CN102590703A - Single-phase grounding failure route selection method of resonance grounding system based on zero-sequence transient charge - Google Patents

Abstract

The invention discloses a single-phase grounding failure route selection method of a resonance grounding system based on zero-sequence transient charge, comprising the main steps: collecting a three-phase current signal and a three-phase voltage signal of a distribution network feeder bus as input quantity of a route selection element; performing decoupling calculation to obtain zero-sequence current and zero-sequence voltage of the feed lines, and filtering the power frequency component in the corresponding electric quantity; figuring out zero-sequence transient charge quantity accumulated during a failure transient process according to the zero-sequence transient current of the feed lines; and comparing the relative coefficient values of the obtained zero-sequence transient voltage with the zero-sequence transient electric charge quantity of the feed lines to judge whether the feed line with minimal relative coefficient is the failure feed line, so as to finish the identification of the failure feed line. The method disclosed by the invention can reliably identify the failure feed line under various failure conditions, an emulation result indicates that the method has high sensitivity and reliability under various operation working conditions, and the method has good anti-interference capability and has no special demand on equipment, so that the method can be used for realizing fast failure diagnosis of the resonance grounding system.

Description

Resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge

Technical field

The present invention relates to a kind of resonant earthed system fault line selection method for single-phase-to-ground fault in the electric system based on zero sequence transient state electric charge.

Background technology

At present, adopt the resonant earthed system of arc suppression coil because behind the circuit generation singlephase earth fault, fault current receives the compensation of arc suppression coil and diminishes, so can be from the horizontal blanking ground arc; Resonant earthed system does not influence the power supply capacity to load because still retention wire voltage three is symmetrical behind the singlephase earth fault simultaneously, therefore allows charging operation 1-2 hour.But development along with power distribution network; The bus feeder line increase year by year and circuit in the use of cable; Make the short circuit electric current increase; Long-play is easy to generate the multipoint earthing fault, thus must in limited working time, judge fault feeder rapidly and accurately, for further the accurate location and the fault eliminating of fault provide foundation.

Failure line selection to the power distribution network resonant earthed system; Receive the compensation of arc suppression coil though power frequency amount energy is big; Fundametal compoment amplitude and direction all can produce bigger variation; Based on this reason, the transient state amount that produces behind the analysis of failure, realization is the focus that the selection method of criterion progressively becomes research and practicability with the transient information.But high resistance earthing fault is the difficult point of route selection always in the power distribution network, because stake resistance is excessive, the amplitude of transient state amount is very little after the fault, and accurate route selection after the resonant earthed system fault is caused very big difficulty.

Summary of the invention

The objective of the invention is to overcome the weak point of existing power distribution network resonant earthed system failure line selection; A kind of resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge is proposed; The route selection of this selection method is highly sensitive, speed is fast, can be for further accurate location of fault and fault eliminating provide foundation more accurately and reliably.

The present invention is for solving its technical matters, and the technical scheme that is adopted is a kind of resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge, the steps include:

A, gather the three-phase current signal and the three-phase voltage signal of each bar feeder line bus end of power distribution network, the sampled data of first semiperiod or holocyclic three-phase current signal and three-phase voltage signal of choosing each bar feeder line behind the singlephase earth fault is as the input quantity of route selection element;

B, the input quantity of the route selection element chosen is carried out decoupling zero, obtain the zero-sequence current component and the zero sequence voltage component of each bar feeder line respectively;

50Hz power frequency component in C, each bar feeder line zero-sequence current of filtering and the residual voltage; Obtain corresponding zero sequence transient current and zero sequence transient voltage, and obtain the zero sequence transient state quantity of electric charge that is accumulated in first selected semiperiod or time in complete period on the feeder line according to the zero sequence transient current of each bar feeder line;

D, set up the corresponding relation of each bar feeder line zero sequence transient state quantity of electric charge and zero sequence transient voltage, calculate the related coefficient of the transient state residual voltage and the zero sequence transient state quantity of electric charge of each bar feeder line, the minimum feeder line of related coefficient is judged to be fault feeder.

Compared with prior art, the invention has the beneficial effects as follows:

One, the relativeness that changes at distribution and each feeder line transient voltage of each feeder line through the transient state quantity of electric charge in half or one-period, accumulated of the present invention; Because the transient information amount of utilizing is accumulation; Improved recognition capability to feeble signal; Overcome high resistance earthing fault and caused the too small shortcoming of transient current information; Solve the extremely faint inaccurate problem of route selection that causes of transient state electric parameters under the high resistance ground situation, improved the sensitivity and the accuracy of resonant earthed system high resistance ground route selection.

Two, singlephase earth fault taking place can produce two transient state processes simultaneously in the resonant earthed system.One is that the fault phase voltage reduces suddenly and the discharge capacity electric current that causes, and another is the charging capacitor electric current that non-fault phase voltage raises and causes suddenly.The discharge capacity electric current flows to the trouble spot through bus, directly constitutes flow cycle through fault phase line mutual-ground capacitor and ground, and the charging capacitor electric current then constitutes path through non-fault phase line mutual-ground capacitor and ground through transformer then.The present invention is through the total charge dosage asking for two transient state charge and discharge process and in first semiperiod or complete period, the accumulate distribution relation with corresponding transient voltage; Investigate both facies relationship numerical value of different feeder lines; This facies relationship numerical value has reflected that more near 1 this feeder line load is stable, it is little to disturb; Opposite this facies relationship numerical value explains that more less than 1 its load sudden change has taken place or received interference; Therefore, the back minimum feeder line decidable of facies relationship numerical value that breaks down is a faulty line.It is without the direction and the size of Direct Recognition transient current, and the route selection criterion is simple, makes things convenient for execute-in-place.

The transient state process that discharges and recharges that self produces when three, being resonant earthed system generation singlephase earth fault owing to the transient state quantity of electric charge of accumulating forms, and does not receive the influence of system neutral degree of compensation, also makes its route selection accurately, reliably; And only need gather the three-phase electricity flow and the voltage of each bar feeder line of bus bar side, not high to equipment requirements, equally, improved the reliability of method.

The transient state amount of capacitor charge and discharge process when four, the present invention only need gather single-phase earthing is generally hundreds of between several KHzs, so the SF scope gets final product at 10kHz～20kHz, sample devices is not had specific (special) requirements, convenient enforcement.

Above-mentioned C is in the step, obtains the specific practice that is accumulated in the zero sequence transient state quantity of electric charge on the feeder line in first selected semiperiod or time in complete period according to the zero sequence transient current of each bar feeder line to be;

Draw the single-phase fault charges accumulated amount

in time in i SI that begins that takes place by following discrete integration formula

$Q_{0i}^{\′n}=Q_{0i-1}^{\′n}+\frac{1}{2}\×(I_{0i-1}^{\′n}-I_{0i}^{\′n})\×\mathrm{\Δt}$

In the formula; is the zero sequence transient current of gathering in i the SI of n bar feeder line, and Δ t is the time in SI; When

or i=T/ Δ t; T is the cycle of three-phase electricity, and the quantity of electric charge of calculating

is the zero sequence transient state quantity of electric charge

that is accumulated in first semiperiod or time in complete period on the n bar feeder line

Adopt this method can calculate the zero sequence transient state quantity of electric charge that each bar feeder line is accumulated easily and fast in access time.

Below in conjunction with embodiment the present invention is done further detailed description.

Description of drawings

The realistic model topological structure of the emulation experiment of Fig. 1 embodiment of the invention.

The relation of the zero sequence transient state quantity of electric charge of feeder line 1-4 and zero sequence transient voltage in the emulation experiment of Fig. 2 embodiment of the invention.

Embodiment

Embodiment

A kind of embodiment of the present invention is that a kind of resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge the steps include:

A, gather the three-phase current signal and the three-phase voltage signal of each bar feeder line bus end of power distribution network, the sampled data of three-phase current signal and three-phase voltage signal in first semiperiod (being 10ms) or complete period (20ms) of choosing each bar feeder line behind the single-phase fault is as the input quantity of route selection element.

B, the input quantity of the route selection element chosen is carried out decoupling zero, obtain the zero-sequence current component and the zero sequence voltage component of each bar feeder line respectively.

During decoupling zero, can adopt various existing decoupling zeros to carry out, carry out as adopting the symmetrical components conversion, specific as follows:

$\left[\begin{array}{c}{I}_1\\ I_2\\ {\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">I</figure-callout>}}_0\end{array}\right]=\frac{1}{3}\left[\begin{array}{ccc}1& \mathrm{\&alpha;}& {\mathrm{\&alpha;}}^2\\ 1& {\mathrm{\&alpha;}}^2& \mathrm{\&alpha;}\\ 1& 1& 1\end{array}\right]\left[\begin{array}{c}{I}_A\\ I_B\\ I_C\end{array}\right]---\left(1\right)$

$\left[\begin{array}{c}{U}_1\\ U_2\\ {\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">U</figure-callout>}}_0\end{array}\right]=\frac{1}{3}\left[\begin{array}{ccc}1& \mathrm{\&alpha;}& {\mathrm{\&alpha;}}^2\\ 1& {\mathrm{\&alpha;}}^2& \mathrm{\&alpha;}\\ 1& 1& 1\end{array}\right]\left[\begin{array}{c}{U}_A\\ U_B\\ U_C\end{array}\right]---\left(2\right)$

In the formula (1), I _A, I _B, I _CBe respectively A, B, C phase current that each bar feeder line measures at the bus place; I ₀Be zero-sequence current; I ₁Be forward-order current; I ₂Be negative-sequence current.

In the formula (2), U _A, U _B, U _CBe respectively A, B, C phase voltage that each bar feeder line measures at the bus place; U ₀Be residual voltage; U ₁Be positive sequence voltage; U ₂Be negative sequence voltage.

In formula (1) and (2), α is a twiddle factor, and its expression formula is:

$\mathrm{\&alpha;}=e^{{j120}^0}=-\frac{1}{2}+j\frac{\sqrt{3}}{2}---\left(3\right)$

${\mathrm{\&alpha;}}^2=e^{j{240}^0}=-\frac{1}{2}-j\frac{\sqrt{3}}{2}---\left(4\right)$

Three preface components that asymmetric current-voltage information behind the singlephase earth fault is transformed into symmetry, the feeder line zero-sequence current component I that wherein obtains will take place through above symmetrical components conversion ₀, zero sequence voltage component U ₀Be the information that next-step operation needs.

50Hz power frequency component in C, each bar feeder line zero-sequence current of filtering and the residual voltage; Obtain corresponding zero sequence transient current and zero sequence transient voltage, and obtain the zero sequence transient state quantity of electric charge that is accumulated in first selected semiperiod or time in complete period on the feeder line according to the zero sequence transient current of each bar feeder line.

In this example, obtain the specific practice that is accumulated in the zero sequence transient state quantity of electric charge on the feeder line in first selected semiperiod or time in complete period according to the zero sequence transient current of each bar feeder line and be;

Draw the single-phase fault charges accumulated amount

in time in i SI that begins that takes place by following discrete integration formula

$Q_{0i}^{\&prime;n}=Q_{0i-1}^{\&prime;n}+\frac{1}{2}\&times;(I_{0i-1}^{\&prime;n}+I_{0i}^{\&prime;n})\&times;\mathrm{\&Delta;t}$

In the formula;

is the zero sequence transient current of gathering in i the SI of n bar feeder line, and Δ t is the time in SI; When

or i=T/ Δ t; T is the cycle (20ms) of three-phase electricity, and the quantity of electric charge of calculating

is the zero sequence transient state quantity of electric charge

that is accumulated in first semiperiod or time in complete period on the n bar feeder line

D, set up the corresponding relation of each bar feeder line zero sequence transient state quantity of electric charge and zero sequence transient voltage, calculate the related coefficient of the transient state residual voltage and the zero sequence transient state quantity of electric charge of each bar feeder line, the minimum feeder line of related coefficient is judged to be fault feeder.

The computing formula of the related coefficient of the transient state residual voltage of each bar feeder line and the zero sequence transient state quantity of electric charge is:

${\mathrm{\&rho;}}_n=\frac{\mathrm{Cov}({\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">U</figure-callout>}}_0^{\&prime;n},{\mathrm{<figure-callout\; id="0"\; label="Q"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">Q</figure-callout>}}_0^{\&prime;n})}{\sqrt{D\left({\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">U</figure-callout>}}_0^{\&prime;n}\right)}\&CenterDot;\sqrt{D\left({\mathrm{<figure-callout\; id="0"\; label="Q"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">Q</figure-callout>}}_0^{\&prime;n}\right)}}$

In the formula, ρ _nRepresent the zero sequence transient voltage amount of n bar feeder line and the related coefficient of the zero sequence transient state quantity of electric charge,

Represent the zero sequence transient voltage amount of n bar feeder line and the covariance of the zero sequence transient state quantity of electric charge,

The variance of representing the zero sequence transient voltage amount of n bar feeder line,

The variance of representing the zero sequence transient state quantity of electric charge of n bar feeder line.

Emulation experiment:

For checking the inventive method above method has been carried out emulation experiment, The simulation experiment result shows that its route selection is highly sensitive, and route selection speed is fast, and route selection accurately and reliably.

In conjunction with an actual motion line parameter circuit value, the single supply 4 feeder line resonant earthed systems of building electric pressure and be 35kV are empirical model, and circuit is the overhead transmission line model of frequency dependence.Its topology is as shown in Figure 1.Correlation parameter is: the length of feeder line 1 is 30km, and the length of feeder line 2 is 19km, and the length of feeder line 3 is 10km, and feeder line 4 length are 6km.The positive and negative preface impedance Z of overhead transmission line ₁=Z ₂=0.25542+j0.37294 Ω/km, positive and negative preface admittance Y ₁=Y ₂=j3.0803 * 10 ^-6S/km, zero sequence impedance Z ₀=0.51664+j1.48516 Ω/km, zero sequence admittance Y ₀=j1.47574326 * 10 ^-6S/km, the arc suppression coil compensation degree is set to over-compensation 10%, and signal pickup assembly is installed in each bar feeder line bus end and carries out the data acquisition of three-phase fault electric current and three-phase fault voltage.

Data sampling rate is 20kHz, and it is one-period that data window length is got 414 points, supposes that feeder line 1 apart from bus l=18km place A phase earth fault, transition resistance R=2000 Ω takes place at t=0.3243s.Then can calculate: the zero sequence transient state quantity of electric charge that feeder line 1-4 accumulated in first cycle, the facies relationship numerical value ρ of the corresponding zero sequence transient state quantity of electric charge and zero sequence transient voltage ₁=-0.1084, ρ ₂=0.9992, ρ ₃=0.9986, ρ ₄=0.9951.According to criterion condition, ρ ₁Minimum is so feeder line 1 is a fault feeder.Fig. 2 does, feeder line 1-4 is at the zero sequence transient state quantity of electric charge and the relation curve of zero sequence transient voltage of each accumulation constantly of first cycle, and the curve of the straight line that levels off among Fig. 2 distribution is a feeder line 2; 3,4 relation curve, and the curve of random distribution is the fault feeder curve; Feeder line 2 also is described; The zero sequence transient state quantity of electric charge and zero sequence transient voltage are the positively related relation of highly linear on 3,4, and the zero sequence transient state quantity of electric charge and zero sequence transient voltage do not have tangible correlationship on the feeder line 1.

Following table 1 and table 2 have provided the route selection result of the inventive method under the operating mode of different faults distance and different faults stake resistance.

The route selection result of (time of failure is 0.3243s, transition resistance R=2800 Ω) was relatively when table 1 for feeder line 1 A phase earth fault took place at the different distance place:

Table 1

√: expression protection route selection result is with actual that the fault feeder result is set is consistent

Table 2 is feeder line 1 (time of failure is 0.3243s, fault distance l=15km) route selection result's when with different grounding resistance A phase earth fault taking place comparison.

Table 2

√: expression protection route selection result is with actual that the fault feeder result is set is consistent

The route selection result of table 1 and table 2 shows that under the working condition of various fault distances and fault ground resistance, the zero sequence transient state quantity of electric charge of fault feeder and the degree of correlation of zero sequence transient voltage all are starkly lower than healthy feeder line.The accurate also easy operating personnel of its route selection result read, and confirm that this inventive method has very high reliability and practicality.

More than test not consideration of noise influence; Be the adaptability of checking the present invention in practical engineering application; To the three-phase current and the voltage signal stack white Gaussian noise that collect, the signal that simulation may occur in practical application disturbs, with the route selection fiduciary level of checking the present invention under low signal-to-noise ratio.

Singlephase earth fault takes place apart from bus 20km place in feeder line 1; Data sampling rate is 20kHz; Data window length is got (t=0.3243s) 414 sampled points (one-period) after the fault; Table 3 is that (Signal-to-noise ratio, SNR) the route selection result under the situation relatively in the unlike signal signal to noise ratio (S/N ratio) for the inventive method.

Table 3

√: expression protection route selection result is with actual that the fault feeder result is set is consistent

Adding Gauss's noise experiment result shows: the input signal signal to noise ratio (S/N ratio) all can correctly be accomplished failure line selection from 10dB to 70dB.But can find signal to noise ratio (S/N ratio) when 40dB is above, the zero sequence transient state quantity of electric charge of healthy feeder line and the related coefficient of zero sequence transient voltage explain that all more than 0.95 the zero sequence transient state charge amount distribution of healthy feeder line and zero sequence transient voltage change the linear height.Along with the reduction of signal to noise ratio (S/N ratio), noise affects greatly the electric parameters effective information, and the corresponding with it facies relationship numerical value of the charge amount distribution of fault feeder and healthy feeder line also produces bigger variation.But fault feeder facies relationship numerical value is starkly lower than healthy feeder line all the time.The analysis of comprehensive above fault condition explains that route selection of the present invention is highly sensitive, and antijamming capability is strong, can adapt to on-the-spot practical application.

Claims (2)

1. the resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge the steps include:

A, gather the three-phase current signal and the three-phase voltage signal of each bar feeder line bus end of power distribution network, the sampled data of first semiperiod or holocyclic three-phase current signal and three-phase voltage signal of choosing each bar feeder line behind the singlephase earth fault is as the input quantity of route selection element;

B, the input quantity of the route selection element chosen is carried out decoupling zero, obtain the zero-sequence current component and the zero sequence voltage component of each bar feeder line respectively;

50Hz power frequency component in C, each bar feeder line zero-sequence current of filtering and the residual voltage; Obtain corresponding zero sequence transient current and zero sequence transient voltage, and obtain the zero sequence transient state quantity of electric charge that is accumulated in first selected semiperiod or time in complete period on each bar feeder line according to the zero sequence transient current of each bar feeder line;

D, set up the corresponding relation of each bar feeder line zero sequence transient state quantity of electric charge and zero sequence transient voltage, calculate the related coefficient of the transient state residual voltage and the zero sequence transient state quantity of electric charge of each bar feeder line, the minimum feeder line of related coefficient is judged to be fault feeder.

2. the resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge according to claim 1; It is characterized in that: described C is in the step, obtains the specific practice that is accumulated in the zero sequence transient state quantity of electric charge on each bar feeder line in first selected semiperiod or time in complete period according to the zero sequence transient current of each bar feeder line and is:

Draw the singlephase earth fault charges accumulated amount

in time in i SI that begins that takes place by following discrete integration formula

$Q_{0i}^{\&prime;n}=Q_{0i-1}^{\&prime;n}+\frac{1}{2}\&times;(I_{0i-1}^{\&prime;n}-I_{0i}^{\&prime;n})\&times;\mathrm{\&Delta;t}$

In the formula;

is the zero sequence transient current of gathering in i the SI of n bar feeder line, and Δ t is the time in SI; When

or i=T/ Δ t; T is the cycle of three-phase electricity, and the quantity of electric charge of calculating is the zero sequence transient state quantity of electric charge

that is accumulated in first semiperiod or time in complete period on the n bar feeder line

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