CN101478149A - Wire selection method for power distribution network single phase earthing failure based on transient signal - Google Patents

Abstract

The invention discloses a distribution network single-phase ground fault route selection method based on a transitional quantity signal. The method comprises the following steps: determining the initial time of the fault; the adaptive selection of the characteristic frequency-band; and calculating and comparing the transient zero-sequence current-component amplitude value in the characteristic frequency-band; the invention definitely distinguish the fault line and the healthy line by using the characteristic that the abundant transient high-frequency component is include in the fault current at the moment of occurrence of the single-phase ground fault; and the method can adaptively determine the characteristic frequency-band and perform fault route selection by using the characteristic quantity of the transient zero-sequence current in the characteristic frequency-band, and the success ratio reaches above 99 percent through a great mount of simulation and the field data test, and is far higher than that of the route selection method in the prior art at present. The route selection method can be applied to the fault route selection for the transformer station where the neutral point is not grounded and is not directly grounded.

Description

A kind of one-phase earthing failure in electric distribution network selection method based on transient state amount signal

Technical field

The invention belongs to system for distribution network of power fault detect field, relate to a kind of one-phase earthing failure in electric distribution network selection method, especially a kind of one-phase earthing failure in electric distribution network selection method based on transient state amount signal.

Background technology

China 66kV and following electric pressure electrical network mostly adopt the neutral point indirect earthing mode, under this mode during electrical network generation single phase ground fault, fault current is little, although rules allow to continue operation 1～2 hour, but the voltage of non-ground connection phase becomes line voltage after the fault, system insulation is brought hidden danger and threat, need excise faulty line as early as possible, 2 ground connection are taken place and then cause short circuit accident avoiding.Domestic Small Electric Current Earthing And Routing Device mainly adopts the theoretical and pouring-in method of signal based on the route selection of stable state power frequency component at present.The former starts the route selection program by residual voltage, selects faulty line by comparing each circuit zero-sequence current; The latter is by short circuit by the former limit of ground connection phase PT, utilize the PT secondary side, artificially inject the signal code of a characteristic frequency to system, the path of following the tracks of this signal code is grounded failure line selection, but is subjected to the PT capacity impact owing to inject signal strength signal intensity, and when there is the intermittence arc phenomenon in earth resistance than big or earth point, detect poor effect, reload signal takes place and receiving device owing to need on the line in addition, has strengthened the route selection cost, is unfavorable for promoting.

Though route selection principle and method based on the stable state power frequency component have a variety of, but from authoritative department statistics result, the overall route selection accuracy rate of line selection apparatus is less than 70% in actual motion, some in addition have only 20～30%, falsely drop, the probability of selective reject is very big, the main cause that its route selection accuracy rate is not high is based on that the route selection of stable state power frequency component is theoretical to exist following insurmountable bottleneck:

(1) how to eliminate of the influence of the compensating action of arc suppression coil to the route selection precision;

(2) how to eliminate the influence of transition resistance;

(3) how accurately to discern electric arc intermittence discharge fault over the ground;

(4) instrument transformer precision problem and some other disturbing factor.

Above factor all can influence the stable state composition in the earth fault signal, cause the difference of electric parameters feature between faulty line and the non-fault line to diminish, influence the route selection effect, influence therefore how to eliminate these unfavorable factors is a difficult problem that needs to be resolved hurrily in the little electric current route selection technology.

In recent years, based on the small current earthing wire-selecting method of transient signal,, progressively be applied and promote because have good Fault Identification ability.

The transient signal route selection has following advantage:

1) moment takes place in single phase ground fault, contains abundant transient high frequency component in the fault current, is tens times to tens times under the stable state, utilizes this favorable characteristics can distinguish faulty line clearly and perfects circuit;

2) transient state component satisfies faulty line amplitude maximum equally, and it is reverse that the phase place of faulty line transient state component and other perfect circuit;

3) arc suppression coil is very little for the compensating action of transient high frequency component, and its influence can be ignored, and can not bring substantial influence to correct route selection.

Summary of the invention

The objective of the invention is to overcome the not high shortcoming of route selection accuracy rate in the prior art; a kind of one-phase earthing failure in electric distribution network selection method based on transient state amount signal is provided; this method is when transmission line generation single phase ground fault; contained abundant high frequency transient component in the zero sequence current signal based on faulty line; by extraction to zero-sequence current medium-high frequency transient signal after all protected circuit faults; determine feature band adaptively; compare the transient zero-sequence current feature of each bar circuit under this frequency band, further calculating provides failure line selection information exactly.

The objective of the invention is to solve by the following technical programs:

This one-phase earthing failure in electric distribution network selection method based on transient state amount signal specifically comprises the steps:

1) determines the fault initial time;

After adopting residual voltage amplitude and residual voltage sudden change amount to start definite fault initial time, carry out the self adaptation of feature band and choose;

2) self adaptation of feature band is chosen;

Described feature band is meant a part of frequency band in the first section capacitive frequency band that perfects circuit transient zero-sequence current phase place unanimity, and the described circuit that perfects is meant the circuit that does not break down; Feature band is chosen like this: establish f ₀For the lower-cut-off frequency of feature band, to isolated neutral system, f ₀=0Hz, to through arc suppression coil earthing system, f ₀=150Hz; If f ₁Be upper cut-off frequency, promptly all perfect the minimum value of circuit self series resonance frequency; f ₁Definite method as follows:

If the zero-sequence current of each circuit is i _0k, establish each circuit zero sequence current i _0kFrequency spectrum be I _0k, wherein k is circuit number, and span is 1～m, and m is the outlet number, asks for frequency spectrum I _0k, under each frequency, ask $\mathrm{\Δ}{I}_{0k}=I_{0k}-\underset{h=1}{\overset{m}{\mathrm{\Σ}}}{I}_{0h}/2,$ f _1kFor Δ I appears in each circuit first _0k＜0 pairing frequency is got f _1kIn maximum get f ₁=max{f _1k; Above gained [f ₀, f ₁] be feature band;

3) calculate the also interior transient zero-sequence current component amplitude of comparative feature frequency band;

If I _0kAFor circuit k at feature band [f ₀, f ₁] in all frequencies under amplitude add and, from the fault initial time, respectively the zero-sequence current in power frequency cycle of every circuit is done fast Fourier transform after, with the amplitude addition under each Frequency point, obtain its amplitude sum $I_{}$ ${}_{0\mathrm{kA}}=\underset{f_0}{\overset{f_1}{\mathrm{\Σ}}}{I}_{0k}\left(f\right);$ All I relatively _0kANumerical values recited is selected wherein maximum I _0kA.max, its pairing circuit is faulty line.

The present invention can adaptive definite feature band, and utilize the characteristic quantity of transient zero-sequence current in the feature band to carry out failure line selection, through a large amount of emulation and field data test, the route selection success rate reaches more than 99%, far above present selection method of the prior art.The present invention can be conveniently used in the transformer station of isolated neutral, non_direct ground, and adapts to the variation of earthing mode automatically, need not to adjust.

Description of drawings

Fig. 1 is one when having the simple isolated neutral system generation single phase ground fault of 4 outlets, the phase-frequency characteristic of each circuit zero sequence impedance;

Fig. 2 is an emulation power distribution network model;

Wherein, R _L, L _NSimulate the resistance and the inductance of arc suppression coil respectively; Article six, the outlet parameter is positive sequence impedance Z ₁=0.17+j0.38 Ω/km, positive sequence admittance Y ₁=j3.045 μ S/km, zero sequence impedance Z ₀=0.23+j1.72 Ω/km, zero sequence admittance Y ₀=j1.884 μ S/km; Triangular form connected load Z _L=400+j20 Ω;

Fig. 3 is system line L1 head end A phase earth fault (initial angle θ=90 °, transition resistance R _f=50 Ω, system neutral operate in through the grounding through arc mode) time, each line current frequency spectrum I _0kWith ∑ I _0h/ 2 poor Δ I _0k

Embodiment

The concrete implementing method of scheme described in the present invention is as follows:

(1) FPGA (Field-Programmable Gate Array: field programmable gate array) as the temporary core cell of controlling of sampling and data in the whole acquisition system, to ADC (Analog toDigital Converter: analog/digital converter) implement control, and (zero-sequence current, voltage digital signal into adopted in 50～2MHz) backs, thereby realizes the quick high accuracy real-time data acquisition to the distribution network system of being monitored by second order hardware bandpass filtering temporarily to preserve ADC.At last by MPU (Micro Processor Unit: the data that read the temporal data of FPGA and preserve preceding four cycles of current time microprocessor unit).For the residual voltage signal, whenever adopt into a data point simultaneously, itself and 511 points having adopted before this into will be calculated residual voltage signal fundamental frequency effective value by full-wave fourier algorithm.

(2) when distribution network system generation single phase ground fault, adopt residual voltage sudden change amount to start and the comprehensive start-up criterion of residual voltage amplitude, determine the fault initial time after, enter step (3).Comprehensive start-up criterion is specially: when residual voltage fundamental frequency effective value during greater than 30V, preserve that cycle at detected initial start point place and the residual voltage data of three cycles before thereof, again with sudden change amount criterion Δ u (n)〉k ₁U _Fd+ k ₂U _Ed, redefine position of failure point, in order that find the initial moment point of fault more quickly and accurately.Wherein: n is the sampled point numbering; N is a power frequency cycle sampling number, N=512 (i.e. Zhuan Zhi sample rate f _s=25.6kHz); Δ u (n)=[u (n)-u (n-N)]-[u (n-N)-u (n-2N)]; U _FdBe floating threshold, U _Fd=U (n-N)-2U (n-2N)+U (n-3N); k ₁Be safety factor, k ₁=1.25; k ₂Be safety factor, k ₂=0.06; U _EdThe expression voltage magnitude, U _Ed=100V.Satisfy Δ u (n)〉k ₁U _Fd+ k ₂U _EdSome n, be the fault origination point.

(3) determine the fault initial point after, the zero-sequence current of establishing each circuit is i _0k, the zero-sequence current i in the cycle after the fault of all outlets (m bar) after the extraction fault _0k(n), n=1,2......N.

(4) obtain the zero-sequence current i of each bar outlet respectively _0k(n) effective value $I_{0k}=\sqrt{\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{i_{0k}}^2\left(n\right)/N},$ And with all I _0kBe averaged I _0meanIf among the circuit i I is arranged _0k＜I _0meanDetermine that it is and perfect circuit, the residue circuit is counted m ' bar behind the certain sound circuit of eliminating.

(5) carry out next step judgement for remaining m ' bar circuit: respectively to i _0k(n), n=1,2......m ' utilizes fast Fourier transform (FFT) to obtain remaining the frequency spectrum I of every circuit _0k(f).

Whether (6) differentiate is busbar fault.

Find out the I of all circuits _0k(f) that Frequency point f of amplitude maximum in _Max, the angle of the circuit zero sequence current harmonics on this Frequency point is compared in twos, if the absolute value of its difference has one then to be judged to line fault greater than 90 °, enter step (7); Otherwise, then think bus or the All other routes fault not in monitoring range.

(7) differentiate strong, weak fault.

Strong fault takes place to isolated neutral system with through the strong fault of arc suppression coil earthing system and in the neutral by arc extinction coil grounding system (in the fault initial phase angle greater than 10 degree, transition resistance during less than 500 ohm, circuit transient current energy mainly concentrates on high frequency band) time, adopt self adaptation to catch the transient zero-sequence current Amplitude Comparison line selection algorithm of feature band.When fault a little less than arc suppression coil earthing system, adopt the route selection of zero-sequence current real component; (the ratio K of the shared total current energy of 0～150Hz) energy judges according to every circuit medium and low frequency component.If the K that two or more circuit arranged in the m ' bar circuit is greater than 0.5 then think strong fault takes place, otherwise be weak fault.The calculating of K, be by step (5) calculated the amplitude under each frequency, calculate with all amplitudes of low-frequency band with divided by the amplitude summation of full range band and to get.

(8) if strong fault is then asked for feature band [f ₀, f ₁].

Described feature band is meant a part of frequency band (as shown in Figure 1) in the first section capacitive frequency band that perfects circuit transient zero-sequence current phase place unanimity, and the described circuit that perfects is meant the circuit that does not break down; If f ₀For the lower-cut-off frequency of feature band, establish f ₁Be upper cut-off frequency, promptly all perfect the minimum value of circuit self series resonance frequency; To f in the isolated neutral system ₀=0Hz; F in arc suppression coil earthing system ₀=150Hz.

(9) determine upper cut-off frequency f ₁If the zero-sequence current of each circuit is i _0k, establish each circuit zero sequence current i _0kFrequency spectrum be I _0k, wherein k is circuit number, and span is 1～m, and m is the outlet number, asks for i with fast fourier transform _0kFrequency spectrum I _0k, under each frequency, ask $\mathrm{\Δ}{I}_{0k}=I_{0k}-\underset{h=1}{\overset{m}{\mathrm{\Σ}}}{I}_{0h}/2,$ f _1kFor Δ I appears in each circuit first _0k＜0 pairing frequency is got f _1kIn maximum get f ₁=max{f _1k; Above gained [f ₀, f ₁] be feature band;

(10) establish I _0kAFor circuit k at feature band [f ₀, f ₁] in all frequencies under amplitude add and, from time of failure point, at feature band [f ₀, f ₁] in, respectively the zero-sequence current in power frequency cycle of every circuit is done fast Fourier transform after, with the amplitude addition under each Frequency point, obtain its amplitude sum $I_{}$ ${}_{0\mathrm{kA}}=\underset{f_0}{\overset{f_1}{\mathrm{\Σ}}}{I}_{0k}\left(f\right),$ All I relatively _0kANumerical values recited is selected wherein maximum I _0kA.max, its pairing circuit is faulty line.

(11) if weak fault is then asked zero-sequence current low frequency real component value (it is following to get 150Hz here),, have the peaked circuit of current spectrum and be confirmed as faulty line each frequency zero-sequence current real component stack.

(12) report the route selection result, as if U this moment ₀Still be higher than threshold, then report fault still in continuing; If U ₀Be lower than threshold, then quoted the moment that is lower than threshold value, thought that fault disappears at this moment.

The effect assessment of scheme:

The present invention has good autgmentability and adaptability, and the system or the system scale of different scales change, and the present invention all can meet the demands.Be the example explanation now with a model:

As shown in Figure 2, get circuit L as calculated ₁～L ₆Zero-sequence current i ₀(n) effective value i _0MFor: 2.22,0.29,0.55,0.94,1.15,1.37.Its mean value i _0M.mean=1.09, i _0MI _0M.meanCircuit have 3: L ₁, L ₅, L ₆This three-line listed in the table be determined further i _0M＜i _0M.meanCircuit (L ₂, L ₃, L ₄) be judged as and perfect circuit.

In arc suppression coil earthing system, need to judge weak fault whether: the represented circuit L that goes out among Fig. 2 ₁, L ₅, L ₆The transient state component of electric current in 0～150Hz be i _0.fil, and try to achieve i _0.filEffective value i _0M2.filBe 0.61,0.35,0.24, shown in the 3rd row among the table 3-1, the 4th row provides low frequency zero-sequence current proportion K, and therefrom K is less than λ=0.5 as can be seen, and promptly electric current mainly concentrates on high frequency, therefore can be judged as strong fault.The transient zero-sequence current amplitude that adopts self adaptation to catch feature band compares selection method.

Fig. 3 is Fig. 2 system line L ₁Head end A phase earth fault (initial angle θ=90 °, transition resistance R _f=50 Ω, system neutral operate in through the grounding through arc mode) time, remember each line current frequency spectrum I _0kWith ∑ I _0h/ 2 difference DELTA I _0kCurve chart.Δ I ₀₁Be 1800Hz less than 0 frequency values first, but do not satisfy continuity, continue to judge, determine f ₁=2250Hz.And Δ I ₀₅, Δ I ₀₆All be f less than 0 value first ₀, therefore definite feature band upper cut-off frequency f ₁=2250Hz.

Below provided this time failure line selection computational process median:

Table 3-1

Circuit L ₁, L ₆, L ₅At the interior transient state current component i of feature band [150,2250] _0.tran, in view of the above, the effective value that can calculate transient state current component is 1.76,0.98,0.43.Therefore can judge L ₁Be faulty line.

When system at circuit L ₁(initial angle θ=45 °, transition resistance R during head end A phase ground connection _f=1000 Ω, system neutral operate in through the grounding through arc mode).

Below provide the basic route selection process of this time fault:

Table 3-2

After removal perfected circuit, that remaining was L ₁, L ₅, L ₆, the power current proportion is all greater than λ=0.5, so power frequency amount electric current proportion is bigger, generation be weak fault, adopt meritorious low frequency zero sequence current amplitude selection method relatively.Adopt Fu Shi filtering to ask following each the Frequency point zero-sequence current frequency spectrum of 150Hz, with its stack back tabulation 3-2 the 5th row, these 3 data show L ₁The frequency spectrum maximum, circuit L ₁Be faulty line.

The present invention utilizes single phase ground fault that moment takes place, and the feature that contains abundant transient high frequency component in the fault current is distinguished faulty line clearly and perfected circuit; This method can adaptive definite feature band, and utilize the characteristic quantity of transient zero-sequence current in the feature band to carry out failure line selection, through a large amount of emulation and field data test, the route selection success rate reaches more than 99%, far above present selection method of the prior art.The present invention can be conveniently used in the transformer station of isolated neutral, non_direct ground, and adapts to the variation of earthing mode automatically, need not to adjust.

Claims (1)

1. one-phase earthing failure in electric distribution network selection method based on transient state amount signal is characterized in that following steps:

1) determine the fault initial time:

After adopting residual voltage amplitude and residual voltage sudden change amount to start definite fault initial time, carry out the self adaptation of feature band and choose;

2) self adaptation of feature band is chosen:

Described feature band is meant a part of frequency band in the first section capacitive frequency band that perfects circuit transient zero-sequence current phase place unanimity, and the described circuit that perfects is meant the circuit that does not break down; Feature band is chosen like this: establish f ₀For the lower-cut-off frequency of feature band, to isolated neutral system, f ₀=0Hz, to through arc suppression coil earthing system, f ₀=150Hz; If f ₁Be upper cut-off frequency, promptly all perfect the minimum value of circuit self series resonance frequency; f ₁Definite method as follows:

If the zero-sequence current of each circuit is i _0k, establish each circuit zero sequence current i _0kFrequency spectrum be I _0k, wherein k is circuit number, and span is 1～m, and m is the outlet number, asks for frequency spectrum I _0k, under each frequency, ask ${\mathrm{\ΔI}}_{0k}=I_{0k}-\underset{h=1}{\overset{m}{\mathrm{\Σ}}}{I}_{0h}/2,$ f _1kFor Δ I appears in each circuit first _0k＜0 pairing frequency is got f _1kIn maximum get f ₁=max{f _1k; Above gained [f ₀, f ₁] be feature band;

3) calculate the also interior transient zero-sequence current component amplitude of comparative feature frequency band:

If I _0kAFor circuit k at feature band [f ₀, f ₁] in all frequencies under amplitude add and, from the fault initial time, respectively the zero-sequence current in power frequency cycle of every circuit is done fast Fourier transform after, with the amplitude addition under each Frequency point, obtain its amplitude sum $I_{0\mathrm{kA}}=\underset{f_0}{\overset{f_1}{\mathrm{\Σ}}}{I}_{0k}\left(f\right);$ All I relatively _0kANumerical values recited is selected wherein maximum I _0kA.max, its pairing circuit is faulty line.

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