CN104332968B - Current differential protection method based on HVDC transmission line - Google Patents
Current differential protection method based on HVDC transmission line Download PDFInfo
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Abstract
The invention discloses a kind of current differential protection method based on HVDC transmission line; at the both ends of high-voltage dc transmission electric wire, current transformer is set; the current transformer is acquired to the electric current at high-voltage dc transmission electric wire both ends, and the guard method comprises the following steps：After being analyzed and processed to the direct current transmission line fault pole electric signal to break down, i.e., failure DC power transmission line both sides collection current signal, recycle gained fault component current signal size analysis circuit at virtual condition；Compare the result and the size of set disturbance numerical value of current differential protection calculating, construct and reasonably differentiate.To overcome existing DC power transmission line to face transient response in Fault Identification, the problem of distribution capacity, the method for operation bring relevant interference.
Description
Technical field
The present invention relates to the research field of power system HVDC transmission line relay protection, in particular it relates to a kind of
Current differential protection method based on HVDC transmission line.
Background technology
With the development of China's science and technology, super-pressure, extra-high voltage DC transmission system have obtained extensive fortune in China
With having built up, a plurality of ± 800kV extra high voltage direct current transmission lines under preparation, nothing will be played for China's future electrical energy transportation
Alternative tremendous contribution.In order to ensure above-mentioned line security plays consistently efficiency, it is necessarily required to corresponding reliable relay and protects
Protect to escort.
Due to history reason, restricted by factors such as technology, techniques, control and protection is divided each other unlike ac transmission
The dependent failure of the characteristics of opening, be separate, i.e. straight-flow system sometimes has to eliminate by power flowcontrol.It is special just because of it
Different operation mechanism and control mode, cause the interruption of service of correlation.The DC transmission system to have been put into operation according to China is matched somebody with somebody
Standby relay protection is mainly derived from the fact that ABB AB and SIEMENS companies, therefore involved traditional relay protection herein
It is main to include with the main protection of the compositions such as traveling-wave protection, differential under-voltage protection and with structures such as current differential protection, under-voltage protections
Into back-up protection, be consequently formed the relatively complete relay protection system of DC power transmission line.
The characteristics of traveling-wave protection, is to efficiently utilize the transient fault propagated laterally from trouble point when failure occurs
Traveling wave, reach the purpose for differentiating nature of trouble.The state that each company is reflected when using the characteristic of traveling wave will be different, because
This also embodies micro difference in actuation time, antijamming capability and failure-resilient resistance etc..But traveling-wave protection is most
Big defect is that reliability is poor, is easily influenceed by outside electromagnetic interference, particularly the influence of the disturbing factor such as thunder and lightning, often
Generation false protection can be guided；Secondly, it is whole in failure-resilient resistance, failure resolution sensitivity and protection also to embody traveling-wave protection
It is fixed etc. that there is unsurmountable principle defect；Finally, its acquisition rate and measurement accuracy to data is proposed
Higher technical requirements.
The characteristics of differential under-voltage protection, is that the change for the differential calculation result and actual magnitude for how obtaining voltage is determined
Amount determines the action situation of protection, and it is both the main protection of DC power transmission line, undertakes the back-up protection effect of traveling-wave protection again.
Its responsiveness is slightly later than traveling-wave protection, particularly as differential under-voltage protection, can be exited in traveling-wave protection, voltage change
Rate is not enough to play dependent interaction during starting protection.But failure-resilient resistance ability is low, failure screens poor sensitivity and shortage must
It is its main weakness to want theories integration.
The characteristics of low-voltage variation, is to detect to determine protection act working voltage amplitude position, and it actually makes
The not high and theoretical research also relative deficiency with rate.Low-voltage variation mainly includes circuit and pole controls two kinds, and the former setting valve is relative
It is higher, it act after will start circuit reset routine, and the latter then act after by locking failure pole, therefore beyond circuit protect
The category of shield.It should be in the case where traveling-wave protection, differential under-voltage protection not be moved and current differential protection has little time action
Play its defencive function.But its subject matter be to adjust shortage according to, without direction recognition function and responsiveness still
It is slower etc..
The characteristics of conventional current differential protection, is the topological structure regardless of DC line, and it is exhausted can to ensure that it has
To failure screen selectivity.But extra long distance line distribution capacitance is not accounted in the algorithm and power flowcontrol is in
The influence of high-frequency harmonic, also lack exchange differential protection set by braking amount balance, therefore can only by heighten action threshold or
Person increases the reliability for waiting delay to wait two methods to ensure related protection.Related do can be avoided by heightening action threshold
Caused influence is disturbed, but also reduces the sensitivity of failure examination simultaneously.Delay is waited to be disturbed by increasing
The sensitive effect for screening failure after decay, but the speed protected will be reduced substantially.Actual act speed relatively exchanges differential protection
It is slow many, wait delay to reach second level according to analysis.Due in the regulation process of direct current transportation, power electronics control
Reaction speed relatively faster, therefore repeatedly triggers the action of pole control low-voltage variation and the protection of maximum Trigger Angle, causes locking failure
Pole, circuit therefore O＆M accident as forced outage；Meanwhile the differential protection can hardly screen high resistive fault.
In addition to above-mentioned all is protected, accordingly proposed always according to ripe practical experience in AC system some
Kind other protection schemes, such as electric current transverse differential protection and circuit distance protection, and according to power is presented in direct current transportation
Swing to phenomenon, directional element applicability etc. widely available achievement in research.Because principle also all be present in above-mentioned protection
Limitation, therefore can only be as the miscellaneous function item of back-up protection or a certain protection.
Relay protection often lacks tight qualitative analysis conclusion and believable quantitative estimation result, therefore has to rely on
Analytical conclusions based on ideal model, adjusting for actual adjustment protection is gone by experiment simulation checking, does not differentiate boundary clearly
Limit and nargin is screened, while the target analyzed is excessively dull, lacks relevance and comparative, once the electric letter of any of which one
Number measuring state change all can serious distortion protection overall performance, therefore relay protection-especially in direct current transportation
In-being delayed just turns into a kind of indispensable compensatory device.
In summary, there is following defect in prior art：Existing relay protection often lacks tight qualitative analysis knot
By with believable quantitative estimation result, therefore have to rely on the analytical conclusions based on ideal model, verified by experiment simulation
Adjusting for actual adjustment protection is gone, without clearly resolution boundary and screens nargin, while the target analyzed is excessively dull, lacks
Relevance and comparative, once the measuring state of one electric signal of any of which change all can serious distortion protection it is whole
Body performance.
The content of the invention
It is an object of the present invention in view of the above-mentioned problems, propose a kind of current differential based on HVDC transmission line
Guard method, to overcome existing DC power transmission line to face transient response, distribution capacity, method of operation institute in Fault Identification
The problem of bringing relevant interference.
To achieve the above object, the technical solution adopted by the present invention is：
A kind of current differential protection method based on HVDC transmission line, set at the both ends of high-voltage dc transmission electric wire
Current transformer, the current transformer are acquired to the electric current at high-voltage dc transmission electric wire both ends, and the guard method includes
Following steps：
Step 1: after being analyzed and processed to the direct current transmission line fault pole electric signal to break down, i.e. failure
DC power transmission line both sides collection current signal, recycle gained fault component current signal size analysis circuit residing for
In virtual condition；
Step 2：The result and the size of set disturbance numerical value, construction for comparing current differential protection calculating are reasonably sentenced
Not.
Preferably, the step 2 compare current differential protection calculating result with it is set disturb numerical value size it is specific
For：
After grid collapses, measured on the both ends current transformer of protected circuit and obtain current failure component
Data；After corresponding protection is triggered, the out-of-balance current result corresponding to external area error will necessarily pass through the delay of setting
Cycle and startup threshold filter out；Troubles inside the sample space acquired results contrast, two kinds of failure acquired results can ensure to obtain can
By distinguishing, following distinguishing rule thus can be built：
|f(Δim+Δin) | ＞ Iset
In formula, Δ imWith Δ inThe sampled current value at DC power transmission line both ends, I are represented respectivelysetFor line current mutual inductance
Maximum uneven full dose current data of the device secondary side measurement in longer integration/sampled value obtained by accumulative and period.
Preferably, above-mentioned discrimination formula is specially：
When circuit both sides sampled value fault component with it is ultrashort when the current differential that carries out calculate and meet：
In formula, I 'setIt is that line current transformer secondary side is measured in extremely short integration/sampled value obtained by accumulative and period
Maximum imbalance fault current weight data；T '=5ms be sampled value current differential it is ultrashort when the time of integration；mK1I′set
In m be within the time of integration corresponding current signal sampled data points；K1For the real number more than 1, to screen urgent shape
The safety factor of state；K is the time multiple for repeating integral and calculating, and it is the integer more than or equal to 1.
Preferably, above-mentioned discrimination formula is specially：
Meet when the current differential that circuit both sides power frequency fault component is carried out with the delay of power frequency multiple calculates：
In formula, I "setAdopted for the measurement of line current transformer secondary side obtained by normal, in general integration/accumulative and period
The maximum imbalance fault current weight data of sample value；T "=20ms is the time of integration of sampled value current differential power frequency period；
mK2Is″etIn m be within the time of integration corresponding current signal sampled data points；K2For the real number more than 1, to screen
The safety factor of general state；K is the time multiple for repeating integral and calculating, and it is the integer not less than 1.
Preferably, it is 3~5 for the span of the k.
Preferably, above-mentioned discrimination formula is specially：The electric current carried out when circuit both sides sampled value fault component is with overlength
Differential calculate meets：
In formula, I " 'setIt is that line current transformer secondary side is measured in longer integration/sampled value obtained by accumulative and period
Maximum imbalance fault current weight data；When T " '=100-1000ms is the integration of sampled value current differential ultra-delay
Between；mK3IT″′setIn m be sampled data points corresponding within the time of integration；K3It is general to screen for the real number more than 1
The safety factor of state；K is the time multiple for repeating integral and calculating, and it is the integer more than or equal to 1.
Preferably, above-mentioned discrimination formula is specially：Under certain special method of operation, fault component cannot ensure stabilization
Obtain, increase a current differential calculating formula during electric current full dose overlength：
In formula, I4 setIt is that line current transformer secondary side is measured in longer integration/sampled value obtained by accumulative and period
Maximum uneven full dose current data；T4For electric current full dose overlength when differential time of integration, in order to formula (3) protection structure
Good cooperation, typically requires T4＞ T " '；mK3I4 setIn m be sampled data points corresponding within the time of integration；K4For
Real number more than 1, k are the time multiples for repeating integral and calculating, and it is the integer more than or equal to 1.
Technical scheme has the advantages that：
Technical scheme, the current signal according to obtained by circuit form intrinsic state change characteristic, reference
The electric distributed constant feature of transmission line of electricity, know the target signature for distinguishing its state and calculate function.Using based on integration/tired
The examination characteristic of meter and current differential protection algorithm constructs the integrated configuration improvement project of super high voltage direct current electricity transmission line protection.
To overcome, existing DC power transmission line faces transient response in Fault Identification, distribution capacity, the method for operation bring correlation
The problem of interference.Protection seting and the threshold of action according to corresponding to being set the rate request of protection act, thus structure can
The mutually coordinated protection seting with power electronics control beat, and it is relatively complete in responsiveness, sensitivity etc. formation
Configuration.
Below by drawings and examples, technical scheme is described in further detail.
Brief description of the drawings
Fig. 1 a are the sampled value fault component electric state relation external fault line principle frame described in the embodiment of the present invention
Figure；
Fig. 1 b are the sampled value fault component electric state relation internal fault line principle frame described in the embodiment of the present invention
Figure；
Fig. 2 is the line principle block diagram of the sampled value full dose electric state relation described in the embodiment of the present invention；
Fig. 3 is the line principle block diagram of sampled value load component electric state relation；
Fig. 4 reflects delay time with acting the corresponding pass of threshold by each differential relaying algorithm described in the embodiment of the present invention
System's figure.
Embodiment
The preferred embodiments of the present invention are illustrated below in conjunction with accompanying drawing, it will be appreciated that described herein preferred real
Apply example to be merely to illustrate and explain the present invention, be not intended to limit the present invention.
Specific embodiment is：
Step 1：The direct current transmission line fault pole electric signal to break down is analyzed and processed and then utilized
Virtual condition at the size analysis circuit of gained fault component current signal.When fault component current signal obtained by circuit
Amplitude it is bigger, the state of corresponding circuit is more serious, only shorten protection act time delay, it is ensured that accurately and timely identify
Failure, and reduce and damaged caused by failure.
By the established Equivalent Physical concept in transmission line of alternation current and its computational methods, with reference to HVDC transmission line
Actual motion feature, obtain the time-domain calculation form that current integration/accumulative sum is respectively held in protected area.
When HVDC transmission system and its relevant device break down or disturbed, according to the electric net of linear iteraction
The characteristics of network, DC line respectively hold electric current and by according to reflected DC component and the situations of each harmonic component on the line
In the obvious equivalency transform of present condition and linear iteraction relation, can thus obtain more clearly differentiating that conclusion is used to screen respectively
The failure of type.
Step 2：The result and the size of set disturbance numerical value, construction for comparing current differential protection calculating are reasonably sentenced
Not.
After grid collapses, total energy, which measures, on the both ends current transformer of protected circuit obtains current failure point
The data of amount, and it is able to ensure that the startup threshold that can be more than related protection.After corresponding protection is triggered, external area error institute
Corresponding out-of-balance current result will necessarily be filtered out by the delay cycle and startup threshold rationally set；Obtained by troubles inside the sample space
As a result contrast, two kinds of failure acquired results can ensure reliably to be distinguished.Thus following criterion can be built：
|f(Δim+Δin) | ＞ Iset (1)
The comprehensive embodiment of protecting effect relaying configuration shown in formula (1).After the protection of setting is activated, above-mentioned criterion expires
During sufficient operation condition, internal fault can be reliably judged to, is exactly event outside area at the time of above-mentioned criterion no longer meets operation condition
Barrier or system disturbance, the determination of system running state can effectively improve the overall performance of protection.
The conclusion made according to qualitative analysis, the time-domain calculation method of multi-form current differential protection is respectively started.
When transmission line of electricity promotes the increment of above-mentioned phase induced current effectively to measure for some reason, you can poor to start corresponding temporal current
Dynamic protection algorism.
When circuit both sides sampled value fault component with it is ultrashort when the current differential that carries out calculate and meet：
In formula, I 'setIt is that line current transformer secondary side is measured in extremely short integration/sampled value obtained by accumulative and period
Maximum imbalance fault current weight data；T '=5ms be sampled value current differential it is ultrashort when the time of integration；mK1I′set
In m be within the time of integration corresponding current signal sampled data points；K1For the real number more than 1, to screen urgent shape
The safety factor of state；K is the time multiple for repeating integral and calculating, and it is the integer more than or equal to 1；Integration/accumulative and formula electricity
Flowing differential protection is.
Formula (2) algorithm compares the algorithm of Traditional DC transmission line of electricity current differential protection：|Δim(t)+Δin(t) | ＞
Iset, the calculating link of integration/accumulative sum is added, there is certain filter effect, can effectively reduce same period out-of-balance current
Amplitude, the relative sensitivity for improving protection.Thus the criterion formula (2) of established protection act, you can with suitable for high pressure
The DC power transmission line demand that relay protection is screened in the case of the state of emergency, mainly for the short circuit of high current at protection exit
Failure.
Meet when the current differential that circuit both sides power frequency fault component is carried out with the delay of power frequency multiple calculates：
In formula, I "setAdopted for the measurement of line current transformer secondary side obtained by normal/in general integration/accumulative and period
The maximum imbalance fault current weight data of sample value；T "=20ms is the time of integration of sampled value current differential power frequency period；
mK2I″setIn m be within the time of integration corresponding current signal sampled data points；K2For the real number more than 1, to screen
The safety factor of general state；K is the time multiple for repeating integral and calculating, and it is the integer not less than 1, in order to meet that state is discriminated
Other to need with the good delay of other protection structures to coordinate simultaneously, it is 3~5 that can generally take k values.
Formula (3) algorithm has longer integration/accumulative and calculating time, and its low-pass filter effect is stronger, therefore in failure
Formula (2) is substantially better than in the sensitivity of examination, and both form good cooperation in terms of protection act speed.Formula (3) is calculated
Method compensate for the defects of Traditional DC transmission line of electricity current differential protection just, be adapted to transmission line of electricity completely in general state
In the case of the demand screened of relay protection, and the most important foundation of innovation achievement of the present invention.
Equally, the current differential carried out when circuit both sides sampled value fault component is with overlength, which calculates, to be met：
In formula, I " 'setIt is that line current transformer secondary side is measured in longer integration/sampled value obtained by accumulative and period
Maximum imbalance fault current weight data；When T " '=100-1000ms is the integration of sampled value current differential ultra-delay
Between；mK3I″′setIn m be sampled data points corresponding within the time of integration；K3It is general to screen for the real number more than 1
The safety factor of state；K is the time multiple for repeating integral and calculating, and it is the integer more than or equal to 1；Instantaneous value current differential
Protect and be for Traditional DC transmission line of electricity current differential protection algorithm, integration/accumulative and formula current differential protection.
Equally, formula (4) algorithm compares the algorithm of Traditional DC transmission line of electricity current differential protection：|Δim(t)+Δin(t)|
＞ Iset, add the calculating link of integration/accumulative sum.This innovatory algorithm can effectively reduce each current component amplitude attenuation
And influenceed caused by nonstoichiometric oxide, thus not only there is certain filter effect, equally can also substantially reduce the same period
The amplitude of out-of-balance current, the relative sensitivity for improving protection；And by the increased above-mentioned calculation of institute can be very
It is reduced significantly protection delay time.Thus the criterion formula (4) of established protection act, possesses the energy of higher fault-resistant resistance
Power, go for the HVDC transmission line demand that relay protection is screened under microvariations state status completely.
Under certain special method of operation (such as during reclosing), fault component cannot ensure that stabilization obtains, this
Current differential calculating formula during invention one electric current full dose overlength of increase：
In formula, I4 setIt is that line current transformer secondary side is measured in longer integration/sampled value obtained by accumulative and period
Maximum uneven full dose current data；T4For electric current full dose overlength when differential time of integration, in order to formula (4) protection structure
Good cooperation, typically requires T4＞ T " '；mK3I4 setIn m be sampled data points corresponding within the time of integration；K4For
Real number more than 1, to screen the safety factor of general state.
The sharpest edges of formula (4) current differential protection algorithm are have load component on the formula that its current differential calculates
Effect, improve the stability and reliability of differential calculating, be adapted to DC power transmission line relay under mild state and protect
Protect the demand of stable detection.The characteristics of for temporal current full dose differential protection, the integral algorithm of formula (4) eliminates from principle
Various adverse effects caused by power electronics regulation and control, it is unstable to export smaller brought load component including regulation and control electric energy
Influence etc., merge These characteristics, eventually become the main feature that the present invention innovates.In order to protected with formula (3) protection
Form good cooperation on operation time limit, the shortest time interval of formula (4) integration need one definitely more than formula (3) it is fixed when
Between the cycle, it is general it is contemplated that suitably extending several 20mS cycles again.
The algorithm of above-mentioned four kinds of current differential protections：The fault component based differential protection protection carried out when ultrashort can quickly isolate tight
The serious short trouble that anxious state is reflected, the fault component based differential protection protection carried out that is delayed with power frequency multiple can isolate general shape
Short trouble corresponding to state, play a part of quick main protection, and the fault component based differential protection protection carried out during overlength can be isolated
The minor failure that microvariations state is applicable, turn into the II segmentation unit relay protections with the time limit, the differential protection of full dose is made
For the back-up protection of above-mentioned all protections, the modular relay protection system of complete HVDC transmission line is thus formed.Should
All running environment especially suitable for DC transmission system are protected, form seamless, round-the-clock protection element.
Under the extra-high straightening of kilometer of ± 800kV length more than 2000 from Jiuquan to Xiangtan, Hunan Province is newly planned with national grid
It is the research that target carries out modular relay protection integrated configuration to flow transmission system.As illustrated in figs. 1A and ib, m, n generation respectively
Table Jiuquan and Xiangtan, Hunan Province, both sides are equipped with device current transformer, and line current signal passes through after current transformer obtains
Sampling keeps, with after A/D conversions, being sent to microcomputer main system, and can be directly according to the result of sampled value fault component electric current sum
Determine whether internal fault occurs.
(in analysis voltage distribution relation, the influence of line distribution capacitance can be ignored) according to shown in Fig. 1 a and Fig. 1 b,
With trouble point virtual voltage u 'FFor reference, characteristic of the analysis DC power transmission line in area's internal and external fault, according to linear iteraction
Principle, the feelings of DC component and related higher harmonic components are likely to occur when occurring abnormal according to DC power transmission line
Condition, u 'FIt can be expressed as：
In formula, U0For involved DC Steady component；KTIt is the ratio of direct current transient state component and DC Steady component；k0
For the damping time constant of direct current transient state component；f1For work frequency；I is the whole secondary multiple of the higher hamonic wave in this failure；i
∈ Φ are the set for being related to all high frequency harmonic components of this failure；UiFor effective amplitude of i higher harmonic components；For i times
The initial phase of harmonic component；kiFor the damping time constant of i order harmonic components.
According to shown in Fig. 1 a, when running into external area error, the voltage of circuit both sides can be presented qualitatively as：
Parameter in formula (7) is as shown in Figure 1a.D represents the length of protected circuit；Consider extra long distance direct current transportation
The influence of line distribution capacitance, if capacitance per unit length is c, so for external area error, the result of calculation of current differential protection
It is exactly the capacitance current of circuit, estimates according to lumped parameter model：
Formula (8) is brought into formula (2) it can be found that because the time interval of integration/accumulative sum is most short, therefore can only ensure to filter
Except part high frequency harmonic components, therefore result of calculation has higher out-of-balance current, influences the sensitivity screened to failure, this
Kind algorithm may be only available for the short trouble of high current.
Formula (8) is brought into formula (3) it can be found that due to the time interval proper extension of integration/accumulative sum, therefore can be protected
Card filters out the constant all whole secondary high frequency harmonic components of amplitude, effectively reduces out-of-balance current, improves the spirit of failure examination
Sensitivity, go for the short trouble of normal condition.
Formula (8) is brought into formula (4) it can be found that because the time interval or delay time of integration/accumulative sum are most long, because
This can ensure to overcome by amplitude change and nonstoichiometric oxide bring the influence of out-of-balance current, and failure is screened sensitive
Degree is further lifted, and is particularly adapted to the short trouble of weak pattern system.
Equally, according to shown in Fig. 1 b, when running into troubles inside the sample space, the voltage of circuit both sides can be presented qualitatively as：
The result of calculation of current differential protection be exactly circuit capacitance current and fault current and：
Line distribution capacitance electric current is effectively decayed in integration/accumulative and calculating, it should be noted that failure electricity
Stream.Transient fault electric current is relatively difficult to analyze, and stable fault currents can use DC line rated voltage UECome with related resistors
Description：
When ignoring line distribution capacitance electric current, the result of calculation of current differential protection with formula (11) fault resstance value with
Abort situation and respective change, and it is relevant with system operation mode.So, according to the result of formula (11) and formula (2)-formula (4)
Protection threshold value contrast after can determine by corresponding current differential protection algorithm starting tripping.
For the current differential protection algorithm of full dose shown in Fig. 2, Fig. 3 and formula (5), can be divided into according to linear iterative method
Two parts of fault component and load component.For DC power transmission line, the current differential protection of load component can be defined as：
imL(t)+inL(t)≈0 (12)
Therefore, the characteristic of full dose current differential protection algorithm can be retouched with the current differential protection of fault component completely
State.
As shown in figure 4, the failure removal sequential of transmission line of electricity, t1Moment breaks down for transmission line of electricity, t2Moment is failure
The action setting time of current differential calculating, t are carried out when component is ultrashort3Moment is that the delay of fault component power frequency multiple carries out electric current
The action setting time of differential calculating, t4The action setting time of current differential calculating, t are carried out when moment is fault component overlength5
The action setting time that current differential calculates when moment is full dose overlength.When transmission line malfunction, (the generation moment is t=t1) hair
After life, i.e. t1＜ t ＜ t2When, the obtained threshold value highest of equivalent action is now converted, is in mainly for transmission line of electricity
The examination of failure under the state of emergency, related action delay time are determined on the basis of 5mS, are completed when judging and are determined to protect
After whether acting, terminate the calculating of correlation.Work as t2＜ t ＜ t3When, the foundation of now determination action threshold value depends primarily on really
The minimum out-of-balance current requirement protected required for power frequency multiple delaying current differential protection, and the reference mesh of other protection contrasts
Mark, the examination of failure under general state is in mainly for transmission line of electricity；Ibid, the related action delay time is determined with 20mS
On the basis of, after judging completion and determining whether protection acts, situation is same as above.Work as t3＜ t ＜ t4When, now convert
The equivalent action threshold value arrived will be significantly lower than the former, and the examination of failure under microvariations state is in mainly for transmission line of electricity,
The related action delay time determines substantially to be much larger than 20mS.Work as t4＜ t ＜ t5When, now convert obtained equivalent action door
Threshold value will be minimum, and the examination of failure under mild state is in mainly for transmission line of electricity, and the current differential as full dose is protected
Shield brings the action delay time of correlation most long.According to the qualitative analysis of above-mentioned acting characteristic it is recognised that working as system
Operation is under any one mode, all at least ensures have more than one specific protected modes to be adapted to, and in reality
Guarantee to overcome to greatest extent the influence of out-of-balance current in, it is ensured that the reliability of protection and sensitivity, thus structure
Into the improvement project for going out a kind of modular protection integrated configuration of HVDC transmission line.
The inventive method is in super, extra high voltage direct current transmission line actual motion, the fault component according to caused by failure
The electric variation characteristic of the intrinsic periodicity of electric current, the numerical value conversion of analysis current model essence and physical link feature, propose one
Kind is based on integration/accumulative and current differential protection transmission line malfunction property discriminating method, the action door of current differential protection
Sill and protection time delayses it is closely related, institute do not influenceed in this approach by other factorses outside state, while this method and
The control method of existing DC power transmission line can get along amiably and peacefully, complementary use, can effectively improve reliability and the spirit of protection
Sensitivity.It is expected to the effective means as the modular nature of trouble identification of super-pressure long range DC power transmission line novel intelligent.
, should on the basis that high-performance computer is protected, wide frequency domain digital communication and intelligent electronic mutual inductance treatment technology are increasingly mature
Method has a good application prospect.
Finally it should be noted that：The preferred embodiments of the present invention are the foregoing is only, are not intended to limit the invention,
Although the present invention is described in detail with reference to the foregoing embodiments, for those skilled in the art, it still may be used
To be modified to the technical scheme described in foregoing embodiments, or equivalent substitution is carried out to which part technical characteristic.
Within the spirit and principles of the invention, any modification, equivalent substitution and improvements made etc., it should be included in the present invention's
Within protection domain.
Claims (5)
1. a kind of current differential protection method based on HVDC transmission line, electricity is set at the both ends of high-voltage dc transmission electric wire
Current transformer, the current transformer are acquired to the electric current at high-voltage dc transmission electric wire both ends, it is characterised in that the protection
Method comprises the following steps：
Step 1: after being analyzed and processed to the direct current transmission line fault pole electric signal to break down, i.e., failure is straight
The current signal of transmission line of electricity both sides collection is flowed, at the size analysis circuit for recycling gained fault component current signal
Virtual condition；
Step 2：Compare the result and the size of set disturbance numerical value of current differential protection calculating, construct and reasonably differentiate；Institute
State step 2 compare current differential protection calculating result with it is set disturb numerical value size be specially：
After grid collapses, measured on the both ends current transformer of protected circuit and obtain the number of current failure component
According to；After corresponding protection is triggered, the out-of-balance current result corresponding to external area error will necessarily pass through the delay week of setting
Phase and startup threshold filter out；Troubles inside the sample space acquired results contrast, two kinds of failure acquired results can ensure to obtain reliably
Distinguish, thus can build following discrimination formula：
|f(Δim+Δin) | ＞ Iset
In formula, Δ imWith Δ inThe sampled current value at DC power transmission line both ends, I are represented respectivelysetFor line current transformer two
Maximum uneven full dose current data of the secondary side measurement in longer integration/sampled value obtained by accumulative and period；Above-mentioned differentiation is public
Formula is specially：
When circuit both sides sampled value fault component with it is ultrashort when the current differential that carries out calculate and meet：
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In formula, I 'setMeasured for line current transformer secondary side in extremely short integration/sampled value obtained by accumulative and period most
Large unbalance fault component current data；T '=5ms be sampled value current differential it is ultrashort when the time of integration；mK1I′setIn m
For the sampled data points of the corresponding current signal within the time of integration；K1, can for screen the state of emergency for the real number more than 1
By coefficient；K is the time multiple for repeating integral and calculating, and it is the integer more than or equal to 1.
2. the current differential protection method according to claim 1 based on HVDC transmission line, it is characterised in that on
Stating discrimination formula is specially：
Meet when the current differential that circuit both sides power frequency fault component is carried out with the delay of power frequency multiple calculates：
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In formula, I "setIt is that the measurement of line current transformer secondary side integrates/sampled value obtained by accumulative and period in normal, in general
Maximum imbalance fault current weight data；T "=20ms is the time of integration of sampled value current differential power frequency period；
mK2I″setIn m be within the time of integration corresponding current signal sampled data points；K2For the real number more than 1, to screen
The safety factor of general state；K is the time multiple for repeating integral and calculating, and it is the integer not less than 1.
3. the current differential protection method according to claim 2 based on HVDC transmission line, it is characterised in that institute
The span for stating k is 3~5.
4. the current differential protection method according to claim 1 based on HVDC transmission line, it is characterised in that on
Stating discrimination formula is specially：The current differential carried out when circuit both sides sampled value fault component is with overlength, which calculates, to be met：
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In formula, I " 'setMeasured for line current transformer secondary side in longer integration/sampled value obtained by accumulative and period most
Large unbalance fault component current data；T " '=100-1000ms is the time of integration of sampled value current differential ultra-delay；
mK3I″′setIn m be sampled data points corresponding within the time of integration；K3For the real number more than 1, to screen general state
Safety factor；K is the time multiple for repeating integral and calculating, and it is the integer more than or equal to 1.
5. the current differential protection method according to claim 1 based on HVDC transmission line, it is characterised in that on
Stating discrimination formula is specially：Under certain special method of operation, fault component cannot ensure that stabilization obtains, and increase an electric current
Current differential calculating formula during full dose overlength：
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In formula, I4 setThe maximum in longer integration/sampled value obtained by accumulative and period is measured for line current transformer secondary side
Uneven full dose current data；T4For electric current full dose overlength when differential time of integration, mK3I4 setIn m be within the time of integration
Corresponding sampled data points；K4For the real number more than 1, to screen the safety factor of general state；K is to repeat integral and calculating
Time multiple, it is integer more than or equal to 1.
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| CN104979807A (en) * | 2015-06-25 | 2015-10-14 | 国家电网公司 | High voltage direct current transmission line current differential protection integrated configuration method |
| CN109599835B (en) * | 2018-10-29 | 2020-04-17 | 全球能源互联网研究院有限公司 | Power protection method and equipment for FACTS device |
| CN111812456B (en) * | 2020-07-02 | 2022-10-21 | 国网江苏省电力有限公司检修分公司 | Power transmission line fault positioning method, device and system |
| CN112803478B (en) * | 2021-01-05 | 2021-10-29 | 湖南大学 | Active injection type single-end protection method for micro-grid based on phase polarity characteristics |
| CN115356586A (en) * | 2022-08-01 | 2022-11-18 | 北京四方继保工程技术有限公司 | Double-end time synchronization method and system for power transmission line |
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