arbitrary technical scheme, preferably, described the first computing unit 204 specifically for, zero mould current traveling wave of zero mould current traveling wave of described reference line and each described other feeder lines is intersected respectively to wavelet transformation and calculate, to obtain respectively the multiple intersection small echo power spectral densities between zero mould current traveling wave of described reference line and zero mould current traveling wave of each described other feeder lines; Multiple described intersection small echo power spectral densities are normalized, and determine the multiple described time-frequency set between other feeder lines described in described reference line and every according to the multiple intersection small echo power spectral densities after normalization, determine the set of described target time-frequency according to multiple described time-frequency set, wherein, calculate described time-frequency set by following formula:Wherein, A represents described time-frequency set, and s represents scale factor, and τ represents the time shift factor, and x represents described reference line, and k represents described k article of feeder line, Wxk(s, τ) represents the described intersection small echo power spectral density between described reference line x and described k article of feeder line, σxRepresent the zero mould current traveling wave standard deviation of described reference line x, σkThe zero mould current traveling wave standard deviation that represents described k article of feeder line, p is arbitrary numerical value.
In this technical scheme, by multiple intersection small echo power spectral densities of intersecting between the capable ripple of zero moding circuit of reference line and the zero mould current traveling wave of each other feeder lines that wavelet transformation calculates are normalized, wherein, can use the variance of zero mould current traveling wave to be normalized the plurality of intersection small echo power spectral density, then calculate multiple time-frequency set according to the multiple intersection small echo power spectral densities after normalization, therefore, pass through technique scheme, can determine more exactly multiple time-frequency set, thereby determine the set of target time-frequency according to multiple time-frequency set more exactly.
In addition, in the time of p=0.3, the multiple time-frequency set that calculate are best multiple time-frequency set, secondly, and because the initial wave head of zero mould current traveling wave is the strongest signal of correlation in all wave heads of zero mould current traveling wave, therefore, no matter what value p gets, and all initial wave head can be included in multiple time-frequency set, also just explanation, when other numerical value in p gets 0.3 neighborhood, also can determine more exactly multiple time-frequency set.
In above-mentioned arbitrary technical scheme, preferably, described the first computing unit 204 comprises: the second determining unit 2042, and for using the highest the overlapping region medium frequency of multiple described time-frequency set and time arbitrary time-frequency set the earliest as the set of described target time-frequency.
In this technical scheme, by using the highest the overlapping region medium frequency of multiple time-frequency set and time arbitrary time-frequency set the earliest as the set of target time-frequency, thereby can in the set of target time-frequency, determine exactly the initial wave head of zero mould current traveling wave of every circuit, wherein, this overlapping region is irregularly shaped, comprises one or disconnected multiple time-frequency set. For example,, if when overlapping region only comprises a time-frequency set, using this time-frequency set as the set of target time-frequency; If while comprising disconnected multiple time-frequency set in overlapping region, using arbitrary time-frequency set the highest multiple time-frequency set medium frequencys as the set of target time-frequency; If in overlapping region, comprise the frequency of disconnected multiple time-frequency set and multiple time-frequency set be the highest, using the arbitrary time-frequency set the earliest of time in multiple time-frequency set as the set of target time-frequency.
In above-mentioned arbitrary technical scheme, preferably, described the first determining unit 206 specifically for, select feeder line that amplitude maximum in described multiple initial wave head and polarity is different from other initial wave heads as described faulty line; If or the polarity of described multiple initial wave heads is consistent, using the bus of described distribution system as described faulty line.
In this technical scheme, by selecting feeder line that amplitude maximum in multiple initial wave heads and polarity is different from other initial wave heads as faulty line, can determine more exactly faulty line. In addition, if the polarity of multiple initial wave heads is all consistent, also just illustrating that all feeder lines are perfects circuit, and the bus that can judge distribution system is faulty line.
How to describe the multiple small echo power spectral densities of intersecting between zero mould current traveling wave of computing reference circuit and zero mould current traveling wave of each other feeder lines below in detail.
For zero mould current traveling wave of arbitrary feeder line, its continuous wavelet power spectral density can calculate by following formula:
Wherein, Wx(s, τ) represents continuous wavelet power spectral density, s (s > 0) represent scale factor, τ represents the time shift factor, x (t) represents zero mould current traveling wave of arbitrary feeder line,The conjugate function that represents mother wavelet function, t represents the time.
Because Morlet small echo has good Time-Frequency Localization feature, therefore, can select Morlet small echo as mother wavelet function, the expression formula of this mother wavelet function is:
Wherein,Represent mother wavelet function, w0Represent constant, j represents complex factor, and t represents the time.
Then, calculate the intersection small echo power spectral density between zero mould current traveling wave of reference line and zero mould current traveling wave of arbitrary feeder line by following formula:
Wherein, Wxy(s, τ) represents intersection small echo power spectral density, Wx(s, τ) represents the continuous wavelet power spectral density of zero mould current traveling wave of arbitrary feeder line,Represent the conjugate function of the continuous wavelet power spectral density of zero mould current traveling wave of reference line.
The value of intersection small echo power spectral density is larger, show that the degree of correlation between zero mould current traveling wave of reference line and zero mould current traveling wave of arbitrary feeder line is higher, because noise has mutual irrelevance, therefore, under noise conditions, the small echo power spectral density of intersecting is extremely low, effectively anti-noise.
Preferably, in the time calculating the continuous wavelet power spectral density of zero mould current traveling wave of arbitrary feeder line, can introduce Fourier transformation and realize the quick calculating of the continuous wavelet power spectral density of zero mould current traveling wave of arbitrary feeder line, its formula is as follows:
Wherein, Wx(s, τ) represents continuous wavelet power spectral density, and s represents scale factor,Represent the Fourier transformation of zero mould current traveling wave x (t) of arbitrary feeder line,Represent the conjugate function of mother wavelet functionFourier transformation, f represents frequency.
Its discrete form is:
Wherein, Wx(s, k) represents the continuous wavelet power spectral density of discrete form, and s represents scale factor,Represent the Fourier transformation of zero mould current traveling wave x (t) of discrete form,Represent the conjugate function of the mother wavelet function of discrete formFourier transformation, fkRepresent the frequency of discrete form, δtRepresent sampling interval duration, k is integer.
More than be described with reference to the accompanying drawings technical scheme of the present invention, can have effectively improved accuracy and the reliability of failure line selection.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations. Within the spirit and principles in the present invention all, any amendment of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (10)
1. a fault line selection method for single-phase-to-ground fault for distribution system, is characterized in that, comprising:
Obtain zero mould current traveling wave of all feeder lines in distribution system, and according to described zero mould electric currentRow ripple is determined reference line;
Described reference line will be removed in zero mould current traveling wave of described reference line and described all feeder linesZero mould current traveling wave of other feeder lines outside road intersects respectively wavelet transformation and calculates multipleTime-frequency set, determines the set of target time-frequency according to multiple described time-frequency set;
In the set of described target time-frequency, determine every that corresponds respectively in described all feeder linesThe multiple initial wave head of zero mould current traveling wave of feeder line, and determine according to described multiple initial wave headsFaulty line.
2. the fault line selection method for single-phase-to-ground fault of distribution system according to claim 1, its spyLevy and be, the described step of determining reference line according to described zero mould current traveling wave, specifically comprises:
Calculate the energy value of zero mould current traveling wave of described every feeder line, and will be corresponding to maximum energyThe feeder line of value is as described reference line, wherein,
Calculate each described energy value by following formula:
Wherein, EkRepresent described energy value, i0kRepresent zero mould current traveling wave of k article of feeder line,N represents sampling sequence number, and N represents total number of sample points.
3. the fault line selection method for single-phase-to-ground fault of distribution system according to claim 1, its spyLevy and be, described will be in zero mould current traveling wave of described reference line and described all feeder lines except instituteThe zero mould current traveling wave of stating other feeder lines outside reference line intersects respectively wavelet transformation and calculatesObtain multiple time-frequency set, determine that according to multiple described time-frequency set the set of target time-frequency specifically comprises:
By zero mould electric current of zero mould current traveling wave of described reference line and each described other feeder linesRow wavelength-division does not intersect wavelet transformation calculates, capable to obtain respectively zero mould electric current of described reference lineMultiple intersection small echo power spectrums between zero mould current traveling wave of ripple and each described other feeder linesDegree;
Multiple described intersection small echo power spectral densities are normalized, and multiple according to after normalizationThe small echo power spectral density of intersecting is determined described in described reference line and every many between other feeder linesIndividual described time-frequency set, determines the set of described target time-frequency according to multiple described time-frequency set, wherein,
Calculate described time-frequency set by following formula:
Wherein, A represents described time-frequency set, and s represents scale factor, and τ represents the time shift factor, x tableShow described reference line, k represents described k article of feeder line, Wxk(s, τ) represents described reference lineDescribed intersection small echo power spectral density between road x and described k article of feeder line, σxDescribed in expressionThe zero mould current traveling wave standard deviation of reference line x, σkRepresent zero mould electricity of described k article of feeder linePopular ripple standard deviation, p is arbitrary numerical value.
4. the fault line selection method for single-phase-to-ground fault of distribution system according to claim 3, its spyLevy and be, the described step of determining the set of described target time-frequency according to multiple described time-frequency set, comprising:
By the highest the overlapping region medium frequency of multiple described time-frequency set and time arbitrary time-frequency collection the earliestCooperation is the set of described target time-frequency.
5. according to the singlephase earth fault choosing of the distribution system described in any one in claim 1 to 4Line method, is characterized in that, describedly determines that according to described multiple initial wave heads faulty line specifically comprises:
Select amplitude maximum in described multiple initial wave head and polarity to be different from the feeder line of other initial wave headsCircuit is as described faulty line; Or
If the polarity of described multiple initial wave heads is consistent, using the bus of described distribution system as describedFaulty line.
6. a single-phase earth fault line selection device for distribution system, is characterized in that, comprising:
Acquiring unit, for obtaining zero mould current traveling wave of all feeder lines of distribution system, and rootDetermine reference line according to described zero mould current traveling wave;
The first computing unit, for by zero mould current traveling wave of described reference line and described all feeder linesZero mould current traveling wave of other feeder lines in circuit except described reference line intersects respectively littleWave conversion calculates multiple time-frequency set, determines the set of target time-frequency according to multiple described time-frequency set;
The first determining unit, in the set of described target time-frequency, determines and corresponds respectively to described instituteThere is the multiple initial wave head of zero mould current traveling wave of every feeder line in feeder line, and according to instituteState multiple initial wave heads and determine faulty line.
7. the single-phase earth fault line selection device of distribution system according to claim 6, its spyLevy and be, described acquiring unit comprises:
The second computing unit, for calculating the energy value of zero mould current traveling wave of described every feeder line,And using the feeder line corresponding to maximum energy value as described reference line, wherein,
Calculate each described energy value by following formula:
Wherein, EkRepresent described energy value, i0kRepresent zero mould current traveling wave of k article of feeder line,N represents sampling sequence number, and N represents total number of sample points.
8. the single-phase earth fault line selection device of distribution system according to claim 6, its spyLevy and be, described the first computing unit specifically for,
By zero mould electric current of zero mould current traveling wave of described reference line and each described other feeder linesRow wavelength-division does not intersect wavelet transformation calculates, capable to obtain respectively zero mould electric current of described reference lineMultiple intersection small echo power spectrums between zero mould current traveling wave of ripple and each described other feeder linesDegree;
Multiple described intersection small echo power spectral densities are normalized, and multiple according to after normalizationThe small echo power spectral density of intersecting is determined described in described reference line and every many between other feeder linesIndividual described time-frequency set, determines the set of described target time-frequency according to multiple described time-frequency set, wherein,
Calculate described time-frequency set by following formula:
Wherein, A represents described time-frequency set, and s represents scale factor, and τ represents the time shift factor, x tableShow described reference line, k represents described k article of feeder line, Wxk(s, τ) represents described reference lineDescribed intersection small echo power spectral density between road x and described k article of feeder line, σxDescribed in expressionThe zero mould current traveling wave standard deviation of reference line x, σkRepresent zero mould electricity of described k article of feeder linePopular ripple standard deviation, p is arbitrary numerical value.
9. the single-phase earth fault line selection device of distribution system according to claim 8, its spyLevy and be, described the first computing unit comprises:
The second determining unit, for by the highest the overlapping region medium frequency of multiple described time-frequency set and timeBetween arbitrary time-frequency set the earliest as the set of described target time-frequency.
10. according to the singlephase earth fault choosing of the distribution system described in any one in claim 6 to 9Line apparatus, is characterized in that, described the first determining unit specifically for,
Select amplitude maximum in described multiple initial wave head and polarity to be different from the feeder line of other initial wave headsCircuit is as described faulty line; Or
If the polarity of described multiple initial wave heads is consistent, using the bus of described distribution system as describedFaulty line.
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