CN102879671B - Method for judging inrush current locking of equivalent instantaneous inductance for protection of extra-high voltage regulating transformer - Google Patents
Method for judging inrush current locking of equivalent instantaneous inductance for protection of extra-high voltage regulating transformer Download PDFInfo
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Abstract
The invention discloses a method for judging inrush current locking of an equivalent instantaneous inductance for protection of an extra-high voltage regulating transformer belonging to the technical field of relay protection of a power system. The method comprises the steps as follows: firstly, calculating action currents and brake currents of A phase, B phase and C phase of the extra-high voltage regulating transformer, and judging if the phases enter into action areas of ratio brake characteristics by comparing the action currents and the brake currents; for the phases entering into the action areas, calculating a voltage of an equivalent port of the voltage regulating transformer according to the voltage on the medium-voltage side of a main transformer in the extra-high voltage transformer by utilizing a voltage transformation method, and calculating the equivalent instantaneous inductance variances sigma Li of the phases; and if the equivalent instantaneous inductance variances are higher than a threshold value epsilon, namely sigma Li > epsilon, judging that the phases generate an inrush current, locking the phases for protection, otherwise, judging that the phases have a failure, and finally outputting a judgment result. According to the method, the identification problem of the inrush current and an inter-turn/turn ground failure when the extra-high voltage regulating transformer is deeply saturated is emphatically solved, the essential difference of the failure and the inrush current is reflected, and the reliability for protection of the extra-high voltage regulating transformer is effectively improved.
Description
Patent field
The invention belongs to the technical field of relay protection of electric system, the equivalent instantaneous inductor of particularly a kind of extra-high voltage adjustable transformer protection shoves locking method of discrimination.
Background technology
UHV transmission is a brand-new cause of world power grid development field, is in the forward position of electrical network development in science and technology, does not have ripe experience both at home and abroad at present.1000kV extra-high voltage transformer structure is special; be made up of main body transformer and adjustable transformer two parts; main-transformer high, medium and low voltage side adopts the winding connection mode of Yn, Yn, d11; rated capacity is 1000/1000/334MVA; the rated voltage of each side is 1050/3:525/3 ± 4 × 1.25%:110kV; and adopt neutral point non-excitation pressure adjustment mode; there is very large difference with traditional transformer device structure, especially have employed the split voltage regulating mode of external adjustable transformer and be configured with independent tap-changing windings and compensative winding differential protection (as shown in Figure 1).But present existing magnetizing inrush current discrimination principle is all aimed at the research that traditional transformer is carried out, and might not identify excitation surge current exactly when being applied to extra-high voltage transformer.Actual extra-high voltage pressure regulation transformer differential protection adopts phase-splitting closedown mode and traditional secondary harmonic brake scheme, but relevant theoretical analysis and simulation study show: the special construction due to extra-high voltage transformer and the change along with core material, the secondary harmonic component that extra-high voltage transformer three phase excitation is shoved likely is in below second harmonic threshold value, and phase-splitting closedown mode can cause malfunction; And remote long transmission line transmission of electricity when making internal fault transient current produce larger second harmonic, can tripping be caused.Specifically, generally, during extra-high voltage transformer idle-loaded switching-on, pressure regulation become three phase excitation shove in secondary harmonic component much larger than 15%, utilize traditional secondary harmonic wave locking criterion, can effectively latch-up protection; But when main transformer or pressure regulation become containing larger remanent magnetism, pressure regulation may be caused under some combined floodgate condition to become in shoving one lower than 15%, be minimumly even low to moderate 5%, may malfunction be caused, as shown in Figure 3.As shown in Figure 2 when dropping in three-phase shortcircuit or double earthfault, fault phase secondary harmonic component, far below 15%, namely has the secondary harmonic component of two difference streams at least lower than 15%; Healthy phases shows as feature of shoving, and its secondary harmonic component is very high.But when dropping in the fault of single-phase turn-to-turn/all over the ground, only have the secondary harmonic component of a difference stream lower than 15%, excitation surge current waveform time saturated with pressure regulation varying depth is similar, as shown in Figure 3 b.Therefore, apply the locking of second harmonic phase-splitting the most widely criterion exists limitation in the protection of extra-high voltage pressure regulation transformer differential.
In recent years, utilize the field excitation branch line nonlinear characteristic of transformer to differentiate that the thought of excitation surge current is suggested, and receive publicity gradually because it has good recognition effect in theory.Ge Baoming, in the sea of learning, Wang Xianghang, Deng at " Automation of Electric Systems .2004, the algorithm utilizing the variation characteristic of equivalent instantaneous inductor to come differentiating transformer exciting surge and internal fault current is proposed in " new algorithm based on equivalent instantaneous inductor discrimination of Transformer " delivered 28(7): 44-48 ", but this method of discrimination of equivalent instantaneous inductor variable quantity that utilizes has some limitations: one, for the transformer with the Y-Δ mode of connection, because transformer both sides current phase is inconsistent, certain measure must be taked to adjust poor mobile equilibrium, but no matter take what kind of measure, capital causes the difference stream calculated to there is certain deviation with reality difference stream, therefore, the nonlinearities change feature of static exciter branch road cannot be portrayed exactly, they are two years old, at the former limit winding that extra-high voltage pressure regulation becomes, voltage measurement element is installed and does not meet engineering reality, that is directly cannot measure the port voltage of former limit winding, thus accurately cannot calculate equivalent instantaneous inductor, this all limits the employing of equivalent instantaneous inductor method.In sum, in the ordinary course of things, this criterion based on equivalent instantaneous inductor does not have practicality.Therefore; differentiate utilizing equivalent instantaneous inductor variation characteristic on the idea basis shoved; break through the obstacle existed when it is applied to differential protection of ultra-high voltage transformer; seek a kind of new algorithm being applicable to the protection of extra-high voltage pressure regulation transformer differential and just seem particularly important; with reference to Ge Baoming, in the sea of learning, Wang Xianghang; etc. " new algorithm based on equivalent instantaneous inductor discrimination of Transformer " delivered (" Automation of Electric Systems " .2004,28(7): 44-48).
Summary of the invention
The object of the invention is the problem for above-mentioned extra-high voltage adjustable transformer differential protection reliability deficiency; the equivalent instantaneous inductor proposing the protection of a kind of extra-high voltage adjustable transformer shoves locking method of discrimination; extra-high voltage adjustable transformer by three independently single transformer form; adopt the Y-Δ mode of connection; it is inner that the TA5 that secondary side is installed is connected to Δ side winding; there is not phase differential in former secondary current measured thus, can directly ask for difference current i accurately
d;
It is characterized in that, comprise the following steps:
1) first obtain action current and the stalling current of the A phase of extra-high voltage adjustable transformer, B phase and C phase, action current is
, stalling current is
, wherein,
with
be respectively the secondary current of the former avris of adjustable transformer and secondary side current transformer, (with reference to " relay protection of power system " China Electric Power Publishing House that Zhang Baohui, Yin Xianggen etc. write, second edition .2010 March: 166-177);
2) to A, B, C three-phase comparison electric current and stalling current respectively, the active region entering ratio-restrained characteristic is judged whether;
When i phase is in braking district, by the equivalent instantaneous inductor variances sigma L of i phase
ibe set to one and be greater than the constant (ε is threshold value) of ε and (a large amount of emulation experiments shows to leave enough nargin, correctly can distinguish when threshold value ε gets 0.01 ~ 1 and shove and internal fault, herein, described ε gets 0.1, constant of putting is set as 1), i phase is A phase, B phase or C phase, and σ L represents the variable quantity calculated by the equivalent instantaneous inductor in a cycle;
When i phase enters active region, then the analysis of equivalent instantaneous inductor variable quantity is carried out to i phase, and calculate the equivalent instantaneous inductor variances sigma L of i phase
i;
3) if equivalent instantaneous inductor variance is higher than threshold value ε, i.e. σ L
i> ε, be then judged to and shove, and this phase of locking is protected, otherwise is judged to this phase fault;
4) judged result is exported.
Excitation surge current and the fault current difference on waveform is just a kind of characterizes phenomenon, not the two the most essential difference, and the most basic reason producing excitation surge current is that transformer core is saturated and causes magnetizing inductance to occur cyclical variation.
Described equivalent instantaneous inductor variable quantity analytic process is as follows:
(1) first defining equivalent instantaneous inductor is the equivalent instant excitation inductance of entering viewed from the winding port of former limit, and its computing formula is as follows:
M in formula in round bracket represents the value of m sampled point, T
srepresent sampling interval, i
(m)represent the transformer primary secondary winding current difference of m sampled point, u
(m)represent the former limit winding port magnitude of voltage of m sampled point.
By the phase voltage u of bus
p, adjustable transformer no-load voltage ratio K
1,, and the no-load voltage ratio K of main-transformer public winding and low pressure winding
2pressure regulation can be calculated and become former limit winding port equivalent voltage
;
(2) basis
calculate equivalent instantaneous inductor, wherein u is the equivalent voltage u that step (1) calculates
1, i is former vice-side winding difference stream, and the m in round bracket represents the value of m sampled point, T
srepresent sampling interval;
(3) basis
try to achieve equivalent instantaneous inductor mean value, wherein L
(i)for the equivalent instantaneous inductor L that step (2) calculates
(m), N represents the sampling number of a cycle;
(4) basis
calculate equivalent instantaneous inductor variance, wherein L
avefor the equivalent instantaneous inductor mean value that step (3) calculates.
During excitation surge current, equivalent instantaneous inductor is acute variation, and during internal fault, its equivalent instantaneous inductor perseverance is constant.So, whether change based on equivalent instantaneous inductor and change violent degree, excitation surge current and internal fault current can be differentiated completely, utilizing the concept of average and variance to identify the variable quantity of equivalent instantaneous inductor herein, shown in (2), (3):
In formula, N represents the sampling number of a cycle, L
averepresent the mean value of N number of equivalent instantaneous inductor in a cycle, σ (L) represents the variable quantity calculated according to the equivalent instantaneous inductor in a cycle.If ε is threshold value, if σ (L) > is ε, is judged to and shoves, otherwise be judged to this phase fault.
Utilize equivalent instantaneous inductor variable quantity must accurately to calculate premised on equivalent instantaneous inductor to distinguish excitation surge current and internal fault current, and calculate the port voltage u that equivalent instantaneous inductor needs to obtain adjustable transformer former limit winding
1, and the difference i of transformer primary secondary winding current accurately
d, but, directly cannot measure at the port voltage of the former limit winding of adjustable transformer, equivalent pressure regulation can only be obtained by the method for indirect calculation and become former limit winding port voltage.
The described method by indirect calculation obtains the adjustable transformer former limit winding port voltage of equivalence, if the port voltage of adjustable transformer former limit winding is u
1(as shown in Figure 4) gear, residing for combined floodgate time-division contact obtains the ratio K of adjustable transformer no-load voltage ratio and the former vice-side winding number of turn
1, so adjustable transformer vice-side winding voltage is
.Again because of adjustable transformer vice-side winding and main-transformer low pressure winding parallel, if the no-load voltage ratio of main-transformer public winding and low pressure winding is K
2, then public winding voltage is
.If the phase voltage at 500KV bus place is u
p(voltage transformer (VT) (PT) can installed by bus is asked for), then
Namely
Therefore normal running, external fault and the idle-loaded switching-on Shi Douke above formula that shoves asks for pressure regulation change primary side voltage.And when there is the fault of single-phase turn-to-turn/all over the ground, umber of turn there occurs change, and in formula, K value and actual value are not inconsistent, the u calculated
1amplitude and measured value not etc., do not use this u
1the equivalent instantaneous inductor numerical value calculated has deviation.But u
1changing Pattern do not change, the equivalent instantaneous inductor Changing Pattern therefore calculated with adopt actual u
1there is no essential distinction, and the key of this diagnostic method is the Changing Pattern of equivalent instantaneous inductor but not its numerical values recited, so the equivalent voltage that formula (5) can be adopted completely to calculate goes to ask for equivalent instantaneous inductor.
Attachedly Figure 6 shows that new criterion action flow chart.
The invention has the beneficial effects as follows that the equivalent instantaneous inductor of extra-high voltage adjustable transformer proposed by the invention protection shoves locking method of discrimination, emphasis solve the extra-high voltage adjustable transformer degree of depth saturated time shove and the discriminating of the fault of turn-to-turn/all over the ground.The pressure regulation that the present invention obtains equivalence by the method for indirect calculation becomes former limit winding port voltage; excitation surge current and internal fault can be divided in right area; substantially not by the impact that the adjustable transformer degree of depth is saturated; effectively breach the engineer applied bottleneck directly cannot measuring former limit winding port voltage, will the scope of application of this method of equivalent instantaneous inductor variation characteristic discrimination of Transformer be utilized to extend to extra-high voltage adjustable transformer differential protection field first.Extra-high voltage pressure regulation becomes the equivalent instantaneous inductor locking new criterion that shoves and does not rely on secondary harmonic component in difference stream, and faults and the essential distinction of shoving, shove when especially the adjustable transformer degree of depth is saturated and single-phase turn-to-turn/this kind of easy alias condition of fault all over the ground.Therefore new criterion is to the reliability improving extra-high voltage transformer protection, guarantees that differential protection quick and precisely action has important practical meaning in engineering.
Accompanying drawing explanation
Fig. 1 is the single-phase schematic diagram of adjustable transformer longitudinal differential protection principle wiring.
Fig. 2 be second harmonic trend during adjustable transformer shoves and air-drop time fault phase secondary harmonic component
Fig. 3 is the situation that main-transformer contains larger remanent magnetism and the situation of dropping in large turn-to-turn (all over the ground) short circuit.
Fig. 4 is the phase structure figure of extra-high voltage transformer.
Fig. 5 is ratio-restrained characteristic.
Fig. 6 is new criterion action flow chart.
Embodiment
The equivalent instantaneous inductor that the present invention proposes the protection of a kind of extra-high voltage adjustable transformer shoves locking method of discrimination, is explained below in conjunction with accompanying drawing.
Figure 4 shows that the phase structure figure of extra-high voltage transformer.Extra-high voltage adjustable transformer by three independently single transformer form, adopt the Y-Δ mode of connection, it is inner that the TA5 that secondary side is installed is connected to Δ side winding, and former secondary current measured does not thus exist phase differential, can directly ask for difference current i accurately
d;
It is characterized in that, comprise the following steps:
1) first obtain action current and the stalling current of the A phase of extra-high voltage adjustable transformer, B phase and C phase, as shown in Figure 1, action current is
, stalling current is
, wherein,
with
be respectively the secondary current (with reference to " relay protection of power system " that Zhang Baohui, Yin Xianggen etc. write, China Electric Power Publishing House, second edition .2010 March: 166-177) that pressure regulation becomes former avris and secondary side current transformer;
2) by comparison electric current and stalling current, judge whether this phase enters the active region of ratio-restrained characteristic;
When i phase is in braking district, by the equivalent instantaneous inductor variances sigma L of i phase
ibe set to one and be greater than the constant (ε is threshold value) of ε and (a large amount of emulation experiments shows to leave enough nargin, correctly can distinguish when threshold value gets 0.01 ~ 1 and shove and internal fault, herein, described ε gets 0.1, constant of putting is set as 1), i phase is A phase, B phase or C phase, and σ L represents the variable quantity according to being calculated by the equivalent instantaneous inductor in a cycle;
When i phase enters active region, then the analysis of equivalent instantaneous inductor variable quantity is carried out to i phase, and calculate the equivalent instantaneous inductor variances sigma L of i phase
i;
3) if equivalent instantaneous inductor variance is higher than threshold value ε, i.e. σ L
i> ε, be then judged to and shove, and this phase of locking is protected, otherwise is judged to this phase fault;
4) judged result is exported.
Excitation surge current and the fault current difference on waveform is just a kind of characterizes phenomenon, not the two the most essential difference, and the most basic reason producing excitation surge current is that transformer core is saturated and causes magnetizing inductance to occur cyclical variation.
Described equivalent instantaneous inductor variable quantity analytic process is as follows:
(1) first defining equivalent instantaneous inductor is the equivalent instant excitation inductance of entering viewed from the winding port of former limit, and its computing formula is as follows:
M in formula in round bracket represents the value of m sampled point, T
srepresent sampling interval, i
(m)represent the transformer primary secondary winding current difference of m sampled point, u
(m)represent the former limit winding port magnitude of voltage of m sampled point.
By the phase voltage u of bus
p, adjustable transformer no-load voltage ratio K
1,, and the no-load voltage ratio K of main-transformer public winding and low pressure winding
2pressure regulation can be calculated and become former limit winding port equivalent voltage
;
(2) basis
calculate equivalent instantaneous inductor, wherein u is the equivalent voltage u that step (1) calculates
1, i is former vice-side winding difference stream, and the m in round bracket represents the value of m sampled point, T
srepresent sampling interval;
(3) basis
try to achieve equivalent instantaneous inductor mean value, wherein L
(i)for the equivalent instantaneous inductor L that step (2) calculates
(m), N represents the sampling number of a cycle;
(4) basis
calculate equivalent instantaneous inductor variance, wherein L
avefor the equivalent instantaneous inductor mean value that step (3) calculates.
During excitation surge current, equivalent instantaneous inductor is acute variation, and during internal fault, its equivalent instantaneous inductor perseverance is constant.So, whether change based on equivalent instantaneous inductor and change violent degree, excitation surge current and internal fault current can be differentiated completely, utilizing the concept of average and variance to identify the variable quantity of equivalent instantaneous inductor herein, shown in (2), (3):
In formula, N represents the sampling number of a cycle, L
averepresent the mean value of N number of equivalent instantaneous inductor in a cycle, σ (L) represents the variable quantity calculated according to the equivalent instantaneous inductor in a cycle.If ε is threshold value, if σ (L) > is ε, is judged to and shoves, otherwise be judged to this phase fault.
Utilize equivalent instantaneous inductor variable quantity must accurately to calculate premised on equivalent instantaneous inductor to distinguish excitation surge current and internal fault current, and calculate the port voltage u that equivalent instantaneous inductor needs to obtain adjustable transformer former limit winding
1, and the difference i of transformer primary secondary winding current accurately
d, but, directly cannot measure at the port voltage of the former limit winding of adjustable transformer, equivalent pressure regulation can only be obtained by the method for indirect calculation and become former limit winding port voltage.
The described method by indirect calculation obtains the adjustable transformer former limit winding port voltage of equivalence, if the port voltage of adjustable transformer former limit winding is u
1(as shown in Figure 4) gear, residing for combined floodgate time-division contact obtains the ratio K of adjustable transformer no-load voltage ratio and the former vice-side winding number of turn
1, so adjustable transformer vice-side winding voltage is
.Again because of adjustable transformer vice-side winding and main-transformer low pressure winding parallel, if the no-load voltage ratio of main-transformer public winding and low pressure winding is K
2, then public winding voltage is
.If the phase voltage at 500KV bus place is u
p(voltage transformer (VT) (PT) can installed by bus is asked for), then
Namely
Therefore normal running, external fault and the idle-loaded switching-on Shi Douke above formula that shoves asks for pressure regulation change primary side voltage.And when there is the fault of single-phase turn-to-turn/all over the ground, umber of turn there occurs change, and in formula, K value and actual value are not inconsistent, the u calculated
1amplitude and measured value not etc., do not use this u
1the equivalent instantaneous inductor numerical value calculated has deviation.But u
1changing Pattern do not change, the equivalent instantaneous inductor Changing Pattern therefore calculated with adopt actual u
1there is no essential distinction, and the key of this diagnostic method is the Changing Pattern of equivalent instantaneous inductor but not its numerical values recited, so the equivalent voltage that formula (5) can be adopted completely to calculate goes to ask for equivalent instantaneous inductor.
Figure 6 shows that new criterion action flow chart.
Embodiment
Become A phase winding 5% turn-to-turn fault for extra-high voltage pressure regulation, according to Fig. 5, differentiate flow process, adopt new criterion to become excitation surge current to pressure regulation and differentiate:
1, first obtain action current and the stalling current of A phase, B phase and C phase, obtain I
op.A=4.25p.u, I
op.B=0.18 p.u, I
op.C=0.09p.u, I
res.A=3.06p.u, I
res.B=0.34 p.u, I
res.C=0.27p.u, wherein p.u represents perunit value, and comparative result is that A phase is in differential protection active region, and B, C phase brake district in differential protection;
2, the equivalent instantaneous inductor variances sigma L of A phase is calculated
i, obtain σ L
a=0.002, by the equivalent instantaneous inductor variances sigma L of B, C phase
iput 1, i.e. σ L
b=1, σ L
c=1;
3, A equivalent instantaneous inductor variances sigma L
alower than ε (ε=0.1), then A phase is judged to single-phase fault; B equivalent instantaneous inductor variances sigma L
bhigher than ε, then B phase is judged to and shoves; C equivalent instantaneous inductor variances sigma L
chigher than ε, then C phase is judged to and shoves;
Therefore the protection of pressure regulation transformer differential can be made accurately to distinguish excitation surge current and internal fault according to new criterion; compensate for well second harmonic locking criterion None-identified pressure regulation varying depth saturated time shove and the defect of the fault of single-phase turn-to-turn/all over the ground, avoid the differential protection misoperation that excitation surge current causes.
Claims (2)
1. the equivalent instantaneous inductor of extra-high voltage adjustable transformer protection shoves locking method of discrimination; extra-high voltage adjustable transformer by three independently single transformer form; adopt the Y-Δ mode of connection; it is inner that the TA5 that secondary side is installed is connected to Δ side winding; there is not phase differential in former secondary current measured thus, can directly ask for difference current i accurately
d;
It is characterized in that, comprise the following steps:
1) first obtain action current and the stalling current of the A phase of extra-high voltage adjustable transformer, B phase and C phase, action current is
Stalling current is
Wherein,
with
be respectively the secondary current of the former avris of adjustable transformer and secondary side current transformer;
2) to A, B, C three-phase comparison electric current and stalling current respectively, judge whether this phase enters the active region of ratio-restrained characteristic;
When i phase is in braking district, by the equivalent instantaneous inductor variances sigma L of i phase
ibe set to the constant that is greater than ε, and leave enough nargin, herein, ε is threshold value, and i phase is A phase, B phase or C phase, and σ L represents the variable quantity calculated by the equivalent instantaneous inductor in a cycle;
When threshold value ε gets 0.01 ~ 1, correctly can distinguish and shove and internal fault; When i phase enters active region, then the analysis of equivalent instantaneous inductor variable quantity is carried out to i phase, and calculate the equivalent instantaneous inductor variances sigma L of i phase
i;
3) if equivalent instantaneous inductor variance is higher than threshold value ε, i.e. σ L
i> ε, be then judged to and shove, and this phase of locking is protected, otherwise is judged to this phase fault;
4) judged result is exported;
Excitation surge current and the fault current difference on waveform is just a kind of characterizes phenomenon, not the two the most essential difference, and the most basic reason producing excitation surge current is that transformer core is saturated and causes magnetizing inductance to occur cyclical variation;
Described equivalent instantaneous inductor variable quantity analytic process is as follows:
(1) first defining equivalent instantaneous inductor is the equivalent instant excitation inductance of entering viewed from the winding port of former limit, and its computing formula is as follows:
M in formula in round bracket represents the value of m sampled point, T
srepresent sampling interval, i
(m)represent the transformer primary secondary winding current difference of m sampled point, u
(m)represent the former limit winding port magnitude of voltage of m sampled point;
By the phase voltage u of bus
p, adjustable transformer no-load voltage ratio K
1,, and the no-load voltage ratio K of main-transformer public winding and low pressure winding
2calculate pressure regulation and become former limit winding port equivalent voltage
(2) basis
calculate equivalent instantaneous inductor, wherein u is the equivalent voltage u that step (1) calculates
1, i is former vice-side winding difference stream, and the m in round bracket represents the value of m sampled point, T
srepresent sampling interval;
(3) basis
try to achieve equivalent instantaneous inductor mean value, wherein L
(i)for the equivalent instantaneous inductor L that step (2) calculates
(m), N represents the sampling number of a cycle;
(4) basis
calculate equivalent instantaneous inductor variance, wherein L
avefor the equivalent instantaneous inductor mean value that step (3) calculates;
During excitation surge current, equivalent instantaneous inductor is acute variation, and its equivalent instantaneous inductor perseverance is constant during internal fault, so, whether change based on equivalent instantaneous inductor and change violent degree, can differentiate excitation surge current and internal fault current completely, utilize the concept of average and variance to identify the variable quantity of equivalent instantaneous inductor herein, shown in (2), (3):
In formula, N represents the sampling number of a cycle, L
averepresent the mean value of N number of equivalent instantaneous inductor in a cycle, σ (L) represents the variable quantity calculated according to the equivalent instantaneous inductor in a cycle; If ε is threshold value, if σ (L) > is ε, is judged to and shoves, otherwise be judged to this phase fault;
Utilize equivalent instantaneous inductor variable quantity must accurately to calculate premised on equivalent instantaneous inductor to distinguish excitation surge current and internal fault current, and calculate the port voltage u that equivalent instantaneous inductor needs to obtain adjustable transformer former limit winding
1, and the difference i of transformer primary secondary winding current accurately
d, but, directly cannot measure at the port voltage of the former limit winding of adjustable transformer, equivalent pressure regulation can only be obtained by the method for indirect calculation and become former limit winding port voltage.
2. the equivalent instantaneous inductor of extra-high voltage adjustable transformer protection according to claim 1 shoves locking method of discrimination; it is characterized in that; the described method by indirect calculation obtains the adjustable transformer former limit winding port voltage of equivalence, if the port voltage of adjustable transformer former limit winding is u
1, the gear residing for combined floodgate time-division contact obtains the ratio K of adjustable transformer no-load voltage ratio and the former vice-side winding number of turn
1, so adjustable transformer vice-side winding voltage is
again because of adjustable transformer vice-side winding and main-transformer low pressure winding parallel, if the no-load voltage ratio of main-transformer public winding and low pressure winding is K
2, then public winding voltage is
if the phase voltage at 500KV bus place is u
p, the voltage transformer (VT) that this phase voltage is installed by bus is asked for, then
Namely
Therefore ask for pressure regulation when normal operation, external fault and idle-loaded switching-on shove with above formula and become primary side voltage; And when there is the fault of single-phase turn-to-turn/all over the ground, umber of turn there occurs change, and in formula, K value and actual value are not inconsistent, the u calculated
1amplitude and measured value not etc., do not use this u
1the equivalent instantaneous inductor numerical value calculated has deviation; But u
1changing Pattern do not change, the equivalent instantaneous inductor Changing Pattern therefore calculated with adopt actual u
1there is no essential distinction, and the key of this diagnostic method is the Changing Pattern of equivalent instantaneous inductor but not its numerical values recited, so the equivalent voltage that formula (5) can be adopted completely to calculate goes to ask for equivalent instantaneous inductor.
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| CN104977488B (en) * | 2015-06-30 | 2018-01-12 | 昆明理工大学 | A kind of transformer excitation flow recognition method based on difference current gradient angle approximate entropy |
| CN108429229B (en) * | 2018-04-27 | 2020-02-21 | 东南大学 | Method for judging excitation inrush current of no-load transformer in phase selection reclosing process of circuit breaker |
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| CN110018372B (en) * | 2019-04-09 | 2021-06-08 | 国网陕西省电力公司电力科学研究院 | Transformer protection method based on excitation impedance fluctuation characteristics |
| CN110850171B (en) * | 2019-11-29 | 2021-09-17 | 国网山东省电力公司青岛供电公司 | Evaluation method for DC resistance qualification degree of voltage regulating transformer |
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