CN104820165A - Same-tower double-circuit direct current transmission line fault line selection method based on single pole information - Google Patents

Abstract

The invention discloses a same-tower double-circuit direct current transmission line fault line selection method based on single pole information. The method includes the following steps: 1. voltage variations of four polar lines are calculated; 2. if the upper layer polar lines satisfy conditions, step 3 is carried out, and if the lower layer polar lines satisfy conditions, a step 4 is carried out; 3. If the low frequency harmonic wave amplitude satisfies a minimum value requirement, an amplitude ratio of low frequency and high frequency harmonic waves is continued to be obtained, if a specific value is larger than 1, the line of the pole is judged to be in fault, and otherwise travelling wave protection of the pole is locked; and 4. a voltage variation delay is sampled, if only one mutation wave head is detected in a data processing time window, the step 3 is carried out, if at least two mutation wave heads are detected in the data processing time window, polarity and amplitude relations of two continuous wave heads are compared, if the polarities are both positive and the amplitude relation satisfies a condition of a certain multiple, the line of the pole is judged to be in a non-near-end fault, and otherwise, travelling wave protection of the pole is locked. The same-tower double-circuit direct current transmission line fault line selection method based on single pole information has the advantages of high sensitivity, strong quick-action performance, difficult occurrence of misjudgment and the like.

Description

A kind of same-tower double-circuit direct-current transmission line fault line selection based on one pole information

Technical field

The present invention relates to a kind of electric system HVDC Transmission Technology, particularly a kind of same-tower double-circuit direct-current transmission line fault line selection based on one pole information.

Background technology

China's natural energy resources skewness and the energy and the asymmetric present situation of population distribution, make high voltage dc transmission technology have open application prospect at home.Compare high-voltage AC transmission technology, high voltage dc transmission technology has that unit price is low, through-put power is large, two ends exchange without the need to advantages such as synchronous operation, regulating and controlling are rapid, therefore uses high voltage dc transmission technology to be conducive to improving the dirigibility etc. of the economic target of electric system, technical indicator, reliability of operation and scheduling.

In order to ensure the safe and reliable operation of electric system, the protection of HVDC (High Voltage Direct Current) transmission line is significant.At present, HVDC (High Voltage Direct Current) transmission line protection in the world adopts traveling-wave protection mostly, and utilize the electric current and voltage travelling waves propagating into protection point to carry out fault distinguishing, protection is short for detection time.But due to increase and the transmission of electricity corridor anxiety of transmission line capability, common-tower double-return DC power transmission line puts into operation just day by day.Common-tower double-return DC line has two loop line roads, and there are positive pole, negative pole in each loop line road, arbitrary pole line failure, and wave traveling process of being expert at all can to other three pole line influence fault electric parameters.Therefore, how reliably to distinguish fault and non-faulting polar curve, most important for the DC line traveling-wave protection based on transient.But do not replace due to common-tower double-return DC power transmission line; polarity on each polar curve of each line mould and topotype traveling-wave component that are coupled out during different polar curve earth fault and amplitude is caused to there are differences; and velocity of wave is not identical yet, this considerably increases the difficulty of the existing traveling-wave protection scheme identification fault polar curve based on one pole line information structure.If solve the problem by means of only the mode improving setting valve, impact to the sensitivity of protection, the fault traveling wave propagating characteristic that therefore must make full use of common-tower double-return DC line is solved.

Summary of the invention

The object of the invention is to overcome the shortcoming of prior art and deficiency, a kind of same-tower double-circuit direct-current transmission line fault line selection based on one pole information is provided, this same-tower double-circuit direct-current transmission line fault line selection, for the different fault transient property difference of common-tower double-return DC power transmission line levels polar curve, adopts the method for combination to realize the failure line selection object of upper strata polar curve and lower floor's polar curve.Be applicable to existing common-tower double-return DC power transmission line, sensitivity is high, and quick-action is strong, not easily judges by accident, and tolerance transition resistance ability also increases.

Object of the present invention is achieved through the following technical solutions: a kind of same-tower double-circuit direct-current transmission line fault line selection based on one pole information, comprises following steps:

(1) get current time before a certain particular moment instantaneous voltage as with reference to amount, deduct by the instantaneous voltage of current time the voltage variety that reference quantity obtains four polar curves.Wherein four polar curves 1P, 1N, 2P, 2N represent, 1P, 2N are on the upper strata of same shaft tower, and 1N, 2P are in the lower floor of same shaft tower.1P, 1N are respectively electrode line, the negative line on the first loop line road, and 2P, 2N are respectively electrode line, the negative line on the second loop line road, then the voltage variety of four polar curves is respectively Δ u _1P, Δ u _1N, Δ u _2P, Δ u _2N.

(2) the voltage change ratio du of every root polar curve is calculated _1P/ dt, du _1N/ dt, du _2P/ dt, du _2N/ dt, is multiplied by-1 by the voltage change ratio of 1P, 2P polar curve simultaneously, to ensure that reference value is positive polarity.The voltage change ratio and threshold value that calculate acquisition are compared, are shown below:

du/dt≥du _set/dt，

Its at the middle and upper levels 1P, 2N polar curve satisfy condition and proceed to step (3), lower floor's 1N, 2P polar curve satisfies condition and proceeds to step (4).

(3) the moment t meeting step (2) conditional is preserved ₁, by voltage variety time delay t _desample, extract moment t by time frequency analysis function ₁the low-frequency harmonics amplitude W at place _lwith high-frequency harmonic amplitude W _h, then data are compared as follows:

$\left\{\begin{array}{c}{W}_L\≥W_{\mathrm{Lset}}\\ \frac{W_L}{W_H}\≥K_{\mathrm{up}1}\end{array}\right.,$

Meet above formula and be then judged as this pole line fault, otherwise the traveling-wave protection of this pole of locking.

(4) by voltage variety time delay t _desample, use the time frequency analysis function identical with step (3) to extract wave head polarity and amplitude.Preserve sudden change wave head number n.If a sudden change wave head only detected in data processing time window, proceed to step (3); If at least two sudden change wave heads detected in data processing time window, the polarity of more continuous two wave heads and magnitude relation, if meet following formula:

$\left\{\begin{array}{c}{v}_{\max .n}>0\\ v_{\max .n+1}>0\\ \frac{v_{\max .n+1}}{v_{\max .n}}\≥K_{\mathrm{down}}\\ n\≥1\end{array}\right.,$

Then be judged as the non-near terminal fault in this polar curve road, no person's locking this pole traveling-wave protection.Wherein v _maxnfor sudden change wave head modulus maximum.

Preferably, in step (1), the voltage variety of four described circuits is the value before current instantaneous value deducts 10ms, is steady-state value before fault occurs with what guarantee that line voltage distribution in the 10ms after line failure deducts, obtain line voltage distribution fault amount, adopt following formula to calculate:

$\left\{\begin{array}{c}\mathrm{\Δ}{u}_{1P}=u_{1P}\left(t\right)-u_{1P}(t-\mathrm{\Δt})\\ {\mathrm{\Δu}}_{1N}=u_{1N}\left(t\right)-u_{1N}(t-\mathrm{\Δt})\\ \mathrm{\Δ}{u}_{2P}=u_{2P}\left(t\right)-u_{2P}(t-\mathrm{\Δt})\\ \mathrm{\Δ}{u}_{2N}=u_{2N}\left(t\right)-u_{2N}(t-\mathrm{\Δt})\end{array}\right.,$

Wherein, u _1Pt () represents the instantaneous voltage of polar curve 1P in t, Δ u _1Prepresent the voltage jump amount of circuit 1P after protection starting, the rest may be inferred by analogy for it, and Δ t=10ms is the time interval of current time and particular moment.

Preferably, in step (2), the method for calculating voltage rate of change is the maximal value of getting three sampled point differential values, for 1P, is shown below:

${\mathrm{du}}_{1P}/\mathrm{dt}\left(t\right)=\max \{\frac{u_{1P}\left(t\right)-u_{1P}(t-t_{d1})}{t_{d1}},\frac{u_{1P}(t-t_{d1})-u_{1P}(t-{2t}_{d1})}{t_{d1}},\frac{u_{1P}(t-2t_{d1})-u_{1P}(t-3t_{d1})}{t_{d1}}\},$

Wherein, t _d1for sampling time interval.In order to obtain the numerical value of positive polarity, after the voltage variety of 1P, 2P polar curve is multiplied by-1, calculate rate of change again.

Preferably, in step (3), preserve the moment t meeting step (2) conditional ₁, for 1P polar curve, by voltage variety Δ u _1P(t) time delay t _de=3t _d1rear use time frequency analysis function extracts harmonic content.Time-frequency material calculation is t _d2, data processing time window length is T=Nt _d2, N>=100.Δ u will be exported after time frequency analysis process _1Pthe time-frequency matrix of (t) in matrix, row vector represents discrete time-domain coordinate, and column vector represents discrete frequency domain coordinate, and matrix element amplitude represents the corresponding harmonic amplitude size in corresponding moment.Extract matrix middle t ₁the column vector in moment, low-order harmonic crest meter formula is:

$W_L=\underset{2\≤f\≤\frac{N}{10}}{\mathrm{\Σ}}{D}_{\mathrm{\Δ}{u}_{1P}}(t_1,f),$

Higher hamonic wave crest meter formula is:

$W_H=\underset{\frac{2N}{5}\≤f\≤\frac{N}{2}}{\mathrm{\Σ}}{D}_{\mathrm{\Δ}{u}_{1P}}(t_1,f),$

Preferably, in step (4), for 1N polar curve, by voltage variety Δ u _1N(t) time delay t _de=3t _d1the identical time frequency analysis function of rear use extracts wave head polarity and amplitude, and data processing time window length is T.Sudden change wave head modulus maximum is: extracting method for get matrix wherein a row element differentiate is carried out to the time, derivative be zero point be Local modulus maxima, namely suddenly change wave head.If extract f ₁row element, then the corresponding moment calculating formula of wave head of suddenling change is:

$\frac{\∂D_{{\mathrm{\Δu}}_{1N}}(t,f_1)}{\∂t}{|}_{t=t_n}=0;$

Preserve sudden change wave head number, polarity and amplitude information.If continuous two sudden change wave head polarity are just, and second wave head amplitude and first wave head Amplitude Ration are greater than K _down, be then judged as this pole line fault, otherwise the traveling-wave protection of this pole of locking.

The present invention adopts diverse ways to carry out failure line selection to upper strata polar curve and lower floor's polar curve, take full advantage of the fault transient feature of different polar curve, and only make use of monopolar line voltage transient information, in step (4), described data processing time window only needs 1 millisecond.

Object of the present invention also can be realized by following scheme: calculate this polar curve road voltage variety; Calculate this polar curve road voltage change ratio; Judge whether line voltage distribution rate of change meets minimum conditions, satisfied then extract voltage variety time-frequency characteristics by time frequency analysis function; Upper strata polar curve extracts low-frequency harmonics amplitude and high-frequency harmonic amplitude, if low-frequency harmonics amplitude meets minimum value requirement and low high-frequency harmonic Amplitude Ration is greater than 1, then judges this pole line fault; Sudden change wave head number, polarity and amplitude information in lower floor's polar curve extraction time window, if sudden change wave head number is 1, extract low-frequency harmonics amplitude and high-frequency harmonic amplitude, if low-frequency harmonics amplitude meets minimum value requirement and low high-frequency harmonic Amplitude Ration is greater than 1, then judge this polar curve road near terminal fault, if sudden change wave head number is greater than 1, continuous two wave head polarity are all positive polarity, and second wave head amplitude and first wave head Amplitude Ration are greater than K _down, then the non-near terminal fault in this polar curve road is judged as.

The principle of failure line selection of the present invention is as follows: similar with the fault Electromagnetic Coupling Characteristic of single time DC line, and four polar curves of common-tower double-return DC line can intercouple out when fault four modulus traveling-waves.Find according to electromagnetic coupled analysis result, the fault transient characteristic of upper strata polar curve is not identical with the fault transient characteristic of lower floor's polar curve, therefore needs to study respectively constructing on fault-line selecting method.PSCAD/EMTDC electromagnetic transient simulation software is utilized to build common-tower double-return DC power transmission line model, as follows to analysis of simulation result:

1, upper strata 1P polar curve fault transient characteristic;

Arrange fault to 1P polar curve in different circuit distance to emulate, obtain four line voltage variable quantity comparison diagrams as shown in (Fig. 3 (a) (b)).In Fig. 3 (a), solid line is 1P line voltage waveform, and dotted line is the 2N line voltage waveform of same layer.1P line voltage wave head amplitude is comparatively large, and after ripple, amplitude is mild, and therefore low-order harmonic content is larger.There is an impulse wave head in 2N line voltage waveform, after ripple, amplitude is very little, and wave head is mainly higher harmonic content.Fig. 3 (b) is that change in voltage amplitude is all less to layer 1N polar curve and 2P line voltage oscillogram, and therefore low-order harmonic content is also less.To sum up waveform characteristic analysis; propose using low-order harmonic content as fault initiating additional criteria; again using low-order harmonic content and higher harmonic content ratio as upper strata polar curve failure line selection criterion, the traveling-wave protection malfunction that same layer causes pole fault and thunderbolt disturbance effectively can be avoided.

2, lower floor 1N polar curve fault transient characteristic;

In different circuit distance, fault simulation is arranged to 1N polar curve, obtains four line voltage variable quantity oscillograms as shown in (Fig. 4 (a) (b)).In Fig. 4 (a), solid line is 1N line voltage waveform, and dotted line is the 2P line voltage waveform of same layer.1N line voltage has two voltage wave heads in the same way, and 2P line voltage has two reverse voltage wave heads, and two voltage wave head amplitudes have certain proportionate relationship.Fig. 4 (b) is to layer line voltage oscillogram, and the voltage wave head on polar curve is discontented with the certain proportionate relationship of foot.Under circuit top failure condition, voltage wave hair is raw to be overlapped, cannot the polarity of more continuous two voltage wave heads and magnitude relation, but 1N line voltage low-frequency harmonics content is larger, all the other polar curve low-frequency harmonics content are less, and frequency characteristic difference can be relied in this case to carry out failure line selection.In the line in far-end fault situation, because 2P line voltage coupling amount is comparatively large, low-order harmonic content is also comparatively large, therefore relies on frequency characteristic effectively cannot distinguish 1N polar curve fault and 2P polar curve fault.

According to waveform characteristic analysis, if circuit only detects a sudden change wave head in set time window, low-order harmonic content in fault pole is higher than non-faulting pole in this case, therefore proceeds to step (3) and carries out failure line selection.If circuit detects at least two sudden change wave heads in set time window, in this case the low-order harmonic content of 1N polar curve and 2P polar curve is close, failure line selection cannot be carried out according to step (3), therefore proceed to step (4) and utilize wave head polarity and magnitude relation to carry out failure line selection.The polarity of sudden change wave head and contained harmonic amplitude is extracted by time frequency analysis function.

Because the fault transient characteristic of upper strata polar curve is not identical with lower floor polar curve, therefore the present invention adopts combined fault route selection method, formulates different failure line selection schemes respectively to levels polar curve, improves the sensitivity of protection to Fault Identification.The fault-line selecting method of upper and lower two-layer polar curve can not be used mutually.

Setting principle;

Voltage change ratio criterion of adjusting definite value needs the impact considering external area error.Because line end is equiped with smoothing reactor, the row ripple that external area error is transmitted is weakened becomes level and smooth, and rate of change reduces.Therefore voltage change ratio criterion definite value is avoid the maximum rate of change that external area error causes to set.The sampling interval calculating rate of change is t _d1, the starting protection criterion when voltage change ratio exceedes threshold value.

After upper strata 1P, 2N polar curve meets voltage change ratio criterion, preserve fault initiating moment t ₁and enter failure line selection link.In order to obtain the Time-Frequency Information of complete sudden change wave head, by voltage variety time delay t _deafter carry out time-frequency conversion again.The time frequency analysis function of application accurately must extract harmonic amplitude.In order to obtain the high-frequency harmonic information of sudden change wave head, data sampling rate should be high as far as possible, and sampled data is many as far as possible.The time-frequency material calculation t that the present invention adopts _d2=0.01ms, sampled data output N=100, time window T=1ms, but be not limited to this.Voltage variety can export N × N time-frequency matrix of corresponding time window respectively after time frequency analysis process row matrix vector t represents discrete time-domain coordinate, and column vector f represents discrete frequency domain coordinate.Wherein the positive harmonic amplitude coefficient frequently of row matrix element representation, after row represents negative harmonic amplitude coefficient frequently.Because positive and negative frequency amplitude is equal, before therefore only need getting row matrix element calculates.T in matrix ₁column vector corresponding to moment represents harmonic content distribution situation contained by this moment wave head, and overtone order is from low toward high growth.Before getting the matrix element sum of row is low-order harmonic amplitude W _l, get walk to the matrix element sum of row is higher hamonic wave amplitude W _h.The threshold value W of low-order harmonic amplitude _lsetsetting principle is, minimum low-order harmonic amplitude during critical transition resistance ground connection occurs circuit.W _lbe greater than W _h, therefore ratio K _upminimum value is 1.

After lower floor polar curve 1N, 2P meet voltage change ratio criterion definite value, obtain time-frequency matrix through identical time frequency analysis process in extraction matrix, wherein a row element carries out differentiate to the time, obtains sudden change wave head information.If two or more sudden change wave heads detected, more continuous two wave head polarity and amplitude, for 1N polar curve, during its this pole fault, two wave head polarity are just, and second wave head amplitude and first wave head Amplitude Ration are greater than 5, therefore K _downsetting principle for meeting line mould ripple u _p3with line mould ripple u _p2amplitude Ration, according to calculating data can be set to 5 times.

The present invention has following advantage and effect relative to prior art:

The first, quick-action is strong; The present invention only need make use of shorter fault wave head (in 1ms) time-frequency transient characterisitics, can identify fault polar curve fast, is conducive to DC line protection action excision fault within the shorter time.

The second, transition resistance ability is tolerated strong; The present invention mainly utilizes the time-frequency characteristics ratio relation of fault traveling wave, can eliminate the impact of transition resistance, as long as voltage change ratio meets fault initiating criterion, accurately can carry out failure line selection.

Three, reliability is high; The present invention takes full advantage of the fault transient characteristic of common-tower double-return DC line, carries out failure line selection differentiation targetedly to different circuit, and the traveling-wave protection of non-faulting polar curve can be reliably failure to actuate.

Four, the present invention only needs this polar curve road voltage variety information, can meet common-tower double-return DC line fault route selection function without the need to communication port between circuit, possesses engineer applied and is worth.

Accompanying drawing explanation

Fig. 1 is upper strata polar curve fault-line selecting method process flow diagram.

Fig. 2 is lower floor's polar curve fault-line selecting method process flow diagram.

Fig. 3 (a) is the upper strata line voltage waveform changing trend diagram that 1-P polar curve fault causes.

Fig. 3 (b) is lower floor's line voltage waveform changing trend diagram that 1-P polar curve fault causes.

Fig. 4 (a) is lower floor's line voltage waveform changing trend diagram that 1N polar curve fault causes.

Fig. 4 (b) is the upper strata line voltage waveform changing trend diagram that 1N polar curve fault causes.

Fig. 5 (a) is Δ u under 1P polar curve fault and 2N polar curve fault _1Pwave head comparison diagram.

Fig. 5 (b) is Δ u under 1P polar curve fault and 2N polar curve fault _1Pfrequency characteristic comparison diagram.

Fig. 6 (a) is Δ u under 1N polar curve fault and 2P polar curve fault _1Nwave head comparison diagram.

Fig. 6 (b) is Δ u under 1N polar curve fault and 2P polar curve fault _1Nfrequency characteristic comparison diagram.

Fig. 7 is Δ u under 1N polar curve fault and 2P polar curve fault _1Nwave head polarity comparison diagram.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.

Embodiment

As depicted in figs. 1 and 2, a kind of common-tower double-return direct current transmission line fault route selection combined method based on one pole transient information, comprises following steps:

(1) as shown in Fig. 3 (a) He Fig. 3 (b), before getting current time a certain particular moment instantaneous voltage as with reference to amount, deduct by the instantaneous voltage of current time the voltage variety that reference quantity obtains four polar curves.Wherein four polar curves 1P, 1N, 2P, 2N represent, 1P, 2N are on the upper strata of same shaft tower, and 1N, 2P are in the lower floor of same shaft tower.1P, 1N are respectively electrode line, the negative line on the first loop line road, and 2P, 2N are respectively electrode line, the negative line on the second loop line road, then the voltage variety of four polar curves is respectively Δ u _1P, Δ u _1N, Δ u _2P, Δ u _2N.Calculating formula is as follows:

$\left\{\begin{array}{c}\mathrm{\Δ}{u}_{1P}=u_{1P}\left(t\right)-u_{1P}(t-\mathrm{\Δt})\\ {\mathrm{\Δu}}_{1N}=u_{1N}\left(t\right)-u_{1N}(t-\mathrm{\Δt})\\ \mathrm{\Δ}{u}_{2P}=u_{2P}\left(t\right)-u_{2P}(t-\mathrm{\Δt})\\ \mathrm{\Δ}{u}_{2N}=u_{2N}\left(t\right)-u_{2N}(t-\mathrm{\Δt})\end{array}\right.,$

Wherein, u _1Pt () represents the instantaneous voltage of polar curve 1P in t, Δ u _1Prepresent the voltage jump amount of circuit 1P after protection starting, the rest may be inferred by analogy for it, and Δ t=10ms is the time interval of current time and particular moment.

(2) the voltage change ratio du of every root polar curve is calculated _1P/ dt, du _1N/ dt, du _2P/ dt, du _2N/ dt, is multiplied by-1 by the voltage change ratio of 1P, 2P polar curve simultaneously, to ensure that reference value is positive polarity.The voltage change ratio and threshold value that calculate acquisition are compared, are shown below:

du/dt≥du _set/dt，

Its at the middle and upper levels 1P, 2N polar curve satisfy condition and proceed to step (3), lower floor's 1N, 2P polar curve satisfies condition and proceeds to step (4).

(3) as shown in Fig. 5 (a) He Fig. 5 (b), the moment t meeting step (2) conditional is preserved ₁, by voltage variety time delay t _desample, extract moment t by time frequency analysis function ₁the low-frequency harmonics amplitude W at place _lwith high-frequency harmonic amplitude W _h, then data are compared as follows:

$\left\{\begin{array}{c}{W}_L\≥W_{\mathrm{Lset}}\\ \frac{W_L}{W_H}\≥1\end{array}\right.,$

Meet above formula and be then judged as this pole line fault, otherwise the traveling-wave protection of this pole of locking.

(4) as shown in Fig. 6 (a) He Fig. 6 (b), by voltage variety time delay t _desample, use the time frequency analysis function identical with step (3) to extract wave head polarity and amplitude information.If a sudden change wave head only detected in data processing time window, proceed to step (3); If at least two sudden change wave heads detected in data processing time window, more continuous two wave head v _max.n, v _max.n+1polarity and magnitude relation, if meet following formula:

$\left\{\begin{array}{c}{v}_{\max .n}>0\\ v_{\max .n+1}>0\\ \frac{v_{\max .n+1}}{v_{\max .n}}\≥K_{\mathrm{down}}\\ n\≥1\end{array}\right.,$

Then be judged as the non-near terminal fault in this polar curve road, otherwise the traveling-wave protection of this pole of locking.

As shown in Figure 7, adopt PSCAD/EMTDC simulation software, cross the systematic parameter of DC engineering with reference to small stream Lip river, build one-tower double-circuit DC transmission system model.Common-tower double-return double back DC power transmission line model adopts and builds according to frequency parameter model, total track length 1254km, overhead line structures parameter multiple-circuit on same tower is trapezoidal profile, upper strata polar curve is 1P, 2N, lower floor's polar curve is 1N, 2P, G1, G2 are respectively ground wire, the horizontal range l3 of two ground wires is 28.4m, the horizontal range l1 of polar curve 1P and 2N is 14.5m, the horizontal range l2 of polar curve 1N and 2P is 19.2m, the distance h1 on lower floor's polar curve and ground is 18m, and the vertical range h2 of upper strata polar curve and lower floor's polar curve is 15m, and the vertical range h3 of ground wire and upper strata polar curve is 22m.In addition, the cross-line degree of depth of transmission line of electricity is 16m, and the cross-line degree of depth of ground wire is 11m.Then, on the basis of DC transmission system model, according to the common-tower double-return direct current transmission line fault route selection combined method that the present invention proposes, build voltage variety computing module based on every polar curve road, voltage change ratio computing module, time frequency analysis module.Wherein time frequency analysis module application is to the Time-Frequency Tool Box in MATLAB software, and the present invention's application S-transformation time frequency analysis function is example.Use the methods such as function restructuring to improve the time frequency analysis performance of time frequency analysis functions, and be applied to same-tower double-circuit direct-current transmission line fault line selection also belongs to and the present invention relates to content.Time frequency analysis module plays difference in functionality according to levels polar curve, and the calculated rate of time frequency analysis module is 100kHz.Respectively in distance rectification side different circuit distance, short trouble is arranged to every bar polar curve, comprise metallic earthing fault and 300 Ω transition resistance earth faults.Because two loop line roads are symmetrical, therefore only provide a loop line road failure line selection result, as shown in table 1 Yu table 2, table 1 is 1-P polar curve failure line selection result, and table 2 is 1-N polar curve failure line selection result.

Table 1

Table 2

There are 300 Ω transition resistance ground fault condition with circuit herein to verify fault-line selecting method.When 300 Ω transition resistance ground connection, circuit low-frequency harmonics content is minimum is 102kV, is to retain nargin, be multiplied by be less than 1 sensitivity coefficient as threshold value, for 90kV.The sampling rate of time frequency analysis process is 100kHz, and sampling time window is 1ms.

Grey data sufficient criterion certification condition with thumb down in table.Can be found by table 1 data, 1P polar curve is when this pole line fault, and voltage change ratio, low-frequency harmonics amplitude and low high-frequency harmonic Amplitude Ration all meet failure line selection requirement, make traveling-wave protection action message.During 1N polar curve metallicity fault, the voltage change ratio of 1P polar curve induction meets threshold value requirement, and the low-frequency harmonics amplitude responded to when near terminal fault have also exceeded 90kV, but is less than 1 due to low high-frequency harmonic Amplitude Ration, and therefore traveling-wave protection is reliably failure to actuate.During 2P polar curve fault, the voltage change ratio of 1P polar curve induction does not meet threshold value requirement, and protection does not start.During 2N polar curve near terminal fault, voltage change ratio is negative polarity, and protection does not start, and when away near terminal fault, low high-frequency harmonic Amplitude Ration is less than 1, therefore protects and is reliably failure to actuate.When 300 Ω transition resistance earth fault, because between polar curve, fault induction amount is very little, be therefore unlikely to cause false protection.

Can be found by table 2 data, 1N polar curve, when circuit near terminal fault, only detects 1 sudden change wave head, uses low high frequency Amplitude Ration can distinguish fault polar curve and perfect polar curve in sampling time window.1N polar curve, when away from circuit near terminal fault, detects at least two sudden change wave heads in sampling time window, wherein during 1N polar curve fault, continuous two sudden change wave head polarity are just, and second wave head amplitude and first wave head Amplitude Ration are greater than K _down=5, all the other polar curves do not meet this condition.Utilize wave head polarity and magnitude relation accurately can distinguish this pole fault and all the other are to pole fault, protection action message.

Above-described embodiment is the present invention's preferably embodiment; but embodiments of the present invention are not limited by the examples; change, the modification done under other any does not deviate from Spirit Essence of the present invention and principle, substitute, combine, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.

Claims (6)

1. based on a same-tower double-circuit direct-current transmission line fault line selection for one pole information, it is characterized in that, comprise following steps:

(1) get current time before a certain particular moment instantaneous voltage as with reference to amount, deduct by the instantaneous voltage of current time the voltage variety that reference quantity obtains four polar curves;

(2) voltage change ratio of every root polar curve is calculated, the voltage change ratio and threshold value that calculate acquisition are compared, if upper strata 1P, 2N polar curve satisfies condition, proceed to step (3), if lower floor's 1N, 2P polar curve satisfies condition, proceed to step (4);

(3) the moment t meeting step (2) conditional is preserved ₁, by voltage variety time delay t _desample, extract moment t by time frequency analysis function ₁the low-frequency harmonics amplitude W at place _lwith high-frequency harmonic amplitude W _h; If low-frequency harmonics amplitude meets minimum value requirement, continue to ask low frequency and high-frequency harmonic Amplitude Ration, ratio is greater than 1 and is judged as this pole line fault, otherwise the traveling-wave protection of this pole of locking;

(4) by voltage variety time delay t _desample, use the time frequency analysis function identical with step (3) to extract wave head polarity and amplitude; If a sudden change wave head only detected in data processing time window, proceed to step (3); If at least two sudden change wave heads detected in data processing time window; more continuous two wave head polarity and magnitude relation, if polarity is all positive polarity and the satisfied 5 times of conditions of magnitude relation, be then judged as the non-near terminal fault in this polar curve road; otherwise, the traveling-wave protection of this pole of locking.

2. the same-tower double-circuit direct-current transmission line fault line selection based on one pole information according to claim 1, is characterized in that, in step (1), the computing formula of voltage variety is:

$\left\{\begin{array}{c}\mathrm{\Δ}{u}_{1P}=u_{1P}\left(t\right)-u_{1P}(t-\mathrm{\Δt})\\ \mathrm{\Δ}{u}_{1N}=u_{1N}\left(t\right)-u_{1N}(t-\mathrm{\Δt})\\ \mathrm{\Δ}{u}_{2P}=u_{2P}\left(t\right)-u_{2P}(t-\mathrm{\Δt})\\ \mathrm{\Δ}{u}_{2N}=u_{2N}\left(t\right)-u_{2N}(t-\mathrm{\Δt})\end{array}\right.,$

Wherein, u _1Pt () represents the instantaneous voltage of polar curve 1P in t, Δ u _1Prepresent the voltage jump amount of circuit 1P after protection starting, u _2Pt () represents the instantaneous voltage of polar curve 2P in t, Δ u _2Prepresent the voltage jump amount of circuit 2P after protection starting, Δ t=10ms is the time interval of current time and particular moment.

3. the same-tower double-circuit direct-current transmission line fault line selection based on one pole information according to claim 1, it is characterized in that, in step (2), the computing method of voltage change ratio are the maximal value of getting three sampled point Backward divided difference numerical differentiation values, and the computing formula calculating 1P polar curve is:

$d{u}_{1P}/\mathrm{dt}\left(t\right)=\max \{\frac{u_{1P}\left(t\right)-u_{1P}(t-t_{d1})}{t_{d1}},\frac{u_{1P}(t-t_{d1})-u_{1P}(t-2t_{d1})}{t_{d1}},\frac{u_{1P}(t-2t_{d1})-u_{1P}(t-3t_{d1})}{t_{d1}}\},$

Wherein, t _d1for sampling time interval, in order to obtain the numerical value of positive polarity, after the voltage variety of 1P, 2P polar curve is multiplied by-1, calculate rate of change again.

4. the same-tower double-circuit direct-current transmission line fault line selection based on one pole information according to claim 1, it is characterized in that, step (3), only for upper strata polar curve and section bottom polar curve failure condition, preserves the moment t meeting step (2) conditional ₁, by voltage variety time delay t _de=3t _d1through the process of time frequency analysis function, export a time-frequency matrix D _{Δ u}(t, f), extracts t in matrix ₁the column element that moment is corresponding, calculate low-frequency harmonics amplitude and high-frequency harmonic amplitude, and compare, calculating formula and comparison expression are:

$\left\{\begin{array}{c}{W}_L=\underset{2\≤f\≤\frac{N}{10}}{\mathrm{\Σ}}{D}_{\mathrm{\Δ}{u}_{1P}}(t_1,f)\\ W_H=\underset{\frac{2N}{5}\≤f\≤\frac{N}{2}}{\mathrm{\Σ}}{D}_{\mathrm{\Δ}{u}_{1P}}(t_1,f)\\ W_L\≥W_{\mathrm{Lset}}\\ \frac{W_L}{W_H}\≥1\end{array}\right.,$

Wherein, W _lfor low-frequency harmonics amplitude, W _hfor high-frequency harmonic amplitude; If W _lbe greater than W _lsetand W _lwith W _hratio be greater than 1, then export 1, the traveling-wave protection action of this pole.

5. the same-tower double-circuit direct-current transmission line fault line selection based on one pole information according to claim 1, it is characterized in that, in step (4), only for lower floor's polar curve partial fault situation, use in the time frequency analysis function extraction time window identical with step (3) number of the wave head that suddenlys change, polarity and amplitude information, if detect, sudden change wave head number is 1, proceed to step (3), if detect, sudden change wave head number has 2 at least, then the polarity of more continuous two wave heads and magnitude relation; If two wave head polarity is positive polarity and the Amplitude Ration of second wave head amplitude and first wave head amplitude is greater than K _down, then export 1, the traveling-wave protection action of this pole, comparison expression is:

$\left\{\begin{array}{c}{v}_{\max .n}>0\\ v_{\max .n+1}>0\\ \frac{v_{\max .n+1}}{v_{\max .n}}\≥K_{\mathrm{down}}\\ n\≥1\end{array}\right.,$

Wherein, for sudden change wave head modulus maximum, extract the corresponding moment t of sudden change wave head _ncalculating formula be: $\frac{\∂D_{\mathrm{\Δ}{u}_{1N}}(t,f_1)}{\∂t}{|}_{t=t_n}=0.$

6. the same-tower double-circuit direct-current transmission line fault line selection based on one pole information according to claim 1, is characterized in that, in step (4), described data processing time window only needs 1 millisecond.