CN110441659A - A kind of fault distinguishing method of HVDC transmission line - Google Patents
A kind of fault distinguishing method of HVDC transmission line Download PDFInfo
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- CN110441659A CN110441659A CN201910822232.8A CN201910822232A CN110441659A CN 110441659 A CN110441659 A CN 110441659A CN 201910822232 A CN201910822232 A CN 201910822232A CN 110441659 A CN110441659 A CN 110441659A
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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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- 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
- G01R31/088—Aspects of digital computing
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Abstract
The invention discloses a kind of fault distinguishing methods of HVDC transmission line, are related to Relay Protection Technology in Power System field.The fault distinguishing method; using the electrical quantity of rectification side and inverter side as the raw information of criterion; by the positive difference current and cathode difference current that convert and calculate compensation point on acquisition transmission line of electricity; by the multilevel iudge of difference current and setting protection threshold value, the breakdown judge of HVDC transmission line is realized；The fault distinguishing method overcomes the influence of DC power transmission line parameter distribution characteristic, interpolar coupled characteristic when differential protection judges, avoids the malfunction of differential protection, improves protection sensitivity.
Description
Technical field
The invention belongs to Relay Protection Technology in Power System fields more particularly to a kind of more compensation points of utilization to calculate differential electricity
Stream judges the method for high voltage direct current transmission line fault.
Background technique
High voltage dc transmission technology, because it is remote with transmission distance, electrical energy transportation capacity is big, the interconnection of good economy performance, multiterminal,
The advantages such as limiting short-circuit current, since nineteen fifties since Sweden's Gothland DC transmission engineering puts into operation,
It is gradually unfolded in the power system using tide.
Currently, being directed to the research of HVDC transmission system relay protection, DC grid fault transient feature is faced mostly
The problems such as equipment performances such as special, converter fault control complexity and dc circuit breaker are poor.DC transmission system failure hair
After life, relay protection is reliable, identifies fault section rapidly, accurate isolated fault point, ensures that dump power grid is steady, transient state
Stability is for a long time the criterion of DC grid Protection Technology development.Compared to conventional AC system protection, high straightening
After stream transmission system breaks down, fault current rapid increase, without natural zero-crossing point, therefore in failure selectivity, quick-action, spirit
In quick property, protection of direct current supply line will face more problems.At the same time, traditional protection for example overcurrent protection, distance protection,
Current differential protection applicability in high-voltage direct current is lower.Current differential protection of direct current electric transmission line is currently as soft straight work
Line backup protection in journey, though it can be realized DC line fault identification and fault section location in principle level, according to
It is old by transmission distance span farther out, route distribution parameter feature is obvious, current differential protection criterion is vulnerable to line distribution capacitance electricity
Stream the factors such as influences and restricts, the threshold value for needing appropriate mix and protection delay to prevent malfunction, sensitivity, quick-action be difficult by
DC grid receives.
HVDC transmission line transmission distance is remote, for the influence for avoiding line parameter circuit value distribution character, differential protection delay
Investment.Gao Shuping etc. proposes HVDC transmission line current differential protection new principle, it is disclosed that utilizing mid-point computation electricity
The HVDC transmission line Differential Protection Theory of stream, and on HVDC transmission system control characteristic analysis foundation, it gives
High and low definite value Protection criteria and threshold setting principle are gone out.Due to the influence of transmission line of electricity interpolar coupled characteristic, in midpoint electric current
It can be introduced in calculating process and perfect pole out-of-balance current, cause monopole failure to perfect polar curve road differential protection malfunction, so that having
The differential protection forfeiture of absolutely selective naturally selects pole ability, to avoid false protection, needs to improve protection threshold value, reduces
Differential protection sensitivity.
Summary of the invention
In view of the deficiencies of the prior art, the present invention provides a kind of fault distinguishing method of HVDC transmission line, utilizes
Compensation point constitutes differential current protection criterion, eliminates the influence of transmission line parameter distribution character, interpolar coupled characteristic, realizes high
Direct current transmission line fault is pressed quickly, reliably to differentiate.
The present invention is to solve above-mentioned technical problem by the following technical solutions: a kind of HVDC transmission line
Fault distinguishing method, comprising the following steps:
Step 1: obtaining the measured value of transmission line of electricity rectification side and inverter side electrical quantity respectively；
Step 2: the ground of transmission line of electricity rectification side, inverter side is respectively obtained according to the measured value of electrical quantity in the step 1
Mould electrical quantity and line mould electrical quantity；
Step 3: it is based on Transmission Line Distributed Parameter model, it is electrical according to rectification side, the ground mould of inverter side in the step 2
Amount and line mould electrical quantity seek the corresponding ground mould calculating current and line mould calculating current of rectification side at compensation point respectively, and compensate
Inverter side corresponding ground mould calculating current and line mould calculating current at point；
Step 4: according to rectification side, inverter side corresponding ground mould calculating current and line mould meter at compensation point in the step 3
It calculates electric current and respectively obtains the corresponding positive compensation point calculating current of rectification side and cathode compensation point calculating current and inverter side pair
The positive compensation point calculating current and cathode compensation point calculating current answered；
Step 5: being compensated according to the corresponding positive compensation point calculating current of rectification side, inverter side in the step 4 and cathode
Point calculating current, seeks the difference current of positive compensation point, the difference current of cathode compensation point respectively；
Step 6: compared with the difference current of compensation point positive in the step 5 is protected threshold value with setting, if it is greater than
Setting protection threshold value, then be transmission line of electricity anode troubles inside the sample space；
Compared with the difference current of cathode compensation point in the step 5 is protected threshold value with setting, protected if it is greater than setting
Threshold value is protected, then is transmission line of electricity cathode troubles inside the sample space.
Fault distinguishing method of the invention, by rectification side, inverter side electric current measured value through decoupling change get in return rectification side,
The ground mould electric current and line mould electric current of inverter side, then obtain rectification side at compensation point, inverter side corresponding ground mould calculating current and line
Then mould calculating current obtains the corresponding positive compensation point calculating current of rectification side, inverter side and cathode by decoupling inverse transformation
Thus compensation point calculating current acquires the difference current of positive compensation point and the difference current of cathode compensation point, finally by difference
Whether streaming current and setting comparing to determine for threshold value of protection occur transmission line of electricity troubles inside the sample space, eliminate transmission line parameter point
The influence of cloth characteristic avoids the malfunction of differential protection.
Further, in the step 1, rectification side electrical quantity includes the positive electrode current of rectification side, cathode voltage, cathodal current
And cathode voltage, inverter side electrical quantity include the positive electrode current of inverter side, cathode voltage, cathodal current and cathode voltage.
Further, in the step 2, electrical quantities measurement value gets the ground mould electricity of rectification side, inverter side in return through decoupling change
Tolerance and line mould electrical quantity, ground mould electrical quantity include ground mould electric current and ground mode voltage, and line mould electrical quantity includes line mould electric current and line
Mode voltage specifically decouples transformation for mula are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side, iΨ_p(t) rectification side or inverter side anode electricity are indicated
The measured value of stream, iΨ_n(t) measured value of rectification side or inverter side cathodal current, i are indicatedΨ_e(t) rectification side or inverter side are indicated
Ground mould electric current, iΨ_l(t) the line mould electric current of rectification side or inverter side is indicated；
In formula, uΨ_p(t) measured value of rectification side or inverter side cathode voltage, u are indicatedΨ_n(t) rectification side or inversion are indicated
The measured value of side cathode voltage, uΨ_e(t) the ground mode voltage of rectification side or inverter side, u are indicatedΨ_l(t) rectification side or inversion are indicated
The line mode voltage of side.
The positive electrode current and cathodal current that intercouple are decoupled into mutually independent ground mould electric current and line mould electric current, to disappear
Except the influence of transmission line of electricity interpolar coupling.
Further, in the step 3, compensation point is multiple, and the quantity of compensation point is by perfecting pole out-of-balance current
Size determine；When troubles inside the sample space occurs, reduced by the way that multiple compensation points are arranged on the transmission line compensation point with
The distance between fault point avoids to eliminate the influence of transmission line of electricity interpolar coupled characteristic and perfects pole out-of-balance current
Cause to perfect pole false protection.
Further, multiple compensation points are uniformly distributed on the transmission line, and this compensation point selection mode can guarantee defeated
When any point failure of line fault pole, the minimum range of compensation point distance fault point in same distance range, so as to
Enough effectively limitations perfect pole out-of-balance current, avoid monopolar grounding fault and perfect pole differential protection misoperation, improve differential
Protection sensitivity utmostly reduces calculation amount, promotes calculating speed.
Further, when compensation point be it is multiple, when carrying out fault distinguishing, successively from the compensation point farthest apart from rectification side
Differentiate, is troubles inside the sample space when the difference current being calculated at all compensation points is all larger than setting protection threshold.
Further, in the step 3, rectification side or inverter side corresponding ground mould calculating current or line mould calculating current
Calculation formula are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side,E, l respectively indicates ground modulus or line mould
Amount,Indicate rectification side or inverter side corresponding ground mould calculating current or line mould calculating current,Table
Show the characteristic impedance of transmission line of electricity, L0、C0Respectively indicate inductance, the capacitor of transmission line of electricity unit length, R0Indicate transmission line of electricity list
The resistance of bit length, t indicate current time,Indicate transmission time, lΨIndicate required compensation point to rectification side
Distance or inverter side distance,Indicate the ground mode voltage or line mode voltage of rectification side or inverter side,Indicate rectification
The ground mould electric current or line mould electric current of side or inverter side.
Further, in the step 4, rectification side, inverter side corresponding ground mould calculating current and line mould meter at compensation point
It calculates electric current and obtains the corresponding positive compensation point calculating current of rectification side, inverter side and cathode compensation point calculating electricity through decoupling inverse transformation
Stream, specifically decouples reconstructed formula are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side, iΨ_cal_p(t,lΨ) indicate rectification side or inverter side
Corresponding anode compensation point calculating current, iΨ_cal_n(t,lΨ) indicate that rectification side or the corresponding cathode compensation point of inverter side calculate electricity
Stream, iΨ_cal_e(t,lΨ) indicate rectification side or inverter side corresponding ground mould calculating current, iΨ_cal_l(t,lΨ) indicate rectification side or
The corresponding line mould calculating current of inverter side, t indicate current time, lΨDistance or inverter side of the compensation point required by indicating to rectification side
Distance.
Further, in the step 5, the calculating of the difference current of the difference current or cathode compensation point of positive compensation point
Formula are as follows:
|Idiff_φ|=| iR_cal_φ(t,lR)+iI_cal_φ(t,lI)|
In formula, φ=p, n, p, n respectively indicate the anode of transmission line of electricity, cathode, Idiff_φIndicate positive or negative pole compensation point
Difference current, iR_cal_φ(t,lR) indicate that the corresponding positive compensation point calculating current of rectification side or cathode compensation point calculate electricity
Stream, iI_cal_φ(t,lI) indicate the corresponding positive compensation point calculating current of inverter side or cathode compensation point calculating current, lRIt indicates to mend
Repay the distance for a little arriving rectification side, lIDistance of the expression compensation point to inverter side.
Further, in the step 6, setting protection threshold value is by power transmission line electrical parameter and rated current, guarantor
It protects safety factor and system constant current control current margins to determine, and according to system disturbance and transmission line of electricity external area error
When maximum imbalance current adjusted.
Beneficial effect
Compared with prior art, the fault distinguishing method of HVDC transmission line proposed by the present invention, with rectification side and
Raw information of the electrical quantity of inverter side as criterion obtains the differential of positive compensation point on transmission line of electricity by converting and calculating
The difference current of electric current and cathode compensation point realizes high pressure by the multilevel iudge of difference current and setting protection threshold value
The breakdown judge of DC power transmission line；The fault distinguishing method overcomes the DC power transmission line parameter point when differential protection judges
The influence of cloth characteristic, coupled characteristic avoids the malfunction of differential protection, improves protection sensitivity.
Method of discrimination of the present invention, without increasing any hardware device, practical implementation value is high.
Detailed description of the invention
It, below will be to attached drawing needed in embodiment description in order to illustrate more clearly of technical solution of the present invention
It is briefly described, it should be apparent that, the accompanying drawings in the following description is only one embodiment of the present of invention, general for this field
For logical technical staff, without creative efforts, it is also possible to obtain other drawings based on these drawings.
Fig. 1 is the schematic diagram of mesohigh DC transmission system of the embodiment of the present invention；
Fig. 2 perfects the analysis chart of pole out-of-balance current, Fig. 2 when being single compensation point differential protection in the embodiment of the present invention
It (a) be monopolar grounding fault point is compensation point, Fig. 2 (b) is that fault point is nearly rectification side monopolar grounding fault；
Positive (failure pole) is mended when Fig. 3 is nearly rectification side failure (fault point distance rectification side 0.1D) in the embodiment of the present invention
Repay point (compensation point SRApart from rectification side 0.25D), cathode (perfecting pole) compensation point (compensation point SRDifference apart from rectification side 0.25D)
Streaming current contrast simulation figure；
Positive (failure pole) is mended when Fig. 4 is nearly rectification side failure (fault point distance rectification side 0.1D) in the embodiment of the present invention
Repay point (compensation point SMApart from rectification side 0.5D), cathode (perfecting pole) compensation point (compensation point SMApart from the differential of rectification side 0.5D)
Current vs' analogous diagram；
Positive (failure pole) is mended when Fig. 5 is nearly rectification side failure (fault point distance rectification side 0.1D) in the embodiment of the present invention
Repay point (compensation point SIApart from rectification side 0.75D), cathode (perfecting pole) compensation point (compensation point SIDifference apart from rectification side 0.75D)
Streaming current contrast simulation figure；
Fig. 6 is nearly rectification side in the embodiment of the present invention, nearly inverter side fault traveling wave propagation timing diagram；
Fig. 7 is the flow chart that three compensation points carry out differential protection judgement in the embodiment of the present invention；
Fig. 8 is that (apart from rectification side 10km, metallic earthing event occurs nearly rectification side failure for anode in the embodiment of the present invention
Barrier) troubles inside the sample space differential protection simulation results figure；
Fig. 9 is point failure in transmission line of electricity in the embodiment of the present invention (cathode occurs through 300 Ω transition resistance ground faults)
Troubles inside the sample space differential protection simulation results figure；
Figure 10 is that (outside rectification side smoothing reactor, route interpolar is former for interpolar failure outside rectification lateral areas in the embodiment of the present invention
Barrier) differential protection simulation results figure；
Figure 11 is that (outside inverter side smoothing reactor, route interpolar is former for interpolar failure outside inversion lateral areas in the embodiment of the present invention
Barrier) differential protection simulation results figure；
Figure 12 is that (apart from rectification side 990km, metallic earthing event occurs nearly inverter side failure for cathode in the embodiment of the present invention
Barrier) rectification side, inverter side current simulations figure；
Figure 13 is that (apart from rectification side 990km, metallic earthing event occurs nearly inversion end failure in the embodiment of the present invention for cathode
Barrier) conventional differential current protection simulation results show figure；
Figure 14 is that (apart from rectification side 990km, metallic earthing event occurs nearly inverter side failure for cathode in the embodiment of the present invention
Barrier) differential current protection of the present invention simulation results show figure；
Wherein, 1- converting plant, 2- Inverter Station, 3- current measuring unit, 4- transmission line of electricity, 5- voltage measurement unit.
Specific embodiment
With reference to the attached drawing in the embodiment of the present invention, the technical solution in the present invention is clearly and completely described,
Obviously, described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.Based in the present invention
Embodiment, those of ordinary skill in the art's every other embodiment obtained without creative labor,
It shall fall within the protection scope of the present invention.
A kind of fault distinguishing method of HVDC transmission line provided by the present invention, comprising the following steps:
1, the measured value of transmission line of electricity rectification side and inverter side electrical quantity is obtained respectively.
As shown in Figure 1, HVDC transmission system includes converting plant 1, Inverter Station 2 and transmission line of electricity 4, in converting plant 1
With measuring unit is equipped in Inverter Station 2, measuring unit includes current measuring unit 3 and voltage measurement unit 5, is surveyed by electric current
The measured value that unit 3 obtains rectification side and inverter side electric current is measured, rectification side and inverter side voltage are obtained by voltage measurement unit 5
Measured value.Rectification side electrical quantity includes the positive electrode current of rectification side, cathode voltage, cathodal current and cathode voltage, inverter side electricity
Tolerance includes the positive electrode current of inverter side, cathode voltage, cathodal current and cathode voltage.
2, according to rectification side in step 1 or inverter side anode current measurement value and cathodal current measured value respectively through decoupling change
Get transmission line of electricity rectification side, the ground mould electrical quantity of inverter side and line mould electrical quantity in return, ground mould electrical quantity include ground mould electric current and
Ground mode voltage, line mould electrical quantity include line mould electric current and line mode voltage.
The positive electrode current and cathodal current to intercouple is transformed into mutually independent ground mould electric current and line mould electric current through decoupling,
To eliminate the influence of positive and negative anodes transmission line of electricity interpolar coupling, the specific formula of Current Decoupling transformation are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side, iΨ_p(t) rectification side or inverter side anode electricity are indicated
The measured value of stream, iΨ_n(t) measured value of rectification side or inverter side cathodal current, i are indicatedΨ_e(t) rectification side or inverter side are indicated
Ground mould electric current, iΨ_l(t) the line mould electric current of rectification side or inverter side is indicated.
The specific formula of voltage decoupling transformation are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side, uΨ_p(t) rectification side or inverter side anode electricity are indicated
The measured value of pressure, uΨ_n(t) measured value of rectification side or inverter side cathode voltage, u are indicatedΨ_e(t) rectification side or inverter side are indicated
Ground mode voltage, uΨ_l(t) the line mode voltage of rectification side or inverter side is indicated.
3, be based on Transmission Line Distributed Parameter model, according to the ground mould electrical quantity of rectification side in step 2 or inverter side (mould
Electric current, mode voltage) and line mould electrical quantity (line mould electric current, line mode voltage) seek rectification side corresponding ground mould at compensation point respectively
Inverter side corresponding ground mould calculating current and line mould calculating current at calculating current and line mould calculating current and compensation point are mended
The specific formula for calculation of rectification side or inverter side corresponding ground mould calculating current or line mould calculating current is as follows at repaying:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side,E, l respectively indicates ground modulus or line mould
Amount,Indicate rectification side or inverter side corresponding ground mould calculating current or line mould calculating current,
Indicate the characteristic impedance of transmission line of electricity, L0、C0Respectively indicate inductance, the capacitor of transmission line of electricity unit length, R0Indicate transmission line of electricity
The resistance of unit length, t indicate current time,Indicate transmission time, lΨIndicate required compensation point to rectification
The distance l of sideROr the distance l of inverter sideI,Indicate the ground mode voltage or line mode voltage of rectification side or inverter side,It indicates
The ground mould electric current or line mould electric current of rectification side or inverter side.
Compensation point is the simulated point being arranged on the transmission line, constitutes differential guarantor by the difference current at these simulated points
Criterion is protected, to judge troubles inside the sample space.The setting of compensation point on the transmission line actually refers to compensation point in positive power transmission line
Setting on road and cathode transmission line of electricity, and the compensation point on positive and negative electrode transmission line of electricity is one-to-one.For example, compensation point
SR、SM、SIActually criticize the compensation point S on extremelyR、SM、SIWith the compensation point S on cathodeR、SM、SI, positive compensation point SR、SM、
SIWith cathode compensation point SR、SM、SIPosition on positive and negative anodes transmission line of electricity is one-to-one.
Compensation point can be to be single or multiple, and single compensation point can solve the influence of transmission line of electricity distribution character, but
The influence of transmission line of electricity interpolar coupled characteristic is not can solve.Compensation point is uniformly distributed on the transmission line, and quantity is by perfecting
The size of pole out-of-balance current determines.When monopole troubles inside the sample space occurs for transmission line of electricity, by being arranged on the transmission line
To reduce the distance between compensation point and fault point, (there is phase therewith in any fault point to multiple compensation points (being greater than or equal to two)
Close compensation point), ensure that the difference current at least one sound extremely upper compensation point is less than setting protection threshold value with this, thus
It ensure that and perfect pole protection not malfunction.That is the quantity of compensation point is determined by perfecting the size of pole out-of-balance current.
Troubles inside the sample space refers to that transmission line malfunction, external area error refer to the Arbitrary Fault except protected circuit；Failure pole
Perfect pole out-of-balance current when monopole troubles inside the sample space to be not zero.
4, according to rectification side, inverter side corresponding ground mould calculating current and line mould calculating current pass through at compensation point in step 3
Decoupling inverse transformation respectively obtains the corresponding positive compensation point calculating current of rectification side and cathode compensation point calculating current and inversion
The corresponding positive compensation point calculating current in side and cathode compensation point calculating current, specifically decouple reconstructed formula are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side, iΨ_cal_p(t,lΨ) indicate rectification side or inverter side
Corresponding anode compensation point calculating current, iΨ_cal_n(t,lΨ) indicate that rectification side or the corresponding cathode compensation point of inverter side calculate electricity
Stream, iΨ_cal_e(t,lΨ) indicate rectification side or inverter side corresponding ground mould calculating current, iΨ_cal_l(t,lΨ) indicate rectification side or
The corresponding line mould calculating current of inverter side, t indicate current time, lΨDistance l of the compensation point required by indicating to rectification sideROr inversion
The distance l of sideI。
5, electricity is calculated according to the corresponding positive compensation point calculating current of rectification side in step 4 or inverter side and cathode compensation point
Stream, seeks the difference current of positive compensation point and the difference current of cathode compensation point, the calculating of compensation point difference current respectively
Formula are as follows:
|Idiff_φ|=| iR_cal_φ(t,lR)+iI_cal_φ(t,lI)| (5)
In formula, φ=p, n, p, n respectively indicate the anode of transmission line of electricity, cathode, Idiff_φIndicate positive or negative pole compensation point
Difference current, iR_cal_φ(t,lR) indicate that the corresponding positive compensation point calculating current of rectification side or cathode compensation point calculate electricity
Stream, iI_cal_φ(t,lI) indicate the corresponding positive compensation point calculating current of inverter side or cathode compensation point calculating current, lRIt indicates to mend
Repay the distance for a little arriving rectification side, lIDistance of the expression compensation point to inverter side.
6, it compared with the difference current of compensation point positive in step 5 being protected threshold value with setting, is protected if it is greater than setting
Threshold value is then transmission line of electricity anode troubles inside the sample space；By the difference current of cathode compensation point in step 5 and setting protection threshold value
Compare, protects threshold value if it is greater than setting, be then transmission line of electricity cathode troubles inside the sample space.
When there are multiple compensation points, when being differentiated since the compensation point farthest apart from rectification side, successively differentiate, In
It is troubles inside the sample space when the difference current being calculated at all compensation points is all larger than setting protection threshold.When transmission line of electricity occurs
When failure, fault traveling wave is propagated to route both ends respectively from fault point, and route both ends are installed with measuring unit, single using measurement
The electric current of the electrical quantity computing electric power line compensation point of member measurement, in turn, inverter side information is transferred to rectification by communication channel
Side constitutes differential protection criterion using the electrical quantity of rectification side and inverter side.When troubles inside the sample space occurs for failure pole, according to traveling wave
Time chart analysis is propagated it is found that multiple compensation points apart from rectification side from the distant to the near, corresponding to difference current successively is more than setting
Protection threshold value is (that is, the difference current apart from rectification side farthest compensation point is first greater than setting protection threshold value, apart from rectification side
Most nearby after the difference current of compensation point be more than setting protection threshold value, apart from rectification side compensation point distance from the distant to the near, compensation
Point difference current is greater than setting protection threshold value to rear by elder generation).Therefore, according to compensation point apart from rectification side distance, from the distant to the near
The difference current and setting protection threshold value for successively comparing compensation point, constitute differential protection process.
Setting protection threshold value (i.e. setting valve) be by power transmission line electrical parameter (for example, transmission line of electricity impedance and lead
Receive), the rated current of HVDC transmission system, protection safety factor and system constant current control current margins determine
, and adjusted according to maximum imbalance current when system disturbance and transmission line of electricity external area error.
In the present invention, setting principle is consistent, when each compensation point setting valve is all larger than system disturbance and route external area error
Maximum imbalance current.
In Fig. 1, iR_pIt (t) is measured value, the u of the positive electrode current of rectification sideR_pBe (t) measured value of rectification side cathode voltage,
iR_nIt (t) is measured value, the u of rectification side cathodal currentR_nIt (t) is the measured value of rectification side cathode voltage；iI_pIt (t) is inverter side
Measured value, the u of positive electrode currentI_pIt (t) is measured value, the i of inverter side cathode voltageI_nIt (t) is the measurement of inverter side cathodal current
Value, uI_nIt (t) is the measured value of inverter side cathode voltage, t is current time.
As shown in Fig. 2 (a), when monopole failure occur in compensation point S, do not have between rectification side, inverter side and compensation point S
There are other fault branches, the corresponding positive compensation point calculating current of rectification side, cathode compensation point calculating current are respectively iR_cal_p
(t,lR)、iR_cal_n(t,lR), the corresponding positive compensation point calculating current of inverter side, cathode compensation point calculating current are respectively
iI_cal_p(t,lI)、iI_cal_n(t,lI), utilize iR_cal_p(t,lR) and iI_cal_p(t,lI) failure pole (anode) compensation is calculated
The difference current of point S is ig, the difference current for perfecting pole (cathode) is zero.Due to the distribution of high pressure long range DC power transmission line
Parameter characteristic, distribution capacity will generate charging and discharging currents, but by Fig. 2 (a) it is found that utilizing rectification side, the corresponding compensation of inverter side
The single compensation point differential protection criterion that point calculating current is constituted is not influenced by transient state characteristics of distributed parameters.
As shown in Fig. 2 (b), when monopole fault point and compensation point are inconsistent, with nearly rectification side fault point (fault point F
Between rectification side R and compensation point S) for.There is no other fault branches between inverter side I and compensation point S, inverter side is corresponding
Positive compensation point calculating current, cathode compensation point calculating current are respectively iI_cal_p(t,lI)、iI_cal_n(t,lI)；Rectification side R with
There are fault branch, the corresponding positive electrode fault point calculating currents of rectification side, cathode fault point calculating current difference between compensation point S
For iR_cal_p(t,xR)、iR_cal_n(t,xR), xRIndicate that the distance between fault point F and rectification side R, the corresponding anode of rectification side are mended
Repay a calculating current, cathode compensation point calculating current is respectively iR_cal_p(t,lR)、iR_cal_n(t,lR).Because where the F of fault point
Failure pole, to perfect pole fault branch electric current be respectively ig, 0 (perfect pole fault-free branch, so for 0), so after the F of fault point
The actual current for including is (iR_cal_p(t,xR)、iR_cal_n(t,xR))、(ig, 0) two parts.Due to DC power transmission line interpolar coupling
Cooperation is used, during the difference current of compensation point S calculates, the fault branch electric current i of failure polegIt will be introduced into and perfect pole, this
When, compensation point S failure pole (anode), to perfect pole (cathode) difference current be respectively ig_cal_p(t,xF)、ig_cal_n(t,xF), xFTable
Show the distance between fault point F and compensation point S.
For purposes of illustration only, the present invention, which perfects pole out-of-balance current to monopolar grounding fault in a frequency domain first, carries out theoretical point
Analysis, and then simulating, verifying is carried out in the time domain.According to power transmission line electrical amount frequency-domain calculations formula, decoupling transformation and decoupling contravariant
Formula is changed, Transmission Line Distributed Parameter model, (failure pole) compensation point S, cathode (perfecting pole) the compensation point S difference of anode are based on
The theoretical calculation formula of streaming current is as follows:
Wherein, Ip_cal_diffIndicate the difference current theoretical value of positive compensation point, In_cal_diffIndicate the difference of cathode compensation point
Streaming current theoretical value, xFIndicate the distance between fault point F and compensation point S, IgFor positive (failure pole) fault branch electric current,The respectively ground of transmission line of electricity
Mould, line mould propagation coefficient, R0_e、R0_lRespectively transmission line of electricity unit length ground mould resistance, line mould resistance, L0_e、L0_lRespectively
Transmission line of electricity unit length ground mould inductance, line mould inductance, C0_e、C0_lRespectively transmission line of electricity unit length ground mould capacitor, line mould
Capacitor.
By formula (6) it is found that due to transmission line of electricity interpolar coupling influence, transmission line of electricity ground mould, line mould parameter not phase
Deng, when transmission line of electricity occur monopole failure when, perfecting pole, there are out-of-balance current In_cal_diff=Ig·[cosh(γ0_l·xF)-
cosh(γ0_e·xF)]/2, and perfect pole out-of-balance current with distance x between fault point F and compensation point SFIncrease and increase.
Although single compensation point can solve the influence of transmission line parameter distribution character, divided according to formula (6)
It analyses single compensation point not and can solve the influence of transmission line of electricity interpolar coupled characteristic, it is more to constitute to introduce multiple compensation points as a result,
The difference current criterion of compensation point realizes the fast and reliable differentiation of transmission line of electricity area internal and external fault, improves differential protection sensitivity.
Embodiment
Calculation amount and protective value in order to balance, the present embodiment is using the benefit apart from rectification side 0.25D, 0.50D, 0.75D
Repay point SR、SM、SICarry out calculating current and constitute differential protection criterion (other compensation point Choices are equally possible), D indicates power transmission line
The length on road.When the selection mode of this compensation point can guarantee transmission line malfunction pole any point failure, compensation point distance
The minimum range of fault point perfects pole out-of-balance current within the scope of 0.25D, so as to effectively limit, and avoids monopole ground connection
Failure perfects pole differential protection misoperation, improves differential protection sensitivity.Consider differential protection reliability, chooses safety factor
It is 1.4, setting protection threshold value Iop_fdFor 0.05IN, and set protection threshold value Iop_fdLess than constant current control current margins
0.1IN(INFor rated current).
Compensation point SR、SM、SIDifferential protection criterion are as follows:
Based on distributed parameter model, compensation point S is calculated according to the electrical quantity of measurement and formula (1)~(4)R、SM、SIPlace
Rectification side or the corresponding positive compensation point calculating current of inverter side and cathode compensation point calculating current, seek further according to formula (7)
The difference current of positive, cathode compensation point, as compensation point SR、SM、SIThe difference current at place is more than setting protection threshold value
When, it is determined as troubles inside the sample space.For example, positive compensation point SIDifferential protection criterion beIndicate compensation point SIThe corresponding anode compensation of the rectification side at place
Point calculating current,Indicate compensation point SIThe corresponding positive compensation point calculating current of the inverter side at place.
In formula (7),Indicate compensation point SIThe corresponding positive or negative pole compensation point of the rectification side at place calculates electricity
Stream,Indicate compensation point SIThe corresponding positive or negative pole compensation point calculating current of the inverter side at place,Indicate compensation
Point SITo the distance of rectification side,Indicate compensation point SITo the distance of inverter side；Indicate compensation point SMPlace
The corresponding positive or negative pole compensation point calculating current of rectification side,Indicate compensation point SMThe inverter side at place is corresponding
Positive or negative pole compensation point calculating current,Indicate compensation point SMTo the distance of rectification side,Indicate compensation point SMTo inversion
The distance of side；Indicate compensation point SRThe corresponding positive or negative pole compensation point calculating current of the rectification side at place,Indicate compensation point SRThe corresponding positive or negative pole compensation point calculating current of the inverter side at place,Indicate compensation point
SRTo the distance of rectification side,Indicate compensation point SRTo the distance of inverter side, Iop_fdIndicate setting protection threshold value, t expression is worked as
The preceding moment.
Compensation point SR、SM、SIDifference current contrast simulation figure it is as in Figure 3-5, by Fig. 3-5 compare it is found that simulating, verifying
It is consistent with theoretical formula (6) analysis result: when 1) transmission line of electricity anode monopolar grounding fault occurs for bipolar direct current transmission system, just
There are difference currents for pole (failure pole), simultaneously because transmission line of electricity interpolar coupling, cathode (perfecting pole) has uneven electricity
Stream；2) perfect distance dependent between the extremely upper fault point of pole out-of-balance current size and failure, compensation point, when fault point is located at route head
End, compensation point SR、SM、SIDistance successively increases between the F of fault point, and out-of-balance current is sequentially increased.
When transmission line of electricity breaks down, fault traveling wave is propagated to route both ends respectively from fault point, and specific traveling wave passes
Defeated timing diagram is as shown in fig. 6, Fig. 6 (a), 6 (b) respectively indicate the nearly rectification side of route, nearly inverter side failure, Δ tstIndicate that communication is prolonged
When, tR、tM、tIRespectively fault traveling wave reaches compensation point SR、SM、SIMoment at the latest, route both ends are installed with electrical measurement
Unit is measured, electrical quantities measurement unit includes current measuring unit and voltage measurement unit, calculates route using measurement electrical quantity and mends
Electric current a little is repaid, in turn, inverter side information is transferred to rectification side by communication channel, constitutes differential protection using both ends electrical quantity
Criterion.In view of the pilot protection communications time is about twice of traveling wave propagation time, for nearly rectification side, nearly inverter side
Failure has tI< tM< tR, i.e., close inverter side compensation point SIThe movement of differential protection criterion is rapider.
Therefore, nearly inverter side compensation point S is calculated firstIDifference current, as compensation point SIDifference stream is greater than setting protection threshold
When, calculate line build-out point SMDifference current, as compensation point SMWhen difference stream is greater than setting protection threshold, nearly rectification side compensation is calculated
Point SRDifference current, as compensation point SRWhen difference stream is greater than setting protection threshold, it is determined as transmission line of electricity troubles inside the sample space, based on distribution
Parameter model is as shown in Figure 7 using the HVDC transmission line differential protection process of more compensation point electric currents.
Simulating, verifying carried out to different faults situation (DC power transmission line troubles inside the sample space, external area error), and with tradition
Differential protecting method contrast simulation is verified as seen in figures 8-14.Wherein, the method for the invention is respectively adopted to route in Fig. 8, Fig. 9
Nearly rectification side plus earth failure, route midpoint cathode high resistance earthing fault carry out simulating, verifying；This is respectively adopted in Figure 10, Figure 11
Invention the method carries out simulating, verifying to interpolar failure outside line commutation side, inverter side line areas.As seen from Figure 8, when
Metallic earthing failure occurs for anode, and positive compensation point difference current is more than setting protection threshold, cathode compensation point SI、SMDifference
Streaming current is more than protection threshold, compensation point SRDifference current is less than setting protection threshold, therefore positive current differential protection is dynamic
Make, cathode differential protection is failure to actuate.Positive and negative electrode protection action analysis is analyzed with Fig. 8 in Fig. 9-11.Above-mentioned emulation and analysis
Show no matter in route generating region, external area error, the differential protection electric current that the method for the invention acquires can accurate judgement,
High reliablity.Figure 12-14 the method for the invention and conventional differential guard method compare simulating, verifying, wherein Tu12Wei
Fault current waveform figure, Figure 13 are the difference current simulation result of conventional differential method, and Figure 14 is the difference of the method for the invention
Streaming current simulation result.From Figure 13 and Figure 14 comparative analysis: for failure pole (cathode), conventional differential Protection criteria, sheet
The invention differential protection criterion, the difference current that the two is calculated are more than setting protection threshold, and differential protection is just
Positive motion is made；For perfecting pole (anode), due to not considering the influence of route transient state capacitance current, interpolar coupling, pass
System current differential protection is more than setting protection threshold merely with the difference current that rectification side, inverter side measurement electric current are calculated,
Differential protection misoperation, and differential current protection method of the present invention consider line parameter circuit value distribution character and interpolar coupling
The influence of characteristic constitutes joint type differential protection criterion using more compensation point calculating currents, it is defeated to avoid high pressure long range direct current
The influence of electric line distribution capacity charging and discharging currents, while significantly limiting and perfecting pole out-of-balance current, differential protection is reliable
Not malfunction.
According to the verification result of Fig. 8-14, it can be deduced that the differential current protection criterion that the method for the invention is constituted is not necessarily to
Construct high and low threshold, without the cooperation that is delayed, the transmission line of electricity time zone internal and external fault that breaks down differentiates reliable, and when monopole failure is strong
Extremely reliable not malfunction, protection sensitivity are high entirely.
A kind of fault distinguishing method of HVDC transmission line of the present invention, has the advantage that
1, using the compensation point differential current protection criterion of the method for the invention building not by the shadow of capacitance current
It rings, can be put into failure overall process, avoid differential protection misoperation, improve protection quick-action, sensitivity；
2, the more compensation point differential current protection criterions constructed using the method for the invention can be avoided transmission line of electricity hair
Perfect pole false protection when raw monopolar grounding fault, has failure and select pole ability, and Time-Series analysis is propagated according to fault wave, provide
Protection process, improves protection sensitivity.
Above disclosed is only a specific embodiment of the invention, but scope of protection of the present invention is not limited thereto,
Anyone skilled in the art in the technical scope disclosed by the present invention, can readily occur in variation or modification,
It should cover in protection scope of the present invention.
Claims (10)
1. a kind of fault distinguishing method of HVDC transmission line, which comprises the following steps:
Step 1: obtaining the measured value of transmission line of electricity rectification side and inverter side electrical quantity respectively；
Step 2: the ground mould electricity of transmission line of electricity rectification side, inverter side is respectively obtained according to the measured value of electrical quantity in the step 1
Tolerance and line mould electrical quantity；
Step 3: be based on Transmission Line Distributed Parameter model, according to rectification side in the step 2, the ground mould electrical quantity of inverter side and
Line mould electrical quantity is sought at compensation point respectively at rectification side corresponding ground mould calculating current and line mould calculating current and compensation point
Inverter side corresponding ground mould calculating current and line mould calculating current；
Step 4: according to rectification side, inverter side corresponding ground mould calculating current and line mould calculate electricity at compensation point in the step 3
Stream respectively obtains the corresponding positive compensation point calculating current of rectification side and cathode compensation point calculating current and inverter side is corresponding
Positive compensation point calculating current and cathode compensation point calculating current；
Step 5: according to the corresponding positive compensation point calculating current of rectification side, inverter side in the step 4 and cathode compensation point meter
Electric current is calculated, seeks the difference current of positive compensation point, the difference current of cathode compensation point respectively；
Step 6: compared with the difference current of compensation point positive in the step 5 is protected threshold value with setting, if it is greater than setting
Threshold value is protected, then is transmission line of electricity anode troubles inside the sample space；
Compared with the difference current of cathode compensation point in the step 5 is protected threshold value with setting, if it is greater than setting protective door
Threshold value is then transmission line of electricity cathode troubles inside the sample space.
2. fault distinguishing method as described in claim 1, which is characterized in that in the step 1, rectification side electrical quantity includes whole
Flowing the positive electrode current in side, cathode voltage, cathodal current and cathode voltage, inverter side electrical quantity includes the positive electrode current of inverter side, anode
Voltage, cathodal current and cathode voltage.
3. fault distinguishing method as described in claim 1, which is characterized in that in the step 2, electrical quantities measurement value is through decoupling
Transformation obtains rectification side, the ground mould electrical quantity of inverter side and line mould electrical quantity, and ground mould electrical quantity includes ground mould electric current and ground mould electricity
Pressure, line mould electrical quantity includes line mould electric current and line mode voltage, specifically decouples transformation for mula are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side, iΨ_p(t) rectification side or the positive electrode current of inverter side are indicated
Measured value, iΨ_n(t) measured value of rectification side or inverter side cathodal current, i are indicatedΨ_e(t) ground of rectification side or inverter side is indicated
Mould electric current, iΨ_l(t) the line mould electric current of rectification side or inverter side is indicated；
In formula, uΨ_p(t) measured value of rectification side or inverter side cathode voltage, u are indicatedΨ_n(t) indicate that rectification side or inverter side are negative
The measured value of pole tension, uΨ_e(t) the ground mode voltage of rectification side or inverter side, u are indicatedΨ_l(t) rectification side or inverter side are indicated
Line mode voltage.
4. fault distinguishing method as described in claim 1, which is characterized in that in the step 3, compensation point is multiple, and is mended
Repaying quantity a little is determined by perfecting the size of pole out-of-balance current.
5. fault distinguishing method as claimed in claim 4, which is characterized in that multiple compensation points uniformly divide on the transmission line
Cloth.
6. fault distinguishing method as claimed in claim 4, which is characterized in that when compensation point be it is multiple, carry out fault distinguishing
When, successively differentiate from the compensation point farthest apart from rectification side, the difference current being calculated at all compensation points, which is all larger than, to be set
It is troubles inside the sample space when protecting threshold surely.
7. fault distinguishing method as described in claim 1, which is characterized in that in the step 3, rectification side or inverter side are corresponding
Ground mould calculating current or line mould calculating current calculation formula are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side,E, l respectively indicates ground modulus or linear modulus,Indicate rectification side or inverter side corresponding ground mould calculating current or line mould calculating current,It indicates
The characteristic impedance of transmission line of electricity, L0、C0Respectively indicate inductance, the capacitor of transmission line of electricity unit length, R0Indicate transmission line of electricity unit
The resistance of length, t indicate current time,Indicate transmission time, lΨIndicate that required compensation point arrives rectification side
The distance of distance or inverter side,Indicate the ground mode voltage or line mode voltage of rectification side or inverter side,Indicate rectification side
Or the ground mould electric current or line mould electric current of inverter side.
8. fault distinguishing method as described in claim 1, which is characterized in that rectification side at compensation point, inverse in the step 4
Become side corresponding ground mould calculating current and line mould calculating current and obtains the corresponding anode benefit of rectification side, inverter side through decoupling inverse transformation
A calculating current and cathode compensation point calculating current are repaid, reconstructed formula is specifically decoupled are as follows:
In formula, Ψ=R, I, R, I respectively indicate rectification side, inverter side, iΨ_cal_p(t,lΨ) indicate that rectification side or inverter side are corresponding
Positive compensation point calculating current, iΨ_cal_n(t,lΨ) indicate rectification side or the corresponding cathode compensation point calculating current of inverter side,
iΨ_cal_e(t,lΨ) indicate rectification side or inverter side corresponding ground mould calculating current, iΨ_cal_l(t,lΨ) indicate rectification side or inversion
The corresponding line mould calculating current in side, t indicate current time, lΨIndicate required compensation point to rectification side distance or inverter side away from
From.
9. fault distinguishing method as described in claim 1, which is characterized in that in the step 5, the differential electricity of positive compensation point
The calculation formula of the difference current of stream or cathode compensation point are as follows:
|Idiff_φ|=| iR_cal_φ(t,lR)+iI_cal_φ(t,lI)|
In formula, φ=p, n, p, n respectively indicate the anode of transmission line of electricity, cathode, Idiff_φIndicate the difference of positive or negative pole compensation point
Streaming current, iR_cal_φ(t,lR) indicate the corresponding positive compensation point calculating current of rectification side or cathode compensation point calculating current,
iI_cal_φ(t,lI) indicate the corresponding positive compensation point calculating current of inverter side or cathode compensation point calculating current, lRIndicate compensation
Point arrives the distance of rectification side, lIDistance of the expression compensation point to inverter side.
10. fault distinguishing method as described in claim 1, which is characterized in that in the step 6, setting protection threshold value is
It is determined by power transmission line electrical parameter and rated current, protection safety factor and system constant current control current margins,
And it is adjusted according to maximum imbalance current when system disturbance and transmission line of electricity external area error.
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