CN102842890A - Realizing method of current change rate protection - Google Patents

Abstract

The invention discloses a realizing method of current change rate protection, wherein a long data window mean algorithm is combined with a short data window mean algorithm, and the comprehensive logic judgment of mutually matching the two data window mean algorithms with different lengths well solves the contradiction of quickness and reliability of the current change rate protection to improve the integral performance of the rail direct current protection.

Description

A kind of implementation method of current changing rate protection

Technical field

The implementation method of current changing rate protection belongs to electrical technology field.

Background technology

Along with developing rapidly of urban rail transit in China in recent years, DC traction power-supply system has obtained application more and more widely.In DC traction power-supply system; Because the direct-current short circuit electric current is different from alternating current, dc switch disjunction prospective short circuit current stationary value is difficulty very, therefore; Require dc switch before fault current reaches the expection stationary value, just not answer the disjunction fault current, and more little good more.Because the current changing rate protection is distinguish short-circuit fault current and locomotive starting current effectively, can protect and be used as in fault early period of origination fast detecting to fault in the first-selection of subway direct current protecting.The sensitivity and the reliability that how to guarantee the current changing rate protection are one of key points of protection.

Summary of the invention

The object of the present invention is to provide a kind of current changing rate protection implementation method, solve the rapidity of current changing rate protection and the contradiction between the reliability preferably, improved the overall performance of track direct current protecting.

The current changing rate protection is divided into current increment protection and current-rising-rate protection.

The current increment protection if monitoring current increment Delta I is higher than corresponding setting value, and continues the corresponding time, then protection action outlet.In-plant nonmetal character short trouble (metallicity direct short-circuit fault is tripped by the electromagnetic tripping apparatus of circuit breaker self) during current increment Δ I protection is primarily aimed at.

The current-rising-rate protection starts Δ T (for setting value) afterwards if monitor the current changing rate protection, and current increment value Δ I then protects the action outlet greater than minimum threshold definite value.Be primarily aimed at remote or resistive type fault.

The general average value filtering algorithm that adopts in direct current, i.e. the R point data window algorithm of averaging.If it is bigger that the R value is chosen, filter effect is good, and computational accuracy is higher, can cause the current changing rate protection to delay start-up time, thereby has influence on choosing of current reference value in the current changing rate protection, is difficult to satisfy the sensitivity demand of protection.Less but if the R value is chosen, protection has higher rapidity and sensitivity, but has the malfunction possibility.

The present invention provides a kind of implementation method of current changing rate protection, it is characterized in that, comprises following steps:

1) data acquisition: the acquired original by FPGA completion data, after the first Filtering Processing of the intermediate value method of average, data are stored among the data buffer area i [N+1], N is that the data sampling of 20ms is counted;

2) calculate current-rising-rate K value:

Current-rising-rate K computing formula K=di/dt;

K ₁[k]＝(i[k]-i[k-z ₁])/t ₁；

K ₂[k]＝(i[k]-i[k-z ₂])/t ₂；

Wherein:

K representes the current sampling point counting, between 0 to N+1, circulates;

The current sampling data that i [k] expression k is ordered;

I [k-z ₁] expression k-z ₁The current sampling data of point;

I [k-z ₂] expression k-z ₂The current sampling data of point;

t ₁Expression k point and k-z ₁The time interval between the point;

t ₂Expression k point and k-z ₂The time interval between the point;

K ₁[k], K ₂[k] is illustrated respectively in t ₁The time interval, t ₂First current-rising-rate under the time interval, the instantaneous value of second current-rising-rate.

3) data filtering:

31) data window R: be used for the number of data points of calculating mean value, R can not be greater than N+1;

32) data window R chooses smaller value R ₁, calculate current average Calculate the mean value of first current-rising-rate $K_{1R}=\frac{1}{R_1}\underset{m=0}{\overset{R_1}{\mathrm{\Σ}}}{K}_{(k-m)};$

33) data window R chooses higher value R ₂, calculate the mean value of second current-rising-rate $K_{2R}=\frac{1}{R_2}\underset{m=0}{\overset{R_2}{\mathrm{\Σ}}}{K}_{(k-m)}.$

4) current changing rate protection starting component: as the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RAll, then be judged to current changing rate protection starting component and start greater than starting threshold value; If current changing rate protection starting component starts, as the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RAll less than returning threshold value, current changing rate protection starting component just returns.

5) choosing of current reference value: do not start at current changing rate protection starting component, and the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RDuring all less than the startup threshold value, the current reference value of real-time update current changing rate protection, current reference value power taking levelling average I _FRInstantaneous value; Mean value K when first current-rising-rate _1RMean value K with second current-rising-rate _2RAmong both any one stops to upgrade when starting threshold value.

6) current increment protection: when current changing rate protection starting component starts, get into increment protection logic determines, increment protection logic determines adopts current average I _FRInstantaneous value subtracts the current reference value as the protection input value; If the protection input value is protected definite value greater than increment, and satisfied time-delay demand, then increment protection action; If the increment protection is moved, then no longer judge starting component, need only judge that whether input value protects definite value less than increment, if satisfy condition, then returns.

7) current-rising-rate protection: when current changing rate protection starting component starts; Get into current-rising-rate protection logic determines; Current-rising-rate picks up counting, if current changing rate protection starting component starts and last till the time-delay of adjusting of current-rising-rate protection always, then adopts current average I _FRInstantaneous value subtracts the current reference value as input value, if the smallest incremental definite value that input value is protected greater than current-rising-rate, then current-rising-rate protection action.

The software that operates in the CPU that DSP is a core CPU has been realized the implementation method that this current changing rate is protected.Experimental test shows that the current changing rate protection is after this method is handled, and definite value precision, operate time and stability satisfy the requirement of track direct current protecting system fully.

The beneficial effect that the present invention reached: this method combines the advantage of long data window mean value algorithm and short data window mean value algorithm; The integrated logic that adopts two kinds of different length data window mean value algorithms to cooperatively interact is judged; Solve the rapidity of current changing rate protection and the contradiction between the reliability preferably, improved the overall performance of track direct current protecting.

Embodiment

Further describe in the face of the present invention down.Following examples only are used for technical scheme of the present invention more clearly is described, and can not limit protection scope of the present invention with this.

Method of measurement proposed by the invention mainly embodies on the software inner with operating in DSP, and concrete steps are following:

1) data acquisition: the acquired original by FPGA accomplishes data after the first Filtering Processing of the intermediate value method of average, is stored in data among the data buffer area i [N+1]; Accomplished the acquired original of data earlier by FPGA, frequency acquisition F can reach 40K, and median filtering method is got 4 point data, removes maximum and minimum value, and remaining two values are asked on average, and this mean value is stored among the data buffer area i [N+1], and wherein N gets 200.

2) calculate current-rising-rate K value:

Current-rising-rate K computing formula K=di/dt;

K ₁[k]＝(i[k]-i[k-z ₁])/t ₁；

K ₂[k]＝(i[k]-i[k-z ₂])/t ₂；

Wherein: z ₁=10, z ₂=30;

K representes the current sampling point counting, circulation between 0 to 201;

The current sampling data that i [k] expression k is ordered;

I [k-z ₁] expression k-z ₁The current sampling data of point;

I [k-z ₂] expression k-z ₂The current sampling data of point;

t ₁Expression k point and k-z ₁The time interval between the point;

t ₂Expression k point and k-z ₂The time interval between the point;

K ₁[k], K ₂[k] is illustrated respectively in t ₁The time interval, t ₂First current-rising-rate under the time interval, the instantaneous value of second current-rising-rate.

3) data filtering:

31) data window R chooses smaller value R ₁=10, calculate current average I _FR, calculate the mean value K of first current-rising-rate _1R

32) data window R chooses higher value R ₂=30, calculate the mean value K of second current-rising-rate _2R

4) current changing rate protection starting component: as the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RAll, then be judged to current changing rate protection starting component and start greater than starting threshold value; If current changing rate protection starting component starts, as the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RAll less than returning threshold value, current changing rate protection starting component just returns;

5) choosing of current reference value: do not start at current changing rate protection starting component, and the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RDuring all less than the startup threshold value, the current reference value of real-time update current changing rate protection, current reference value power taking levelling average I _FRInstantaneous value; Mean value K when first current-rising-rate _1RMean value K with second current-rising-rate _2RAmong both any one stops to upgrade when starting threshold value;

6) current increment protection: when current changing rate protection starting component starts, get into increment protection logic determines, increment protection logic determines adopts current average I _FRInstantaneous value subtracts the current reference value as the protection input value; If the protection input value is protected definite value greater than increment, and satisfied time-delay demand, then increment protection action; If the increment protection is moved, judge no longer then whether current changing rate protection starting component starts, need only judge that whether input value protects definite value less than increment, if satisfy condition, then returns;

7) current-rising-rate protection: when current changing rate protection starting component starts; Get into current-rising-rate protection logic determines; Current-rising-rate picks up counting, if current changing rate protection starting component starts and last till the time-delay of adjusting of current-rising-rate protection always, then adopts current average I _FRInstantaneous value subtracts the current reference value as input value, if the smallest incremental definite value that input value is protected greater than current-rising-rate, then current-rising-rate protection action.

Above embodiment is merely explanation technological thought of the present invention, can not limit protection scope of the present invention with this, every technological thought that proposes according to the present invention, and any change of on the technical scheme basis, being done all falls within the protection range of the present invention.

Claims (1)

1. the implementation method of a current changing rate protection is characterized in that, may further comprise the steps:

1) data acquisition: the acquired original by FPGA completion data, after the first Filtering Processing of the intermediate value method of average, data are stored among the data buffer area i [N+1], N is that the data sampling of 20ms is counted;

2) calculate current-rising-rate K value:

Current-rising-rate K computing formula K=di/dt;

K ₁[k]＝(i[k]-i[k-z ₁])/t ₁；

K ₂[k]＝(i[k]-i[k-z ₂])/t ₂；

Wherein:

K representes the current sampling point counting, between 0 to N+1, circulates;

The current sampling data that i [k] expression k is ordered;

I [k-z ₁] expression k-z ₁The current sampling data of point;

I [k-z ₂] expression k-z ₂The current sampling data of point;

t ₁Expression k point and k-z ₁The time interval between the point;

t ₂Expression k point and k-z ₂The time interval between the point;

K ₁[k], K ₂[k] is illustrated respectively in t ₁The time interval, t ₂First current-rising-rate under the time interval, the instantaneous value of second current-rising-rate.

3) data filtering:

31) data window R: be used for the number of data points of calculating mean value, R can not be greater than N+1;

32) data window R chooses smaller value R ₁, calculate current average

, calculate the mean value of first current-rising-rate $K_{1R}=\frac{1}{R_1}\underset{m=0}{\overset{R_1}{\mathrm{\Σ}}}{K}_{(k-m)}$

33) data window R chooses higher value R ₂, calculate the mean value of second current-rising-rate $K_{2R}=\frac{1}{R_2}\underset{m=0}{\overset{R_2}{\mathrm{\Σ}}}{K}_{(k-m)}.$

4) current changing rate protection starting component: as the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RAll, then be judged to current changing rate protection starting component and start greater than starting threshold value; If current changing rate protection starting component starts, as the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RAll less than returning threshold value, current changing rate protection starting component just returns.

5) choosing of current reference value: do not start at current changing rate protection starting component, and the mean value K of first current-rising-rate _1RMean value K with second current-rising-rate _2RDuring all less than the startup threshold value, the current reference value of real-time update current changing rate protection, current reference value power taking levelling average I _FRInstantaneous value; Mean value K when first current-rising-rate _1RMean value K with second current-rising-rate _2RAmong both any one stops to upgrade when starting threshold value.

6) current increment protection: when current changing rate protection starting component starts, get into increment protection logic determines, increment protection logic determines adopts current average I _FRInstantaneous value subtracts the current reference value as the protection input value; If the protection input value is protected definite value greater than increment, and satisfied time-delay demand, then increment protection action; If the increment protection is moved, then no longer judge starting component, need only judge that whether input value protects definite value less than increment, if satisfy condition, then returns.

7) current-rising-rate protection: when current changing rate protection starting component starts; Get into current-rising-rate protection logic determines; Current-rising-rate picks up counting, if current changing rate protection starting component starts and last till the time-delay of adjusting of current-rising-rate protection always, then adopts current average I _FRInstantaneous value subtracts the current reference value as input value, if the smallest incremental definite value that input value is protected greater than current-rising-rate, then current-rising-rate protection action.