CN103323728B - Based on singlephase earth fault and the Xuhanting oral solution recognition methods of whole wave energy Ratios - Google Patents

Abstract

The present invention relates to a kind of singlephase earth fault based on whole wave energy Ratios and Xuhanting oral solution recognition methods, belong to Relay Protection Technology in Power System field.The present invention extracts the residual voltage data of latter two cycle of fault, after respectively wavelet transformation being carried out to it, by square summation of the wavelet reconstruction coefficient under each yardstick after conversion, its most high-frequency energy value, by the most high-frequency energy value of the most high-frequency energy value of first cycle than second cycle, reliably realize the identification of one-phase earthing failure in electric distribution network and Xuhanting oral solution like this according to itself and the magnitude relationship of setting threshold value.This method principle is comparatively simple, can identify Xuhanting oral solution within a short period of time; Robustness is good, has not by advantages such as arc resistance fault, nonlinear-load affect, greatly reduces the requirement to hardware sampling rate, have stronger practicality.

Description

Based on singlephase earth fault and the Xuhanting oral solution recognition methods of whole wave energy Ratios

Technical field

The present invention relates to a kind of singlephase earth fault based on whole wave energy Ratios and Xuhanting oral solution recognition methods, belong to Relay Protection Technology in Power System field.

Background technology

Under normal operation, usual neutral by arc extinction coil grounding power distribution network is in over-compensation state, when the feeder line that bus puts into operation increases or the factor such as system operation mode change causes capacity current to increase, automatic tuning apparatus can regulate arc suppression coil input from the change of motion tracking capacitance current, at this moment system may enter into full compensating coefficient, thus generation resonance overvoltage, resonance overvoltage closely even may exceed neutral point displacement voltage during singlephase earth fault, and this phenomenon is referred to as Xuhanting oral solution.When the rising of neutral point voltage causes due to singlephase earth fault, should regulate arc suppression coil that tuning-off degree is reduced, regulate to full compensation direction; If Xuhanting oral solution phenomenon, then should regulate arc suppression coil that its tuning-off degree is increased, regulate to the direction that over-compensation increases, to eliminate series resonance, make System recover normal.

Relatively neutral point displacement voltage when single-phase earthing and Xuhanting oral solution, can see that the two is as broad as long on steady state values, is difficult to be distinguished these two kinds of methods of operation by the size of the steady-state value of neutral point displacement voltage.Shown by practical operating experiences, existing two kinds of methods are effective to identification Xuhanting oral solution.One, after occurring that neutral point voltage raises, regulates arc suppression coil gear change, distinguish the two by the change of monitoring the neutral point voltage caused thus.Another kind method is that the rate of rise by monitoring residual voltage distinguishes singlephase earth fault and Xuhanting oral solution.But above-mentioned two kinds of windows that method takes are all longer, are unfavorable for Timeliness coverage singlephase earth fault.

Summary of the invention

The technical problem to be solved in the present invention be overcome existing identification singlephase earth fault and Xuhanting oral solution window that method takes longer, be unfavorable for the weak point of Timeliness coverage singlephase earth fault.

Technical scheme of the present invention is: a kind of singlephase earth fault based on whole wave energy Ratios and Xuhanting oral solution recognition methods, extract the residual voltage data of latter two cycle of fault, respectively wavelet transformation is carried out to it, by square summation of the wavelet reconstruction coefficient under each yardstick after conversion, obtain its energy value, by the most high-frequency energy value of the most high-frequency energy value of first cycle than second cycle, obtain value, according to itself and setting threshold value magnitude relationship reliably realize the identification of one-phase earthing failure in electric distribution network and Xuhanting oral solution.

One-phase earthing failure in electric distribution network and Xuhanting oral solution recognition methods are specifically carried out according to step below:

(1) after power distribution network generation singlephase earth fault, starting element starts immediately, can obtain fault residual voltage according to the three-phase voltage that protection installation place records :

(A)

In formula: , , be respectively faulty line A, B, C three-phase voltage; k=1,2,3 n, nfor sample sequence length;

(2) extract the residual voltage data of latter two cycle of one-phase earthing failure in electric distribution network, utilize wavelet transformation technique to decompose it, extract each frequency band energy, if discrete signal x( n), to the wavelet coefficient under each decomposition scale carry out single reconstruct after, the component of signal obtained comprise the frequency band range of information such as formula shown in (B):

(B)

In formula, d _j ( n) be the wavelet reconstruction coefficient of signal high fdrequency component; a _j ( n) be the wavelet reconstruction coefficient of signal low frequency component; f _s for the sample frequency of signal; j=1,2,3 ... J, J are maximum decomposition scale, original signal sequence x( n) can be expressed as each component and, namely

x( n)= (C)

Order d _{m+ 1} ( n)= a _m ( n), then have

x( n)= (D)

In formula, m is wavelet transform dimension;

(3) for orthogonal wavelet transformation, after conversion the energy of each yardstick can directly reconstruct by its single after square the obtaining of wavelet reconstruction coefficient, namely

(E)

Here choose two cycles of db4 small echo to selected residual voltage signal and carry out 6 layers of wavelet decomposition respectively, namely herein ; The energy value of each layer frequency band is obtained according to formula (E);

(4) the most high-frequency energy value that after setting fault, first cycle obtains after wavelet transformation as e ₁₁, the most high-frequency energy value of second cycle is e ₁₂, both notes ratio ρfor:

(F)

(5) after power distribution network generation Xuhanting oral solution, obtain the residual voltage data of two cycle, utilize step in said method (1) to step (4) to try to achieve the most high-frequency energy value of two cycles respectively, and get its ratio ;

(6) according to ratio with set threshold value between relationship distinguish singlephase earth fault and Xuhanting oral solution:

When ρ>= ρ _settime, be judged to be singlephase earth fault;

When ρ< ρ _settime, be judged to be Xuhanting oral solution.

Principle of work of the present invention is:

Along with feeder line in distribution be on the increase, system line capacitance current over the ground also increases day by day, the power distribution network of neutral by arc extinction coil grounding is made to enter into full compensating coefficient possibly, thus cause resonance overvoltage, its value closely even may exceed neutral point displacement voltage during singlephase earth fault, produces Xuhanting oral solution phenomenon.Because Xuhanting oral solution is power frequency variation, in theory not containing HF voltage composition, and the neutral excursion voltage that singlephase earth fault causes contains abundant HF voltage composition.

Therefore the high-frequency energy feature that the present invention passes through to comprise in analysis feeder line residual voltage information completes the identification to singlephase earth fault and Xuhanting oral solution.By extracting the residual voltage data of fault latter two cycle, respectively wavelet transformation being carried out to it, by square summation of the wavelet reconstruction coefficient under each yardstick after conversion, obtaining its energy value, choose the most high-frequency energy value E of first cycle ₁₁than the most high-frequency energy value E of second cycle ₁₂? , obtain after value, according to itself and set threshold value between relation reliably realize to singlephase earth fault and Xuhanting oral solution identification:

When ρ>=ρ _settime, be judged to be singlephase earth fault;

When ρ< ρ _settime, be judged to be Xuhanting oral solution.

The invention has the beneficial effects as follows:

1, this method principle is comparatively simple, ageing good, can realize the identification of Xuhanting oral solution within the time of two cycles.

2, this method utilizes the method for energy, and its robustness is good, does not affect by arc resistance fault, nonlinear-load etc.

3, lower to the requirement of hardware sampling rate, there is stronger practicality.

Accompanying drawing explanation

Fig. 1 is the distribution network system structural drawing for emulating in embodiment: in figure, l ₁, l ₃, l ₅overhead feeder, l ₄xian – cable mixing feeder line, l ₂, l ₆cable feeder line, G is infinitely great power supply, and T is main-transformer, T _zbe zigzag transformer, L is arc suppression coil, and R is the damping resistance of arc suppression coil;

Fig. 2 is the fault angle of embodiment 1 feeder line when being 5 ° l ₁residual voltage oscillogram;

Fig. 3 is the fault angle of embodiment 2 feeder line when being 90 ° l ₁residual voltage oscillogram;

Feeder line when Fig. 4 is Xuhanting oral solution in embodiment l ₁residual voltage oscillogram.

Embodiment

Embodiment 1: as shown in Figure 1: 110kV/35kV one-phase earthing failure in electric distribution network realistic model, in figure, supply voltage is 110kV, become after 35kV through transformer and be delivered to load side, it has 6 feeder lines, and Z-shaped transformer neutral point is by arc suppression coil resistance in series ground connection.Overhead feeder l ₁=15km, l ₃=18km, l ₅=30km ， Xian – cable mixing feeder line l ₄=17km, its overhead feeder 12km, cable 5km, cable feeder line l ₂=6km, l ₆=8km.Wherein, overhead feeder is JS1 rod-type, LGJ-70 type wire, span 80m, and cable feeder line is YJV23-35/95 type cable.G in this electrical network is infinitely great power supply; T is main-transformer, and no-load voltage ratio is 110kV/35kV, and connection set is Y _n/ d11; T _zit is zigzag transformer; L is arc suppression coil; R is the damping resistance of arc suppression coil.Feeder line adopts overhead transmission line, overhead line-cable hybrid line and cable line three kinds of circuits.Load selects firm power load model.Distance feeder line l ₁there is singlephase earth fault in 5km place, top, stake resistance 20 Ω, fault angle is 5 °, and sample frequency is 10kHz.

(1) after power distribution network breaks down, starting element starts immediately, feeder line l ₁residual voltage waveform as shown in Figure 2, after the time window data choosing latter two cycle of fault carry out wavelet transformation respectively, by square summation of the wavelet reconstruction coefficient under each yardstick after conversion, obtains its energy value;

(2) the most high-frequency energy value of first cycle is tried to achieve e ₁₁=35339, second most high-frequency energy value of cycle e ₁₂=5079.6, threshold value setting get 1.5 according to the reliability of recognition methods, =35339/5079.6=6.957 > ρ _set=1.5, so can feeder line be judged l ₁for fault feeder.

Embodiment 2:110kV/35kV one-phase earthing failure in electric distribution network realistic model is identical with embodiment 1, distance feeder line l ₁there is singlephase earth fault in 5km place, top, stake resistance 20 Ω, fault angle is 90 °, and sample frequency is 10kHz.

By the method that embodiment 1 is identical, feeder line l ₁residual voltage waveform as shown in Figure 3, and tries to achieve the most high-frequency energy value ratio of first cycle and second cycle =13198 > ρ _set=1.5, so can feeder line be judged l ₁for singlephase earth fault feeder line.

Embodiment 3:110kV/35kV distribution network system realistic model, with embodiment 1, after magnitude of voltage is out-of-limit, obtains two cycle residual voltage data.

Should based on the singlephase earth fault of whole wave energy Ratios and the step of Xuhanting oral solution recognition methods with embodiment 1.

The residual voltage waveform obtained by emulation experiment as shown in Figure 4, and tries to achieve the most high-frequency energy value ratio of first cycle and second cycle =1.2943 < =1.5, so can judge that system there occurs Xuhanting oral solution phenomenon.

In addition, in different faults angle and Xuhanting oral solution situation after fault first cycle with the most high-frequency energy of second cycle than as shown in table 1.This ratio in singlephase earth fault situation much larger than 1, and close to 1 during Xuhanting oral solution, from table 1, this method can effectively, reliable recognition singlephase earth fault and Xuhanting oral solution.

By reference to the accompanying drawings the specific embodiment of the present invention is explained in detail above, but the present invention is not limited to above-mentioned embodiment, in the ken that those of ordinary skill in the art possess, can also make a variety of changes under the prerequisite not departing from present inventive concept.

Claims (2)

1. the singlephase earth fault based on whole wave energy Ratios and Xuhanting oral solution recognition methods, it is characterized in that: the residual voltage data extracting latter two cycle of fault, respectively wavelet transformation is carried out to it, by square summation of the wavelet reconstruction coefficient under each yardstick after conversion, obtain its energy value, by the most high-frequency energy value of the most high-frequency energy value of first cycle than second cycle, obtain ρ value, according to itself and setting threshold value ρ _setmagnitude relationship reliably realize the identification of one-phase earthing failure in electric distribution network and Xuhanting oral solution;

According to ratio ρ and set threshold value ρ _setbetween relationship distinguish singlephase earth fault and Xuhanting oral solution:

As ρ>=ρ _settime, be judged to be singlephase earth fault;

As ρ < ρ _settime, be judged to be Xuhanting oral solution.

2. the singlephase earth fault based on whole wave energy Ratios according to claim 1 and Xuhanting oral solution recognition methods, is characterized in that: one-phase earthing failure in electric distribution network and Xuhanting oral solution recognition methods are specifically carried out according to step below:

(1) after power distribution network breaks down, starting element starts immediately, can obtain fault residual voltage u according to the three-phase voltage that protection installation place records ₀:

$u_0\left(k\right)=\frac{1}{3}\left(u_A\right(k)+u_B(k)+u_C(k\left)\right)---\left(A\right)$

In formula: u _a(k), u _b(k), u _ck () is respectively faulty line A, B, C three-phase voltage; K=1,2,3 ... N, N are sample sequence length;

(2) the residual voltage data of latter two cycle of distribution network failure are extracted, wavelet transformation technique is utilized to decompose it, extract each frequency band energy, if discrete signal x (n), to the wavelet coefficient under each decomposition scale carry out single reconstruct after, the component of signal obtained comprise the frequency band range of information such as formula shown in (B):

$\left\{\begin{array}{c}{D}_j\left(n\right):\&lsqb;2^{-(j+1)}{f}_s,2^{-j}{f}_s\&rsqb;\\ A_j\left(n\right):\&lsqb;0,2^{-(j+1)}{f}_s\&rsqb;\end{array}\right.---\left(B\right)$

In formula, D _jn wavelet reconstruction coefficient that () is signal high fdrequency component; A _jn wavelet reconstruction coefficient that () is signal low frequency component; f _sfor the sample frequency of signal; J=1,2,3 ... J, J are maximum decomposition scale, original signal sequence x (n) can be expressed as each component and, namely

$x\left(n\right)=A_m\left(n\right)+\underset{j=1}{\overset{m}{\&Sigma;}}{D}_j\left(n\right)---\left(C\right)$

Make D _m+1(n)=A _mn (), then have

$x\left(n\right)=\underset{j=1}{\overset{m+1}{\&Sigma;}}{D}_j\left(n\right)---\left(D\right)$

In formula, m is wavelet transform dimension;

(3) for orthogonal wavelet transformation, after conversion the energy of each yardstick can directly reconstruct by its single after square the obtaining of wavelet reconstruction coefficient, namely

$E_j\left(n\right)=D_j^2\left(n\right)---\left(E\right)$

Choose two cycles of db4 small echo to selected residual voltage signal and carry out 6 layers of wavelet decomposition respectively, be i.e. j=1 herein, 2 ..., 6; The energy value of each layer frequency band is obtained according to formula (E);

(4) the most high-frequency energy value that after setting fault, first cycle obtains after wavelet transformation is as E ₁₁, the most high-frequency energy value of second cycle is E ₁₂, both notes ratio ρ is:

$\mathrm{\&rho;}=\frac{E_{11}}{E_{12}}---\left(F\right)$

(5) according to ratio ρ and set threshold value ρ _setbetween relationship distinguish singlephase earth fault and Xuhanting oral solution:

As ρ>=ρ _settime, be judged to be singlephase earth fault;

As ρ < ρ _settime, be judged to be Xuhanting oral solution.