CN105655977B - Earthing protection method for stator based on third harmonic voltage variable quantity differential principle - Google Patents
Earthing protection method for stator based on third harmonic voltage variable quantity differential principle Download PDFInfo
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- CN105655977B CN105655977B CN201610168740.5A CN201610168740A CN105655977B CN 105655977 B CN105655977 B CN 105655977B CN 201610168740 A CN201610168740 A CN 201610168740A CN 105655977 B CN105655977 B CN 105655977B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
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Abstract
The invention discloses a kind of earthing protection method for stator based on third harmonic voltage variable quantity differential principle; the Sustainable use neutral point third harmonic voltage variable quantity through the corrected generator terminal third harmonic voltage variable quantity of real-time regulation coefficient with synthesizing differential voltage and brake voltage; and differential differentiation is carried out, it can effectively distinguish the normal fluctuation of Stator ground fault and generator third harmonic voltage.Assistant criteria sets the braking threshold value of floating according to high-pressure side third harmonic voltage variable quantity, avoids the malfunction caused by main transformer high-pressure side third harmonic voltage changes.The present invention improves the sensitivity of Large-scale machine set third harmonic voltage stator single phase ground fault protection, and reduce protection is influenceed by unit operation change.
Description
Technical field
The present invention relates to a kind of earthing protection method for stator based on third harmonic voltage variable quantity differential principle, belong to hair
Motor stator one-phase ground protection technical field.
Background technology
The stator ground-fault currents of high-rating generator are larger, more serious to stator core scaling loss, easily trigger phase fault
Or turn-to-turn short circuit, serious threat unit it is safe for operation.Conventional stator ground fault protection mainly has injected type stator ground protection
With double frequency stator ground fault protection.
Injected type stator ground protection has more application in Large-scale machine set, and its advantage is obvious, can direct measurement ground connection electricity
Resistance, sensitivity is consistent in theory and shuts down unaffected.But the protection needs a set of extra supply-injected, cost is higher, and
Manufacturer personnel on site correcting process is complicated when protection device puts into operation, and the working characteristics that ground connection becomes secondary side current transformer is generating electricity
Still need to improve during machine working conditions change.These unfavorable factors limit the all-round popularization of injected type stator ground protection.
Double frequency stator ground fault protection is protected by zero-sequence fundamental voltage and formed with third harmonic voltage protection.Zero-sequence fundamental voltage
Protect simple and reliable, but dead band near neutral point be present.The type of third harmonic voltage protection is more, can react neutral point
Neighbouring earth fault, but it is relatively low in the middle part sensitivity of stator winding or even dead band be present.By fundamental wave zero sequence during actual use
Voltage principle is combined with third harmonic voltage principle and realizes 100% stator ground fault protection.Because double frequency stator ground fault protection is former
Reason is simple, and cost is low, and protective value is reliable, and the generator protection of dual is at least a set of to select double frequency stator grounding to protect
Shield.
For Large-scale machine set, the sensitivity of zero-sequence fundamental voltage protection is easily influenceed by unit direct-to-ground capacitance, if generator unit
Direct-to-ground capacitance is larger, and the low sensitivity region of zero-sequence fundamental voltage protection will be existing near neutral point to expansion in the middle part of winding
Third harmonic voltage, which is protected to be engaged with zero-sequence fundamental voltage protection, can run into the problem of sensitivity is inadequate.Therefore, protected in microcomputer
Protect under the background that performance improves constantly, the stator ground fault protection of third harmonic voltage principle is still evolving, and proposes more Gao Ling
The stator ground fault protection scheme of sensitivity is necessary.
The content of the invention
Purpose：It is engaged to solve zero-sequence fundamental voltage protection with the protection of traditional third harmonic voltage applied to large scale computer
Under-sensitive problem during group, the present invention propose that a kind of stator grounding based on third harmonic voltage variable quantity differential principle is protected
Maintaining method, there is higher sensitivity and reliability.
Technical scheme：The present invention is using the third harmonic voltage variable quantity of generator neutral point and through real-time regulation coefficient school
The generator terminal third harmonic voltage variable quantity just crossed synthesizes differential voltage U3dAnd brake voltage U3r, and use criterion U3d>U3rCarry out
Differential differentiation, if it is satisfied, protection act；To prevent the interference of high-pressure side third harmonic voltage, increase assistant criteria, according to height
Press side third harmonic voltage variable quantity that the braking threshold value U of floating is setdt, can be real when high-pressure side third harmonic voltage changes
When adjustment braking door, if U3d>Udt, then with criterion U3d>U3rDifferentiation result and door export；Neutral point, generator terminal and high-pressure side
Memory time Δ t during third harmonic voltage variable quantity calculates at least needs 4 primitive periods；Criterion U3d>U3rWith U3d>UdtExtremely
Persistently meet 2 primitive periods less, protection could act.
Using the third harmonic voltage variable quantity of generator neutral point and through the corrected generator terminal of real-time regulation coefficient three times
Harmonic voltage variable quantity synthesizes differential voltage U3dAnd brake voltage U3r, and use criterion U3d>U3rCarry out differential differentiation, step
It is as follows：
Step 1：Generator neutral point residual voltage, generator terminal residual voltage are sampled to obtain instantaneous value Un、Us；
Step 2：Using fourier algorithm to instantaneous value Un、UsCalculated, obtain current neutral point third harmonic voltage
VectorCurrent generator terminal third harmonic voltage vectorThe neutral point third harmonic voltage vector of preceding time ΔtThe generator terminal third harmonic voltage vector of preceding time Δt
Step 3：Calculate neutral point third harmonic voltage variable quantityGenerator terminal triple-frequency harmonics
Voltage variety
Step 4：Calculate real-time regulation coefficientThen differential voltage is calculatedBrake voltageWherein KsetIt is restraint coefficient, take 0.6~
0.9；
Step 5：Judge U3d、U3rRelation whether meet U3d>U3r, if it is satisfied, protection act.
To prevent the interference of high-pressure side third harmonic voltage, increase assistant criteria, become according to high-pressure side third harmonic voltage
Change amount sets the braking threshold value U of floatingdt, braking door can be adjusted in real time when high-pressure side third harmonic voltage changes, such as
Fruit U3d>Udt, while meet U3d>U3r, protection act；Step is as follows：
5a：Main transformer high-pressure side residual voltage is sampled to obtain instantaneous value Eh；
5b：By fourier algorithm to instantaneous value EhCalculated, obtaining current high-pressure side third harmonic voltage vector isThe main transformer high-pressure side third harmonic voltage vector of preceding time Δt is
5c：Calculate high-pressure side third harmonic voltage variable quantity
5d：Calculate generator third harmonic voltage amplitudeThen braking threshold voltage is calculatedBecome the high and low pressure side third harmonic voltage coefficient of coup based on γ, it is defeated in this as definite value
Enter, calculation formula isWherein ω3For triple-frequency harmonics angular frequency, it is worth for 942.5rad/s, CM
Based on become high and low pressure side and be often coupled electric capacity, CfFor the relatively total capacitance of generator three, CtFor generator generator terminal external equipment over the ground
Total capacitance, Z3nFor the equivalent impedance ground of generator neutral point triple-frequency harmonics, Z when ground connection becomes ground connection3nBecome equivalent for neutral ground
Resistance, Z during grounding through arc3nFor neutral point arc suppression coil triple-frequency harmonics induction reactance, 1/Z when earth-free3nIt is zero.
Preferably, the memory time Δ t during neutral point, generator terminal, high-pressure side third harmonic voltage variable quantity calculate
At least need 4 primitive periods.
Preferably, differential voltage U3d, brake voltage U3rAnd braking door UdtRelation U3d>U3rWith U3d>UdtMust
At least two primitive period must continuously be met, protection could act.
Beneficial effect：Stator ground fault protection side provided by the invention based on third harmonic voltage variable quantity differential principle
Method, using the third harmonic voltage variable quantity of generator neutral point and through the corrected generator terminal triple-frequency harmonics electricity of real-time regulation coefficient
Press variable quantity to synthesize differential voltage and brake voltage, and carry out differential differentiation, can effectively distinguish Stator ground fault with generating electricity
Machine third harmonic voltage normal variation, improve the stability of stator ground fault protection.GPF (General Protection False scheme does not detect main transformer high pressure
The third harmonic voltage of side, the third harmonic voltage of high-pressure side and generator can not separately be considered, for prevent malfunction use compared with
For reliable and fixed restraint coefficient, sensitivity can not improve.Assistant criteria in the present invention considers high-pressure side triple-frequency harmonics
The interference of voltage, with very high sensitivity when third harmonic voltage is constant in high-pressure side, when high-pressure side third harmonic voltage becomes
Braking threshold value can be adjusted during change in real time, ensures that sensitivity prevents from malfunctioning again as far as possible.
Brief description of the drawings
Fig. 1 TV installation site figures；
Triple-frequency harmonics equivalent circuit during Fig. 2 generator normal operations；
Fig. 3 generator stator ground triple-frequency harmonics equivalent circuits；
Third harmonic voltage vector during Fig. 4 operating condition normal variations；
Third harmonic voltage vector during Fig. 5 stator groundings；
The processing procedure schematic diagram of Fig. 6 present invention.
Embodiment
The present invention is further described below in conjunction with the accompanying drawings.
Fig. 1 is the TV installation site figures of the present invention.G represents generator in figure, and T represents main transformer, and TV1 is set end voltage mutual inductance
Device, TV2 represent generator neutral point voltage transformer (or grounding transformer or arc suppression coil), and TV3 is main transformer high side voltage
Transformer.
Third harmonic voltage equivalent circuit (generator unit stator winding leakage reactance and resistance when Fig. 2 is generator normal operation
Much smaller than stator winding capacitance to earth, ignore stator winding leakage reactance and resistance).Wherein CfIt is the relatively total capacitance of stator winding 3,
CtFor generator terminal equipment total capacitance over the ground, CMBased on become high and low pressure side and be often coupled electric capacity, Z3nFor neutral ground change or arc blowout wire
The equiva lent impedance under triple-frequency harmonics is enclosed,It is generator third harmonic voltage,For generator terminal third harmonic voltage,For in
Property point third harmonic voltage,Based on become high-pressure side saturation caused by third harmonic voltage.
Fig. 3 is that stator ground fault triple-frequency harmonics equivalent circuit (ignores high-pressure side third harmonic voltage, due to CMIt is much smaller than
Cf, and unpredictable high-pressure side third harmonic voltage phase, existing third harmonic voltage principle Analysis of Stator Ground Fault Protection are neglected
Slightly high-pressure side third harmonic voltage).R in figuregFor fault ground resistance, generator third harmonic voltage is divided into by grounding resistance
Two partsWithDifferential main criterion in the present invention obtains on the basis of high-pressure side third harmonic voltage is ignored, and
Assistant criteria specially considers the influence of high-pressure side third harmonic voltage.
Fig. 4 is that unit operation operating mode normally changes the vectogram for causing generator third harmonic voltage to change (assuming that generating electricity
The initial phase of machine third harmonic voltage is 0 °), Fig. 4 is obtained on the basis of Fig. 2.In Fig. 4Respectively be change before neutral point and generator terminal third harmonic voltage vector, unit
Operating condition change when generator third harmonic voltage byIt is changed into
Respectively be change after neutral point and generator terminal third harmonic voltage vector.Because ground connection parameter keeps constant, neutral point, generator terminal
The third harmonic voltage variable quantity of both sides maintains the phase relation before change, by introducing suitable coefficientBy generator terminal three
Subharmonic voltage variable quantity It is corrected toMakeWith neutral point triple-frequency harmonics electricity
Press variable quantityIt is equal in magnitude, in opposite direction.Expression formula is
ω in formula3For triple-frequency harmonics angular frequency, it is worth for 942.5rad/s, Z3nIt is neutral ground change or arc suppression coil
Triple-frequency harmonics equiva lent impedance.AnalysisPhase angle：(the Z in grounding through arc3n=j ω3Ln), high-rating generator uses
Undercompensation mode, that is, work asWhen,Due to Ct<Cf, it is not difficult to obtainSoPhase
Parallactic angle is 0 degree；In earth-free mode, Phase angle be also 0 degree；(the Z in the case where being grounded change mode3n=Rn),Phase
Parallactic angle is between 0~90 degree.
Fig. 5 is that generator unit stator single-phase earthing causes neutral point, the vectogram of generator terminal both sides third harmonic voltage change (false
If the initial phase of generator third harmonic voltage is 0 °, generator third harmonic voltage is constant before and after ground connection), Fig. 5 is to scheme
2nd, obtained on the basis of Fig. 3.The implication of voltage sign illustrates with reference to figure 4 in Fig. 5.It is clear to neutral point, generator terminal triple-frequency harmonics electricity
Press variable quantityWithIt is equal.Equally, by generator terminal third harmonic voltage variable quantityIt is corrected toAccording to right aboveThe analysis at phase angle, it can be seen thatWithAngle must be acute angle, and both will not make composite vectorAmplitude substantially weaken.
Based on the analysis to Fig. 5~6, utilizeWithThe amplitude of composite vector is as differential voltage, base
In the actuating quantity U of third harmonic voltage variable quantity differential principle stator ground fault protection3dWith braking amount U3rIt is defined as
K in formulasetFor restraint coefficient.Acting main criterion is
U3d＞ U3r (3)
Main criterion does not consider high-pressure side third harmonic voltageInfluence, define hereinVariable quantity be
According to Fig. 2,Being transferred to low-pressure side causes the third harmonic voltage variable quantity of generator neutral point and generator terminal to be
γ is high and low pressure side third harmonic voltage carry-over factor in formula, and expression formula is
Formula (5) substitutes into caused protection act amount when formula (2) can obtain high-pressure side third harmonic voltage change
When the actuating quantity is more than the braking amount U in formula (2)3rWhen, protection meeting malfunction is engaged, it is necessary to increase assistant criteria.
Assistant criteria is
U3d>Udt (8)
U in formuladtTo brake door, mainly hiding the interference of high-pressure side third harmonic voltage variable quantity.According to formula
(7) error that mutual inductor sample, device computing etc. may be brought, is considered, braking threshold value may be configured as
In formula, generator third harmonic voltage amplitude
According to the parameter of a 300MW generator transformer group, there is provided specific embodiment of the invention.Required specific ginseng
Number：Generator unit stator three-phase windings total capacitance C over the groundfFor 0.528 μ F, generator generator terminal external equipment total capacitance C over the groundtFor
0.348 μ F (the μ F of the shock wave of three-phase containing generator terminal Absorption Capacitance 0.3), main transformer high and low pressure side coupled capacitor CMFor 0.0047 μ F, ground connection
The equivalent grounding resistance of neutral point is R when becoming ground connectionn=3636 Ω, variable quantity calculating memory time Δ t is 80ms.
Embodiments of the invention method is as shown in fig. 6, specifically include following steps：
Step 1：Generator neutral point residual voltage, generator terminal residual voltage, main transformer high-pressure side residual voltage are sampled
Obtain instantaneous value Un(k)、Us(k)、Eh(k)；
Step 2：Utilize full wave Fourier algorithm(N takes 24, X (k)
Inputted for instantaneous value) to the instantaneous value U in step 1n(k)、Us(k)、Eh(k) carry out that each third harmonic voltage is calculated
It is complex vector located：Current neutral point third harmonic voltage vectorCurrent generator terminal third harmonic voltage vectorWhen
Preceding high-pressure side third harmonic voltage vectorPreceding 80ms neutral point third harmonic voltage vectorPreceding 80ms
Generator terminal third harmonic voltage vectorPreceding 80ms main transformer high-pressure side third harmonic voltage vector
Step 3：Calculate neutral point third harmonic voltage variable quantityGenerator terminal triple-frequency harmonics electricity
Press variable quantityHigh-pressure side third harmonic voltage variable quantity
Step 4：Calculate real-time regulation coefficientThen differential voltage is calculated
Brake voltageKsetTake 0.75；
Step 5：Calculate generator third harmonic voltage amplitudeThen braking threshold voltage is calculatedγ takes 0.00756；
Step 6：Calculate main criterion U3d＞ U3rWith assistant criteria U3d＞ UdtWhether meet, if main criterion and assistant criteria
Meet simultaneously and continuously more than 40ms, protection act.
Described above is only the preferred embodiment of the present invention, it should be pointed out that：For the ordinary skill people of the art
For member, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications also should
It is considered as protection scope of the present invention.
Claims (6)
1. a kind of earthing protection method for stator based on third harmonic voltage variable quantity differential principle, including, it is characterised in that：Bag
It is as follows to include step：
Step 1：Generator neutral point residual voltage, generator terminal residual voltage are sampled to obtain instantaneous value Un、Us；
Step 2：Using fourier algorithm to instantaneous value Un、UsCalculated, obtain current neutral point third harmonic voltage vectorCurrent generator terminal third harmonic voltage vectorThe neutral point third harmonic voltage vector of preceding time ΔtThe generator terminal third harmonic voltage vector of preceding time Δt
Step 3：Calculate neutral point third harmonic voltage variable quantityGenerator terminal third harmonic voltage
Variable quantity
Step 4：Calculate real-time regulation coefficientThen differential voltage is calculated
Brake voltageWherein KsetIt is restraint coefficient, takes 0.6~0.9；
Step 5：Judge U3d、U3rRelation whether meet U3d>U3r, if it is satisfied, protection act.
2. the earthing protection method for stator according to claim 1 based on third harmonic voltage variable quantity differential principle, its
It is characterised by：To prevent the interference of high-pressure side third harmonic voltage, increase assistant criteria, become according to high-pressure side third harmonic voltage
Change amount sets the braking threshold value U of floatingdt, braking door can be adjusted in real time when high-pressure side third harmonic voltage changes, such as
Fruit U3d>Udt, while meet U3d>U3r, protection act；Comprise the following steps that：
5a：Main transformer high-pressure side residual voltage is sampled to obtain instantaneous value Eh；
5b：By fourier algorithm to instantaneous value EhCalculated, obtaining current high-pressure side third harmonic voltage vector is
The main transformer high-pressure side third harmonic voltage vector of preceding time Δt is
5c：Calculate high-pressure side third harmonic voltage variable quantity
5d：Calculate generator third harmonic voltage amplitudeThen braking threshold value is calculatedBecome the high and low pressure side third harmonic voltage coefficient of coup based on γ, it is defeated in this as definite value
Enter, calculation formula isWherein ω3For triple-frequency harmonics angular frequency, it is worth for 942.5rad/s, CM
Based on become high and low pressure side and be often coupled electric capacity, CfFor the relatively total capacitance of generator three, CtFor generator generator terminal external equipment over the ground
Total capacitance, Z3nFor the equivalent impedance ground of generator neutral point triple-frequency harmonics.
3. the earthing protection method for stator according to claim 2 based on third harmonic voltage variable quantity differential principle, its
It is characterised by：The Z3n, when ground connection becomes ground connection, Z3nBecome an equivalent resistance for neutral ground；When connecing grounding through arc
When, Z3nFor neutral point arc suppression coil triple-frequency harmonics induction reactance, when earth-free, 1/Z3nIt is zero.
4. the earthing protection method for stator according to claim 1 based on third harmonic voltage variable quantity differential principle, its
It is characterised by：Memory time in the neutral point third harmonic voltage variable quantity, the calculating of generator terminal third harmonic voltage variable quantity
Δ t at least needs 4 primitive periods.
5. the earthing protection method for stator according to claim 2 based on third harmonic voltage variable quantity differential principle, its
It is characterised by：Memory time Δ t during the high-pressure side third harmonic voltage variable quantity calculates at least needs 4 primitive periods.
6. the earthing protection method for stator according to claim 1 or 2 based on third harmonic voltage variable quantity differential principle,
It is characterized in that：When protective condition meets at least two primitive period, protection could act.
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| CN201610168740.5A CN105655977B (en) | 2016-03-23 | 2016-03-23 | Earthing protection method for stator based on third harmonic voltage variable quantity differential principle |
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| CN201610168740.5A CN105655977B (en) | 2016-03-23 | 2016-03-23 | Earthing protection method for stator based on third harmonic voltage variable quantity differential principle |
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Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107240905B (en) * | 2017-08-03 | 2018-11-23 | 南京国电南自电网自动化有限公司 | A kind of third harmonic voltage earthing protection method for stator |
| CN107887886B (en) * | 2017-10-20 | 2019-02-26 | 国电南瑞科技股份有限公司 | A kind of improved triple-frequency harmonics stator grounding ratio criterion |
| CN110048372B (en) * | 2018-01-15 | 2021-08-03 | 长沙理工大学 | Improved high-voltage generator stator single-phase earth fault protection method |
| CN108808624B (en) * | 2018-06-20 | 2019-10-11 | 西安热工研究院有限公司 | A kind of stator of steam turbine generator Earth design method according to voltage vector angle relationship |
| CN109038495B (en) * | 2018-08-24 | 2019-11-12 | 南京国电南自电网自动化有限公司 | A kind of differential earthing protection method for stator of highly sensitive third harmonic voltage |
| CN109633350B (en) * | 2018-12-12 | 2020-12-15 | 国网山东省电力公司电力科学研究院 | Method and system for detecting virtual grounding reason of generator stator of load direct supply system |
| CN109449898B (en) * | 2018-12-12 | 2020-02-14 | 国网山东省电力公司电力科学研究院 | Method and system for solving load direct supply system generator stator unreal grounding fault |
| CN113708343B (en) * | 2020-05-22 | 2023-09-08 | 南京南瑞继保电气有限公司 | Stator grounding protection method and device for salient pole generator and electronic equipment |
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