CN105977914A - Zero-sequence over-current protection method and device for transformers in inner bridge way - Google Patents

Abstract

The invention discloses a zero-sequence over-current protection method and device for transformers in an inner bridge way. The method comprises the steps as follows: zero-sequence current of an inlet wire side current transformer, the zero-sequence current of an inner bridge side current transformer and the vector sum of the zero-sequence current are obtained separately; and if any one of the zero-sequence current of the inlet wire side current transformer, the zero-sequence current of the inner bridge side current transformer and the vector sum is greater than a protective threshold, circuit breakers between the transformers and inlet wires are cut off. According to the technical scheme provided by the embodiment of the invention, the problem of low sensitivity of a traditional zero-sequence over-current protection method is solved.

Description

The method and device of transformator zero-sequencedirectional protection under interior bridge mode

Technical field

The present invention relates to microcomputer type relay protection technical field, particularly relate in one transformator zero sequence under bridge mode and cross stream The method and device of protection.

Background technology

Transformator is the visual plant of power system, once breaks down, by the normal power supply of system and equipment safety Bring serious impact, and the important defence line of the tranformer protection isolated fault point reliable after breaking down, timely that is it.Continuing In " four property " of electric protection, susceptiveness refers to the protective relaying device fault to occurring in its protection domain or irregular operating shape The respond of state, susceptiveness sensitivity coefficient is weighed.Wherein the minimum of fault parameter, calculated maximum are can according to reality The least favorable method of operation, fault type and the short dot of energy calculates.The size of sensitivity coefficient determines when fault occurs and protects Protect whether can action message, thus be the important indicator weighing protection.

In tranformer protection, high-pressure side winding when zero-sequencedirectional protection is directly grounded operation as transformer neutral point, High-pressure side lead-out wire and the back-up protection of busbar grounding fault and the back-up protection of adjacent power line-to-ground fault.Work as power transformation Stand when using internal bridge connection (mainly 110kV transformer station), owing to high voltage side of transformer does not installs current transformer TA, because of And use the measured value of inlet wire side TA and Nei Qiao side TA to take vector and participate in the logical operations of high voltage side of transformer back-up protection.This Time use self-produced zero stream, i.e. in tranformer protection " high-pressure side zero sequence is crossed stream and used self-produced zero stream " control word when zero-sequencedirectional protection When putting 1, traditional self-produced zero-sequencedirectional protection uses self-produced zero stream of inlet wire side TA and self-produced zero flow vector of Nei Qiao side TA and conduct Criterion.

But analyze and show, under three kinds of methods of operation that interior bridging power station is likely to occur, when outside Nei He district of transformator district When there is earth fault (as at the K1 of Fig. 2 and at the K2 of Fig. 3) at the most close two, in tradition criterion, zero sequence crosses stream guarantor The sensitivity protected considerably reduces.

Summary of the invention

In view of this, the embodiment of the present invention provides method and the dress of transformator zero-sequencedirectional protection under a kind of interior bridge mode Put, the problem low to solve the sensitivity of tradition zero-sequencedirectional protection method.

First aspect, embodiments provides a kind of method of transformator zero-sequencedirectional protection under interior bridge mode, bag Include:

Obtain the zero-sequence current of inlet wire side current transformer, the zero-sequence current of Nei Qiao side current transformer, and two respectively The vector of person；

If above-mentioned three is arbitrary more than protection threshold value, then disconnect the chopper between transformator and inlet wire.

Second aspect, embodiments provides the device of transformator zero-sequencedirectional protection under a kind of interior bridge mode, bag Include the transformator of internal bridge, inlet wire side current transformer, Nei Qiao side current transformer and chopper, it is characterised in that also wrap Include:

Zero-sequence current acquisition module, for obtaining the zero-sequence current of described inlet wire side current transformer, described interior bridge respectively The zero-sequence current of side current transformer, and both vectors；

Overcurrent protection action module, for arbitrary more than when protecting threshold value above-mentioned three, disconnect described transformator and enters Described chopper between line.

The method and device of transformator zero-sequencedirectional protection under a kind of interior bridge mode that the embodiment of the present invention provides, by dividing Not Huo Qu the zero-sequence current of inlet wire side current transformer, the zero-sequence current of Nei Qiao side current transformer, and both vectors, Above-mentioned three being constituted or door computing, the most above-mentioned three is arbitrary more than when protecting threshold value, disconnects breaking between transformator and inlet wire Road device, this programme relative to existing only with self-produced zero flow vector of both sides current transformer and the method as criterion, it is to avoid During transformator external short-circuit fault, the problem of zero-sequencedirectional protection susceptiveness difference, improve transformator zero-sequencedirectional protection Sensitivity, makes protection action message.

Accompanying drawing explanation

By the detailed description that non-limiting example is made made with reference to the following drawings of reading, other of the present invention Feature, purpose and advantage will become more apparent upon:

Fig. 1 is the method flow of transformator zero-sequencedirectional protection under a kind of interior bridge mode that the embodiment of the present invention one provides Figure；

Fig. 2 is singlephase earth fault figure in 2 times transformator districts of the method for operation that the embodiment of the present invention one provides；

Fig. 3 is singlephase earth fault figure outside 2 times transformator districts of the method for operation that the embodiment of the present invention one provides；

Fig. 4 is singlephase earth fault sequence diagrams in 2 times transformator districts of the method for operation that the embodiment of the present invention two provides；

Fig. 5 is singlephase earth fault sequence diagrams outside 2 times transformator districts of the method for operation that the embodiment of the present invention two provides；

Fig. 6 is singlephase earth fault figure in 3 times transformator districts of the method for operation that the embodiment of the present invention three provides；

Fig. 7 is singlephase earth fault figure outside 3 times transformator districts of the method for operation that the embodiment of the present invention three provides；

Fig. 8 is singlephase earth fault sequence diagrams in 3 times transformator districts of the method for operation that the embodiment of the present invention three provides；

Fig. 9 is singlephase earth fault sequence diagrams outside 3 times transformator districts of the method for operation that the embodiment of the present invention three provides；

Figure 10 is the apparatus structure of transformator zero-sequencedirectional protection under a kind of interior bridge mode that the embodiment of the present invention four provides Figure.

Detailed description of the invention

The present invention is described in further detail with embodiment below in conjunction with the accompanying drawings.It is understood that this place is retouched The specific embodiment stated is used only for explaining the present invention, rather than limitation of the invention.It also should be noted that, in order to just Part related to the present invention is illustrate only rather than full content in description, accompanying drawing.

It also should be noted that, for the ease of describe, accompanying drawing illustrate only part related to the present invention rather than Full content.It should be mentioned that, some exemplary embodiments are described before being discussed in greater detail exemplary embodiment Become the process or method described as flow chart.Although operations (or step) is described as the process of order by flow chart, but It is that many of which operation can be implemented concurrently, concomitantly or simultaneously.Additionally, the order of operations can be by again Arrange.The most described process can be terminated, it is also possible to have the additional step being not included in accompanying drawing. Described process can correspond to method, function, code, subroutine, subprogram etc..

Embodiment one

Fig. 1 is the method flow of transformator zero-sequencedirectional protection under a kind of interior bridge mode that the embodiment of the present invention one provides Figure.The method of the present embodiment can be performed by the device of transformator zero-sequencedirectional protection under interior bridge mode, and described device can pass through The mode of software and/or hardware realizes.As it is shown in figure 1, transformator zero-sequencedirectional protection under the interior bridge mode of the present embodiment offer Method specifically include:

The zero-sequence current of S110, respectively acquisition inlet wire side current transformer, the zero-sequence current of Nei Qiao side current transformer, with And both vectors.

If the above-mentioned three of S120 is arbitrary more than protection threshold value, then disconnect the chopper between transformator and inlet wire.

Internal bridge and outer bridging line are only applicable to two transformators, the wiring of two inlet wires.Interior bridge mode is that mother exists The inner side of two transformer switches, near transformer side.Outer bridge mode is the mother outside at two transformer switches, near entering Line side.The present embodiment is introduced the interior bridge mode needing to consider tranformer protection, referring to figs. 2 and 3, two inlet wire the first inlet wires 1 and second inlet wire 2 be connected to the first transformator 3 and the second transformator 4, bus is positioned at two chopper 1DLs' and 2DL Side, near transformer side.Inlet wire side current transformer TA1 and TA2 is installed on internal bridge inlet wire side, is used for gathering inlet wire side three Phase current, Nei Qiao side current transformer TA3 is installed on internal bridge Nei Qiao side, is used for gathering Nei Qiao side three-phase current.

When any point occurs single-phase or biphase ground short circuit fault in power system, system will produce zero sequence electricity Stream.Now, there will be a residual voltage in earth fault, zero-sequence current will be produced under this voltage effect.

Only have forward-order current when system is properly functioning, just produce negative-sequence current and zero sequence electricity when unbalanced fault occurs Stream, i.e. negative-sequence current and zero-sequence current is produced by trouble point.The short circuit path of positive and negative sequence is closed to electric power generating composition by short dot Closing loop, zero sequence short circuit path is constituted closed-loop path by short circuit grounding point to transformer grounding point.

In the present embodiment, the high-pressure side of described transformator is star-connection, the neutral-point solid ground of described star-connection. If high-pressure side is delta connection, then there is no zero-sequence current, therefore need not arrange zero-sequencedirectional protection；If star-star connection, But isolated neutral, zero-sequence current is little, also need not arrange zero-sequencedirectional protection；If star-star connection, and neutral point Being directly grounded, then have zero-sequence current, if having reached high-pressure side protection act value, then starting zero-sequencedirectional protection.If transformator is High-pressure side star-connection, low-pressure side delta connection, with reference to Fig. 2 or Fig. 3, then zero-sequence current component is filtered by delta connection side Removing, low-pressure side no longer has zero-sequence current.

It is noted that, described zero-sequence current is preferably self-produced zero stream.Self-produced zero stream is to be passed through by inside protection device Logic circuit or program calculate and are formed by stacking by three-phase current vector, and external zero-sequence current is to be synthesized by current transformer or special Zero sequence current mutual inductor is directly formed.In actual application, due to external zero sequence current mutual inductor polarity may wrong, for Ensureing the correctness of zero sequence direction, the zero sequence direction of protection device can use self-produced residual voltage and self-produced zero-sequence current.This In scheme, obtain inlet wire side current transformer and the three-phase current of Nei Qiao side current transformer the most respectively, inside protection device By three-phase current vector superposition, obtain self-produced zero stream of inlet wire side current transformer and Nei Qiao side current transformer.By both Self-produced zero stream does vector, then obtained inlet wire side current transformer self-produced zero stream, self-produced the zero of Nei Qiao side current transformer Stream, and both vectors.

Internal bridge connection is commonly available to 110kV transformer station, and typical wiring figure, as in figure 2 it is shown, arrange simple, possesses one Fixed reliability and motility, use equipment few, and cost is low.It is suitable to arrange.It has the following characteristics that be applicable to circuit longer, Transformator is not required to the situation often switched；It is properly functioning that line fault does not affect transformator, and the switching of transformator can cause circuit Deactivate；It is applicable to the main connection mode design of the penetration electric substation not quite or almost without penetration.

For 110kV internal bridge connection, there is following several method of operation:

The method of operation 1, the first inlet wire 1 and the second inlet wire 2 fanout operation；

The method of operation 2, it is standby that the first inlet wire 1 runs that the second inlet wire 2 is standby, the second inlet wire 2 runs the first inlet wire 1；

The method of operation 3, two inlet wires all run with interior bridge, it is adaptable to have situation during penetration.

For the method for operation 1 because the first inlet wire 1 and the second inlet wire 2 fanout operation be not related to outside Nei He district of district point, zero Sequence overcurrent protection is protected with conventional transformer, therefore it is not repeated by the embodiment of the present invention.

Transformator zero-sequencedirectional protection method under existing interior bridge mode, by using self-produced zero stream in inlet wire side and Nei Qiao side Self-produced zero flow vector and composition logical operations are applied to zero-sequencedirectional protection.But for singlephase earth fault, transformator district Outside Nei Huo district during single-phase earthing, the direction of the zero-sequence current flowing through bus is contrary.

Referring to figs. 2 and 3, Fig. 2 and Fig. 3 is respectively the fault of unidirectional ground connection outside Nei He district of 2 times transformator districts of the method for operation Figure, now the first inlet wire 1 runs, and the second inlet wire 2 is standby.In Fig. 2, zero-sequence current, by short dot K1, divides three parts 3I₁₀、3I₂₀ And 3I₃₀Flow to the first inlet wire 1 respectively, the earth point of the second transformator 4 and the earth point of the first transformator 3, wherein, zero-sequence current 3I₂₀The right side is flowed in the drawings by left.In Fig. 3, zero-sequence current, by short dot K2, divides two parts 3I₂₀And 3I₄₀Flow to the left side respectively prop up Road and the earth point of the second transformator 4.3I₂₀After flowing to left side branch road, it is divided into two parts 3I₁₀And 3I₃₀Flow to the first inlet wire respectively 1 and first earth point of transformator 3.3I is drawn by Fig. 2 and Fig. 3₂₀In above-mentioned two situations, the sense of current is contrary.Therefore Only choose 3I₁₀And 3I₂₀Vector to be used as the criterion of overcurrent protection be inaccurate, outside district during singlephase earth fault, spirit Sensitivity can be decreased obviously.The present embodiment gathers the zero-sequence current 3I of inlet wire side current transformer TA1 respectively₁₀, Nei Qiao side electric current is mutual The zero-sequence current 3I of sensor TA3₂₀, and both vectors are as the criterion of zero-sequenceprotection, when any one value is more than protection threshold During value, start zero-sequencedirectional protection, disconnect the chopper between transformator and inlet wire, increase the sensitive of zero-sequencedirectional protection Degree.Here chopper refers to be currently under closure state, and connects the open circuit of the inlet wire in work and transformator Device, such as, chopper 1DL and 3DL in Fig. 2 or Fig. 3.

The method of transformator zero-sequencedirectional protection under the interior bridge mode that the embodiment of the present invention one provides, by obtain respectively into The zero-sequence current of line side current transformer, the zero-sequence current of Nei Qiao side current transformer, and both vectors, by above-mentioned three Person is constituted or door computing, and the most above-mentioned three is arbitrary starts zero-sequencedirectional protection more than when protecting threshold value, and this programme is relative to existing Only with self-produced zero flow vector of both sides current transformer and the method as criterion, it is to avoid transformator external short-circuit fault Time, the problem of zero-sequencedirectional protection susceptiveness difference, improve the sensitivity of transformator zero-sequencedirectional protection, make protection reliably move Make.

Embodiment two

The embodiment of the present invention is on the basis of embodiment one, to the transformator under bridge mode interior in embodiment one in operation side In the case of formula 2, outside Nei He district of district, during singlephase earth fault, zero-sequence protection method is analyzed.

Owing to the first inlet wire 1 runs, the second inlet wire 2 is standby and the second inlet wire 2 runs, the first inlet wire 1 standby mode principle Identical.The present embodiment runs with the first inlet wire 1, is analyzed, referring to figs. 2 and 3 shown as a example by the second inlet wire 2 is standby.

As in figure 2 it is shown, when (at the K1 of high-pressure side) singlephase earth fault in the first transformator 3 district, its fault sequence diagrams is such as Shown in Fig. 4, it is assumed that singlephase earth fault is A phase mutually, I_KA1For A phase forward-order current, I_KA2For A phase negative-sequence current, I_KA0For A phase zero Sequence electric current.Same, U_KA1、U_KA2And U_KA0It is respectively the positive sequence of A phase, negative phase-sequence and residual voltage.When A phase ground connection, I_KA1=I_KA2 =I_KA3, U_KA1+U_KA2+U_KA0=0.With reference to Fig. 4, X_s1、X_s2And X_s0It is respectively system positive sequence, negative phase-sequence and zero-sequence reactance, X_T10And X_T20 Represent the first transformator 3 and zero sequence impedance of the second transformator 4 respectively.Then self-produced zero stream of inlet wire side current transformer TA1 3I₁₀, the zero-sequence current 3I of Nei Qiao side current transformer TA3₂₀And the two vector is respectively as follows:

$3I_{10}=\frac{X_{T10}}{X_{s0}\left|\right|X_{T20}+X_{T10}}\·\frac{X_{T20}}{X_{s0}+X_{T20}}\·I_0---\left(1\right)$

$3I_{20}=\frac{X_{T10}}{X_{s0}\left|\right|X_{T20}+X_{T10}}\·\frac{X_{s0}}{X_{s0}+X_{T20}}\·I_0---\left(2\right)$

$3{\stackrel{\·}{I}}_{10}+3{\stackrel{\·}{I}}_{20}=\frac{X_{T10}}{X_{s0}\left|\right|X_{T20}+X_{T10}}\·I_0---\left(3\right)$

As it is shown on figure 3, when (at K2) A phase earth fault in the first transformator 3 district, its fault sequence diagrams is as shown in Figure 5. The then self-produced zero stream 3I of inlet wire side current transformer TA1₁₀, the zero-sequence current 3I of Nei Qiao side current transformer TA3₂₀And the two arrow Measure and be respectively as follows:

$3I_{10}=\frac{X_{T20}}{X_{s0}\left|\right|X_{T10}+X_{T20}}\·\frac{X_{T10}}{X_{s0}+X_{T10}}\·I_0---\left(4\right)$

$3I_{20}=\frac{X_{T20}}{X_{s0}\left|\right|X_{T10}+X_{T20}}\·I_0---\left(5\right)$

$3{\stackrel{\·}{I}}_{10}+3{\stackrel{\·}{I}}_{20}=-\frac{X_{T20}}{X_{s0}\left|\right|X_{T10}+X_{T20}}\·\frac{X_{s0}}{X_{T10}+X_{s0}}\·I_0---\left(6\right)$

Now calculate according to real data, make the following assumptions:

1, consider that 110kV system short-circuit level is between 5kA～35kA.

2, choosing reference capacity 100MVA, reference voltage is 110kV.

3, the zero sequence impedance of system is 3 times of positive sequence impedance.

4, two system averages short circuit currents, corresponding sequence impedance is equal.

5,110kV Transformer Short Circuit Impedance percentage ratio is 10.5%, and capacity is 50MVA.

6, two transformer parameters are consistent.

The corresponding each impedance perunit values of 2 times different short circuit currents of the method for operation can be drawn, perunit value concrete by data above Numerical value is as shown in table 1.

Table 1

Short circuit current (KA)	Xs1	Xs2	Xs0	XT10	XT20
						35	0.015	0.015	0.045	0.21	0.21
25	0.021	0.021	0.063	0.21	0.21
						20	0.026	0.026	0.079	0.21	0.21
15	0.035	0.035	0.105	0.21	0.21
						10	0.0525	0.0525	0.1575	0.21	0.21
5	0.105	0.105	0.315	0.21	0.21

Singlephase earth fault at 2 times K1 of the method for operation, is combined formula (1) by table 1～(3) to can be calculated inlet wire side electric current mutual The self-produced zero stream 3I of sensor TA1₁₀, Nei Qiao side current transformer TA3 self-produced zero stream 3I₂₀And the two vector, as shown in table 2.

Table 2

Short circuit current (KA)	3I10	3I20	3I10+3I20
				35	0.7I0	0.15I0	0.85I0
25	0.62I0	0.19I0	0.81I0
				20	0.57I0	0.21I0	0.78I0
15	0.5I0	0.25I0	0.75I0
				10	0.4I0	0.3I0	0.7I0
5	0.25I0	0.375I0	0.625I0

Singlephase earth fault at 2 times K2 of the method for operation, is combined formula (4) by table 1～(6) to can be calculated inlet wire side electric current mutual The self-produced zero stream 3I of sensor TA1₁₀, Nei Qiao side current transformer TA3 self-produced zero stream 3I₂₀And the two vector, as shown in table 3.

Table 3

Short circuit current (KA)	3I10	3I20	3I10+3I20
				35	0.7I0	0.85I0	0.15I0
25	0.62I0	0.81I0	0.19I0
				20	0.57I0	0.78I0	0.21I0
15	0.5I0	0.75I0	0.25I0
				10	0.4I0	0.7I0	0.3I0
5	0.25I0	0.625I0	0.375I0

For table 2, at K1 during singlephase earth fault, because inlet wire side current transformer TA1 is self-produced zero stream 3I₁₀With interior bridge The self-produced zero stream 3I of side current transformer TA3₂₀Vector more than any of which value, so using its vector to come and protection threshold value Compare, when its vector is more than protection threshold value, trigger zero-sequencedirectional protection circuit.Available sensitivity coefficient Klm sentences The susceptiveness of disconnected method.Sensitivity coefficient is the ratio of fault current during action and protection threshold value, in certain scope, sensitive Coefficient is the highest, and susceptiveness is the strongest.Such as, protection threshold value is set as 0.1I₀, when short circuit current is 35KV, Klm=0.85I₀/ 0.1I₀=8.5.At K1 during singlephase earth fault, use traditional method identical with the susceptiveness of the calculating of the present embodiment scheme.

For table 3, at K2 during singlephase earth fault, the self-produced zero stream 3I of inlet wire side current transformer TA1₁₀With Nei Qiao side electricity The self-produced zero stream 3I of current transformer TA3₂₀Vector compare 3I₂₀Little, because now 3I₂₀Direction there occurs change.Use vector Judging, susceptiveness is poor.Such as, set protection threshold value and be similarly 0.1I₀, by vector with protection threshold ratio relatively, try to achieve Sensitivity coefficient Klm=0.15I₀/0.1I₀=1.5, the present embodiment scheme first obtains 3I₁₀=0.7I₀, 3I₂₀=0.85I₀And 3I₁₀+ 3I₂₀=0.15I₀, draw maximum 3I therein₂₀=0.85I₀, so sensitivity coefficient Klm=0.85I₀/0.1I₀=8.5.Institute Obtaining sensitivity coefficient in the conventional way is 1.5, and this programme sensitivity coefficient is 8.5, and the susceptiveness of zero-sequencedirectional protection method obtains Improve.

Transformator under interior bridge mode in the case of the method for operation 2, is connect by the present embodiment two to single-phase outside Nei He district of district Earth fault situation compares, and traditional method is compared with this programme, and result show that this programme is for single-phase outside district Earth fault, susceptiveness is greatly improved compared with traditional method.

Embodiment three

Fig. 6 is singlephase earth fault figure in 3 times transformator districts of the method for operation that the embodiment of the present invention three provides.Fig. 7 is this Singlephase earth fault figure outside 3 times transformator districts of the method for operation that inventive embodiments three provides.The embodiment of the present invention is in embodiment one On the basis of embodiment two, to transformator in embodiment one in the case of the method for operation 3, single-phase earthing event outside Nei He district of district During barrier, zero-sequence protection method is analyzed.

In the method for operation 3, two inlet wires all run with interior bridge, and with reference to Fig. 6, i.e. chopper 1DL, 2DL and 3DL closes, interior Certain penetration is had on bridge.Self-produced zero stream 3I as inlet wire side current transformer TA1₁₀, Nei Qiao side current transformer TA3 Zero-sequence current 3I₂₀And in the two vector, have one to be more than protection threshold value, then cut-off breaker 1DL, 2DL and 3DL.Because two Bar inlet wire runs simultaneously, so there are two systems under this method of operation, and the first system taken as the leading factor with the first inlet wire 1 and with the The second system that two inlet wires 2 are taken as the leading factor.

As shown in Figure 6, at K1 during singlephase earth fault, it is also assumed that A phase ground connection, its fault sequence network figure such as Fig. 8 institute Show.Wherein X_s11、X_s12And X_s10For the first system positive sequence, negative phase-sequence and zero-sequence reactance, X_s21、X_s22And X_s20For second system positive sequence, Negative phase-sequence and zero-sequence reactance, X_T10、X_T20First transformator 3 and the zero sequence impedance of the second transformator 4 respectively.Inlet wire side current transformer The self-produced zero stream 3I of TA1₁₀, the zero-sequence current 3I of Nei Qiao side current transformer TA3₂₀And the two vector is respectively as follows:

$3I_{10}=\frac{X_{T10}}{X_{s10}\left|\right|X_{s20}\left|\right|X_{T20}+X_{T10}}\·\frac{X_{s20}\left|\right|X_{T20}}{X_{s10}+X_{s20}\left|\right|X_{T20}}\·{I^{\′}}_0---\left(7\right)$

$3I_{20}=\frac{X_{T10}}{X_{s10}\left|\right|X_{s20}\left|\right|X_{T20}+X_{T10}}\·\frac{X_{s10}}{X_{s10}+X_{s20}\left|\right|X_{T20}}\·{I^{\′}}_0---\left(8\right)$

$3{\stackrel{\·}{I}}_{10}+3{\stackrel{\·}{I}}_{20}=\frac{X_{T10}}{X_{s10}\left|\right|X_{s20}\left|\right|X_{T20}+X_{T10}}\·{I^{\′}}_0---\left(9\right)$

As it is shown in fig. 7, at K2 during singlephase earth fault, its fault sequence network figure is as shown in Figure 9.Inlet wire side Current Mutual Inductance The self-produced zero stream 3I of device TA1₁₀, the zero-sequence current 3I of Nei Qiao side current transformer TA3₂₀And the two vector is respectively as follows:

$3I_{10}=\frac{X_{s20}\left|\right|X_{T20}}{X_{s20}\left|\right|X_{T20}+X_{s10}\left|\right|X_{T10}}\·\frac{X_{T10}}{X_{T10}+X_{s10}}\·{I^{\′}}_0---\left(10\right)$

$3I_{20}=\frac{X_{s20}\left|\right|X_{T20}}{X_{s20}\left|\right|X_{T20}+X_{s10}\left|\right|X_{T10}}\·{I^{\′}}_0---\left(11\right)$

$3{\stackrel{\·}{I}}_{10}+3{\stackrel{\·}{I}}_{20}=-\frac{X_{s20}\left|\right|X_{T20}}{X_{s20}\left|\right|X_{T20}+X_{s10}\left|\right|X_{T10}}.\frac{X_{s10}}{X_{T10}+X_{s10}}\·{I^{\′}}_0---\left(12\right)$

The hypothesis that the present embodiment real data is made is with above-described embodiment two.3 times different short circuit electricity of the method for operation can be drawn The corresponding each impedance perunit value in road, the concrete numerical value of perunit value is as shown in table 4.

Table 4

Short circuit current (KA)	Xs11	Xs12	Xs10	Xs21	Xs22	Xs20	XT10	XT20
									35	0.03	0.03	0.09	0.03	0.03	0.09	0.21	0.21
25	0.042	0.042	0.126	0.042	0.042	0.126	0.21	0.21
									20	0.052	0.052	0.158	0.052	0.052	0.158	0.21	0.21
15	0.07	0.07	0.21	0.07	0.07	0.21	0.21	0.21
									10	0.105	0.105	0.315	0.105	0.105	0.315	0.21	0.21
5	0.21	0.21	0.63	0.21	0.21	0.63	0.21	0.21

Singlephase earth fault at 3 times K1 of the method for operation, is combined formula (7) by table 4～(9) to can be calculated inlet wire side electric current mutual The self-produced zero stream 3I of sensor TA1₁₀, Nei Qiao side current transformer TA3 self-produced zero stream 3I₂₀And the two vector, as shown in table 5.

Table 5

Short circuit current (KA)	3I10	3I20	3I10+3I20
				35	0.35I′0	0.5I′0	0.85I′0
25	0.31I′0	0.5I′0	0.81I′0
				20	0.29I′0	0.5I′0	0.79I′0
15	0.25I′0	0.5I′0	0.75I′0
				10	0.2I′0	0.5I′0	0.7I′0
5	0.125I′0	0.5I′0	0.625I′0

Singlephase earth fault at 3 times K2 of the method for operation, is combined formula (10) by table 4～(12) can be calculated inlet wire side electric current The self-produced zero stream 3I of transformer TA1₁₀, Nei Qiao side current transformer TA3 self-produced zero stream 3I₂₀And the two vector, as shown in table 6.

Table 6

Short circuit current (KA)	3I10	3I20	3I10+3I20
				35	0.35I′0	0.5I′0	0.15I′0
25	0.315I′0	0.5I′0	0.185I′0
				20	0.285I′0	0.5I′0	0.215I′0
15	0.25I′0	0.5I′0	0.25I′0
				10	0.2I′0	0.5I′0	0.3I′0
5	0.125I′0	0.5I′0	0.375I′0

Same, for table 5, at K1 during singlephase earth fault, because self-produced zero stream of inlet wire side current transformer TA1 3I₁₀Zero stream 3I self-produced with Nei Qiao side current transformer TA3₂₀Vector more than any of which value, the scheme of the present embodiment is becoming In depressor district, during single-phase earthing, sensitivity with traditional scheme is the same.Such as, protection threshold value is set as 0.1I '₀, work as short circuit current During for 35KV, the sensitivity coefficient of traditional method and this programme is all Klm=0.85I '₀/0.1I′₀=8.5.

For table 6, at K2 during singlephase earth fault, the self-produced zero stream 3I of inlet wire side current transformer TA1₁₀With Nei Qiao side electricity The self-produced zero stream 3I of current transformer TA3₂₀Vector compare 3I₂₀Little.When using vector to judge, susceptiveness is then deteriorated.Example As, set protection threshold value and be similarly 0.1I '₀, by vector with protection threshold ratio relatively, try to achieve sensitivity coefficient Klm=0.15I '₀/ 0.1I′₀=1.5, the present embodiment scheme first obtains 3I₁₀=0.35I '₀, 3I₂₀=0.5I '₀And 3I₁₀+3I₂₀=0.15I '₀, draw Maximum 3I therein₂₀=0.5I '₀, so sensitivity coefficient Klm=0.5I '₀/0.1I′₀=5.Obtain sensitive in the conventional way Coefficient is 1.5, and this method sensitivity coefficient is 5, and the susceptiveness of zero-sequencedirectional protection method is improved.

The embodiment of the present invention three to transformator in the case of the method for operation 3, to singlephase earth fault feelings outside Nei He district of district Condition compares, and traditional method is compared with this programme, and result show that this programme is for single-phase earthing outside district equally Fault, susceptiveness is greatly improved compared with traditional method.

Embodiment four

Figure 10 is the apparatus structure of transformator zero-sequencedirectional protection under a kind of interior bridge mode that the embodiment of the present invention four provides Figure.As shown in Figure 10, including the transformator 101 of internal bridge, inlet wire side current transformer 102, Nei Qiao side current transformer 103 With chopper 104, it is characterised in that also include:

Zero-sequence current acquisition module 105, for obtaining the zero-sequence current of inlet wire side current transformer 102, Nei Qiao side respectively The zero-sequence current of current transformer 103, and both vectors；

Overcurrent protection action module 106, for above-mentioned three arbitrary more than protection threshold value time, disconnect transformator 101 with Chopper 104 between inlet wire.

Further, inlet wire side current transformer 102 is installed on internal bridge inlet wire side, is used for gathering inlet wire side three-phase electricity Stream；Nei Qiao side current transformer 103 is installed on internal bridge Nei Qiao side, is used for gathering Nei Qiao side three-phase current.

Further, described zero-sequence current is self-produced zero stream.

Further, transformator 101 is the 110kV transformator of internal bridge.

Further, the high-pressure side of transformator 101 is star-connection, the neutral-point solid ground of described star-connection.

The embodiment of the present invention four provides the device of transformator zero-sequencedirectional protection under a kind of interior bridge mode, passes through zero-sequence current Acquisition module obtains the zero-sequence current of inlet wire side current transformer, the zero-sequence current of Nei Qiao side current transformer, and two respectively The vector of person, above-mentioned three arbitrary more than protection threshold value time, overcurrent protection action module cut-off breaker, transformator is carried out Protection.This programme improves the sensitivity of transformator zero-sequencedirectional protection, makes protection action message.

Said apparatus can perform transformator zero-sequencedirectional protection under the interior bridge mode that any embodiment of the present invention is provided Method, possesses the corresponding functional module of execution method and beneficial effect.

Note, above are only presently preferred embodiments of the present invention and institute's application technology principle.It will be appreciated by those skilled in the art that The invention is not restricted to specific embodiment described here, can carry out for a person skilled in the art various obvious change, Readjust and substitute without departing from protection scope of the present invention.Therefore, although by above example, the present invention is carried out It is described in further detail, but the present invention is not limited only to above example, without departing from the inventive concept, also Other Equivalent embodiments more can be included, and the scope of the present invention is determined by scope of the appended claims.

Claims (10)

1. the method for transformator zero-sequencedirectional protection under bridge mode in a kind, it is characterised in that including:

The zero-sequence current of acquisition inlet wire side current transformer respectively, the zero-sequence current of Nei Qiao side current transformer, and both Vector；

If above-mentioned three is arbitrary more than protection threshold value, then disconnect the chopper between transformator and inlet wire.

Method the most according to claim 1, it is characterised in that:

Described inlet wire side current transformer is installed on internal bridge inlet wire side, is used for gathering inlet wire side three-phase current；

Described Nei Qiao side current transformer is installed on internal bridge Nei Qiao side, is used for gathering Nei Qiao side three-phase current.

Method the most according to claim 1, it is characterised in that:

Described zero-sequence current is self-produced zero stream.

Method the most according to claim 1, it is characterised in that:

Described transformator is the 110kV transformator of internal bridge.

Method the most according to claim 1, it is characterised in that:

The high-pressure side of described transformator is star-connection, the neutral-point solid ground of described star-connection.

6. a device for transformator zero-sequencedirectional protection under bridge mode in, including transformator, the inlet wire side electric current of internal bridge Transformer, Nei Qiao side current transformer and chopper, it is characterised in that also include:

Zero-sequence current acquisition module, for obtaining the zero-sequence current of described inlet wire side current transformer respectively, described Nei Qiao side electricity The zero-sequence current of current transformer, and both vectors；

Overcurrent protection action module, for above-mentioned three arbitrary more than protection threshold value time, disconnect described transformator and inlet wire it Between described chopper.

Device the most according to claim 6, it is characterised in that:

Described inlet wire side current transformer is installed on internal bridge inlet wire side, is used for gathering inlet wire side three-phase current；

Described Nei Qiao side current transformer is installed on internal bridge Nei Qiao side, is used for gathering Nei Qiao side three-phase current.

Device the most according to claim 6, it is characterised in that:

Described zero-sequence current is self-produced zero stream.

Device the most according to claim 6, it is characterised in that:

Described transformator is the 110kV transformator of internal bridge.

Device the most according to claim 6, it is characterised in that:

The high-pressure side of described transformator is star-connection, the neutral-point solid ground of described star-connection.