CN107069682A - A kind of HVDC transmission line back-up protection method based on DC control system - Google Patents
A kind of HVDC transmission line back-up protection method based on DC control system Download PDFInfo
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- CN107069682A CN107069682A CN201710304839.8A CN201710304839A CN107069682A CN 107069682 A CN107069682 A CN 107069682A CN 201710304839 A CN201710304839 A CN 201710304839A CN 107069682 A CN107069682 A CN 107069682A
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The present invention relates to a kind of HVDC transmission line back-up protection method based on DC control system, belong to Relay Protection Technology in Power System field.DC control side can produce different responses when different zones break down in high-voltage direct current, using failure during transverter Trigger Angle ɑ, inverter shut-off angle γ, the difference of two end valve sides to direct current outlet region flow Δ IreWith Δ IinvVariation characteristic can accurately distinguish out internal fault external fault, transverter Trigger Angle ɑ responses can identify rectification side fault in ac transmission system and to pole line fault, inverter side shut-off angle γ can identify inverter side fault in ac transmission system, and introduce valve side to the difference stream signal delta I in direct current outlet regionreWith Δ IinvTo recognize valve side to outlet zone fault.Reliability of Microprocessor of the present invention is high, quick action, and anti-transition resistance ability is strong, can meet far-end fault.There is important references meaning for the configuration of actual high-voltage DC transmission engineering line backup protection.
Description
Technical field
The present invention relates to a kind of HVDC transmission line back-up protection method based on DC control system, belong to electric power
System relay protection technical field.
Background technology
At present, China's power system has been realized on national network, remote, large capacity transmission.The year two thousand twenty is expected, I
The DC transmission engineering that state builds will account for 60% up to 50 remainders, wherein extra-high voltage direct-current transmission engineering.Due to DC transmission line
Road voltage class is high, and geographical environment is complicated along the line, thus its probability broken down is also very high, has badly influenced direct current transportation
The security and stability of system.
At present, the main protection scheme of DC power transmission line includes traveling-wave protection, differential under-voltage protection, DC differential protection
Deng[5], but its core technology then mainly rested in a small number of external manufacturer's hands, and protection structure principle, adaptive setting are according to then
It is still undisclosed, cause China's DC transmission system relaying configuration and adjust, in terms of protection device upgrading usually in passive
Situation, so that being caused on China's alternating current-direct current series-parallel connection safe stability of power system level significantly influences.
HVDC transmission system typically using differential under-voltage protection and vertical even differential protection as back-up protection, but differential
The acting characteristic for criterion that under-voltage protection is under-voltage and the factor such as transition resistance and DC control system parameter are closely related;Longitudinal differential
Protect controlled systematic influence larger and in order to hide external area error, its action delay is up to 1.1s.
The content of the invention
After a kind of HVDC transmission line based on DC control system
DC control side can produce different responses when different zones break down in standby guard method, high-voltage direct current, utilize event
The difference stream variation characteristic in transverter Trigger Angle, inverter shut-off angle and two end valve sides to direct current outlet region can be accurate during barrier
Internal fault external fault is distinguished, so as to quickly and accurately be acted to troubles inside the sample space.
The technical scheme is that:
A kind of HVDC transmission line back-up protection method based on DC control system, is concretely comprised the following steps:
(1) in straight-flow system the outlet of rectification side direct current to the region of inverter side direct current outlet be HVDC transmission line,
The failure occurred in this region is troubles inside the sample space, and protection act, remaining failure is external area error, and protection is failure to actuate;
(2) in real time monitoring rectification side and inverter side difference stream signal, rectification side difference stream signal be rectifying valve at electric current with
Rectification side direct current outlet difference between currents, are designated as Δ Ire;The difference stream signal of inverter side is electric current and inverter side direct current at inversion valve
Outlet difference between currents, are designated as Δ Iinv;The electricity for hindering for some reason and producing in DC transmission system is detected with the two difference stream signals
Free component is flowed, as Δ IreOr Δ IinvMore than difference stream protection act electric current threshold value Iset, then illustrate have in DC transmission system
Failure is produced, and starts back-up protection, starts Trigger Angle α criterions after protection blocking terminates to determine whether the area of failure generation
Domain;
(3) by blocking time tsLocking after, start α criterions, the method for discrimination of α criterions is:
Rectification side Trigger Angle α sampled value is extracted by the pole control units of measurement of DC transmission system, by sampled value with setting
Fixed threshold value αsetIt is compared, if sampled value α<αsetInvalid, judgement belongs to external area error, and protection resets;If so, then
Start γ criterions to determine whether the region of failure generation;
(4) method of discrimination of γ criterions is:
Units of measurement is controlled by pole and extracts the sampled value that inverter side turns off angle γ, by sampled value and the threshold value γ of settingset
It is compared, if sampled value γ>γsetIt is invalid, then judge category external area error, protection resets;If so, start difference stream criterion
To determine whether the region of failure generation;
(5) difference stream criterion method of discrimination is:
To difference stream Δ IreWith Δ IinvSampled, judge difference stream Δ Ire>IsetWith Δ Iinv>IsetWhether set up, Ren Heyi
Formula is set up, and can determine whether failure is respective regions failure, belongs to external area error, and protection resets;Such as two formulas are all invalid, then are determined as area
Internal fault.
Step (3) the blocking time tsJudgement is specially:
To avoid the interference of decay free component that non-linear element after failure produces to each physical quantity, at the same with system master
Protection cooperation, blocking time t is set after protection startss, take free component to decay to the time used in zero and escape main protection institute
With numerical value in the time, one greatly is used as blocking time ts。
The action setting valve α of step (3) the α criterionssetSetting program be:
Actual parameter based on DC transmission system builds simulation model, in the rectification side alternating current circuit of analogue system and right
Failure under various extreme cases is set on polar curve road, system rectification side Trigger Angle in the case of obtaining various extreme failures is emulated and goes out
Existing maximum αmax, adjust αset=k1αmax, k1For safety factor.
The action setting valve γ of step (4) the γ criterionssetSetting program be:
Failure under setting various extreme cases on the inverter side alternating current circuit of analogue system, emulation obtains various extreme
The maximum γ that inverter side shut-off angle occurs in the case of failuremax, adjust γset=k2γmax, k2For safety factor.
Step (5) it is described difference stream criterion setting scheme be specially:
Blocking time tsAfter end, the free component of non-linear element release decays to 0 substantially, and the interference of free component is made
With disappearance, if this time difference stream signal delta IreOr Δ IinvStill above setting valve, illustrate that failure betides difference stream signal protection
In region, that is, rectifying valve or inversion valve, to direct current outlet region, this region belongs to outside protection zone, therefore protection resets;If
Difference stream signal is less than setting valve, then judges that failure is betided in HVDC transmission line, protection act.
The present invention principle be:
1st, protection domain
Protection scope of the present invention is DC power transmission line total length, and circuit is event outside the area for need identification with exterior domain
Barrier, is broadly divided into:To pole line fault, rectification side fault in ac transmission system, inverter side fault in ac transmission system, rectification side outlet event
Barrier, 5 kinds of inverter side outlet failure.
2nd, protection starts
Straight-flow system is broken down, and back-up protection should not be influenceed quickly by fault distance, transition resistance and fault type
Accurately start.It can all cause system electrical amount to be mutated by institute is faulty, cause each non-thread hence into electromagnetic transient
Property element release free component, and Δ IreWith Δ IinvThe signal of difference stream criterion comes from smoothing reactor two ends electric current, and electromagnetism is temporary
Smoothing reactor repeated charge will bring the obvious difference stream signal in decay concussion during state, and difference stream signal is to system
Each failure is difficult to be influenceed by fault distance and transition resistance, therefore this programme is using actuated type of the difference stream signal as back-up protection
Number.Judge both sides difference stream Δ Ire>IsetOr Δ Iinv>IsetWhether set up, such as set up, then start this back-up protection, in protection blocking
Start Trigger Angle α criterions after end;It is such as invalid, then continue to detect electrical quantity.
Δ I in formulare、ΔIinvRespectively rectifying valve side is to the outlet of sending end direct current and inversion valve side to receiving end direct current outlet
Difference stream signal IsetFor difference stream protection act electric current threshold value, Iset=k1I0, k1For safety factor, I0For troubles inside the sample space locking knot
Higher value in both sides difference stream signal after beam.
3rd, protection blocking
The free component of electromagnetic transient makes electrical quantity acutely shake, and concussion process is lasting for about 300ms, this concussion pair
Adjusting for this back-up protection brings very big interference, freely divides so back-up protection scheme should set related block signal to avoid
Amount.Occur in view of straight-flow system after commutation failure, commutation failure diagnosis should be carried out by straight-flow system and be moved by related protection
Make, therefore back-up protection scheme should set related block signal with commutation failure protection to be coordinated.Due to needing and changing
Mutually unsuccessfully protection cooperates, and will cause back-up protection deferred action, delay time is determined by commutation failure Diagnostic Time, typically
For 200ms or so.The blocking time of back-up protection should take larger in both one, so during the locking of back-up protection scheme
Between take ts=300ms.
4th, Trigger Angle α criterions
When symmetric fault occurs for rectification side AC system, rectification side is rapid under Given current controller effect to be reduced α angles to press down
DC current processed declines, and rectification side, which is finally run on, determines αminControl;Event during symmetrical short-circuit failure occurs for rectification side AC system
Hindering characteristic is:α=αmin=5 °.
When unbalanced fault occurs for rectification side AC system, rectifier exports DC current by continued jitters and then caused straight
Side control mode is in Given current controller and determines α for streamminControl room constantly switching then causes α angles constantly to be fluctuated, and its minimum value is α
=αmin=5 °, maximum αmaxDetermined by fault type, failure spy during asymmetry short circuit fault occurs for rectification side AC system
Property is:α angles are in α=αmin=5 ° to αmaxBetween continued jitters.
Short trouble moment, the increase of rectification side DC current occur for DC line and inverter side DC current reduces.Rectification
Side increases sharply α angles to suppress DC current in the presence of Given current controller.When not considering transition resistance influence, current limiting low-voltage
Link starts effect, and DC current setting valve follows DC voltage and reduced, and rectification side, which is finally run on, determines electric current (minimum current
Limitation) control, fault characteristic during DC line short trouble stable state is:α>αN。
It is similar when the variation tendency at α angles is with this pole line fault due to circuit coupling effect to pole line fault, but width
Degree is very different.
This method recognizes rectification side fault in ac transmission system using Trigger Angle α and to pole line fault.It is single by pole control measurement
Rectification side Trigger Angle α sampled value is extracted in position, judges sampled value α<αsetWhether set up, such as set up, can determine whether failure is rectification
Side fault in ac transmission system or to pole DC line fault, belongs to external area error, and protection resets;It is such as invalid, then start γ criterions.
α in formulasetFor the action setting valve of α criterions, αset=k2αmax, k2For safety factor, αmaxFor rectification side AC system
Each failure and the maximum occurred to Trigger Angle α in electrode systems failure.
5th, angle γ criterions are turned off
When symmetric fault occurs for inverter side AC system, inverter side is always to determine the control of γ angles, in inverter side ac bus
γ angles are caused to reduce in the presence of voltage reduction, to fall amplitude excessive due to inverter side alternating voltage, has determined hold-off angle control device
The error between γ angles setting valve and actual value can not be eliminated, causes γ angles to be less than its rated value.Inverter side AC system occurs
Fault characteristic during symmetrical short-circuit failure is:γ < γN。
When unbalanced fault occurs for inverter side AC system, inverter side control mode and γ angles actual value variation tendency with it is inverse
Become identical during the symmetric fault of side.Inverter side ac bus occur asymmetry short circuit fault when fault characteristic be:γ<γN。
When short trouble occurs for DC line, inverter side is converted to Given current controller by determining the control of γ angles, and in low pressure limit
Reduce current setting in the presence of stream link, and inverter side is run on minimum current limitation, now, the fixed electricity of inverter side
Stream controller setting valve has reduced, and the β angles of output have increased when more normally running, and inverter side DC current reduces and β angles
Increase will have increased when will all cause shut-off angle γ more normally to run.Failure spy during asymmetry short circuit fault occurs for DC line
Property is:γ>γN。
This method distinguishes inverter side fault in ac transmission system using with shut-off angle γ.By pole, control units of measurement extracts inversion
Side turns off angle γ sampled value, judges sampled value γ<γsetWhether set up, such as set up, can determine whether that failure exchanges system for inverter side
System failure, belongs to external area error, and protection resets;Such as invalid, startup difference stream criterion.
γ in formulasetFor the action setting valve of γ criterions, γset=k3γmax, k3For safety factor, γmaxFor inversion top-cross
The maximum that angle γ occurs is turned off in each failure of streaming system.
6th, difference stream criterion
After blocking time terminates, the free component of non-linear element release decays to 0 substantially, judges difference stream signal delta Ire<
IsetWith Δ Iinv<IsetWhether set up, such as both do not set up entirely, then failure betides both sides outlet region, as all set up, occurs
In in area, protection act.
The beneficial effects of the invention are as follows:
1st, this method turns off angle γ to recognize inverter side fault in ac transmission system using inverter side, without electric using transient state
Amount, it is to avoid transient state electrical quantity controlled systematic influence after failure and make the insecure problem of action;
2nd, this protection should be able to be in 300ms or so action messages.Direct current longitudinal difference protection is mainly for detection of distal end high resistance ground
Failure, but its action delay is for up to 1.1s.Thus compared with direct current longitudinal difference protection, this operating time of protection is substantially improved;
3rd, rectification side Trigger Angle α and shut-off angle γ actions trend are hardly influenceed by fault distance;This protection is using whole
Stream side Trigger Angle α and shut-off angle γ reduce influence of the fault distance to protection reliability as criterion.
Brief description of the drawings
Fig. 1 is the wide ± 800kV system for ultra-high voltage transmission model of medium cloud of the embodiment of the present invention and failure modes figure;F1 in figure~
F6 represents troubles inside the sample space, to pole line fault, rectification side outlet failure, inverter side outlet failure, rectification side AC system respectively
Failure, inverter side fault in ac transmission system;
ɑ criterions action situation map when Fig. 2 is different transition resistances of the invention;
γ criterions action situation map when Fig. 3 is different transition resistances of the invention;
Rectification side difference stream criterion Δ I when Fig. 4 is different transition resistances of the inventionreAct situation map;
Inverter side difference stream criterion Δ I when Fig. 5 is different transition resistances of the inventioninvAct situation map;
Fig. 6 be different faults of the present invention apart from when ɑ criterion action situation maps;
Fig. 7 be different faults of the present invention apart from when γ criterion action situation maps;
Fig. 8 be different faults of the present invention apart from when rectification side difference stream criterion Δ IreAct situation map;
Fig. 9 be different faults of the present invention apart from when inverter side difference stream criterion Δ IinvAct situation map.
Embodiment
With reference to the accompanying drawings and detailed description, the invention will be further described.
Embodiment 1:A kind of HVDC transmission line back-up protection method based on DC control system, specific steps
For:
(1) in straight-flow system the outlet of rectification side direct current to the region of inverter side direct current outlet be HVDC transmission line,
The failure occurred in this region is troubles inside the sample space, and protection act, remaining failure is external area error, and protection is failure to actuate;
(2) in real time monitoring rectification side and inverter side difference stream signal, rectification side difference stream signal be rectifying valve at electric current with
Rectification side direct current outlet difference between currents, are designated as Δ Ire;The difference stream signal of inverter side is electric current and inverter side direct current at inversion valve
Outlet difference between currents, are designated as Δ Iinv;The electricity for hindering for some reason and producing in DC transmission system is detected with the two difference stream signals
Free component is flowed, as Δ IreOr Δ IinvMore than difference stream protection act electric current threshold value Iset, then illustrate have in DC transmission system
Failure is produced, and starts back-up protection, starts Trigger Angle α criterions after protection blocking terminates to determine whether the area of failure generation
Domain;
(3) by blocking time tsLocking after, start α criterions, the method for discrimination of α criterions is:
Rectification side Trigger Angle α sampled value is extracted by the pole control units of measurement of DC transmission system, by sampled value with setting
Fixed threshold value αsetIt is compared, if sampled value α<αsetInvalid, judgement belongs to external area error, and protection resets;If so, then
Start γ criterions to determine whether the region of failure generation;
(4) method of discrimination of γ criterions is:
Units of measurement is controlled by pole and extracts the sampled value that inverter side turns off angle γ, by sampled value and the threshold value γ of settingset
It is compared, if sampled value γ>γsetIt is invalid, then judge category external area error, protection resets;If so, start difference stream criterion
To determine whether the region of failure generation;
(5) difference stream criterion method of discrimination is:
To difference stream Δ IreWith Δ IinvSampled, judge difference stream Δ Ire>IsetWith Δ Iinv>IsetWhether set up, Ren Heyi
Formula is set up, and can determine whether failure is respective regions failure, belongs to external area error, and protection resets;Such as two formulas are all invalid, then are determined as area
Internal fault.
Step (3) the blocking time tsJudgement is specially:
To avoid the interference of decay free component that non-linear element after failure produces to each physical quantity, at the same with system master
Protection cooperation, blocking time t is set after protection startss, take free component to decay to the time used in zero and escape main protection institute
With numerical value in the time, one greatly is used as blocking time ts。
The action setting valve α of step (3) the α criterionssetSetting program be:
Actual parameter based on DC transmission system builds simulation model, in the rectification side alternating current circuit of analogue system and right
Failure under various extreme cases is set on polar curve road, system rectification side Trigger Angle in the case of obtaining various extreme failures is emulated and goes out
Existing maximum αmax, adjust αset=k1αmax, k1For safety factor.
The action setting valve γ of step (4) the γ criterionssetSetting program be:
Failure under setting various extreme cases on the inverter side alternating current circuit of analogue system, emulation obtains various extreme
The maximum γ that inverter side shut-off angle occurs in the case of failuremax, adjust γset=k2γmax, k2For safety factor.
Step (5) it is described difference stream criterion setting scheme be specially:
Blocking time tsAfter end, the free component of non-linear element release decays to 0 substantially, and the interference of free component is made
With disappearance, if this time difference stream signal delta IreOr Δ IinvStill above setting valve, illustrate that failure betides difference stream signal protection
In region, that is, rectifying valve or inversion valve, to direct current outlet region, this region belongs to outside protection zone, therefore protection resets;If
Difference stream signal is less than setting valve, then judges that failure is betided in HVDC transmission line, protection act.
Embodiment 2:As shown in figure 1, ± 800kV extra-high voltage direct-current transmission models.In the model, the specified work(of direct current conveying
Rate is 5000MW, and rated current is 3125A, rectification side:The voltage of AC system is 525kV, short-circuit ratio SCR=2.5/840, nothing
Work(compensation capacity is 3000Mvar, and DC filter is 12/24/36 three-tuned filter, per pole convertor unit using 2 12 arteries and veins
Dynamic transverter is connected in series composition, and the voltage of series connection is allocated by ± (400+400) kV.The reactive compensation capacity of inverter side is
3040Mvar, other parameters are consistent with rectification side.DC power transmission line total length is 1500km (Practical Project is 1418km), control
System processed is set up according to international conference on large HV electric systems tissue (CIGRE) direct current transportation standard test system.
As shown in figure 1, f1~f6 regions are counted after occurring various failures to each criterion, 1- tables 4 are the results are shown in Table.
Time difference stream signal statistics occur for failure under 1 f1 of table~various failures in f6 regions
Fault type | f1 | f3 | f4 |
Ire1,2/p.u. | 0.004 | 0.1 | 0.003 |
Iinv1,2/p.u. | 0.004 | 0.001 | 0.1 |
Locking terminates rear poor stream signal statistics under table 2 f1, f3, f4 area fault
Fault type | f1 | f2 | F5 three-phase shortcircuits | F5 single-phase short circuits | F5 line to line fault | F5 line to line fault is over the ground |
αmax/° | 90 | 36 | 5 | 47 | 45 | 25 |
Locking terminates the maximum Data-Statistics that rear α occurs under the various failures in f1, f2, f5 region of table 3
Fault type | f1 | F6 three-phase shortcircuits | F6 single-phase short circuits | F6 line to line fault | F6 line to line fault is over the ground |
γmax/° | 90 | 18 | 36 | 31 | 27 |
Locking terminates the maximum Data-Statistics that rear γ occurs under the various failures in f1, f6 region of table 4
When being adjusted to criterion, it is necessary to assure any this set of failure protection scheme occurs outside area all without malfunction.
So should be on the basis of the failure least easily recognized outside area when adjusting.For start-up criterion, it should be ensured that institute is faulty
It can start, for α criterions, it should be ensured that can recognize that institute is faulty in f2 and f5 regions;For γ criterions, it should be ensured that can know
Institute is faulty in other f6 regions;For difference stream criterion, it should be ensured that can recognize that institute is faulty in f3, f4 region;In summary, α
α in criterion settingmaxShould take in f2 and f5 regions the α angles maximum that may export of faulty middle control system;Its is whole for γ criterions
Definite value should according in f6 regions it is faulty in the γ angles maximum γ that is likely to occurmaxAdjusted;Difference stream criterion setting value meter
Calculating should be on the basis of failure blocking time at initial stage be considered, the difference stream maximum being likely to occur during according to f1 short troubles carries out whole
It is fixed.Adjust and the results are shown in Table 5.
Each criterion setting value of table 5
Illustrate, imitate so that positive pole circuit midpoint 0.1s occurs through 20 Ω, 100 Ω and 200 Ω short troubles respectively as an example
True result is shown in Fig. 7.
From Fig. 2-5, this protection can correct operation when transition resistance is 20 Ω, 100 Ω and 200 Ω.Rectification side is touched
The action degree for sending out angle α and shut-off angle γ is on a declining curve with the increase of transition resistance, and it reaches the time adjusted
It increased, but after locking terminates, be all higher than setting valve and keep stable;Transition resistance limits short circuit to a certain extent
The free component of electric current, thus both sides difference stream amplitude and die-away time will reduce with the increase of transition resistance, and in locking
After end, both sides difference stream criterion stablize with 0 near.In addition, herein by a large amount of emulation, having obtained sheet during DC line fault
" critical " transition resistance of each criterion correct operation of back-up protection is all higher than 300 Ω.
Away from being illustrated exemplified by 100km, 600km, 1400km the positive pole circuit metallic earthing failure of M ends when 0.1s, imitate
True result is as shown in Figure 8.
From Fig. 6-9, during apart from M ends 100km, 600km, 1400km positive pole circuit metallic short circuit failure, this protection
Can correct operation.But with the increase of fault distance, the order harmonic components duration of failure DC voltage at initial stage 2 gradually increases
Greatly, but failure locking at initial stage terminate after be reduced near 0;Rectification side Trigger Angle α and shut-off angle γ action trend hardly by
The influence of fault distance;Fault distance is more remote, rectification side difference stream criterion be down to 0 nearby the required time it is longer, and inverter side is poor
Flow the time required to criterion is down to 0 nearby then with the increase first increases and then decreases of fault distance.
Table 4 gives in Fig. 1 that f2~f6 is under the conditions of different transition resistances and abort situation, this protection act situation.By
Table 4 understands that propose DC line back-up protection remains to action message in distal end high resistance earthing fault herein, while considering protection
Blocking time, data transmission period and Protection criteria calculate the time, and this protection should be able to be in 300ms or so action messages.Direct current is indulged
Difference protection is mainly for detection of distal end high resistance earthing fault, but its action delay is for up to 1.1s.Thus with direct current longitudinal difference protection
Compare, this operating time of protection is substantially improved.
Protection act situation during the difference transition resistance of table 6
Above in association with accompanying drawing to the present invention embodiment be explained in detail, but the present invention be not limited to it is above-mentioned
Embodiment, can also be before present inventive concept not be departed from the knowledge that those of ordinary skill in the art possess
Put that various changes can be made.
Claims (5)
1. a kind of HVDC transmission line back-up protection method based on DC control system, it is characterised in that:Methods described
Concretely comprise the following steps:
(1) outlet of rectification side direct current is HVDC transmission line to the region of inverter side direct current outlet in straight-flow system, is occurred
Failure in this region is troubles inside the sample space, and protection act, remaining failure is external area error, and protection is failure to actuate;
(2) difference of monitoring rectification side and inverter side flows signal in real time, and the difference stream signal of rectification side is electric current and rectification at rectifying valve
Side direct current outlet difference between currents, are designated as Δ Ire;The difference stream signal of inverter side is electric current and inverter side direct current outlet at inversion valve
Locate difference between currents, be designated as Δ Iinv;The electric current for hindering for some reason and producing in DC transmission system is detected with the two difference stream signals certainly
By component, as Δ IreOr Δ IinvMore than difference stream protection act electric current threshold value Iset, then illustrate faulty in DC transmission system
Produce, start back-up protection, start Trigger Angle α criterions after protection blocking terminates to determine whether the region of failure generation;
(3) by blocking time tsLocking after, start α criterions, the method for discrimination of α criterions is:
Rectification side Trigger Angle α sampled value is extracted by the pole control units of measurement of DC transmission system, by sampled value and setting
Threshold value αsetIt is compared, if sampled value α<αsetInvalid, judgement belongs to external area error, and protection resets;If so, then start
γ criterions with determine whether failure occur region;
(4) method of discrimination of γ criterions is:
Units of measurement is controlled by pole and extracts the sampled value that inverter side turns off angle γ, by sampled value and the threshold value γ of settingsetCarry out
Compare, if sampled value γ>γsetIt is invalid, then judge category external area error, protection resets;If so, start difference stream criterion to enter
The region that one step failure judgement occurs;
(5) difference stream criterion method of discrimination is:
To difference stream Δ IreWith Δ IinvSampled, judge difference stream Δ Ire>IsetWith Δ Iinv>IsetWhether set up, any formula into
Vertical, can determine whether failure is respective regions failure, belongs to external area error, and protection resets;Such as two formulas are all invalid, then are determined as event in area
Barrier.
2. the HVDC transmission line back-up protection method according to claim 1 based on DC control system, it is special
Levy and be:
Step (3) the blocking time tsJudgement is specially:
To avoid the interference of decay free component that non-linear element after failure produces to each physical quantity, at the same with system main protection
Coordinate, blocking time t is set after protection startss, take free component to decay to the time used in zero and escape main protection institute's used time
Between in big one of numerical value be used as blocking time ts。
3. the HVDC transmission line back-up protection method according to claim 1 based on DC control system, it is special
Levy and be:
The action setting valve α of step (3) the α criterionssetSetting program be:
Actual parameter based on DC transmission system builds simulation model, in the rectification side alternating current circuit of analogue system and to polar curve
Failure under various extreme cases is set on road, and emulation obtains what system rectification side Trigger Angle in the case of various extreme failures occurred
Maximum αmax, adjust αset=k1αmax, k1For safety factor.
4. the HVDC transmission line back-up protection method according to claim 1 based on DC control system, it is special
Levy and be:
The action setting valve γ of step (4) the γ criterionssetSetting program be:
Failure under setting various extreme cases on the inverter side alternating current circuit of analogue system, emulation obtains various extreme failures
In the case of inverter side shut-off angle occur maximum γmax, adjust γset=k2γmax, k2For safety factor.
5. the HVDC transmission line back-up protection method according to claim 1 based on DC control system, it is special
Levy and be:
Step (5) it is described difference stream criterion setting scheme be specially:
Blocking time tsAfter end, the free component of non-linear element release decays to 0 substantially, and the interference effect of free component disappears
Lose, if this time difference stream signal delta IreOr Δ IinvStill above setting valve, illustrate that failure betides the region of difference stream signal protection
It is interior, that is, rectifying valve or inversion valve, to direct current outlet region, this region belongs to outside protection zone, therefore protection resets;If difference stream
Signal is less than setting valve, then judges that failure is betided in HVDC transmission line, protection act.
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