CN100495851C

CN100495851C - Method for saturating anti-current mutual inductor differential protection

Info

Publication number: CN100495851C
Application number: CNB2005100954415A
Authority: CN
Inventors: 田伟
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-11-16
Filing date: 2005-11-16
Publication date: 2009-06-03
Anticipated expiration: 2025-11-16
Also published as: CN1787313A

Abstract

This invention relates to a method for anti-saturation of a current mutual inductor of differential protection including a method for differential protection anti- TA saturation, the detecting process of a TA saturation testing relay includes the following steps: collecting each side current in the differential loop timely, computing the fault component of the differential current, computing the fault component of the braking current, judging the operation logic of the fault component relay, repeating M times of the above mentioned actions, if N times can meet the needs, then it is considered that the relay acts, judging the fault regions and judging the return of the relay.

Description

A kind of saturated method of anti-current instrument transformer of differential protection

Technical field

The present invention relates to a kind of method that overcomes the saturated influence of current transformer, particularly a kind of saturated method of current transformer of resisting of differential protection.

Background technology

Differential protection is the main salvo of elements such as transformer, generator, high capacity motor and bus; basic principle be the reaction protected element respectively hold inflow current and flow out current phasor and; at the protection zone internal fault; current value in the differential circuit is greater than setting value; the differential protection instantaneous operation; and at the protection external area error, differential protection then should not move.

In recent years, following abnormal conditions repeatedly take place in the high-rating generator transformer group in power system operation:

1. after the external area error excision, because of each side current transformer transient characterisitics difference of transformer causes transformer differential protection or generator transformer group differential protection malfunction;

2. during two parallel operation of transformers, when a no-load transformer drops into, produce and echo surge current because and the aperiodic component in the echo surge current cause that the generator transformer group current transformer transient error of another operation increases, and causes differential protection malfunction.

High-rating generator transformer group protection malfunction meeting causes great economic loss, when serious even may threaten the stabilization of power grids.Therefore, analyze the reason of the problems referred to above and find the method for dealing with problems to have great importance.

Regard protected object as a node, then flow into or the electric current that flows out this node promptly is defined as spill current

According to basic ear hoff's law,

{\dot{I}}_{d} = Σ_{j = 1}^{N} {\dot{I}}_{j},

Be each side electric current.In theory, when external area error,

{\dot{I}}_{d} = 0,

Protective device is failure to actuate.But in fact because current transformer may exist mutual inductor ratio, capacity difference (particularly tranformer protection); the remanent magnetism difference may cause that all current transformer transient state progress of disease error increases; make and produce unsymmetrical current in the differential circuit, can cause differential protection misoperation when serious.

Therefore to reduce the saturated influence to protection of current transformer transient state, avoid outside passing through property of transient state electric current to cause differential protection malfunction be the principal contradiction that realizes that differential protection need solve in the employing measure.

Summary of the invention

Purpose of the present invention is exactly can reduce the saturated influence to differential protection of current transformer transient state in order to overcome the defective of prior art, to provide a kind of, avoid differential protection malfunction not sacrifice simultaneously the differential protection sensitivity of method again.

Technical scheme of the present invention is: the saturated method of a kind of differential protection anti-current instrument transformer, and steps such as data acquisition, data processing and logic determines, the testing process of current transformer saturation detection relay specifically may further comprise the steps:

1. gather each the side electric current in the differential circuit in real time

2. basis

Δ {\dot{I}}_{d} = Δ Σ_{j = 1}^{N} {\dot{I}}_{j}

Calculate difference stream fault component

According to

| Δ {\dot{I}}_{r} | = Δ \frac{1}{2} Σ_{j = 1}^{N} | {\dot{I}}_{j} |

Or

| Δ {\dot{I}}_{r} | = ΔMax {| {\dot{I}}_{1} |, | {\dot{I}}_{2} | \cdot \cdot \cdot, | {\dot{I}}_{j} |}

Calculate stalling current fault component mould

| Δ {\dot{I}}_{r} |;

In the formula, Be the fault component of spill current, Be the fault component of stalling current, down together;

3. basis

\begin{matrix} | Δ {\dot{I}}_{d} | &GreaterEqual; α I_{n} \\ | Δ {\dot{I}}_{d} | &GreaterEqual; K \times | Δ {\dot{I}}_{r} | \end{matrix}

Judge the action logic of difference stream fault component relay, α is the threshold definite value of difference stream fault component relay, and span is 0.2～0.4, is preferably 0.3;

In the formula, I _nBe protected equipment reference side Current Transformer Secondary rated current; K is the restraint coefficient of difference stream fault component relay, down together;

4. repeating step is 1. to step 3. M time, if having satisfy for N time step 3. condition think that then difference flows the actuating of relay of fault component relay;

5. basis

| Δ {\dot{I}}_{r} | &GreaterEqual; β I_{n}

Judge the action logic of stalling current fault component relay; β is the threshold definite value of stalling current fault component relay, and span is 0.1～0.2, is preferably 0.15;

6. repeating step is 1., 2. and 5. M time, if having satisfy for N time step 5. condition then think the actuating of relay of stalling current fault component;

7. fault zone determining step: if only the actuating of relay of poor stream fault component or two relay actuation time difference be not more than 5ms and then be judged to be troubles inside the sample space, otherwise be judged to be external area error;

8. relay returns determining step:

If be judged to be external area error, judge that 1. the disappearance of stalling current fault component begins to repeat to judge from step;

If be judged to be troubles inside the sample space, 1. begin to repeat to judge from step after the involution of the whole group of differential protection task.

Above-mentioned stalling current fault component mould

Algorithm can be:

| Δ {\dot{I}}_{r} | = Δ \frac{1}{2} Σ_{j = 1}^{N} | {\dot{I}}_{j} |

Or

| Δ {\dot{I}}_{r} | = ΔMax {| {\dot{I}}_{1} |, | {\dot{I}}_{2} | \cdot \cdot \cdot, | {\dot{I}}_{j} |} .

Principle of the present invention is:

Current transformer is a kind of nonlinear ferroelectric magnetic cell, and its core sataration will cause progress of disease error to increase, and particularly angular difference increases, if do not adopt an effective measure, only depends on the braking characteristic of differential protection to be difficult to resist.Consider:

1. the current transformer operate as normal carries out the transition to inelastic region at least 5～10ms at linear zone by linear zone;

2. for differential protection, when the generating region internal fault, difference stream fault component and stalling current fault component occur simultaneously; When external area error takes place when, the stalling current fault component appears earlier, difference stream fault component appears in the back, and its time difference promptly is not less than 5ms greater than current transformer transit time.

According to above-mentioned analysis; the present invention is provided with difference stream fault component relay and stalling current fault component relay carries out two logic determines; with difference stream fault component relay and stalling current fault component difference relay actuation time is basic criterion; and adopt many criterions coordination technique; can current transformer enter saturated before fast and reliable ground judge internal fault external fault, resist the saturated influence of current transformer to differential protection.

This method is implemented simple, and physical significance is clear, and the saturated performance of anti-current instrument transformer is guaranteed simultaneously.

Description of drawings

Fig. 1 is a program flow diagram of the present invention

Fig. 2 is the embodiment of the invention 1 a protection equipment for generator biased differential protection program flow diagram

Fig. 3 is the embodiment of the invention 1 a protection equipment for generator A phase ratio differential protection program flow diagram

Embodiment

The present invention has been used to realize the differential protection of elements such as generator, transformer, motor, is that example is described further below with the generator protection:

Embodiment 1

The saturated method of a kind of differential protection anti-current instrument transformer; comprise steps such as data acquisition, data processing and logic determines; the testing process of current transformer saturation detection relay may further comprise the steps; see Fig. 1; because differential relay three phase logics are identical, so only described A phase implementation step among the figure:

2. basis

Δ {\dot{I}}_{d} = Δ Σ_{j = 1}^{N} {\dot{I}}_{j}

Calculate difference stream fault component

According to

| Δ {\dot{I}}_{r} | = Δ \frac{1}{2} Σ_{j = 1}^{N} | {\dot{I}}_{j} |

Or

| Δ {\dot{I}}_{r} | = ΔMax {| {\dot{I}}_{1} |, | {\dot{I}}_{2} | \cdot \cdot \cdot, | {\dot{I}}_{j} |}

Calculate stalling current fault component mould

| Δ {\dot{I}}_{r} |;

In the formula,

Be the fault component of spill current,

Be the fault component of stalling current, down together;

3. basis

\begin{matrix} | Δ {\dot{I}}_{d} | &GreaterEqual; 0.3 I_{n} \\ | Δ {\dot{I}}_{d} | &GreaterEqual; K \times | Δ {\dot{I}}_{r} | \end{matrix}

Judge the action logic of difference stream fault component relay; In the formula, I _nBe reference side Current Transformer Secondary rated current; K is the restraint coefficient of difference stream fault component relay;

5. basis

| Δ {\dot{I}}_{r} | &GreaterEqual; 0.15 I_{n}

Judge the action logic of stalling current fault component relay;

8. relay returns determining step:

This step has been taked the sampled value algorithm based on fault component, and it is saturated to influences of protection fast such as differential protections that this method can effectively be resisted current transformer, and for indivedual sampling bad datas that may occur natural immunity is arranged.

In the determining step of fault zone: if only the actuating of relay of poor stream fault component or two relay actuation times difference be not more than 5ms and then be judged to be troubles inside the sample space, be defined as ' synchronously '; Otherwise be judged to be external area error and be defined as " asynchronous ".

Above-mentioned steps, we are defined as the lock-on relay based on " comprehensive time difference method ".

The differential protection logic is seen Fig. 2 in the present embodiment, comprising:

The initialization of 1. conventional percentage differential relay, lock-on relay;

2. the differential relay entry condition is judged: start for guaranteeing that protection is reliable, any one satisfies condition the jump-value of current of being on duty, spill current constant and lock-on relay, and then protection starts;

3. the differential logic determines of phase-splitting: A, B, the phase-splitting of C three-phase judge that three phase logics are identical, specifically see Fig. 3;

4. lock-on relay returns judgement: if lock-on relay is judged to be external area error, judge that the disappearance of stalling current fault component then drops into lock-on relay once more, guarantee outer troubles inside the sample space, the lock-on relay instant action of changeing in district;

5. the involution of the whole group of differential relay is judged.

Phase-splitting biased differential protection logic is seen Fig. 3 in the present embodiment, comprising:

1. as if direct generating region internal fault, then conventional percentage differential relay, lock-on relay all move, and protection is outlet fast;

2. if external area error takes place, current transformer does not have saturated, and then conventional percentage differential relay, lock-on relay all are failure to actuate, and protect reliable locking;

3. if external area error takes place, current transformer generation transient state or stable state are saturated, and then conventional percentage differential relay action, lock-on relay are failure to actuate, since saturated secondary or the triple-frequency harmonics of certainly leading to of current transformer, the reliable locking of protection after harmonic wave detects;

4. saturated if external area error and current transformer transient state take place earlier; generating region internal fault again subsequently; then conventional percentage differential relay possibility one direct acting, and lock-on relay only moves behind the generating region internal fault, can effectively guarantee the correctness of biased differential protection action.

Can know according to top description; according to judged result based on the lock-on relay of " comprehensive time difference method "; the logic of contrast ratio differential relay reconfigures, and can effectively resist the saturated influence to differential protection of current transformer, has improved the reliability of differential protection greatly.

Claims

1, the saturated method of a kind of differential protection anti-current instrument transformer comprises steps such as data acquisition, data processing and logic determines, it is characterized in that the testing process of current transformer saturation detection relay specifically may further comprise the steps:

2. basis

Δ {\overset{\cdot}{I}}_{d} = Δ Σ_{j = 1}^{N} {\overset{\cdot}{I}}_{j}

Calculate difference stream fault component

According to

| Δ {\overset{\cdot}{I}}_{r} | = Δ \frac{1}{2} Σ_{j = 1}^{N} | {\overset{\cdot}{I}}_{j} |

Or

| Δ {\overset{\cdot}{I}}_{r} | = ΔMax {| {\overset{\cdot}{I}}_{1} |, | {\overset{\cdot}{I}}_{2} | \cdot \cdot \cdot, | {\overset{\cdot}{I}}_{j} |}

Calculate stalling current fault component mould

| Δ {\overset{\cdot}{I}}_{r} |;

In the formula,

Be the fault component of spill current,

Be the fault component of stalling current, down together;

3. basis

\begin{matrix} | Δ {\overset{\cdot}{I}}_{d} | &GreaterEqual; {αI}_{n} \\ | Δ {\overset{\cdot}{I}}_{d} | &GreaterEqual; K \times | Δ {\overset{\cdot}{I}}_{r} | \end{matrix}

Judge the action logic of difference stream fault component relay;

α is the threshold definite value of difference stream fault component relay, and span is 0.2-0.4; I _nBe reference side secondary rated current; K is the restraint coefficient of difference stream fault component relay;

5. basis

| Δ {\overset{\cdot}{I}}_{r} | &GreaterEqual; {βI}_{n}

Judge the action logic of stalling current fault component relay, β is the threshold definite value of stalling current fault component relay, and span is 0.1～0.2;

8. relay returns determining step:

2, the saturated method of differential protection anti-current instrument transformer according to claim 1 is characterized in that, described step 3.

| Δ {\overset{\cdot}{I}}_{d} | &GreaterEqual; {αI}_{n}

In the value of α be 0.3.

3, the saturated method of differential protection anti-current instrument transformer according to claim 1 is characterized in that, described step 5.

| Δ {\overset{\cdot}{I}}_{r} | &GreaterEqual; {βI}_{n}

In the value of β be 0.15.