CN105098738A - Pilot protection method of high-voltage direct current transmission line based on S transformation - Google Patents

Pilot protection method of high-voltage direct current transmission line based on S transformation Download PDF

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CN105098738A
CN105098738A CN201510566344.3A CN201510566344A CN105098738A CN 105098738 A CN105098738 A CN 105098738A CN 201510566344 A CN201510566344 A CN 201510566344A CN 105098738 A CN105098738 A CN 105098738A
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transformation
fault
voltage
transmission line
pole
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CN105098738B (en
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邹贵彬
李钊
高厚磊
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Shandong University
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Shandong University
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Abstract

The invention discloses a pilot protection method of a high-voltage direct current transmission line based on S transformation. The pilot protection method comprises: collecting voltage and current of a protection element connected with positive and negative electrodes of the direct current transmission line, and filtering the voltage and the current; extracting voltage and current mutation data within a set time after a fault, and carrying out S transformation on the mutation data to obtain a complex time-frequency S matrix of voltage and current signals; calculating S transformation phase angles of the voltage and current mutations at each sampling point and a mean of the phase angle difference thereof; establishing a protection criterion of the direct current transmission line, and identifying faults inside and outside the sample space based on the S transformation phase angles of the voltage and current mutations according to the protection criterion; if the fault is a fault inside the sample space, comparing the transient energy of S transformation zero frequency bands of the voltage mutations of the positive and negative electrodes via a rectifying side protection device to judge a fault pole. The pilot protection method disclosed by the invention does not need to synchronize data on both ends of the direct current transmission line and only requires an inversion side to transmit a fault direction identification result to the rectifying side.

Description

A kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation
Technical field
The present invention relates to a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation.
Background technology
Extra-high voltage direct-current transmission technique functions comes from the sixties in 20th century, and due to the fast development of converter, high voltage dc transmission technology was worldwide widely applied in recent years.High voltage direct current transmission has that power delivery is stable, transmission line capability is large, efficiency of transmission is high, can realize the advantages such as long distance power transmission, has become that large Energy Base electric power is sent outside, the important way of asynchronous Power System Interconnection.UHVDC Transmission Lines fed distance is far away, power transmission power large, it is with a varied topography to pass through, and subjects to the fault that thunder and lightning, storm etc. cause, route protection can the safe operation of fast and reliable ground detection failure to DC transmission system significant.
Current operating DC power transmission line Protection Technology provides primarily of ABB or SIEMENS.Main protection configuration traveling-wave protection, utilize the fault traveling wave on circuit to identify fault, quick action, but its reliability and sensitivity is subject to the impact of transition resistance and interference; Slow backup protection configuration electric current longitudinal differential protection, utilize simply adding and establishing protective criterion of the circuit two ends magnitude of current, have absolute selectivity in theory, but the current fluctuation of fault initial stage is comparatively large, need certain time delay to drop into, quick-action is poor.Therefore, need research reliability HVDC (High Voltage Direct Current) transmission line that is high, that do not affect by transition resistance badly to protect.For current DC line protection Problems existing, numerous scholar has carried out large quantity research to HVDC (High Voltage Direct Current) transmission line protection, proposes many useful methods.
" ± 800kV extra high voltage direct current transmission line single-end electrical quantity transient protection " proposes a kind of difference of the transient voltage wavelet energy protecting installation place to record during district's internal and external fault that utilizes to identify the method for fault; the method is without the need to the communication at circuit two ends; there is absolutely selective; but need to utilize wavelet transformation accurately to identify the wave head of the capable ripple of initial voltage, far-end high resistive fault has a negative impact to it.
" the HVDC (High Voltage Direct Current) transmission line protection philosophy based on voltage and current Sudden Changing Rate direction " utilizes the direction character failure judgement of the voltage and current Sudden Changing Rate that protection installation place, DC line both sides records when district's internal and external fault; whether this principle exceeds threshold value according to the integrated value of two kinds of fault-signals forms Protection criteria, but its performance is still by the impact of abort situation, fault resstance.
" utilizing the HVDC (High Voltage Direct Current) transmission line pilot protection new principle of current break characteristic " proposes a kind of method identifying fault according to current break direction, circuit two ends difference; and construct the identical criterion of current break; give its setting principle; the method effective cog region internal and external fault, but the adjusting of high resistive fault and its threshold value of thunder and lightning interference effect.
" protection of extra high voltage direct current transmission line transient state energy ", according to circuit two ends low frequency energy difference feature accurate cog region internal fault and fault pole, the method is simple, reliably, but needs the data stringent synchronization at circuit two ends.
" AnovelpilotdirectionalprotectionschemeforHVDCtransmissio nlinebasedonspecificfrequencycurrent " proposes a kind of current comparison pilot protection method under characteristic frequency; the method has absolute selectivity, but needs the data syn-chronization at circuit two ends equally.
" Anovelwhole-linequick-actionprotectionprincipleforHVDCtr ansmissionlinesusingone-endvoltage " and " Anewwhole-linequick-actionprotectionprincipleforHVDCtran smissionlinesusingone-endcurrent " is respectively by judging whether the integrated value of single ended voltage or one-terminal current under special frequency band exceedes setting threshold to differentiate district's internal and external fault; its quick action; but when there is the far-end fault of long transmission line, the sensitivity of protection possibly cannot meet the demands.
" the HVDC (High Voltage Direct Current) transmission line transient voltage traveling-wave protection based on wavelet transformation " carries out multiscale analysis to transient voltage on the basis of wavelet analysis; utilize the low-and high-frequency capacity volume variance establishing protective criterion of transient; can correct failure judgement, but the result of calculation of wavelet transformation is vulnerable to wavelet basis chooses and the impact of noise.
In summary, existing HVDC (High Voltage Direct Current) transmission line guard method respectively has feature, but does not have quick action, do not affect and highly sensitive method by transition resistance and thunder and lightning interference etc.
Summary of the invention
The present invention is in order to solve the problem, propose a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation, the polar character of voltage and current Sudden Changing Rate when this method analyzes DC line internal fault external fault, utilize the method for S-transformation phase angle difference to carry out the polarity of failure judgement component, and then establishing protective criterion is to identify the internal fault external fault of DC line; Utilize S-transformation to the time frequency analysis of fault-signal, extract the two poles of the earth transient voltage S-transformation zero-frequency energy and, according to ratio size identification fault pole, have fast effectively, the factors such as thunderbolt disturbance, abort situation and transition resistance almost do not affect criterion, do not need two ends data syn-chronization, highly sensitive advantage.
To achieve these goals, the present invention adopts following technical scheme:
Based on a HVDC (High Voltage Direct Current) transmission line longitudinal protection method for S-transformation, comprise the following steps:
(1) gather the voltage and current at the protection component place be connected with DC power transmission line positive and negative electrode, filtering process is carried out to it;
(2) the voltage and current Sudden Changing Rate data after extraction fault in setting-up time, carry out S-transformation to it, obtain the multiple time-frequency s-matrix of voltage and current signal;
(3) according to multiple time-frequency s-matrix, calculating voltage and the S-transformation phase angle of jump-value of current at each sampled point and the average of both phase angle differences;
(4) set up the Protection criteria of DC power transmission line, the protective device of DC line rectification side carries out based on the inside and outside Fault Identification in the district of voltage and current Sudden Changing Rate S-transformation phase angle difference;
(5) if recognition result is DC power transmission line troubles inside the sample space, rectification side protective device compares the transient state energy of the S-transformation zero-frequency band of positive and negative electrode voltage jump amount, carries out the judgement of fault pole.
In described step (2), setting-up time is 5ms.
In described step (3), calculate signal S-transformation phase angle S anconcrete mode be:
S An＝angle(S n)(1)
In formula, s athe multiple time-frequency s-matrix that [m, n] obtains through S-transformation for signal, wherein n is column vector, represents signal amplitude-frequency characteristic at a time; M is row vector, represents the time domain specification of signal under a certain frequency, and each element of matrix characterizes the amplitude information of this signal under a certain characteristic frequency of a certain sampling instant and phase angle information.
In described step (3), the S-transformation phase angle difference Δ S of calculating voltage and jump-value of current signal aiconcrete mode be:
ΔS A i = Σ n = 1 N | S AnI i - S AnU i | ‾ - - - ( 2 )
In formula, i=1 or 2, represents DC power transmission line pole 1 or pole 2, S anIiand S anUibe respectively voltage and the jump-value of current S-transformation phase angle under the n-th sampling instant on the i of pole, N is the sampling number in data window.
In described step (4), concrete Protection criteria is:
In formula, S aR, S aIbe respectively DC power transmission line and differentiate logical value at the fault direction of rectification side and inverter side;
Work as S aRs aIwhen=1, when namely rectification side and inverter side are judged as forward fault simultaneously, be identified as DC line troubles inside the sample space; Work as S aR=0 or S aIwhen=0, be defined as circuit external area error.
In described step (5), the transient state energy of the S-transformation zero-frequency band of the two poles of the earth voltage jump amount and circular be:
W m = Σ n = 1 N E ( m , n ) - - - ( 5 )
In formula, E (m, n)={ abs (S a[m, n]) } 2, represent signal after S-transformation under a certain characteristic frequency the S-transformation transient state energy of a certain sampled point, wherein, m is row vector, and n is column vector, and N is sampling number.
In described step (5), the decision method of fault pole is:
The S-transformation zero-frequency band transient state energy of the positive pole that definition bipolar line homonymy protective device installation place records and cathode voltage Sudden Changing Rate and W z1and W z2ratio be then the identical criterion of fault pole is as follows:
M > k wH, now judge that positive pole breaks down;
M < k wL, now judge that negative pole breaks down;
K wL< M < k wH, be now judged as pole-pole fault;
Wherein, k wLand k wHfor the fixing threshold of criterion.
Beneficial effect of the present invention is:
(1) polarity of S-transformation phase angle difference identification voltage and current Sudden Changing Rate is utilized, thus identification internal fault external fault, utilize the two poles of the earth voltage jump amount S-transformation zero-frequency band transient state energy and the fault pole of ratio cog region internal fault, under the sample frequency of 100kHz, only need the data window of 5ms to complete judgement, quick-action is strong;
(2) under various fault initial condition, reliably, rapidly identify fault direction, the factors such as transition resistance, thunderbolt interference and abort situation almost do not affect Protection criteria, and reliability, sensitivity are high;
(3) institute's extracting method does not need the data syn-chronization at DC power transmission line two ends, only needs inverter side to transmit the recognition result of fault direction to rectification side, less demanding to communication port;
(4) recognition methods principle is simple, clear, identifies accurately, is easy to Project Realization, has higher practical value.
Accompanying drawing explanation
Fig. 1 is that DC transmission system simplifies equivalent circuit;
Complementary network when Fig. 2 is DC line troubles inside the sample space;
Complementary network when Fig. 3 is DC line external area error;
Fig. 4 is Fault Identification theory diagram of the present invention;
Fig. 5 is ± 800kV extra high voltage direct current transmission line model;
When Fig. 6 (a) is apart from rectification side 5km place generation pole 1 metallic earthing fault, the change curve schematic diagram of the S-transformation phase angle of voltage and jump-value of current on pole 1 in the 5ms data window that rectification side records;
When Fig. 6 (b) is apart from rectification side 5km place generation pole 1 metallic earthing fault, the change curve schematic diagram of the S-transformation phase angle of voltage and jump-value of current on pole 1 in the 5ms data window that inverter side records;
When Fig. 7 (a) is for converting plant positive electrode bus generation earth fault, the S-transformation phase angle change curve of voltage and jump-value of current on pole 1 in the 5ms data window that rectification side records;
When Fig. 7 (b) is for converting plant positive electrode bus generation earth fault, the S-transformation phase angle change curve of voltage and jump-value of current on pole 1 in the 5ms data window that inverter side records.
Embodiment:
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
As shown in Figure 4, a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation, comprises the following steps:
(1) voltage and current at protection component place that is respectively extremely connected with DC power transmission line of system both sides protection Real-time Collection;
(2) by after the voltage and current filtering of collection, the voltage and current Sudden Changing Rate of 5ms after extraction fault;
(3) protection of system both sides carries out S-transformation to voltage and current Sudden Changing Rate respectively, obtains the multiple time-frequency s-matrix of each signal, asks for the S-transformation phase angle of each signal respectively, obtain the S-transformation phase angle S of voltage and current Sudden Changing Rate at each sampled point anIi, S anUi, then ask for the average of the two phase angle difference, be designated as Δ S ai;
(4) establishing protective criterion, the protection at DC line rectification side place completes the identification of the internal fault external fault based on voltage and current Sudden Changing Rate S-transformation phase angle difference;
(5) if be identified as DC power transmission line troubles inside the sample space, the protection at rectification side place is by comparing the transient state energy of the S-transformation zero-frequency band of the two poles of the earth voltage jump amount and carrying out the identification of fault pole.
In step (4), the recognition principle based on the internal fault external fault of voltage and current Sudden Changing Rate S-transformation phase angle difference is:
Be illustrated in figure 1 DC transmission system and simplify equivalent circuit, this sentences positive DC circuit is example, and negative DC circuit is similar.Z rEC, Z iNVand Z lbe respectively the equivalent impedance of rectification side, inverter side and DC line; i rand u rbe respectively electric current and the voltage of DC line M side; i iand u ibe respectively electric current and the voltage of DC line N side; For ease of analyzing, the electric current positive direction of regulation positive pole and negative pole circuit is all for pointing to transmission line by current conversion station.
Be illustrated in figure 2 complementary network during DC line troubles inside the sample space.According to principle of stacking, during the internal fault of positive DC line areas, be equivalent to and superpose a negative voltage source u in fault point f, Z rLand Z iLbe respectively installation place is protected in fault point line impedance to rectification side and inverter side; Δ u r, Δ i rwith Δ u i, Δ i ibe respectively voltage, the jump-value of current of line commutation side and inverter side protection installation place; R ffor fault earthing resistance.When in line areas, arbitrary place breaks down, have
Δu R＝-Δi RZ REC(6)
Δu I＝-Δi IZ INV(7)
Shown in formula (6) and (7), Δ u rwith Δ i rpolarity contrary, Δ u iwith Δ i ipolarity also contrary.
Be illustrated in figure 3 complementary network when breaking down outside DC line rectification side reactor.As seen from the figure:
Δu R＝Δi R(Z L+Z INV)(8)
Δu I＝-Δi IZ INV(9)
Now, Δ u rwith Δ i rpolarity identical, Δ u iwith Δ i ipolarity contrary.When breaking down outside inverter side reactor, Δ u rwith Δ i rpolarity contrary, Δ u iwith Δ i ipolarity identical.
If system generation AC fault, for DC power transmission line, this situation is equal to DC line external area error, and the polar relationship of voltage, jump-value of current is identical with during above-mentioned DC line generation external area error.
Therefore, during the internal fault of DC power transmission line generating region, the polarity of the voltage and current Sudden Changing Rate that protection installation place, both sides, fault pole detects is contrary; When external area error occurs in the side of DC power transmission line, the polarity of the voltage and current Sudden Changing Rate detected from fault point nearside protection installation place is identical, and opposite side polarity is contrary.
And utilize S-transformation can extract the phase angle information of fault component, therefore after fault, the polarity of voltage and current Sudden Changing Rate can be identified by the S-transformation phase angle difference of two signals, thus realizes the internal and external fault differentiation of DC power transmission line district.
In step (5), compare the transient state energy of the S-transformation zero-frequency band of the two poles of the earth voltage jump amount, carry out the structure of the criterion of fault pole identification:
The S-transformation zero-frequency band transient state energy of the voltage jump amount of the pole 1 that definition bipolar line homonymy protection installation place records and pole 2 and W z1and W z2ratio be now, the identical criterion of fault pole is as follows:
M > k wH, be now judged as breaking down in pole 1;
M < k wL, be now judged as breaking down in pole 2;
K wL< M < k wH, be now judged as pole-pole fault.
In above-mentioned criterion, k wLand k wHfor the fixing threshold of criterion, consider the sensitivity of protection and above-mentioned analysis, k wLvalue be 0.80, k wHvalue be 1.25.
Theoretical and simulation analysis shows, during DC line generation monopolar grounding fault, the S-transformation zero-frequency transient state energy that the extremely upper protection installation place of fault records and the S-transformation zero-frequency transient state energy that perfects pole much larger than homonymy with; Because two electrode structures of Bipolar DC power system are generally identical, when there is pole-pole fault, the zero-frequency transient state energy that the protection of two-wire line homonymy detects is with substantially identical.
Therefore, after troubles inside the sample space occurs, the M detected when route protection installation place is greater than threshold value k wHtime, judge that pole 1 is as fault pole; When M is less than threshold value k wLtime, then judge that pole 2 is as fault pole; When M between time, be judged as pole-pole fault.
In described step (4) and (5), protection installation place, system both sides for the identification process of district's internal and external fault and fault pole is:
All complete in rectification side because the switch off current after DC transmission system fault and system reboot move, therefore pilot protection only needs inverter side to transmit the recognition result of fault direction to rectification side, has been protected the identification of internal fault external fault and fault pole by rectification side.
When inverter side detects S aIwhen=0, illustrate that fault occurs in the reverse of inverter side, now regardless of the protection of rectification side to the differentiation result of fault direction, be all judged as external area error.When inverter side detects S aI=1, when namely fault occurs in the positive direction of inverter side, inverter side transmits fault direction information to rectification side, if the S of now rectification side aR=1, can troubles inside the sample space be judged as, and identify fault pole according to the identical criterion of fault pole.
When rectification side detects S aRwhen=0, showing that fault occurs in the behind of rectification side, now without the need to waiting for the differentiation result of inverter side, can Direct Recognition be external area error; When S being detected aRwhen=1, fault occurs in the positive direction of rectification side, but the fault direction the result whether inner inverter side of still needing in online road is transmitted.
In sum, only have when rectification side is identified as forward fault and receives the forward fault message of inverter side, be just finally identified as the troubles inside the sample space of DC line, and protected the identification of fault pole by rectification side.
Utilize PSCAD to build DC transmission system simulation model, simulating, verifying carried out to institute's extracting method:
1) Modling model
Simulation model according to ± 800kV Kazakhstan-Zheng extra high voltage direct current transmission line actual parameter, the bipolar direct current transmission system simulation model that utilized PSCAD to build, as shown in Figure 5.Wherein, converting plant and Inverter Station all adopt two 12 pulse wave converter valve; Circuit adopts according to frequency model, 6 divisions, total length 2190km.
As shown in Figure 5, the DC line internal fault external fault of diverse location is set in a model, to test the performance of put forward protection.Sample frequency is 100kHz herein, and the data window of S-transformation is 5ms, and the protection of system both sides calculates respectively after start-up criterion starts.
2) troubles inside the sample space emulation
A, metallicity polar region fault.Apart from the F at outlet 5km place of converting plant 1point arranges positive pole circuit and pole 1 earth fault, and transition resistance is 100 Ω.Fig. 6 (a) is depicted as the phase angle change curve of the voltage and current Sudden Changing Rate after the fault of line commutation side, pole 1 in 5ms data window.Fig. 6 (b) is depicted as the phase angle change curve of the voltage and current Sudden Changing Rate after the circuit inverter side fault of pole 1 in 5ms data window.From Fig. 6 (a), Fig. 6 (b), how the phase angle of the voltage and current Sudden Changing Rate no matter circuit both sides detect changes, and the absolute value of difference both it is all about 180 °, and table 1 is the result of calculation of circuit both sides.
Table 1F 1the simulation result of rectification side and inverter side during point failure
ΔS A1/(°) S AROr S AI W Z1/(V 2) W Z2/(V 2) M
Rectification side 173.6 1 153.1 0.5 303.2
Inverter side 182.3 1 30.5 10.0 3.05
From the data in table 1, the S-transformation phase angle difference of the voltage and current Sudden Changing Rate that rectification side protection calculation draws is 173.6 °, and inverter side is 182.3 °, and therefore the polarity of both sides voltage and current Sudden Changing Rate is contrary, S aRs aI=1, conclusion is DC line troubles inside the sample space.Again due to rectification side M=303.2>k wH=1.25, therefore judge that pole 1 is as fault pole, the differentiation result of institute's extracting method is accurate.
B, pole-pole fault.Point place arranges pole-pole fault in the line, and table 2 is the simulation result of rectification side and inverter side.
Table 2F 3the simulation result of rectification side and inverter side during point failure
ΔS A1/(°) ΔS A2/(°) W Z1/(V 2) W Z2/(V 2) M
Rectification side 186.1 174.3 335.9 347.4 0.97
Inverter side 193.2 168.5 313.0 326.5 0.96
From data in table, rectification side the two poles of the earth and inverter side the two poles of the earth all detect that voltage and current Sudden Changing Rate polarity is contrary, i.e. S aRs aI=1.Again because rectification side k wL<M=0.97<k wH, namely S-transformation zero-frequency transient state energy ratio is within threshold value, is therefore judged as pole in district-pole fault, and the differentiation result of institute's extracting method is accurate.
3) simulation and analysis of different faults initial condition
Troubles inside the sample space analysis of Influential Factors.Negative pole circuit (pole 2) troubles inside the sample space is set, investigates different faults distance, different transition resistance to the impact of Protection criteria.Fault condition and simulation result in table 3, R in table ffor fault resistance.
The simulation result of rectification side and inverter side during table 3 negative pole fault
Can be drawn by table 3 emulated data: 1. when different faults distance, different transition resistance, system both sides are the correct failure judgement direction of energy and fault pole all; 2. for the fault of same type, the S-transformation zero-frequency transient state energy calculated under different transition resistance is obvious with change, but last ratio does not affect judged result.
4) thunderbolt interference emulates with fault thunderbolt
To the F of inverter side line outlet place 10km 2point carries out the thunderbolt interference under different initial condition, fault thunderbolt emulation, and simulation result is as shown in table 4.In table, Δ S rA, Δ S iArepresent the positive pole S-transformation phase angle difference of rectification side and inverter side, S a(=S aRs aI) represent the logical calculated value that rectification side obtains.
Table 4F 2the simulation result of some thunderbolt interference fault and lightning fault
From table 4 data, under the interference of different lightning currents, the S-transformation phase angle of circuit both sides, all outside Protection criteria scope, differentiates that result is correct; If thunderbolt circuit also causes fault, the S-transformation phase angle of circuit both sides is all within Protection criteria scope, and protection is judged to be troubles inside the sample space.Simulation result shows that the method effectively can identify thunderbolt interference.
5) external area error emulation
Fault outside a, reactor.As the positive electrode bus F of converting plant 4during place's earth fault, Fig. 7 (a), Fig. 7 (b) show the S-transformation phase angle change curve that positive pole circuit both sides detect.
From Fig. 7 (a), Fig. 7 (b), for the outer fault of positive pole circuit LHA, the S-transformation phase angle change curve of the voltage and current Sudden Changing Rate that rectification side detects almost overlaps, the differential seat angle of the S-transformation phase angle change curve that inverter side detects is always about 180 °, the polar character of voltage and current Sudden Changing Rate when meeting external area error.
For transition resistance during test external area error is on the impact of criterion, equally at F 4place arranges the earth fault of different transition resistance, table 5 show detect in the both sides of both positive and negative polarity circuit voltage, jump-value of current S-transformation data and differentiate result.
Table 5F 4the simulation result of rectification side and inverter side during point failure
From table 5 simulation result, under different transition resistance, circuit both sides all correctly can detect S aR=0, S aI=1, namely fault occurs in the outside of rectification side protection installation place.Due to the effect of electromagnetic coupled, perfect pole and corresponding S-transformation phase angle also can be detected, but do not affect the judgement of fault pole internal fault external fault.
B, AC fault.Without loss of generality, this emulation is at Inverter Station ac bus F 5fault point arranges dissimilar fault, and simulation result is as shown in table 6.
Table 6F 5the simulation result of rectification side and inverter side during point failure
As seen from the results in Table 6, for the various fault types occurring in AC, criterion of carrying can correctly identify fault direction, and institute's extracting method differentiates that result is accurate.
The polar character of circuit both end voltage and jump-value of current when the present invention utilizes DC power transmission line district internal and external fault, first S-transformation is carried out to voltage and current Sudden Changing Rate, try to achieve the S-transformation phase angle difference of voltage and current Sudden Changing Rate, thus the polarity both judging, and then cog region internal and external fault, by comparing the transient state energy of the S-transformation zero-frequency band of the two poles of the earth voltage jump amount and carrying out the identification of fault pole.Simulation analysis shows, under various fault condition, the present invention all correctly can identify internal fault external fault, fault pole and thunder and lightning interference, and highly sensitive, reliability is strong.In addition, this invention only needs the data window of 5ms to calculate, quick action.
By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.

Claims (7)

1., based on a HVDC (High Voltage Direct Current) transmission line longitudinal protection method for S-transformation, it is characterized in that: comprise the following steps:
(1) gather the voltage and current at the protection component place be connected with DC power transmission line positive and negative electrode, filtering process is carried out to it;
(2) the voltage and current Sudden Changing Rate data after extraction fault in setting-up time, carry out S-transformation to it, obtain the multiple time-frequency s-matrix of voltage and current signal;
(3) according to multiple time-frequency s-matrix, calculating voltage and the S-transformation phase angle of jump-value of current at each sampled point and the average of both phase angle differences;
(4) set up the Protection criteria identifying DC transmission line area inside/outside failure, the protective device at DC line rectification side place carries out the identification of the district's internal and external fault based on voltage and current Sudden Changing Rate S-transformation phase angle difference;
(5) if recognition result is DC power transmission line troubles inside the sample space, rectification side protective device compares the transient state energy of the S-transformation zero-frequency band of positive and negative electrode voltage jump amount, carries out the judgement of fault pole.
2. a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation as claimed in claim 1, it is characterized in that: in described step (2), setting-up time is 5ms.
3. a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation as claimed in claim 1, is characterized in that: in described step (3), calculates signal S-transformation phase angle S anconcrete mode be:
S An＝angle(S n)(1)
In formula, s athe multiple time-frequency s-matrix that [m, n] obtains through S-transformation for signal, wherein n is column vector, represents signal amplitude-frequency characteristic at a time; M is row vector, represents the time domain specification of signal under a certain frequency, and each element of matrix characterizes the amplitude information of this signal under a certain characteristic frequency of a certain sampling instant and phase angle information.
4. a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation as claimed in claim 1, is characterized in that: in described step (3), the S-transformation phase angle difference Δ S of calculating voltage and jump-value of current signal aiconcrete formula be:
&Delta;S A i = &Sigma; n = 1 N | S AnI i - S AnU i | &OverBar; - - - ( 2 )
In formula, i=1 or 2, represents DC power transmission line pole 1 or pole 2, S anIiand S anUibe respectively voltage and the jump-value of current S-transformation phase angle under the n-th sampling instant on the i of pole, N is the sampling number in data window.
5. a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation as claimed in claim 1, is characterized in that: in described step (4), concrete Protection criteria is:
In formula, S aR, S aIbe respectively DC power transmission line and differentiate logical value at the fault direction of rectification side and inverter side;
Work as S aRs aIwhen=1, when namely rectification side and inverter side are judged as forward fault simultaneously, be identified as DC line troubles inside the sample space; Work as S aR=0 or S aIwhen=0, be defined as circuit external area error.
6. a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation as claimed in claim 1, is characterized in that: in described step (5), the transient state energy of the S-transformation zero-frequency band of the two poles of the earth voltage jump amount and circular be:
W m = &Sigma; n = 1 N E ( m , n ) - - - ( 5 )
In formula, E (m, n)={ abs (S a[m, n]) } 2, represent signal after S-transformation under a certain characteristic frequency the S-transformation transient state energy of a certain sampled point, wherein, m is row vector, and n is column vector, and N is sampling number.
7. a kind of HVDC (High Voltage Direct Current) transmission line longitudinal protection method based on S-transformation as claimed in claim 1, it is characterized in that: in described step (5), the decision method of fault pole is:
The S-transformation zero-frequency band transient state energy of the voltage jump amount of the positive pole that definition bipolar line homonymy protective device installation place records and negative pole and W z1and W z2ratio be now, the identical criterion of fault pole is as follows:
M > k wH, be now judged as that positive pole breaks down;
M < k wL, be now judged as that negative pole breaks down;
K wL< M < k wH, be now judged as pole-pole fault;
Wherein, k wLand k wHfor the fixing threshold of criterion.
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