CN103326331A - Method for preventing healthy phase bus-bar differential protection mal-operation during circuit reclosing period - Google Patents

Abstract

The invention relates to a method for preventing healthy phase bus-bar differential protection mal-operation during a circuit reclosing period. The method comprises one of the following measures: (1), optimizing secondary system indexes for changing TA for the bus into 5P20, and enabling a value TA which is 8 times of the rated current to be far from 10% of error curve edge; (2), arranging a high-low constant value action area for differential protection; (3), adding harmonic restraining criteria to take up anti-saturation measures in logic and adding the harmonic restraining criteria, wherein the harmonic restraining coefficient is less than 0.1; and (4), and replacing power frequency differential logic by power frequency variable differential logic when the added power frequency variable comprehensive criterion bus generates external faults.

Description

The method of non-fault phase bus differential protection malfunction during the prevention circuit reclosing

Technical field

The present invention relates to a kind of method of preventing non-fault phase bus differential protection malfunction during the circuit reclosing, belong to the relay protection of power system technical field.

Background technology

A few secondary line single phase ground fault successively appearred in 110kV Dongcheng transformer station, Qingdao Power Plant etc. in recent years; the action of bus differential or line differential protection, circuit breaker trip cause the major accident of equipment large-area power-cuts when line-breaker overlaps permanent fault; relevant devices has not only been excised in the generation of fault, has also influenced the stable operation of electrical network.

For example; 110kV Dongcheng transformer station circuit single phase ground fault, when line-breaker overlapped permanent fault, the secondary current waveform of circuit seriously distorted; cause the bus differential protecting misoperation thus, the major accident that has caused the II of transformer station bus to have a power failure.

Behind the line failure circuit breaker trip, take the reclosing means to remedy the switch trip that causes owing to the impermanency fault, the loss that line outage causes.But when the circuit reclosing, occur for non-fault line, non-fault phase bus differential protection and line differential protection action problems affect the due effect of reclosing, also disturbed faults analysis and processing simultaneously.

Bus differential or line differential protection action when line-breaker overlaps permanent fault, the circuit breaker trip problem is very serious, though in the data before relevant report is arranged, the type of its fault, the problem thinking that solves with analysis differ greatly.Be similar to the circuit single phase ground fault that occurs in the operation transformer station that above-mentioned example says, when line-breaker overlapped permanent fault, the problem of bus differential protecting misoperation never found reason and the processing method of fault for a long time.

Summary of the invention

Purpose of the present invention is exactly for addressing the above problem, and a kind of method of preventing non-fault phase bus differential protection malfunction during the circuit reclosing is provided, and it efficiently solves the problem of non-fault phase bus differential protection misoperation during the circuit reclosing.

For achieving the above object, the present invention adopts following technical scheme:

A kind of method of preventing non-fault phase bus differential protection malfunction during the circuit reclosing comprises in the following measure at least:

(1) optimizes the electrical secondary system index

(2) differential protection arranges height definite value active region

(3) increase the harmonic braking criterion

In logic, take the measure of anti-saturation, increase the harmonic braking criterion, harmonic braking coefficient value＜0.1;

(4) increase the power frequency variation comprehensive criterion

During bus generation external area error, replace the differential logic of power frequency with the differential logic of power frequency variation.

In described (1), optimize the electrical secondary system index, the TA that bus is used is replaced by 5P20, guarantee that 8 times load current value TA is away from the edge of 10% error curve.

In described (2), differential protection arranges low definite value and adjusts by Icdzd=0.4In, and In is the secondary rated current, band 0.1s deferred action outlet; High-set setting is pressed Icdzd=1.5In, is not with time-delay 0s action outlet.

The invention has the beneficial effects as follows: as long as above 4 measures can play a role jointly, just can solve the problem of non-fault phase bus differential protection misoperation during the circuit reclosing.Avoided effectively thus that protection malfunction, switch mis-jumping, signal mistake are sent out, a series of problems of unit mistakenly stop; Thereby the shock effect of having avoided the equipment large-area power-cuts that electrical network is caused.

Description of drawings

Fig. 1, the position of transformer substation system structure and fault point

Fig. 2, TA electrical secondary system key wiring diagram

Fig. 3, line fault record ripple figure

Fig. 4, busbar fault record ripple figure

Fig. 5, remanent magnetism is to the current waveform figure of TA properties influence

Fig. 6, ratio differential element operating characteristics curve

Fig. 7, the TA equivalent circuit

Fig. 8,10% error curve of faulty line 4 bus protection TA actual measurement

Fig. 9, the work block diagram of II bus differential protection

Figure 10, the record ripple figure during the blue or green southern line fault of 220kV.

Embodiment

Embodiment: (be example with 110kV Dongcheng transformer station)

The present invention has analyzed the example that solves non-fault phase bus differential protection malfunction during the circuit reclosing, has showed detection method in trouble-shooting, in the reason of determining non-fault phase bus differential protection malfunction and setting up the work of doing aspect the rational index system.

110kV Dongcheng transformer station circuit 8.4km place single phase ground fault; when line-breaker overlaps permanent fault; the secondary current waveform of circuit seriously distorts, and causes the II differential protection misoperation thus, the major accident that has caused the II of transformer station bus to have a power failure.The generation of fault has not only been excised equipment, has been interrupted sending out normally powered operation, and the while has caused very also for the safe and stable operation of partial electric grid and seriously influences.

Fault has been carried out a large amount of inspections and experiment work after taking place at the scene, and the insulation resistance of TA secondary circuit is tested, and has got rid of the factor of 2 ground connection of secondary circuit; Voltage-current characteristic, secondary impedance are tested, and the result shows it is that the secondary impedance height has caused the saturated of short circuit current; Waveform to electric current is analyzed, and adopt cranking test and the method for simulation magnetic after effect to confirm, the reason of current waveform distortion is the influence of remanent magnetism, and remanent magnetism makes TA be in transient state saturation condition, the saturated distortion that causes progress of disease characteristic to degenerate and then cause secondary current of transient state.TA takes the anti-saturation measure; Differential protection has taked to arrange high and low definite value active region; Problem is solved increase measure such as harmonic braking link in logic after.

The moving behavior of bus differential mistake protection action is analyzed when below Dongcheng transformer station circuit being overlapped permanent fault.

One, phenomenon of the failure

On August 3rd, 2010,18:57:25, earth fault, route protection would trip take place in the #4 of transformer station circuit 8.4km place, 110kV Dongcheng.Switch is through overlapping permanent fault after the time-delay of adjusting, route protection is would trip again, and meanwhile, II bus protection B moves mutually, all devices that this bus of tripping connects, and Fig. 1 is seen in the position of system configuration and fault point.Phenomenon of the failure at that time has following doubtful point.

(1) unsymmetrical current of big poor protection is consistent with the II bus protection, but why big poor protection does not move;

(2) II bus protection B moves mutually during circuit generation earth fault, be II protection malfunction, or there is fault in the II bus and correct operation;

(3) II bus protection A differs stream much larger than B, C phase, but A protects not action mutually, and B has moved mutually;

When (4) circuit for the first time earth fault took place, the II bus protection is action not, has but moved after the coincidence;

(5) is the saturated serious reason of fault current wherein during circuit generation earth fault?

Two, checking process

Center on the doubtful point in the phenomenon of the failure, secondary circuits such as #4 circuit TA have been carried out comprehensive inspection.The wiring of TA secondary circuit is example with the bus protection, and sketch is seen Fig. 2.

1, megger test

The loop	Measured value (M Ω)	The loop	Measured value (M Ω)
				Route protection 421	80	Bus differential protection 310	30
Between the 421AB	300	Between the 31OAB	400
				Between the 421BC	500	Between the 31OBC	500
Between the 421CA	400	Between the 31OCA	200
				Between the 421AN	2000	Between the 31OAN	1500
Between the 421BN	1500	Between the 31OBN	2000
				Between the 421CN	1000	Between the 31OCN	2000

The insulation resistance that detects is qualified, can determine that there is not the phenomenon of 2 ground connection in the TA secondary, that is to say that the misoperation of bus differential protecting and the problem of TA secondary ground connection have nothing to do.

2, TA no-load voltage ratio test

As shown in Figure 1, the no-load voltage ratio of faulty line TA is 600/5, so the no-load voltage ratio result is correct.

3, TA polarity test

Result of the test shows that the output of TA is positive polarity, so polarity is correct.

4, D.C. resistance test

The D.C. resistance result who tests is correct.

5, TA secondary load ac impedance measurement

Separate	A0	B0	C0
				421 impedances (Ω)	4.2	4.1	4.1
310 impedances (Ω)	4.1	4.1	4.1

6, volt-ampere characteristic test

(1) 421 current circuit (terminal box TA side)

(2) 310 current circuits (terminal box TA side)

Measured data result is correct.

7, the 110kV of transformer station bus protection electric current phasor test

Measured bus protection electric current phasor result is correct.

8, failure wave-recording inspection

Circuit and bus protection failure wave-recording are seen Fig. 3, Fig. 4,

9, influence the test of TA characteristic about remanent magnetism

In order to verify remanent magnetism to the TA properties influence, to one among two TA, secondary coil 120 circles feed the electric current of 5A, amount to excitation 600 ampere-turns, and two TA feed electric current 20Ie simultaneously then, and then both poor stream reaches more than the 6Ie, and this value is enough to cause the action protected.Record ripple figure during test is seen Fig. 5.

Three, bus protection principle brief introduction

Bus differential protecting is made of split-phase type percentage differential element, and TA polar requirement branch road TA end of the same name is in bus bar side, and female connection TA end of the same name is in the female side of I section.The big difference of bus refers to the differential circuit that all branch currents constitute except bus connection switch and block switch, I(II) differential circuit that constitutes of the little difference of section bus all branch currents of referring to connect on this section bus.The big poor percentage differential of bus is used and is differentiated in the bus district and external area error, and little poor percentage differential is used for selecting fault bus.Percentage differential element operating criterion is:

$I_{\mathrm{cd}}=\left|\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{I}_j\right|;$ $\left|\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{I}_j\right|>I_{\mathrm{cdzd}};$ $\left|\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{I}_j\right|>K\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\left|I_j\right|$

Wherein: I _Cd-differential starting current; M-connection way; K is ratio brake coefficient; I _jIt is the electric current of j Connection Element; I _CdzdBe differential current starting definite value.Its operating characteristics curve as shown in Figure 6.

Four, determine the TA10% error curve

Adopt the exciting characteristic curve method of TA can obtain 10% error curve, way is as follows:

(1) the excitation impedance characteristic curve of TA

The equivalent circuit of TA is seen Fig. 7.Among Fig. 7, Z ₁Be primary impedance, Z ₂' be the secondary winding impedance, Z _LCBe excitation impedance, I _LCBe exciting current.With the primary side open circuit of TA, Pass between secondary current, the voltage is:

${\stackrel{\·}{U}}_2={\stackrel{\·}{I}}_{\mathrm{LC}}\left(Z_{\mathrm{LC}}{+Z}_2\right)$

Following formula can be write as

$Z_{\mathrm{LC}}+{{\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="HDA00003540291700031.png,HDA00003540291700033.png"\; state="\{\{state\}\}">Z</figure-callout>}}_2}^{\&prime;}{\stackrel{\&CenterDot;}{U}}_2/{\stackrel{\&CenterDot;}{I}}_{\mathrm{LC}}$

Relative Z _LC, Z ₂' can ignore, so the voltage-current characteristic of TA secondary is approximately excitation impedance characteristic, i.e. Z _LC≈ U ₂/ I _LC, and voltage-current characteristic very easily obtains from test.

(2) do 10% error curve

Ordinate with exciting characteristic curve multiply by 0.1 abscissa as 10% error curve, and namely secondary allows impedance Z _r

Z _r＝0.1Z _LC≈0.1U ₂/I _LC

Abscissa with exciting characteristic curve multiply by 2 ordinates as 10% error curve, i.e. primary current multiple m10.

m ₁₀＝2I _LC

(3) Shi Ce 10% error curve (Fig. 8)

Secondary voltage-current characteristic to TA is surveyed, and related data sees Table 1.So three characteristics of the middle term data basically identical is row one phase only.

Bus protection B phase TA performance data table

I(A)	0.1	0.2	0.5	1.0	2.0	3.0	4.0	5.0	10.0	20.0
											U(V)	163	171	178	185	198	207	223	229	239	247
Zr(Ω)	163	85	36	18	10	6.9	5.6	4.5	2.3	1.2
											m10	0.2	0.4	1.0	2.0	4.0	6.0	8.0	10.0	20.0	40.0

Five, the analysis of causes

Be analyzed as follows at the doubtful point in the phenomenon of the failure:

1, the II bus protection is moved big poor protection not have action is the result that logic cooperates

Big poor unsymmetrical current is consistent with the II bus protection; but big poor protection is action not; the reason of II bus protection action is; after faulty line overlaps; the unsymmetrical current of big poor protection is consistent with the II bus protection, but cooperates according to logic, reach definite value after the action of II bus protection formerly; big poor protection action after, the fault big poor protection in back that disappears is returned.

2, the action of II bus protection belongs to misoperation

During circuit generation earth fault, be the malfunction of II bus protection, or is there the fault correct operation in the II bus? by failure wave-recording figure as can be known, busbar voltage was normal after faulty line excised for the first time, and busbar voltage descended after this circuit overlapped fault.Therefore have only circuit to have fault, the bus operation is normal.The action that this shows the II bus protection belongs to misoperation.

3, the misoperation of bus protection is relevant with the distortion of current waveform

When circuit for the first time earth fault took place, why the II bus protection was not moved, but moved after the coincidence? when circuit for the first time earth fault took place, the secondary arc current of the relative fault phase of B, C also existed, but spill current is lighter, and protection is action not.After circuit coincided with permanent fault, the DC component of fault current improved, and unsymmetrical current obviously increases, and spill current reaches the longer duration of definite value, therefore overlapped female differential tripping operation of back B phase II.

4, the distortion of TA secondary current waveform is relevant with remanent magnetism

In service, when operations such as air-drop transformer, emergency stop valve trip and capacitor switching, exist the chance of DC component a lot of in the electric current by current transformer, the DC component of electric current inevitable current transformer in iron core, produce remanent magnetism, remanent magnetism is difficult to eliminate under service conditions.Because the influence of remanent magnetism can make the progress of disease characteristic of current transformer degenerate; To cause current transformer transient state to occur saturated because progress of disease characteristic degenerates; Cause the distortion of TA secondary current waveform because transient state is saturated with influence DC component.

For bus protection, difference also appears in the transient state situation of electric current if the initial condition of TA remanent magnetism is inconsistent, thereby causes the appearance of difference stream, and the stream of being on duty reaches certain degree then can make the protection misoperation.

5, evidence the waveform influence of remanent magnetism to the TA secondary current

Initial period 714 switch TA secondary currents in line fault are the sinusoidal quantity of standard basically, and line-breaker is when overlapping permanent fault, the waveform of TA secondary current seriously distorts, the TA that same model occurred has shown the problem of different qualities in the different periods, and its difference is the influence of remanent magnetism.

In order deeply to understand remanent magnetism to the influence of TA electric current, finished " influencing the test of TA characteristic about remanent magnetism ", the result shows that TA exists under the situation of remanent magnetism, secondary current departs from abscissa and can reach more than 1/2.But; the current recording of protecting during line fault and test waveform Fig. 5 difference are bigger; reason is to test the fault current that can not simulate fully at that time, and test can only illustrate that the influence of remanent magnetism can make current transformer the transient state saturated phenomenon occur, causes the distortion of TA current waveform.

6, A and B are protected mutually between the understanding of action behavior difference

II bus A differs stream much larger than B, C phase, but why A protects not action mutually, B is but action mutually? (1) B

The reason of protection action is due to the transient state component of fault electric current mutually

According to failure wave-recording figure as can be known, relatively then there are electric current in B, C during A phase earth fault, A phase earth fault current 40A, and B, C are relatively about electric current 10A.B, C phase current are the secondary arc currents that fault is provided mutually, are not that the secondary interference waits other factors to cause.

Though A phase spill current is bigger, each cycle has the break time more than 1/3, and this moment, protection was returned, therefore not action outlet of protection.A phase spill current mainly is that saturated influence causes.

B protects the reason of action mutually, is that the waveform transient state component of its fault current is obvious, and spill current reaches the longer duration of definite value, in fact Icd〉Icdzd=0.4In duration 10ms, thus start protection and cause outlet tripping operation.

C B relatively compares gently, and unsymmetrical current is less, protects motionless also reasonable.

(2) the A phase current is saturated irrelevant with 10% error during circuit generation earth fault

A phase TA secondary current reaches 40A during circuit generation earth fault, is equivalent to 8 times load current value, and TA is serious saturated at this moment is not right, may have following problem.

1) the improper or workmanship existing problems of lectotype selection;

2) the secondary circuit impedance exceeds standard, causes 10% error not meet the demands;

3) there is the influence of remanent magnetism, causes so-called transient state saturated.

According to the conclusion that test result analysis is drawn be, saturated and the remanent magnetism of the short circuit current when fault begins is irrelevant, in conjunction with 10% error curve of TA actual measurement as can be known, 8 times load current value TA is near the edge of 10% error, but 10% error does not exceed standard as yet, therefore the A phase current is saturated irrelevant with 10% error, is due to the TA characteristic issues; The A phase current is serious saturated not only relevant with the TA characteristic issues, also relevant with remanent magnetism during the reclosing, irrelevant with 10% error.

It should be noted that B protect mutually misoperation and A phase current saturated between difference very big, the preceding B that once addressed protects the influence of misoperation and remanent magnetism closely related mutually.

Six, the precautionary measures

According to above-mentioned analysis, take following measure in conjunction with on-the-spot situation.

1, promotes the TA specification, optimize the electrical secondary system index

The TA that bus is used is replaced by 5P20, guarantees that 8 times load current value TA is away from the edge of 10% error curve;

2, differential protection arranges height definite value active region

Differential protection arranges low definite value active region, adjusts by Icdzd=0.4In, and In is the secondary rated current, band 0.1s deferred action outlet; The high-set setting active region is adjusted by Icdzd=1.5In, is not with time-delay 0s action outlet.

3, increase the harmonic braking certificate

In logic, take the measure of anti-saturation, increase the harmonic braking link, harmonic braking coefficient value＜0.1.The TA saturation detection element that is constituted by the harmonic braking principle.Its principle utilized TA saturated time difference stream wave distortion and weekly ripple have characteristics such as linear transform area, whether take place saturated according to the wave character detection TA of harmonic component in the difference stream.The TA saturation detection element that this principle realizes has very strong anti-TA saturability.The work block diagram of bus differential protection is seen Fig. 9.

Among Fig. 9, I _Cd-differential starting current; CD-big poor percentage differential element; CD _II-II bus percentage differential element;

SW-bus differential protection control word; YB-bus differential protection is thrown and is moved back pressing plate; U _IIThe locking of-II busbar voltage.

4, increase the power frequency variation comprehensive criterion

During bus generation external area error, because fault begins TA unsaturation still, power frequency variation difference element, power frequency variation impedance hysteresis power frequency variation voltage component, utilize three's sequential relationship to obtain self adaptation impedance weighted Criterion, the saturated difference of injection time stream of TA was different from the characteristics of troubles inside the sample space when this criterion was utilized external area error, and very strong anti-saturation ability is arranged.

After having taked above-mentioned measure, problem is solved.Annex: Figure 10, the record ripple during the blue or green southern line fault of 220kV.

Claims (2)

1. a method of preventing non-fault phase bus differential protection malfunction during the circuit reclosing is characterized in that, comprises in the following measure at least:

(1) optimizes the electrical secondary system index

The TA that bus is used is replaced by 5P20, guarantees that 8 times load current value TA is away from the edge of 10% error curve;

(2) differential protection arranges height definite value active region

(3) increase the harmonic braking criterion

In logic, take the measure of anti-saturation, increase the harmonic braking criterion, harmonic braking coefficient value＜0.1;

(4) increase the power frequency variation comprehensive criterion

During bus generation external area error, replace the differential logic of power frequency with the differential logic of power frequency variation.

2. the method for non-fault phase bus differential protection malfunction during the prevention circuit reclosing as claimed in claim 1, it is characterized in that in described (2), differential protection arranges low definite value and adjusts by Icdzd=0.4In, In is the secondary rated current, band 15ms deferred action outlet; High-set setting is pressed Icdzd=1.5In, is not with time-delay 0s action outlet.

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