CN100416965C - Method for detecting voltage zero cross near fault in travelling wave protection - Google Patents
Method for detecting voltage zero cross near fault in travelling wave protection Download PDFInfo
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- CN100416965C CN100416965C CNB200410079501XA CN200410079501A CN100416965C CN 100416965 C CN100416965 C CN 100416965C CN B200410079501X A CNB200410079501X A CN B200410079501XA CN 200410079501 A CN200410079501 A CN 200410079501A CN 100416965 C CN100416965 C CN 100416965C
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Abstract
The present invention relates to technology for detecting faults near voltage zero passage in traveling-wave protection, which belongs to the technical field of the relay protection in an electric power system. In the method of the present invention, according to the characteristic that when faults near voltage zero passage occur, most of small waves of small dimension of current traveling waves convert waveforms away from a time shaft, when faults not near voltage zero passage occur, most of the small waves of small dimension of the current traveling waves convert the waveforms closely to the time shaft, the formula of a phase to mode transformation matrix T is used for calculating three line traveling waves and the energy thereof, the line traveling wave with the maximum energy is selected to implement small wave transformation, and whether the faults near voltage zero passage occur or not is identified by calculating the number of spots which more than k<w> times as big as that of the maximum value of the small waves of small dimension in the transformation results of the small waves of small dimension. The detection method provided by the present invention, which can distinguish the faults near voltage zero passage from other faults, has the advantages of reliable and effective method, convenient detection, etc.
Description
Technical field:
The present invention relates to the detection method of voltage zero cross near fault in a kind of traveling-wave protection, belong to the relay protection of power system technical field.
Background technology:
The protection philosophy that the existing protective device overwhelming majority is based on the power frequency amount constitutes; capable ripple (transient state) process that it is looked after the fault is interference; manage filtering in addition; only utilize the steady-state quantity (list of references 1 after the fault; 2); steady-state quantity after the fault then is subjected to the influence of fault switching angle hardly, so the protection of power frequency amount is subjected to the influence of fault switching angle hardly.Different with power frequency amount protection is, capable ripple propagation, refraction, the reflexive property formation on the line that traveling-wave protection causes according to fault, and the high-frequency signal that it utilizes fault to cause does not reflect the power frequency amount basically.And the high-frequency signal that fault causes size has much relations with the fault switching angle.Though most faults are faults of insulation breakdown character, insulation breakdown needs certain voltage, and voltage is bigger during therefore most fault, can produce tangible capable ripple after the fault, the probability of voltage zero cross near fault little (list of references 3).But this is not meaning voltage zero cross near fault and can not take place.When at the voltage over zero near fault; the capable ripple that fault produces will be very little; though it is still effective that the traveling-wave protection of some principle is claimed when the voltage zero-cross fault; but this moment, travelling wave signal was very faint, and was superimposed upon on the powerful power frequency amount signal, considered various disturbing factors again; faint travelling wave signal may be difficult to detect in the reality; traveling-wave protection can not correctly detect capable wave-wave head, may cause protecting tripping or malfunction, consequence very serious (list of references 4).Therefore need the recognition methods of voltage zero cross near fault in the traveling-wave protection.
List of references:
[1] Chen Deshu. computer Principles of Relay Protection and technology. Beijing: hydraulic and electric engineering publishing house, 1992
[2] Yang Qixun. microcomputer relaying protection basis. Beijing: China Electric Power Publishing House, 1988
[3] Dong Xinzhou, Ge Yaozhong congratulates tame Lee etc. the status and prospects of transmission line travelling wave protection. and Automation of Electric Systems .2000,24 (9): 56-60
[4] Yang Zhonghao, Dong Xinzhou. the perfect scheme of wave impedance directional relay. electrotechnics journal .2003,18 ():
[5] Dong Xinzhou, He Jiali, Ge Yaozhong. wavelet transformation the 1st is said basic conception. relay .1999,27 (1): 64-67
[6] Dong Xinzhou, He Jiali, Ge Yaozhong. wavelet transformation the 2nd is said wavelet transform. relay .1999,27 (2): 57-60
[7] Dong Xinzhou, He Jiali, Ge Yaozhong. wavelet transformation the 3rd says that dyadic wavelet transform and singularity of signal detect. relay .1999,27 (3): 65-68
Summary of the invention:
The object of the present invention is to provide a kind of detection method reliable, voltage zero cross near fault effectively and in the traveling-wave protection that voltage zero cross near fault can be distinguished from other fault.
Rationale of the present invention is: in system shown in Figure 1, and circuit l
1At distance bus M 10km place single phase ground fault takes place, the fault transition resistance is 10 Ω, and fault switching angle θ is 0 ° (voltage of assumed fault prior fault point is SIN function here), and promptly the voltage of fault point is 0 during fault, circuit l
1The max line mould electric current of bus M side and wavelet transformation (2 thereof
1Yardstick) as shown in Figure 2.Wherein shown in the phase-model transformation matrix T formula, it is transformed to 0 α β γ mold component with the ABC three-phase, and wherein α β γ is three line mold components, and they are linear correlations.As can be seen from Figure 2 not significantly sudden change of current traveling wave, the variation of fault after-current mainly are that the fault point additional voltage source variation of 50Hz causes, compare with row wave-wave head, and its variation is very slow.And the wavelet transformation of low yardstick can equivalence be a high pass filter (list of references 5-7), be equivalent to input signal is carried out difference, so the wavelet transformation value of current traveling wave is very little during the voltage zero-cross fault.Be subjected to the influence of various interference, row wave-wave head is difficult to detect in the reality, and local maximum of wavelet transformation (modulus maximum) and row ripple due in not corresponding (seeing Fig. 2), and identification brings very big difficulty to wave head for this.Can not detect correct wave head, traveling-wave protection can not correct operation, and voltage zero cross near fault must be correctly discerned in visible traveling-wave protection.When fault switching angle θ becomes 20 °, when other condition is constant, circuit l after the fault
1The max line mould electric current of bus M side and wavelet transformation (2 thereof
1Yardstick) as shown in Figure 3.As can be seen from Figure 3; current traveling wave has more significantly sudden change; this is because the additional voltage source of fault is non-vanishing during fault; the wavelet transformation of its mutagenesis is bigger; modulus maximum is corresponding with row ripple due in, and traveling-wave protection can easily detect wave head, can correct operation; and voltage zero cross near fault distinguished from other fault, promptly distinguish above two kinds of situations.
Comparison diagram 2 (b) and Fig. 3 (b) can find, among Fig. 2 (b) most waveforms all away from time shaft, and among Fig. 3 (b) most waveforms all near time shaft.This is because during the voltage zero-cross fault, the voltage of fault point is sudden change not, the wavelet transformation maximum of current traveling wave is caused by the variation of fault point additional voltage source, and this voltage source is sinusoidal, constantly change and rate of change at short notice (as 3ms) change little, so the output waveform of wavelet transformation is away from time shaft; When not being during at voltage zero cross near fault, current traveling wave has more obviously sudden change, it causes the output of bigger wavelet transformation, and " covering " fallen the fault point additional voltage source and changed the wavelet transformation output that causes, makes the output overwhelming majority waveforms of wave conversion near time shaft.So the wavelet transformation according to the low yardstick of current traveling wave can discern away from the degree of time shaft whether the voltage zero-cross fault takes place.
Voltage zero cross near fault detection method in the traveling-wave protection of the present invention; the low yardstick wavelet transformation waveform overwhelming majority of current traveling wave is all away from time shaft during according to voltage zero cross near fault; and not when voltage zero cross near fault in the low yardstick wavelet transformation waveform of current traveling wave the overwhelming majority surpass its maximum K all near this feature of time shaft by calculating among the low yardstick wavelet transformation result
wThe number of point doubly discerns whether voltage zero cross near fault takes place; Concrete implementation step is as follows:
(1) after traveling-wave protection detects the capable ripple of threshold value, starts, note the current traveling wave of three-phase;
(2) use phase-model transformation matrix T formula to calculate three line lines and involve its energy, select a line line ripple of energy maximum to be used for following calculating; The phase-model transformation matrix is
(3) selected line mould is carried out wavelet transformation, and take out 2
1The wavelet transformation of yardstick is W (n) as a result, and wherein n represents sampled point;
(4) the maximum W of searching W (n)
Max
(5) in W (n), seek less than K
wW
MaxPoints N
DownK
wBe a coefficient, K
wValue is 0.07;
(6) work as N
Down/ N
w＞K
W, zdThe waveform that then shows the wavelet transformation result is near time shaft, and fault is not to occur in voltage zero cross near, otherwise the waveform that then shows the wavelet transformation result away from time shaft voltage zero cross near fault has taken place; In the formula:
N
wBe 2
1The total length of wavelet transformation result of yardstick, K
W, zdBe a threshold value, adjusting is 0.5.
The detection method that voltage zero cross near fault can be distinguished from other fault provided by the invention, it is reliable, effectively to have method, and advantage such as easy to detect.
Description of drawings:
Fig. 1 duplicate supply transmission system.
Current traveling wave and wavelet transformation and modulus maximum when Fig. 2 fault switching angle θ is 0 °.
Current traveling wave and wavelet transformation and modulus maximum when Fig. 3 fault switching angle θ is 20 °.
Embodiment:
Studies show that: during owing to voltage zero cross near fault, the wavelet transformation waveform overwhelming majority of current traveling wave is all away from time shaft, and not when voltage zero cross near fault, the wavelet transformation waveform overwhelming majority of current traveling wave is all near time shaft, therefore discerning voltage zero cross near fault should judge on the whole, and can not only judge according to some points in the waveform.The concrete implementation step of this method is as follows:
(1) after traveling-wave protection detects the capable ripple of threshold value, starts, note the current traveling wave of three-phase;
(2) use phase-model transformation matrix T formula to calculate three line lines and involve its energy, select a line line ripple of energy maximum to be used for following calculating; The phase-model transformation matrix is
(3) selected line mould is carried out wavelet transformation, and take out 2
1The wavelet transformation of yardstick is W (n) as a result, and wherein n represents sampled point;
(4) the maximum W of searching W (n)
Max
(5) in W (n), seek less than K
wW
MaxPoints N
DownK
wBe a coefficient, K
wValue is 0.07;
(6) work as N
Down/ N
w＞K
W, zdThe waveform that then shows the wavelet transformation result is near time shaft, and fault is not to occur in voltage zero cross near, otherwise the waveform that then shows the wavelet transformation result away from time shaft voltage zero cross near fault has taken place; In the formula: N
wBe 2
1The total length of wavelet transformation result of yardstick, K
W, zdBe a threshold value, adjusting is 0.5.
The inventor proves that by a large amount of emulation experiments this method is reliable, effective.
Claims (1)
1. voltage zero cross near fault detection method in the traveling-wave protection; the low yardstick wavelet transformation waveform overwhelming majority of current traveling wave is all away from time shaft when it is characterized in that this method according to voltage zero cross near fault; and not when voltage zero cross near fault in the low yardstick wavelet transformation waveform of current traveling wave the overwhelming majority surpass its maximum K all near this feature of time shaft by calculating among the low yardstick wavelet transformation result
wThe number of point doubly discerns whether voltage zero cross near fault takes place; Concrete steps are as follows:
(1) after traveling-wave protection detects the capable ripple of threshold value, starts, note the current traveling wave of three-phase;
(2) use phase-model transformation matrix T formula to calculate three line lines and involve its energy, select a line line ripple of energy maximum to be used for following calculating; The phase-model transformation matrix is
(3) selected line line ripple is carried out wavelet transformation, and take out 2
1The wavelet transformation of yardstick is W (n) as a result; Wherein n represents sampled point;
(4) the maximum W of searching W (n)
Max
(5) in W (n), seek less than K
wW
MaxPoints N
Down: K
wBe a coefficient, K
wValue is 0.07;
(6) work as N
Down/ N
w＞K
W, zdThe time show the wavelet transformation result waveform near time shaft, fault is not to occur in voltage zero cross near, on the contrary voltage zero cross near fault has taken place away from time shaft in the waveform that then shows the wavelet transformation result; In the formula: N
wBe 2
1The total length of wavelet transformation result of yardstick, K
W, zdBe a threshold value, adjusting is 0.5.
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| CN100461575C (en) * | 2006-07-21 | 2009-02-11 | 重庆大学 | Fault line selecting method for distribution system single phase earthing |
| CN105223471A (en) * | 2015-10-15 | 2016-01-06 | 东南大学 | Based on power transmission line fault locating method, the protective relaying device of line parameter circuit value |
| CN109739215B (en) * | 2019-01-21 | 2021-05-04 | 济南大学 | Method for realizing fault initial angle control and automatic traversal in PSCAD |
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| CN1290059A (en) * | 2000-11-08 | 2001-04-04 | 华中科技大学 | Method for protecting power transmission line and travelling wave sensor for it |
| US6324041B1 (en) * | 1999-10-21 | 2001-11-27 | Hughes Electronics Corporation | Protection circuit for traveling wave tubes having multiple input tones |
| CN1141768C (en) * | 2001-12-28 | 2004-03-10 | 清华大学 | Digital travelling wave protection method for power transmission line and its relay and protection system |
| CN1529176A (en) * | 2003-09-30 | 2004-09-15 | 昆明理工大学 | Method for detecting travelling-wave protection device |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6324041B1 (en) * | 1999-10-21 | 2001-11-27 | Hughes Electronics Corporation | Protection circuit for traveling wave tubes having multiple input tones |
| CN1290059A (en) * | 2000-11-08 | 2001-04-04 | 华中科技大学 | Method for protecting power transmission line and travelling wave sensor for it |
| CN1141768C (en) * | 2001-12-28 | 2004-03-10 | 清华大学 | Digital travelling wave protection method for power transmission line and its relay and protection system |
| CN1529176A (en) * | 2003-09-30 | 2004-09-15 | 昆明理工大学 | Method for detecting travelling-wave protection device |
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