CN100495850C

CN100495850C - Anti-current transformer saturation method for protecting line differential action

Info

Publication number: CN100495850C
Application number: CNB200710020328XA
Authority: CN
Inventors: 田伟; 鲁雅斌
Original assignee: TIAN WEI LU YABIN
Current assignee: TIAN WEI LU YABIN
Priority date: 2007-02-14
Filing date: 2007-02-14
Publication date: 2009-06-03
Anticipated expiration: 2027-02-14
Also published as: CN101051742A

Abstract

The method for antisaturation of current transformer includes steps of data collection, data process, and logic judgment: collecting this side current Im in differential circuit in realtime, transferring vector of Im, and relevant logic signal to protector at opposite side with speed of 16 points per cycle; implementing synchronization of collected data between protectors at two sides; in differential circuit, using phase comparison relay (PCR) and ratio differential relay (RDR); using relation of included angle between Im and In on two sides of differential circuit as action condition of directional element; based on action state of directional element to determine whether PCR acts; if yes, then determining fault occurs within section; if PCR and RDR act at same time, then differential protecting instantaneous operation exit; when differential protection starts up, PCR carries out judgment continuously, and PCR is reset after differential protection task of full group is reset.

Description

A kind of saturated method of anti-current instrument transformer of line 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 circuit, 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.

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,

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

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

{\overset{\cdot}{I}}_{d} = 0,

Protective device is failure to actuate.But in fact current transformer may exist the difference of mutual inductor ratio, capacity difference, remanent magnetism difference, both sides current transformer transient characterisitics and degree of saturation, the difference of secondary circuit time constant; may cause that all current transformer transient state progress of disease error increases; when external area error or external area error excision, produce unsymmetrical current in the differential circuit, can cause differential protection misoperation when serious.

Traditional scheme adopts starting current and the restraint coefficient that improves ratio-restrained characteristic, increases the method for floating threshold on the braking amount, the problem that can bring the sensitivity of troubles inside the sample space protective device to reduce like this.Require the on-the-spot current transformer of as far as possible choosing high conformity, but, be difficult to guarantee fully consistent in the construction because the general current transformer of line differential protection device is contained in two transformer stations respectively.

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

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

Technical scheme of the present invention is: the saturated method of a kind of differential protection anti-current instrument transformer, comprise data acquisition, data processing and logic determines step, wherein,

Data acquisition may further comprise the steps:

1. gather this side electric current of protected element in the differential circuit in real time

Data processing may further comprise the steps:

1. with this side electric current A, B, C three phase vectors and interrelated logic information be sent to the offside protective device, the ripple transmission 16 times weekly of above-mentioned information;

2. adopt sampling instant adjustment method to realize that the sampled data of protected element both sides protective device is synchronous based on data channel;

Logic determines may further comprise the steps:

1. in differential circuit, adopt than phase formula relay and percentage differential relay;

2. with this side of protected element electric current in the differential circuit

With the offside electric current

Angle relation, as the direction component operation condition;

3. judge whether move according to the direction component running-active status than phase formula relay;

4. if then be judged to be troubles inside the sample space than the actuating of relay of phase formula;

5. if move simultaneously than phase formula relay and percentage differential relay, then the differential protection instantaneous operation exports;

6. start the back than phase formula relay at differential protection and judge continuously, involution after the involution of the whole group of differential protection task.

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 when current transformer generation transient state and stable state are saturated, because current transformer transient state progress of disease error increases, can cause and produce unsymmetrical current in the differential circuit, even but under the most serious saturated conditions, the both sides sense of current still roughly satisfies physical characteristic, and angular difference can be above 90 °.

According to above-mentioned analysis; the present invention is provided with than phase formula relay and percentage differential relay; carry out two logic determines; with than phase formula relay as the basic criterion that defines internal fault external fault; the transformation condition of process high resistance earthing fault and fault in the complex zone; adopt above-mentioned many criterions coordination technique, judge internal fault external fault reliably, resist the saturated influence of current transformer 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 line protective devices differential protection main program flow chart.

Fig. 3 is A phase ratio differential protection program flow diagram in the embodiment of the invention 1 line protective devices differential protection main program (B, C is identical mutually).

Embodiment

The present invention has been used to realize line differential protection, is that example is described further below with the line differential protection:

Embodiment 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, and the testing process of current transformer saturation detection relay may further comprise the steps, and sees Fig. 1.

2. with this side electric current

A, B, C three phase vectors and interrelated logic information be sent to the offside protective device, the ripple transmission 16 times weekly of above-mentioned information;

3. adopt sampling instant adjustment method to realize that the sampled data of protected element both sides protective device is synchronous based on data channel;

4. in differential circuit, adopt than phase formula relay and percentage differential relay;

5. compare this side of protected element electric current in the differential circuit in real time

With the offside electric current Angle, if

Condition satisfies, then direction component action, otherwise direction component is failure to actuate;

If 6. direction component action in the 30ms that differential protection starts is then thought than the actuating of relay of phase formula, otherwise the necessary continuous action 20ms of direction component then thinks than the actuating of relay of phase formula;

7. if then be judged to be troubles inside the sample space than the actuating of relay of phase formula;

8. if move simultaneously than phase formula relay and percentage differential relay, then the differential protection instantaneous operation exports;

9. start the back than phase formula relay at differential protection and judge continuously, involution after the involution of the whole group of differential protection task.

Above-mentioned steps, we are defined as based on the ratio phase formula relay of " comprehensive phase comparing method " and judge.

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

1. percentage differential relay, than the initialization of phase formula relay;

2. the differential protection entry condition is judged: be to guarantee that protection is reliable to start, and difference of phase currents starting component, self-produced zero-sequence current assistant starting element, low-voltage starting component and utilize that any one satisfies condition in the assistant starting element of TWJ, then protection starts;

3. phase-splitting percentage differential logic determines: A, B, the phase-splitting of C three-phase are judged, whenever judge comprehensively that mutually three phase logics are identical, specifically see Fig. 3 than phase formula relay and percentage differential relay running-active status;

4. the involution of the whole group of differential protection is judged.

Phase-splitting percentage differential logic is seen Fig. 3 in the present embodiment differential protection logic, because differential relay three phase logics are identical, so has only described A phase implementation step among the figure: comprising:

1. if direct generating region internal fault, then percentage differential relay, all move than phase formula relay, protection is outlet fast;

2. if external area error takes place, current transformer does not have saturated, then percentage differential relay, all be failure to actuate the protection locking than phase formula relay;

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

4. saturated if external area error and current transformer transient state take place earlier, generating region internal fault again subsequently, percentage differential relay is moving can a direct acting, and only moves behind the generating region internal fault than phase formula relay, guarantees the correctness of biased differential protection action;

5. if percentage differential relay action, but be failure to actuate than phase formula relay, if it is unsaturated to be judged as current transformer after harmonic wave detects, the high resistance ground state when then being judged as heavy duty moves after during through 2 distributions.

Can know according to top description; according to judged result based on the ratio phase formula relay of " comprehensive phase comparing 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 data acquisition, data processing and logic determines step, wherein,

Data acquisition may further comprise the steps:

1. gather this side electric current I of protected element in the differential circuit in real time _m

Data processing may further comprise the steps:

1. with this side electric current I _mA, B, C three phase vectors and interrelated logic information be sent to the offside protective device, the ripple transmission 16 times weekly of above-mentioned information;

Logic determines may further comprise the steps:

2. with this side of protected element electric current I in the differential circuit _mWith the offside electric current I _nAngle relation, as the direction component operation condition;

2, the saturated method of a kind of differential protection anti-current instrument transformer according to claim 1 is characterized in that, in the described logic determines step, the direction component operation condition is-90 °≤arg (I _m/ I _n)≤90 °.

3, the saturated method of a kind of differential protection anti-current instrument transformer according to claim 1 and 2; it is characterized in that; in the described logic determines step; judgement than the condition of the phase formula actuating of relay is: if direction component action in the 30ms that differential protection starts; then think than the actuating of relay of phase formula; otherwise the necessary continuous action 20ms of direction component then thinks than the actuating of relay of phase formula.