CN101702512A - Negative sequence impedance direction protection method for interior failures of stator winding of steamer generator - Google Patents
Negative sequence impedance direction protection method for interior failures of stator winding of steamer generator Download PDFInfo
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- CN101702512A CN101702512A CN200910237888A CN200910237888A CN101702512A CN 101702512 A CN101702512 A CN 101702512A CN 200910237888 A CN200910237888 A CN 200910237888A CN 200910237888 A CN200910237888 A CN 200910237888A CN 101702512 A CN101702512 A CN 101702512A
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Abstract
The invention relates to a protection method for interior failures of a stator winding of a steam turbine generator, belonging to the technical field of main equipment relay protection of a power system. The protection method is characterized by comprising the following steps of: collecting three-phase voltage and three-phase current from the machine end of the generator, filtering fundamental wave negative sequence components of failure components of phase voltage and phase current, calculating the equivalence negative sequence impedance of the failure components of the machine end, and judging whether unsymmetrical failures are interior failures of a motor winding or exterior failures of the machine end according to the symbol and the size of the negative sequence impedance. Analysis for the calculation of all interior short-circuit failures and single-branch welding disconnection failures which possibly occur and the sensitivity in two typical steam turbine generators shows that the negative sequence impedance direction protection method for failure components has superior sensitivity and protection range for the interior asymmetrical failure (particularly a short-circuit failure among interior turns) of the rotor winding of the steam turbine generator to the other traditional protections, and can provide high-quality protection for interior asymmetrical failures of the steam turbine generator, the natural point side of which only leads out three terminals.
Description
Technical field
The invention belongs to the power system main equipment technical field of relay protection, relate in particular to a kind of based on the symbol of fault component negative sequence impedance and the inner unbalanced fault guard method of generator unit stator winding of size.
Background technology
The inner unbalanced fault of generator unit stator mainly comprises winding internal short circuit fault and single branch disconnection fault, all is the very strong fault of common damage.Can produce very big short circuit current during the large turbo-type generator internal short circuit fault, and single branch disconnection fault not only causes the normal branch current of fault phase obviously to increase but also can produce very big circulation between two branches of non-fault phase, big electric current so all may burn winding and iron core, also can produce destructive serious electromagnetic force.The negative phase-sequence magnetic field that unbalanced fault produces may substantially exceed the design permissible value, causes the major injury of rotor.Therefore, China's Protection Technology rules stipulate that clearly large turbo-type generator need install the alternate and interturn short circuit protection of stator winding.
But the most neutral point side of existing turbo generator are only drawn 3 terminals (referring to Fig. 1); can't dispose zero-sequence current type transverse differential protection, incomplete differential protection and split hydraulic generator turn-to-turn short circuit main protection commonly used such as transverse differential protection mutually; and the complete longitudinal difference protection that possesses mounting condition only can react the phase fault of stator winding, can not move to the turn-to-turn short circuit of stator winding inside and single branch disconnection fault.
The turbo generator interturn short circuit protection that is using at present mainly contains vertical fundamental wave zero sequence overvoltage protection and fault component negative-sequence directional protection, but all has bigger operating dead zone, and the latter generally can't react single branch disconnection fault.In order to improve the security reliability of large turbo-type generator operation, be necessary to study the novel protected principle of inner unbalanced fault and propose new protection criterion.
Summary of the invention
The objective of the invention is to provide the guard method of the inner unbalanced fault of a kind of stator winding for the turbo generator that neutral point side is only drawn 3 terminals.
In order to improve the security reliability of large turbo-type generator operation, the present invention proposes the novel protected method of the inner unbalanced fault of a kind of stator winding.Only draw the turbo generator of 3 terminals for neutral point side, only need to gather three-phase voltage and three-phase current from generator machine end, the first-harmonic negative sequence component of leaching phase voltage and phase current fault component constitutes the characteristic quantity (referring to Fig. 2) of negative sequence impedance direction protection.The invention is characterized in that described method is carried out successively according to the following steps in computer:
(1) at generator machine end three-phase voltage and three-phase current (according to the generator convention, referring to Fig. 3) are sampled, poor by between the neighbouring sample point, the fault component instantaneous value that obtains three-phase voltage and three-phase current is (such as, Δ u
a(k)=u
a(k+1)-u
a(k), u wherein
a(k) be the k time sampled instantaneous value of a phase voltage), and utilize the Fourier filtering algorithm to calculate the fundamental phasors of the fault component of three-phase voltage and three-phase current by instantaneous value
Δ U wherein
aWith
Be the first-harmonic effective value and the phase angle of a phase voltage fault component, Δ U
bWith
Be the first-harmonic effective value and the phase angle of b phase voltage fault component, Δ U
cWith
Be the first-harmonic effective value and the phase angle of c phase voltage fault component, Δ I
aWith
For a phase current fault is divided first-harmonic effective value and phase angle, Δ I
bWith
Be the first-harmonic effective value and the phase angle of b phase current fault component, Δ I
cWith
First-harmonic effective value and phase angle for c phase current fault component.
(2) fundametal compoment effective value and the phase angle according to above-mentioned three-phase voltage and three-phase current fault component (is Δ U
a,
Δ U
b,
Δ U
c,
With Δ I
a,
Δ I
b,
Δ I
c,
), decomposite the first-harmonic negative phase-sequence phasor of false voltage
First-harmonic negative phase-sequence phasor with fault current
(3) according to fault current first-harmonic negative phase-sequence phasor effective value Δ I
2Size judge whether to start fault component negative sequence impedance direction protection: if Δ I
2Greater than 10% of normal operation fundamental current, go to (4), start fault component negative sequence impedance direction protection; Otherwise, go to (1) and continue sampling.
(4) by the first-harmonic negative phase-sequence phasor of false voltage
First-harmonic negative phase-sequence phasor with fault current
Calculate the negative sequence impedance of fault component
(5) based on the fault component negative sequence impedance
Symbol and the criterion expression-form described of size be:
If satisfy above-mentioned criterion, then be judged as the inner unbalanced fault of generator unit stator winding.
The calculating and the sensitivity analysis of all contingent internal short circuit faults of two typical turbo generators and single branch being snapped disconnection fault show; the fault component negative sequence impedance direction protection that the present invention proposes all is better than existing other protection (comprising vertical fundamental wave zero sequence overvoltage protection and fault component negative-sequence directional protection) to the sensitivity and the protection range of stator of steam turbine generator inside unbalanced fault (especially to inner shorted-turn fault), and high-quality protection can be provided for the inner unbalanced fault of turbo generator that neutral point side is only drawn 3 terminals.The operating dead zone of fault component negative sequence impedance direction protection mainly is the homophase different branches shorted-turn faults of two short dots apart from neutral point distance identical (or close), and the reason of akinesia is the first-harmonic negative phase-sequence phasor of fault electric current
Less, as not reach startup negative sequence impedance direction protection threshold value.In fact, only draw the turbo generator of 3 terminals for neutral point side, existing various protections are all very low to the sensitivity of the different branches of this homophase shorted-turn fault.
Description of drawings
Fig. 1 is the traditional outlet method and the protection allocation plan of turbo generator among the present invention.
Fig. 2 divides the schematic diagram of negative sequence impedance direction protection for turbo generator fault among the present invention.
Fig. 3 is the reference direction schematic diagram (generator convention) of turbo generator set end voltage among the present invention and electric current.
Fig. 4 is inner first-harmonic negative phase-sequence equivalent circuit and the negative phase-sequence fundamental phasors figure when asymmetric of electrical network symmetry generator.
Fig. 5 is the inner negative phase-sequence fundamental phasors figure when asymmetric of electrical network symmetry generator.
Fig. 6 is the outside first-harmonic negative phase-sequence equivalent circuit when asymmetric of generator.
Fig. 7 is the outside negative phase-sequence fundamental phasors figure when asymmetric of generator.
Fig. 8 is the homophase different branches shorted-turn faults of a kind of two short dots of No. 1 turbo generator (300MW, stator 54 grooves) actual capabilities generation apart from the same number of turn of neutral point.
Fig. 9 is the schematic diagrames of the various protections of turbo generator to homophase shorted-turn fault action message scope.
Figure 10 is the schematic diagrames of the various protections of turbo generator to phase fault action message scope.
Figure 11 is a flow chart of the present invention.
Embodiment
Principle of the present invention once is described at first in conjunction with the accompanying drawings.
During generator three-phase symmetrical operation, voltage, electric current have only the positive sequence fundametal compoment of symmetry, negative phase-sequence amount and zero sequence amount can occur and unbalanced fault (perhaps asymmetric operation) takes place.Electrical network is still symmetrical if inner unbalanced fault takes place generator, and the negative phase-sequence amount derives from generator so, and negative sequence power flows to electrical network by generator, and the negative phase-sequence equivalent circuit is (r among Fig. 4 as shown in Figure 4
tAnd jX
tRepresent three symmetrical grid power transmission lines and transformer to convert the every all-in resistance mutually and the leakage reactance (actual value) of generating pusher side), first-harmonic negative phase-sequence phasor diagram is (voltage among Fig. 5 as shown in Figure 5
With electric current
Reference direction be defined as the generator convention), negative-sequence current
Lag behind negative sequence voltage
Machine end negative phase-sequence equivalent impedance Z
2Impedance angle
Between 0 ° to 90 °, and owing to X in the real system
t＞r
t,
Should approach 90 °; And outside when unbalanced fault or the operation of generator belt asymmetric load take place, the negative phase-sequence amount derives from electrical network (load) when generator unit stator winding itself symmetry, and negative sequence power flows to generator by electrical network, and the negative phase-sequence equivalent circuit is (R among Fig. 6 as shown in Figure 6
2And jX
2Represent the negative phase-sequence substitutional resistance and the reactance (actual value) of generator), first-harmonic negative phase-sequence phasor diagram is (voltage among Fig. 7 as shown in Figure 7
With electric current
Reference direction still be defined as the generator convention), negative-sequence current
Lead over negative sequence voltage
Machine end negative phase-sequence equivalent impedance Z
2Impedance angle
Between-180 ° to-90 °, and owing to X in the real system
2＞＞R
2,
Should approach-90 °.
According to above-mentioned principle, can judge that unbalanced fault is motor windings internal fault or machine end external fault according to the symbol and the size of the equivalent negative sequence impedance of machine end.For avoiding line voltage to have the erroneous judgement that causes under the asymmetric situation originally, need take the processing method of fault component, promptly constitute the characteristic quantity of negative sequence impedance criterion by the fault component of first-harmonic negative sequence voltage and negative-sequence current.
In order to verify the performance of above-mentioned fault component negative sequence impedance direction protection; be example with two turbo generators (major parameter sees Table 1) below; utilization " multi-loop analysis method "; on the basis of comprehensive internal fault simulation calculation, its performance has been carried out analytical calculation, and carried out performance comparison with the existing interturn short circuit protection of turbo generator (comprising vertical fundamental wave zero sequence overvoltage protection and fault component negative-sequence directional protection).
The major parameter of two turbo generators of table 1
| Rated power | Rated voltage | Rated current | Rated power factor | Whenever a way is in parallel | Number of stator slots | Exciting current during specified operation | Exciting current during the zero load rated voltage | |
| No. 1 generator | ??300??MW | ??20kV | ??10189A | ??0.85 | ??2 | ??54 | ??1819A | ??706A |
| No. 2 generators | ??650??MW | ??20kV | ??20849A | ??0.9 | ??2 | ??42 | ??4503A | ??1480A |
According to the stator winding connection layout that motor manufactory provides, can analyze the type and the number of all internal short circuit faults (comprising) of these two turbo generator actual capabilities generations with groove fault and end fault, as shown in table 2.
Same groove and end fault that two turbo generator actual capabilities of table 2 take place
At networking rated load operation state, table 3～table 5 has been added up the number of defects and the character thereof of fault component negative sequence impedance direction protection that the present invention proposes and the existing vertical fundamental wave zero sequence overvoltage protection of turbo generator, fault component negative-sequence directional protection akinesia respectively.Can see that to these two turbo generators, the fault component negative sequence impedance direction protection that the present invention proposes only can't move to the turn-to-turn short circuit of the different branches of 6 kinds of homophases respectively, operating dead zone is far smaller than two kinds of existing protections in addition.
Under two turbo generator networkings of table 3 rated load operation state, the number of faults and the character thereof of the akinesia of fault component negative sequence impedance direction protection
Under two turbo generators of table 4 networking rated load operation state, the vertically number of faults of fundamental wave zero sequence overvoltage protection akinesia and character thereof (operating value of secondary voltage is adjusted and is 3V, thinks that protection all can not action message to the fault of sensitivity＜1.5)
Under two turbo generator networkings of table 5 rated load operation state; the number of faults of fault component negative-sequence directional protection akinesia and character thereof (operating value is adjusted and is 1% of generator rated capacity, thinks that protection all can not action message to the fault of sensitivity＜1.5)
Further the analysis showed that, the different branches of the homophase of the fault component negative sequence impedance direction protection akinesia that the present invention proposes shorted-turn fault, two short dots and neutral point are all at a distance of the same number of turn.Such as No. 1 turbo generator (stator 54 grooves shown in Figure 8, per minute props up by 9 coils and is in series) a mutually No. 8 coil of the 1st branch road (the slave end is counted) lower floor limit and a mutually the limit, upper strata of No. 8 coil of the 2nd branch road in the turn-to-turn short circuit of end portions cross place generation, the short circuit number of turn is 2 circles, and the short dot of two branches all has only 1 coil apart from neutral point.Under networking rated load operation mode, the effective value and the phase place that calculate each phase set end voltage, electric current and each branch road stable state fundamental current are as follows:
From this example as can be seen, the different branches of the homophase of these class two short dots or close number of turn identical shorted-turn fault apart from neutral point, because the normal current potential of two short dots is just more approaching, though the short-circuit loop electric current is very big, but the short circuit current that this numerical value is very big mainly causes the fault circulation between two fault branches mutually, but smaller to the influence of machine end three-phase voltage and three-phase current.So main still fundamental positive sequence in electric current, the voltage, all very little (U of negative phase-sequence and zero-sequence component
0=139.8V, U
2=187.9V, I
2=758.5A); vertically the sensitivity of fundamental wave zero sequence overvoltage protection and fault component negative-sequence directional protection is all lower; though and the scope at the fault component negative sequence impedance direction protection negative sequence impedance angle that the present invention proposes satisfies operating criterion, because negative-sequence current does not reach startup value (I
2=758.5A, less than normal current (10189A) 10%) also can't move.
By top qualitative analysis, recognize that fault shown in Figure 8 is not only the operating dead zone of the fault component negative sequence impedance direction protection that the present invention proposes, also be the operating dead zone of the existing various protections (also comprising complete longitudinal difference protection) of turbo generator.By more careful statistics; can come the inside shorted-turn fault that the various protections of simple declaration turbo generator can action message and the population size contrast and the inclusion relation of phase fault with Fig. 9 and Figure 10, therefrom also can find out the superior function of fault component negative sequence impedance direction protection.
Claims (2)
1. the negative sequence impedance direction protection method of Stator Coil internal fault is characterized in that described method is carried out successively according to the following steps in computer:
Step 1. is sampled to three-phase voltage and three-phase current at generator machine end, and poor by between the neighbouring sample point, obtains the fault component instantaneous value of three-phase voltage and three-phase current, is expressed as: Δ u
a(k)=u
a(k+1)-u
a(k), Δ u
b(k)=u
b(k+1)-u
b(k), Δ u
c(k)=u
c(k+1)-u
c(k), Δ i
a(k)=i
a(k+1)-i
a(k), Δ i
b(k)=i
b(k+1)-i
b(k), Δ i
c(k)=i
c(k+1)-i
c(k), u wherein
a(k), u
b(k), u
c(k) be the k time sampled instantaneous value of a phase, b phase, c phase voltage, i
a(k), i
b(k), i
c(k) be the k time sampled instantaneous value of a phase, b phase, c phase current;
Step 2. utilizes the Fourier filtering algorithm to calculate the fundamental phasors of the fault component of three-phase voltage and three-phase current according to the sampled instantaneous value of above-mentioned three-phase voltage and three-phase current fault component
And the first-harmonic negative phase-sequence phasor of leaching false voltage
First-harmonic negative phase-sequence phasor with fault current
Δ U wherein
aWith
Be the first-harmonic effective value and the phase angle of a phase voltage fault component, Δ U
bWith
Be the first-harmonic effective value and the phase angle of b phase voltage fault component, Δ U
cWith
Be the first-harmonic effective value and the phase angle of c phase voltage fault component, Δ I
aWith
Be the first-harmonic effective value and the phase angle of a phase current fault component, Δ I
bWith
Be the first-harmonic effective value and the phase angle of b phase current fault component, Δ I
cWith
First-harmonic effective value and phase angle for c phase current fault component;
Step 3. is according to fault current first-harmonic negative phase-sequence phasor effective value Δ I
2Size judge whether to start fault component negative sequence impedance direction protection: if Δ I
2Greater than 10% of normal operation fundamental current, go to step 4, start fault component negative sequence impedance direction protection; Otherwise, go to step 1 and continue sampling;
Step 4. is by the first-harmonic negative phase-sequence phasor of false voltage
First-harmonic negative phase-sequence phasor with fault current
Calculate the negative sequence impedance of fault component
Step 5. is based on the fault component negative sequence impedance
Symbol and the criterion expression-form described of size be:
If satisfy above-mentioned criterion, then be judged as the inner unbalanced fault of generator unit stator winding.
2. the negative sequence impedance direction protection method of Stator Coil internal fault according to claim 1 is characterized in that: the sampled point of a described power frequency period is no less than 12 points.
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|---|---|---|---|
| CN200910237888XA CN101702512B (en) | 2009-11-20 | 2009-11-20 | Negative sequence impedance direction protection method for interior failures of stator winding of steamer generator |
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|---|---|---|---|
| CN200910237888XA CN101702512B (en) | 2009-11-20 | 2009-11-20 | Negative sequence impedance direction protection method for interior failures of stator winding of steamer generator |
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| CN101702512B CN101702512B (en) | 2011-11-09 |
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