CN101662139A - Fault phase-selecting method in oscillation of high-voltage line protection - Google Patents

Abstract

The invention discloses a fault phase-selecting method in the oscillation of high-voltage line protection, which is characterized in that the fault phase-selecting method comprises the following steps: (1) calculation of the impedance changing rate of each circuit; (2) discrimination of the impedance change of each circuit; (3) subarea phase selection in the oscillation: the subarea phase selection in the oscillation is inputted when zero-sequence current I<0> and negative-sequence current *2 are large, and only subareas and corresponding circuits with constant impedance measuring values can be selected; (4) impedance phase selection in the oscillation: discrimination is carried out according to the impedance changing rate of each circuit, if the impedance changing rate of only one circuitis small, the circuit is directly selected; if the impedance changing rates of a plurality of circuits are small, the impedance phase selection is independently carried out on the circuits; if the impedance changing rates of any circuit is large, the circuit is not selected. The method can effectively prevent the wrong selection of the traditional phase-selecting element in the oscillation, ensure that the fault phase in the oscillation can reliably trip and only the fault phase trips, and is beneficial to the safe and reliable running of electric power systems.

Description

Fault phase-selecting method in the vibration of high-voltage line protection

Technical field

The present invention relates to the fault phase-selecting method in the vibration in a kind of high-voltage line protection, belong to the power system automation technology field.

Background technology

Choosing combines mutually with steady-state quantity mutually generally to adopt the choosing of sudden change amount at present in high-voltage line protection, and the sudden change amount is selected and is mainly used in mutually the fault initial stage, adopts the steady-state quantity phase selection element during fault later stage and system oscillation.

The phase problem of selecting in the system oscillation never is well solved, and relaying protection worker both domestic and external has carried out a large amount of research to this.Sudden change amount choosing generally only drops at the fault initial stage mutually in short-term, opens fault bigger the time for oscillating to both sides merit angle swing, and the choosing of sudden change amount mutually may be because jump-value of current sensitivity deficiency and selective reject or falsely drop.Choosing generally is the phase relation of utilizing between negative phase-sequence and the zero-sequence current mutually for stable state, combined impedance selects phase again, this method must could be used under the little situation of system's both sides electrical source voltage angular difference, otherwise may cause falsely dropping phase in oscillatory process because of having used the impedance differentiation.In addition, traditional impedance choosing has when phase-to phase fault or three-phase fault take place well selects phase effect, and in the vibration again during fault because the variation of non-fault phase current voltage cycle, the impedance in each loop of other except that fault loop also constantly changes, and may cause the impedance choosing to be falsely dropped mutually.Therefore, research is applicable in the vibration that the phase selection element of fault has very strong practical and necessity again.

Summary of the invention

Technical problem to be solved by this invention aims to provide the fault phase-selecting method in a kind of vibration of high-voltage line protection, can correctly select the various types of faults in the middle of the vibration.

For addressing the above problem, the present invention is achieved by the following technical solutions:

Fault phase-selecting method in a kind of vibration of high-voltage line protection is characterized in that, may further comprise the steps:

1) calculates each impedance loop variation rate: calculate the resistance value in each loop, and calculate its impedance rate of change respectively;

2) each impedance loop changes differentiation: whether the impedance rate of change in each loop that will calculate and the threshold of setting are made comparisons, differentiate each impedance loop and change;

3) subregion in the vibration selects phase: zero-sequence current

And negative-sequence current

The subregion that drops in the vibration when big selects phase, the subregion choosing in the vibration be mutually condition that impedance is constant in conjunction with traditional subregion phase-selecting method, have only the loop that subregion is chosen and corresponding impedance measurements remains unchanged could be selected;

4) phase is selected in the impedance in the middle of the vibration: the impedance rate of change according to each loop is differentiated, if only exist the impedance rate of change in some loops very little, other impedance loop variation rates are all more directly chosen this loop;

If exist a plurality of impedance loop variation rates little, then separately impedance is done in these several loops again and selected phase; If arbitrary impedance loop variation rate is not all very greatly then chosen any loop.

Operation principle of the present invention is: the impedance of fault loop should remain unchanged in the vibration, and the impedance measurements in other loops all is to do periodic the variation.The present invention proposes according to These characteristics and in conjunction with traditional subregion choosing phase and impedance phase-selecting method.At first calculating the impedance rate of change in 6 loops after entering the vibration flow process, if wherein only have a loop constant, can be this loop fault then certainly, directly can choose.If there are a plurality of impedance loops constant, then the loop that these several measurement impedances are remained unchanged is carried out impedance again and is selected phase, and impedance phase can be chosen less loop.The present invention can reliably select the fault loop in the middle of the vibration, and can not falsely drop.

The invention has the beneficial effects as follows: the falsely dropping of traditional phase selection element based on impedance in the middle of method of the present invention can effectively prevent to vibrate, guarantee that fault can reliably trip in the vibration, and only jump the fault phase, help the safe and reliable operation of electric power system.

Embodiment

Below each step of the present invention is described in detail.

One, the calculating of each impedance loop variation rate

Enter the impedance that just begins to calculate each loop before the out-of-step blocking, the rate of change of impedance can be asked at interval with 5ms or other times.With the alternate loop of BC is the computational methods of example explanation impedance rate of change.Suppose each sampling period is carried out the calculating of each impedance loop, and obtain one group of alternate impedance measurements Z of BC _BC(k).Suppose that each time in sampling interval is T _S, then the rate of change of the alternate impedance of BC is

${\mathrm{\&rho;}}_{\mathrm{BC}}\left(k\right)=\frac{Z_{\mathrm{BC}}\left(k\right)-Z_{\mathrm{BC}}(k-n\&CenterDot;T_S)}{n\&CenterDot;T_S}---\left(1\right)$

Two, each impedance loop changes differentiation

Be that example describes still with the BC loop.If satisfy ρ _BC(k)＜ρ _DZCan judge that then this impedance loop is constant, otherwise judge that this impedance loop changes.ρ _DZBe the sound constant threshold definite value of mutually alternate impedance, this threshold definite value should be relevant with system impedance, by the inner self adaptation of protection, need not to adjust.

Three, the subregion in the vibration selects phase

The subregion choosing mainly is according to zero-sequence current mutually

And negative-sequence current

Phase relation fault type is divided into A, B, three zones of C.

Wherein the A district comprises AG and BCG two class faults, and the B district comprises BG and CAG two class faults, and the C district comprises CG and ABG two class faults.The selection of two class faults in each subregion is to realize by impedance ratio, and to choose the loop must be the constant loop of impedance measurements.With the A district is that example describes, if the alternate impedance of BC is constant, and it drops within the last segment limit of distance and then can choose the BC phase-to phase fault; Otherwise see the impedance in A phase loop, if its impedance measurements is constant, and it drops within the last segment limit of distance and then can choose the AG fault.

Four, phase is selected in the impedance in the middle of the vibration

At first differentiate the impedance rate of change in each loop,, then directly choose this loop if only have the impedance in a loop constant (impedance rate of change is little); If exist a plurality of impedance loops constant, then compare the relative size of these several impedance loops, choose less relatively loop.For example, AB, A, three impedance measurement circuit values of B Z _AB, Z _A, Z _BAll constant, satisfy Z _AB＜kmin (Z _AB, Z _A, Z _B) then the AB loop can be chosen.Wherein k is a safety factor, is chosen as about 0.9.

Below announced the present invention with preferred embodiment, so it is not in order to restriction the present invention, and all technical schemes that scheme obtained of taking to be equal to replacement or equivalent transformation all drop on protection scope of the present invention.

Claims (4)

1. the fault phase-selecting method in the vibration of a high-voltage line protection is characterized in that, may further comprise the steps:

1) calculates each impedance loop variation rate: calculate the resistance value in each loop, and calculate its impedance rate of change respectively;

2) each impedance loop changes differentiation: whether the impedance rate of change in each loop that will calculate and the threshold of setting are made comparisons, differentiate each impedance loop and change;

3) subregion in the vibration selects phase: zero-sequence current

And negative-sequence current The subregion that drops in the vibration when big selects phase, the subregion choosing in the vibration be mutually condition that impedance is constant in conjunction with traditional subregion phase-selecting method, have only the loop that subregion is chosen and corresponding impedance measurements remains unchanged could be selected;

4) phase is selected in the impedance in the middle of the vibration: the impedance rate of change according to each loop is differentiated, if only exist the impedance rate of change in some loops very little, other impedance loop variation rates are all more directly chosen this loop; If exist a plurality of impedance loop variation rates little, then separately impedance is done in these several loops again and selected phase; If arbitrary impedance loop variation rate is not all very greatly then chosen any loop.

2. the fault phase-selecting method in the vibration of high-voltage line protection according to claim 1 is characterized in that: in described step 1), utilize formula (1) to try to achieve alternate impedance rate of change.

${\mathrm{\&rho;}}_{\mathrm{BC}}\left(k\right)=\frac{Z_{\mathrm{BC}}\left(k\right)-Z_{\mathrm{BC}}(k-n\&CenterDot;T_S)}{n\&CenterDot;T_S}---\left(1\right)$

Z wherein _BC(k) be alternate impedance measurements, T _SBe each time in sampling interval, ρ _BC(k) be alternate impedance rate of change.

3. the fault phase-selecting method in the vibration of high-voltage line protection according to claim 1 and 2 is characterized in that: in described step 4), if AB wherein, A, three impedance measurement circuit values of B Z _AB, Z _A, Z _BAll constant, satisfy Z _AB＜kmin (Z _AB, Z _A, Z _B) then the AB loop can be chosen, wherein k is a safety factor.

4. the fault phase-selecting method in the vibration of high-voltage line protection according to claim 3, it is characterized in that: in described step 4), wherein safety factor k is 0.9.