CN102082422A - Method for preventing fault actions of line longitudinal differential protection caused by non-fault phase secondary current abrupt change - Google Patents
Method for preventing fault actions of line longitudinal differential protection caused by non-fault phase secondary current abrupt change Download PDFInfo
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Abstract
A method for preventing fault actions of line longitudinal differential protection caused by non-fault phase secondary current abrupt change comprises the following steps: 1) measuring a phase difference current Idphi, wherein the Idphi is a phase braking current; and 2) when the formula of Idphi>k1Irphi, Idphi>Imkl.Idphi>k2Ir-other is satisfied simultaneously, eliminating the condition of non-fault phase secondary current abrupt change, and turning on the phase difference streaming relay. In the formula, Idphi is a phase difference current, Irphi is a phase braking current, Imkl is a difference threshold, Ir-other is the comprehensive braking amount of the two other phases, k1 and k2 are coefficients, phi=a, b, c, other=bc, ac, ab, wherein a, b and c stand for three phases. The method has the following beneficial effects: through the main criterion of the non-fault phase saturated discrimination, the fault phase electrical character amount is used as the braking factor in a non-fault phase action equation, thereby being capable of reliably preventing non-fault phase fault action in case of non-fault phase secondary current abrupt change.
Description
Technical field
The present invention relates to the saturated differentiation of circuit on power system longitudinal difference protection CT, especially relate to a kind of method of pilot wire relays incorrect operation when preventing the non-fault phase of single-phase fault secondary current sudden change (CT is saturated).
Background technology
External area error CT saturation problem is one of principal element that influences the current differential protection performance.For preventing the saturated differential protection malfunction of external area error CT, protective device all has the ripe saturated criterion of anti-CT both at home and abroad, and as asynchronous method, waveform recognition method etc., differential protection can malfunction when CT is saturated to guarantee line differential protection.
But in some regional on-the-spot actual moving process of domestic in recent years electrical network, behind bus or circuit generation single-phase fault, mutation current (referring to accompanying drawing 1) appears in non-fault phase secondary side, and the behavior of incorrect operation has appearred in non-fault phase current differential protection.Analyze, conclude the common trait of fault case, obtain:
1. single-phase fault in distinguishing, the peaked wave electric current of several cycles appears in non-fault mutually, and non-fault satisfies the current differential protection criterion mutually, and the tripping operation of differential current generation three-phase does not overlap (falsely dropping phase).
2. distinguish outer single-phase fault, the peaked wave electric current of several cycles appears in non-fault mutually, and non-fault satisfies the electric current operating criterion mutually, protects the malfunction of bypassing the immediate leadership.
These two kinds of phenomenons all are the behaviors of non-fault phase differential protection generation malfunction.Get rid of line mutual-inductance in the testing crew investigation process at the scene item by item; increasing-aid current; the influence of factors such as protective device and secondary circuit defective; analyze the wiring of protection and secondary circuit; check the action behavior of protective device; set about from resolving the on-the-spot failure wave-recording information of extracting; according to on-the-spot operating current and voltage waveform; when bus or circuit generation single-phase fault; fault phase short circuit current is not very big; as be rated current 5-6 doubly about; but DC component aperiodic with very big decay; the Current Transformer Secondary side of fault phase does not take place significantly saturated; but be the meet burr mutation current of peaked wave that 2-3 cycle occur of non-fault; the direction of mutation current and the fault direction of short circuit current mutually are anti-phase substantially; non-fault phase current produces distortion, and non-fault phase differential current satisfies the ratio brake criterion, referring to Yuan Yubo etc. and " current transformer three-phase current string to the influence of differential protection " mutually. Automation of Electric Systems; 2010,34 (21): 65-68.Because non-fault phase fault starting and current differential protection move simultaneously, asynchronous method lost efficacy, and was judged to troubles inside the sample space, did not have Blocking Differential Protection, the malfunction of non-fault phase.For single-phase fault in the district, action takes place non-fault mutually makes the tripping operation of differential current protection three-phase not overlap.For the outer single-phase fault in district, the overstep tripping behavior will take place in non-fault mutually, the further expansion of the outage scope that causes the accident.
Because the saturated method of the anti-CT of protective device mainly is that CT can not enter saturation condition at once after utilizing fault now, and the service area (time difference method, asynchronous method) of one section linearity is arranged, utilize this characteristics identification internal fault external fault both at home and abroad.And for secondary current this kind fault signature that suddenlys change, fault starting and current differential are moved simultaneously, and protective device is judged to troubles inside the sample space, and it is saturated not detect CT, and the behavior of non-fault phase malfunction takes place.
The criterion report of malfunction when still finding no at present Line Current Differential Protection and preventing the sudden change of the non-fault phase of single-phase fault secondary current.
Summary of the invention
Technical problem to be solved by this invention is to solve Line Current Differential Protection is protected incorrect operation under the non-fault phase of single-phase fault secondary current sudden change situation situation (troubles inside the sample space is falsely dropped phase, the external area error malfunction).
The technical solution adopted for the present invention to solve the technical problems specifically comprises following several sections:
(1) analysis and the electric parameters feature of the non-fault phase secondary mutation current origin cause of formation
When not considering non-fault phase load electric current, the equivalent electric circuit that can set up as shown in Figure 2 comes the actual loop of simulated field.When A broke down mutually, fault current ia set up correspondent voltage on n line resistance Rn:
un?=?unDC+unAC=iaDC?Rn?+?iaAC?Rn……………………………（1）
That wherein the aperiodic current component produces is unDC, and that the periodic current component produces is unAC.If ignore the little CT impedance of device, can think that un is the exciting voltage that is applied on B, the C phase TA secondary winding.
By the law of electromagnetic induction as can be known:
Just the magnetic linkage of CT equals initial magnetic linkage and adds the integration of exciting voltage for the time.Because unAC is a periodic component, so in one-period, magnetic linkage=0 that unAC produces under the little situation of short circuit current, is not the main cause that produces mutation current.
The magnetic linkage that aperiodic component unDC produces adds up in whole die-away time gradually, when the magnetic linkage that adds up gradually surpasses current transformer exciting voltage flex point value, one be will produce and big exciting current, just visible mutation current in the accompanying drawing 1 become suddenly.And because in and ia are reverse, so it is the exciting voltage of the non-fault phase of voltage un(that in is produced on Rn) also reverse with ia, therefore, non-fault phase exciting current (being mutation current) is reverse with non-fault phase current basically, and field failure record ripple figure has verified this conclusion.
It should be noted that, when aperiodic component decays to less the time, the aperiodic component unDC of n line resistance does not play a major role, and the ac short circuit electric current is to the demagnetizing effect of CT, the exciting voltage of non-fault phase is pulled to less than knee voltage numerical value, and non-fault phase secondary mutation current disappears thereupon.
Test shows that aperiodic component is big more in the fault current, and damping time constant is big more, and the n line resistance is big more in the CT secondary circuit, is easy to generate non-fault phase secondary mutation current more.
The harmonic content of non-fault phase secondary mutation current is much larger than fault phase (subordinate list 1); Non-fault phase secondary mutation current direction and fault phase current are reverse; There is discontinuity in non-fault phase secondary mutation current; Non-fault phase voltage changes very little; Non-fault differs stream and differs stream less than fault.
The non-fault phase fault of table 1 Harmonic Waves component
| ? | Maximum effective value | Account for the first-harmonic ratio |
| First-harmonic | 10.9039A | ? |
| Second harmonic | 1.0548A | 9.7% |
| Triple-frequency harmonics | 1.1166A | 10.2% |
| Four-time harmonic | 0.3449A | 3.2% |
| Quintuple harmonics | 0.4285 | 4% |
| The B phase | Maximum effective value | Account for the first-harmonic ratio |
| First-harmonic | 0.4333A | ? |
| Second harmonic | 0.2279A | 52.6% |
| Triple-frequency harmonics | 0.1352A | 31.2% |
| Four-time harmonic | 0.0817A | 18.9% |
| Quintuple harmonics | 0.07A | 16.2% |
| The C phase | Maximum effective value | Account for the first-harmonic ratio |
| First-harmonic | 2.2148A | ? |
| Second harmonic | 1.4054A | 63.4% |
| Triple-frequency harmonics | 0.8992A | 40.6% |
| Four-time harmonic | 0.6844A | 30.9% |
| Quintuple harmonics | 0.5331A | 24.1% |
(2) the main criterion of the mutually saturated differentiation of non-fault is proposed
The non-fault phase of single-phase fault secondary current when sudden change, fault mutually with non-fault mutually electric parameters evident difference is arranged.Greater than non-fault phase current, fault differs stream and differs stream greater than non-fault as the fault phase current, and non-fault phase secondary mutation current direction and fault phase current are reverse etc.Utilize these characteristics, with fault phase electric characteristic amount as the braking factor (formula 3(a) in the non-fault phase operation equation), and in conjunction with differential ratio equation (formula 3(b)) and differential threshold equation (formula 3(c)), the main criterion of non-fault phase malfunction when formation prevents the sudden change of the non-fault phase of single-phase fault secondary current.
In the formula:
Be the phase differential current,
Be the phase stalling current,
Be differential threshold,
Be the synthetical restraint amount of other two-phase,
,
Be coefficient,
,
When satisfying formula (3), then got rid of the situation of non-fault phase secondary current sudden change, open this phase differential relay.
(3) proposition is based on the auxiliary open criterion of voltage and harmonic wave
Considering increases the main criterion of the mutually saturated differentiation of non-fault, when double earthfault or evolved fault, when the biphase current difference is big, might cause the locking of the main criterion mistake of formula (3) in theory, for reducing this risk, increases by two auxiliary open criterions:
A: the open assistant criteria of harmonic wave, when line fault CT was unsaturated, harmonic wave only can appear at the fault initial stage (with decay fault time); When mutation current appearred in CT, as long as this situation does not disappear, harmonic wave just existed always.Therefore can utilize the ratio of second harmonic and triple-frequency harmonics and first-harmonic to distinguish.
In the formula:
For differing the stream second harmonic,
For differing the stream triple-frequency harmonics,
For differing the stream first-harmonic,
,
Be coefficient.
B: the auxiliary open criterion of voltage, when single-phase fault takes place, in general the fault phase voltage has bigger variation, and non-false voltage changes little, therefore can utilize the size of phase voltage and residual voltage assist to differentiate fault mutually with non-fault mutually, prevent that the main criterion of the mutually saturated differentiation of non-fault from missing locking.
In the formula:
Be phase voltage,
Be residual voltage,
,
Be the voltage threshold.
Beneficial effect of the present invention is as follows: the main criterion of the mutually saturated differentiation of non-fault with fault phase electric characteristic amount as the braking factor in the non-fault phase operation equation, non-fault phase malfunction when reliably preventing the sudden change of non-fault phase secondary current; Based on the auxiliary open criterion of voltage and harmonic wave, when guaranteeing double earthfault takes place, differential protection can not miss locking, the differential protection operating characteristics when not influencing evolved fault simultaneously.Main criterion and assistant criteria cooperate has guaranteed the non-fault of the single-phase fault correctness of Line Current Differential Protection action during the secondary current sudden change mutually, to the not influence of other error protection performance.
Description of drawings
The non-fault phase of Fig. 1 secondary current suddenly change on-the-spot three-phase current waveform (the fault phase: the B phase, the sudden change phase: the C phase)
Exciting current flows in Fig. 2 loop
The mutually saturated main criterion of the non-fault of Fig. 3
The auxiliary open criterion of Fig. 4 voltage
The auxiliary open criterion of Fig. 5 harmonic wave
The saturated total criterion of the anti-CT of Fig. 6 line differential protection
Among the figure, output 1 when the inequality condition satisfies, otherwise export 0;
A. AND gate operation;
B. OR-gate operation.
Embodiment
Below in conjunction with accompanying drawing patent of the present invention is further described, but the invention is not restricted to given example.
The saturated criterion of anti-CT of line differential protection is made of two parts:
1, based on the saturated criterion of conventional CT of time difference method, it is saturated and stable state is saturated to be used to discern the transient state of fault phase CT.Not not within the scope of the present invention, specifically not quite clear.
2: be used to discern the saturated criterion of CT of non-fault phase secondary current sudden change, constitute by following two parts:
(1) the main criterion of the mutually saturated differentiation of non-fault
The non-fault phase of single-phase fault secondary current when sudden change, fault mutually with non-fault mutually electric parameters evident difference is arranged.Greater than non-fault phase current, fault differs stream and differs stream greater than non-fault as the fault phase current, and non-fault phase secondary mutation current direction and fault phase current are reverse etc.Utilize these characteristics, with fault phase electric characteristic amount as the braking factor (formula 3(a) in the non-fault phase operation equation), and in conjunction with differential ratio equation (formula 3(b)) and differential threshold equation (formula 3(c)), the main criterion of non-fault phase malfunction when formation prevents the sudden change of the non-fault phase of single-phase fault secondary current is referring to accompanying drawing 3.
(2) based on the auxiliary open criterion of voltage and harmonic wave
Considering increases the main criterion of the mutually saturated differentiation of non-fault, when double earthfault or evolved fault, when the biphase current difference is big, might cause the locking of the main criterion mistake of formula (3) in theory, for reducing this risk, increases by two auxiliary open criterions:
A: the open assistant criteria of harmonic wave, when line fault CT was unsaturated, harmonic wave only can appear at the fault initial stage (with decay fault time); When mutation current appearred in CT, as long as this situation does not disappear, harmonic wave just existed always.Therefore can utilize the second harmonic of formula (4) and the ratio of triple-frequency harmonics and first-harmonic to distinguish.Referring to accompanying drawing 4.
B: the open assistant criteria of voltage, when single-phase fault takes place, in general the fault phase voltage has bigger variation, non-false voltage changes little, therefore can utilize the size of formula (5) phase voltage and residual voltage assist to differentiate fault mutually with non-fault mutually, prevent that the main criterion of the mutually saturated differentiation of non-fault from missing locking.Referring to accompanying drawing 5.
3: the saturated criterion logic of the anti-CT of whole line differential protection
The saturated criterion of the anti-CT of whole differential protection is made up of two parts: A: be used to discern the saturated criterion of the anti-CT of the saturated time difference method of conventional CT; B: be used to discern the criterion of non-fault phase secondary current sudden change (CT is saturated), comprise: the main criterion of the mutually saturated differentiation of non-fault, the open assistant criteria of harmonic wave, the open assistant criteria of voltage.Referring to accompanying drawing 6.
Claims (3)
1. prevent that non-fault phase secondary current sudden change from causing the method for pilot wire relays malfunction, it is characterized in that, may further comprise the steps:
1) measures the phase differential current
,
Be the phase stalling current
2) when satisfying formula (3), then got rid of the situation of non-fault phase secondary current sudden change, open this phase differential relay,
In the formula:
Be the phase differential current,
Be the phase stalling current,
Be differential threshold,
Be the synthetical restraint amount of other two-phase,
,
Be coefficient,
,
,
The expression three-phase.
2. according to claim 1ly prevent that the sudden change of non-fault phase secondary current from causing the method for pilot wire relays malfunction, it is characterized in that, when satisfying formula (4), open this phase differential relay,
In the formula:
For differing the stream second harmonic,
For differing the stream triple-frequency harmonics,
For differing the stream first-harmonic,
,
Be coefficient.
3. according to claim 1ly prevent that the sudden change of non-fault phase secondary current from causing the method for pilot wire relays malfunction, it is characterized in that, when satisfying formula (5), open this phase differential relay,
In the formula:
Be phase voltage,
Be residual voltage,
,
Be the voltage threshold.
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|---|---|---|---|---|
| CN103278721A (en) * | 2013-06-19 | 2013-09-04 | 国家电网公司 | Method for judging whether transformer is in external fault and CT saturation state |
| CN104201645A (en) * | 2014-09-17 | 2014-12-10 | 北京天能继保电力科技有限公司 | Differential protection method for preventing abnormally great number of sampling values |
| CN105140892A (en) * | 2015-07-21 | 2015-12-09 | 河南行知专利服务有限公司 | Line protection method for power transmission line |
| CN110780160A (en) * | 2019-12-06 | 2020-02-11 | 广东电网有限责任公司 | Arc light high-resistance grounding fault detection method and device |
| CN111987688A (en) * | 2020-07-30 | 2020-11-24 | 许继集团有限公司 | Method for restraining error action of restorable disturbance differential protection |
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2010
- 2010-12-15 CN CN2010105887988A patent/CN102082422A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103278721A (en) * | 2013-06-19 | 2013-09-04 | 国家电网公司 | Method for judging whether transformer is in external fault and CT saturation state |
| CN104201645A (en) * | 2014-09-17 | 2014-12-10 | 北京天能继保电力科技有限公司 | Differential protection method for preventing abnormally great number of sampling values |
| CN104201645B (en) * | 2014-09-17 | 2017-12-01 | 北京天能继保电力科技有限公司 | A kind of abnormal differential protecting method several greatly of anti-sampled value |
| CN105140892A (en) * | 2015-07-21 | 2015-12-09 | 河南行知专利服务有限公司 | Line protection method for power transmission line |
| CN110780160A (en) * | 2019-12-06 | 2020-02-11 | 广东电网有限责任公司 | Arc light high-resistance grounding fault detection method and device |
| CN110780160B (en) * | 2019-12-06 | 2021-10-19 | 广东电网有限责任公司 | Arc light high-resistance grounding fault detection method and device |
| CN111987688A (en) * | 2020-07-30 | 2020-11-24 | 许继集团有限公司 | Method for restraining error action of restorable disturbance differential protection |
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Application publication date: 20110601 |