CN104090209A - Bus protection method based on parameter identification - Google Patents

Abstract

The invention discloses a bus protection method based on parameter identification. The bus protection method mainly includes the steps that values of three-phase voltage and three-phase current at a local end protection installation position are acquired through all branch line protection devices connected with a bus; fault components of the three-phase voltage and current of all the branches connected with the bus are calculated; power frequency fault components of the three-phase voltage and current are extracted through a Fourier algorithm; when a fault start element judges that a fault occurs, bus protection calculation is performed; according to the calculation result of bus protection, whether a fault occurs in a bus area or not is judged. The bus protection method based on parameter identification can overcome the defects that the fault rate and the maintenance difficulty are high and the operation reliability is poor in the prior art, and achieves the advantages of being low in fault rate and maintenance difficulty and good in operation reliability.

Description

A kind of bus bar protecting method based on parameter identification

Technical field

The present invention relates to Relay Protection Technology in Power System field, particularly, relate to a kind of bus bar protecting method based on parameter identification.

Background technology

Bus is the hinge that electric power networks crosses and connects, and connects the equipment such as generator, transformer, transmission line of electricity.Bus protection tripping, may cause power equipment to damage and system break-down; Bus protection malfunction, can cause large area blackout.Although bus-bar fault probability is little compared with transmission line of electricity, if bus protection fault can be destroyed the stable operation of electric system, even cause catastrophic consequence.

Current differential principle because its principle is simple, reliably be widely used in the bus protection of transformer station, brought into play vital role, but this principle is subject to the puzzlement that CT is saturated always in the safe and stable operation of guarantee electric system.When near region external area error occurs bus, the CT of fault branch very easily occurs saturated and causes the damaged and distortion of the secondary side current waveform of this branch road CT, thereby produces false spill current, causes the misoperation of bus differential protecting.Thereby bus differential protecting need be equipped with the saturated recognition component of special CT, identify CT when saturated by the misoperation of bus protection locking bus protection when avoiding external area error.Use the comparatively extensively saturated method of identification of CT to have time difference method, Harmonic Method, method of difference, magnetic brake method etc.In the time of protection blocking can being reduced to bus external area error when although CT is saturated, protect the probability of misoperation, responsiveness that can interfereing with the development property fault bus differential protection, and bus troubles inside the sample space CT may cause the mistake locking of differential protection when saturated.

Therefore, be necessary that further research is different from the bus protection new method of differential protection, improve the reliability of bus protection, this has very strong realistic meaning to improving relay protection performance.

In sum, in realizing process of the present invention, inventor finds at least to exist in prior art the defect such as failure rate is high, maintenance difficulties is large and operational reliability is poor.

Summary of the invention

The object of the invention is to, for the problems referred to above, propose a kind of bus bar protecting method based on parameter identification, to realize failure rate is low, maintenance difficulties is little and operational reliability is good advantage.

For achieving the above object, the technical solution used in the present invention is: a kind of bus bar protecting method based on parameter identification, mainly comprises:

A, by with each branch line line protection device of bus connected, gather three-phase voltage, the three-phase electricity flow valuve of local terminal protection installation place, be designated as:

u _ai(k),u _bi(k),u _ci(k)；i _ai(k),i _bi(k),i _ci(k),i＝1,2…,n；

Wherein, i represents that bus connects i bar branch road, and n represents a way of bus;

Three-phase voltage, the current failure component of b, each branch road of calculating bus connected, be designated as:

Δu _ia(k),Δu _ib(k),Δu _ic(k)，Δi _ia(k),Δi _ib(k),Δi _ic(k)；

C, by Fourier algorithm, extract the power frequency fault component of three-phase voltage current, be designated as respectively:

$\mathrm{\Δ}{\stackrel{\·}{U}}_{\mathrm{ai}}\left(k\right),\mathrm{\Δ}{\stackrel{\·}{U}}_{\mathrm{bi}}\left(k\right),\mathrm{\Δ}{\stackrel{\·}{U}}_{\mathrm{ci}}\left(k\right);\mathrm{\Δ}{\stackrel{\·}{I}}_{\mathrm{ai}}\left(k\right),\mathrm{\Δ}{\stackrel{\·}{I}}_{\mathrm{bi}}\left(k\right),\mathrm{\Δ}{\stackrel{\·}{I}}_{\mathrm{ci}}\left(k\right),i=\mathrm{1,2}...,n;$

D, when fault initiating element is judged fault and is occurred, carry out bus protection calculating;

E, according to the result of calculation of bus protection, judge whether to occur bus troubles inside the sample space.

Further, in step b, the three-phase voltage of described each branch road of calculating bus connected, the computing formula of current failure component are:

$\left\{\begin{array}{c}{\mathrm{\Δu}}_{\mathrm{ij}}\left(k\right)=u_{\mathrm{ij}}\left(k\right)-u_{\mathrm{ij}}(k-\mathrm{pN})\\ {\mathrm{\Δi}}_{\mathrm{ij}}\left(k\right)=i_{\mathrm{ij}}\left(k\right)-i_{\mathrm{ij}}(k-\mathrm{pN})\end{array}\right.j=a,b,c;i=\mathrm{1,2},...n---\left(1\right);$

In formula: p gets positive integer, numerical values recited is determined by protective device; N is every power frequency period sampling number.

Further, in step c, the described computing formula of extracting the power frequency fault component of three-phase voltage current by Fourier algorithm is:

$\left\{\begin{array}{c}\mathrm{\Δ}{\stackrel{\·}{U}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\Δu}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\πmk}}{N}}\\ \mathrm{\Δ}{\stackrel{\·}{I}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\Δi}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\πmk}}{N}}\end{array}\right.j=a,b,c;i=\mathrm{1,2},...n---\left(2\right);$

In formula: N is every power frequency period sampling number; K gets 1 representative and extracts power frequency fault component.

Further, in steps d, described in carry out bus protection calculating computing formula be:

$Y_{\mathrm{diff}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{Y}_i=|\frac{\mathrm{\Δ}{\stackrel{\·}{I}}_1}{\mathrm{\Δ}{\stackrel{\·}{U}}_1}+\frac{\mathrm{\Δ}{\stackrel{\·}{I}}_2}{\mathrm{\Δ}{\stackrel{\·}{U}}_2}+...+\frac{\mathrm{\Δ}{\stackrel{\·}{I}}_n}{\mathrm{\Δ}{\stackrel{\·}{U}}_n}|---\left(3\right);$

$Y_{\mathrm{brak}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{Y_i}^{\′}=\left|\frac{\mathrm{\Δ}{\stackrel{\·}{I}}_1}{\mathrm{\Δ}{\stackrel{\·}{U}}_1}\right|+\left|\frac{\mathrm{\Δ}{\stackrel{\·}{I}}_2}{\mathrm{\Δ}{\stackrel{\·}{U}}_2}\right|+...+\left|\frac{\mathrm{\Δ}{\stackrel{\·}{I}}_n}{\mathrm{\Δ}{\stackrel{\·}{U}}_n}\right|---\left(4\right);$

In formula: Y _diffdefine differential admittance; Y _brakbe defined as braking admittance; N is bus institute chord way; I represents that bus connects i bar branch road.

Further, in step e, described in judge whether to occur the operation of bus troubles inside the sample space, specifically comprise:

According to following criterion, judge whether to occur bus troubles inside the sample space:

If Y _diff>=KY _brak, there is bus troubles inside the sample space;

If Y _diff< KY _brak, there is bus external area error.

Further, consider and escape the impact that maximum imbalance current and bus troubles inside the sample space drain out electric current, generally get restraint coefficient K value for 0.6-0.8.

The bus bar protecting method based on parameter identification of various embodiments of the present invention, owing to mainly comprising: by with each branch line line protection device of bus connected, gather three-phase voltage, the three-phase electricity flow valuve of local terminal protection installation place; Calculate three-phase voltage, the current failure component of each branch road of bus connected; By Fourier algorithm, extract the power frequency fault component of three-phase voltage current; When fault initiating element is judged fault generation, carry out bus protection calculating; According to the result of calculation of bus protection, judge whether to occur bus troubles inside the sample space; Thereby can overcome the defect that in prior art, failure rate is high, maintenance difficulties is large and operational reliability is poor, to realize failure rate is low, maintenance difficulties is little and operational reliability is good advantage.

Other features and advantages of the present invention will be set forth in the following description, and, partly from instructions, become apparent, or understand by implementing the present invention.

Below by drawings and Examples, technical scheme of the present invention is described in further detail.

Accompanying drawing explanation

Accompanying drawing is used to provide a further understanding of the present invention, and forms a part for instructions, for explaining the present invention, is not construed as limiting the invention together with embodiments of the present invention.In the accompanying drawings:

Fig. 1 is the structural representation that the present invention is based on realistic model in the bus bar protecting method of parameter identification;

Fig. 2 the present invention is based on AG fault simulation result figure in the bus bar protecting method median generatrix district of parameter identification, and in bus district, the result of calculation analogous diagram of time difference dynamic admittance breaks down at F1 point place;

Fig. 3 the present invention is based on BC fault simulation result figure in the bus bar protecting method median generatrix district of parameter identification, brakes the result of calculation analogous diagram of admittance when F1 point place breaks down in bus district;

Fig. 4 the present invention is based on AG fault simulation result figure outside the bus bar protecting method median generatrix district of parameter identification, and outside bus district, the result of calculation figure of time difference dynamic admittance breaks down at F2 point place;

Fig. 5 the present invention is based on BC fault simulation result figure outside the bus bar protecting method median generatrix district of parameter identification,, brakes the result of calculation figure of admittance when F2 point place breaks down outside bus district that is.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described, should be appreciated that preferred embodiment described herein, only for description and interpretation the present invention, is not intended to limit the present invention.

According to the embodiment of the present invention, as Figure 1-Figure 5, provide a kind of bus bar protecting method based on parameter identification, be different from a kind of bus protection new method of conventional current differential protection.

The bus bar protecting method based on parameter identification of the present embodiment, specifically comprises the following steps:

(1) bus connects three-phase voltage, the three-phase electricity flow valuve that each branch line line protection device gathers local terminal protection installation place.Be designated as:

u _ai(k),u _bi(k),u _ci(k)；i _ai(k),i _bi(k),i _ci(k),i＝1,2…,n；

Wherein i represents that bus connects i bar branch road, and n represents a way of bus.

(2) calculate bus and connect each branch road three-phase voltage, current failure component

Δu _ia(k),Δu _ib(k),Δu _ic(k)，Δi _ia(k),Δi _ib(k),Δi _ic(k)。Computing formula is as follows:

$\left\{\begin{array}{c}{\mathrm{\&Delta;u}}_{\mathrm{ij}}\left(k\right)=u_{\mathrm{ij}}\left(k\right)-u_{\mathrm{ij}}(k-\mathrm{pN})\\ {\mathrm{\&Delta;i}}_{\mathrm{ij}}\left(k\right)=i_{\mathrm{ij}}\left(k\right)-i_{\mathrm{ij}}(k-\mathrm{pN})\end{array}\right.j=a,b,c;i=\mathrm{1,2},...n---\left(1\right);$

In formula: p gets positive integer, numerical values recited is determined by protective device; N is every power frequency period sampling number.

(3) by Fourier algorithm, extract the power frequency fault component of three-phase voltage current, be designated as respectively:

$\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ai}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{bi}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ci}}\left(k\right);\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ai}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{bi}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ci}}\left(k\right),i=\mathrm{1,2}...,n,$ Computing formula is as follows:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;u}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\&pi;mk}}{N}}\\ \mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;i}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\&pi;mk}}{N}}\end{array}\right.j=a,b,c;i=\mathrm{1,2},...n---\left(2\right);$

In formula: N is every power frequency period sampling number; K gets 1 representative and extracts power frequency fault component.

(4) when fault initiating element is judged fault generation, bus protection is calculated as follows:

$Y_{\mathrm{diff}}=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{Y}_i=|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_1}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_1}+\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_2}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_2}+...+\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_n}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_n}|---\left(3\right);$

$Y_{\mathrm{brak}}=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{Y_i}^{\&prime;}=\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_1}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_1}\right|+\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_2}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_2}\right|+...+\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_n}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_n}\right|---\left(4\right);$

In formula: Y _diffdefine differential admittance; Y _brakbe defined as braking admittance; N is bus institute chord way; I represents that bus connects i bar branch road.

(5) according to following criterion, judge whether to occur bus troubles inside the sample space:

If Y _diff>=KY _brak, there is bus troubles inside the sample space;

If Y _diff< KY _brak, there is bus external area error.

Wherein: consider and escape the impact that maximum imbalance current and bus troubles inside the sample space drain out electric current, generally get restraint coefficient K value for 0.6-0.8.

The present invention proposes a kind of novel bus guard method based on parameter identification; the method connects a branch road admittance by calculating bus; again each admittance summation is taken absolute value and calculates the differential admittance of equivalence of bus, and after each admittance is taken absolute value, sue for peace and calculate the equivalence braking admittance of bus.Magnitude relationship by poor dynamic admittance and braking admittance judges whether fault occurs on bus.

Compare with conventional current differential protection, technical scheme of the present invention, mainly has the following advantages:

Technical scheme of the present invention is come failure judgement position by recognition system parameter, and reflection system architecture is subject to that CT is saturated to be affected littlely in theory, is not subject to the impact of high resistance ground; Due to the not free characteristic of systematic parameter, technical scheme of the present invention does not need the synchronous of each circuit-switched data in theory.

technical scheme of the present invention being applied to bus protection is below described in further detail.

The bus bar protecting method based on parameter identification of above-described embodiment, to be applied to but be not limited to the 500kV bus-bar system that connects four branch roads, specifically comprises the following steps:

(1) bus connects three-phase voltage, the three-phase electricity flow valuve that four branch line line protection devices gather local terminal protection installation place.Be designated as u _ai(k), u _bi(k), u _ci(k); i _ai(k), i _bi(k), i _ci(k), i=1,2,3,4.If sample frequency is 4kHz, every power frequency cycle sampling number N=80 now, sampling time interval Ts=0.25ms.

(2) calculate bus and connect four branch road three-phase voltages, current failure component Δ u _ia(k), Δ u _ib(k), Δ u _ic(k), Δ i _ia(k), Δ i _ib(k), Δ i _ic(k).Computing formula is as follows:

$\left\{\begin{array}{c}{\mathrm{\&Delta;u}}_{\mathrm{ij}}\left(k\right)=u_{\mathrm{ij}}\left(k\right)-u_{\mathrm{ij}}(k-\mathrm{pN})\\ {\mathrm{\&Delta;i}}_{\mathrm{ij}}\left(k\right)=i_{\mathrm{ij}}\left(k\right)-i_{\mathrm{ij}}(k-\mathrm{pN})\end{array}\right.j=a,b,c;i=\mathrm{1,2},\mathrm{3,4}---\left(5\right);$

In formula: p gets 2; N is 80.

(3) by Fourier algorithm, extract the power frequency fault component of three-phase voltage current, be designated as respectively: $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ai}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{bi}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ci}}\left(k\right);\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ai}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{bi}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ci}}\left(k\right),i=\mathrm{1,2},\mathrm{3,4},$ Computing formula is as follows:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;u}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\&pi;mk}}{N}}\\ \mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;i}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\&pi;mk}}{N}}\end{array}\right.j=a,b,c;i=\mathrm{1,2},\mathrm{3,4}---\left(6\right);$

In formula: K gets 1 representative and extracts power frequency fault component.

(4) when fault initiating element is judged fault generation, bus protection is calculated as follows:

$Y_{\mathrm{diff}}=\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{Y}_i=|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_1}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_1}+\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_2}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_2}+\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_3}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_3}+\frac{{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_4}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_4}|---\left(7\right);$

$Y_{\mathrm{brak}}=\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{Y_i}^{\&prime;}=\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_1}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_1}\right|+\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_2}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_2}\right|+\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_3}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_3}\right|+\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_4}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_4}\right|---\left(8\right);$

(5) according to following criterion, judge whether generating region internal fault:

If Y _diff>=KY _brak, there is bus troubles inside the sample space;

If Y _diff< KY _brak, there is bus external area error.

Wherein: consider and escape the impact that maximum imbalance current and bus troubles inside the sample space drain out electric current, restraint coefficient K is 0.6.

More than be the implementing procedure that technical scheme of the present invention is applied to bus protection.

Utilize electromagnetic transient simulation software (EMTP) to set up the 500kV bus-bar system model that has four branch roads, as shown in Figure 1.Emulation sample frequency is made as 4kHz, and distance protecting method data window length is taken as 20ms fast.

Fig. 2 to Fig. 3 is respectively the simulation result of single-phase earthing and phase-to phase fault in bus generating region.As seen from the figure, when technical scheme of the present invention breaks down in bus district, the bus differential admittance of fault phase is greater than the product of braking admittance and restraint coefficient, and the bus differential admittance of healthy phases is much smaller than the product of braking admittance and restraint coefficient.Therefore,, during bus troubles inside the sample space, technical scheme of the present invention can identify bus troubles inside the sample space reliably.

Fig. 4 to Fig. 5 is respectively the simulation result of single-phase earthing and phase-to phase fault outside bus generating region.As seen from the figure, when technical scheme of the present invention breaks down outside bus district, the bus differential admittance of fault phase and healthy phases is all much smaller than the product of braking admittance and restraint coefficient.Therefore,, during bus external area error, technical scheme of the present invention is reliably failure to actuate.

Finally it should be noted that: the foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, although the present invention is had been described in detail with reference to previous embodiment, for a person skilled in the art, its technical scheme that still can record aforementioned each embodiment is modified, or part technical characterictic is wherein equal to replacement.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (6)

1. the bus bar protecting method based on parameter identification, is characterized in that, mainly comprises:

A, by with each branch line line protection device of bus connected, gather three-phase voltage, the three-phase electricity flow valuve of local terminal protection installation place, be designated as:

u _ai(k),u _bi(k),u _ci(k)；i _ai(k),i _bi(k),i _ci(k),i＝1,2…,n；

Wherein, i represents that bus connects i bar branch road, and n represents a way of bus;

Three-phase voltage, the current failure component of b, each branch road of calculating bus connected, be designated as:

Δu _ia(k),Δu _ib(k),Δu _ic(k)，Δi _ia(k),Δi _ib(k),Δi _ic(k)；

C, by Fourier algorithm, extract the power frequency fault component of three-phase voltage current, be designated as respectively:

$\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ai}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{bi}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ci}}\left(k\right);\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ai}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{bi}}\left(k\right),\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ci}}\left(k\right),i=\mathrm{1,2}...,n;$

D, when fault initiating element is judged fault and is occurred, carry out bus protection calculating;

E, according to the result of calculation of bus protection, judge whether to occur bus troubles inside the sample space.

2. the bus bar protecting method based on parameter identification according to claim 1, is characterized in that, in step b, the three-phase voltage of described each branch road of calculating bus connected, the computing formula of current failure component are:

$\left\{\begin{array}{c}{\mathrm{\&Delta;u}}_{\mathrm{ij}}\left(k\right)=u_{\mathrm{ij}}\left(k\right)-u_{\mathrm{ij}}(k-\mathrm{pN})\\ {\mathrm{\&Delta;i}}_{\mathrm{ij}}\left(k\right)=i_{\mathrm{ij}}\left(k\right)-i_{\mathrm{ij}}(k-\mathrm{pN})\end{array}\right.j=a,b,c;i=\mathrm{1,2},...n---\left(1\right);$

In formula: p gets positive integer, numerical values recited is determined by protective device; N is every power frequency period sampling number.

3. the bus bar protecting method based on parameter identification according to claim 1 and 2, is characterized in that, in step c, the described computing formula of extracting the power frequency fault component of three-phase voltage current by Fourier algorithm is:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;u}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\&pi;mk}}{N}}\\ \mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{ij}}\left(k\right)=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;i}}_{\mathrm{ij}}\left(k\right)e^{-\frac{j2\mathrm{\&pi;mk}}{N}}\end{array}\right.j=a,b,c;i=\mathrm{1,2},...n---\left(2\right);$

In formula: N is every power frequency period sampling number; K gets 1 representative and extracts power frequency fault component.

4. the bus bar protecting method based on parameter identification according to claim 3, is characterized in that, in steps d, described in carry out bus protection calculating computing formula be:

$Y_{\mathrm{diff}}=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{Y}_i=|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_1}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_1}+\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_2}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_2}+...+\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_n}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_n}|---\left(3\right);$

$Y_{\mathrm{brak}}=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{Y_i}^{\&prime;}=\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_1}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_1}\right|+\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_2}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_2}\right|+...+\left|\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_n}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_n}\right|---\left(4\right);$

In formula: Y _diffdefine differential admittance; Y _brakbe defined as braking admittance; N is bus institute chord way; I represents that bus connects i bar branch road.

5. the bus bar protecting method based on parameter identification according to claim 4, is characterized in that, in step e, described in judge whether to occur the operation of bus troubles inside the sample space, specifically comprise:

According to following criterion, judge whether to occur bus troubles inside the sample space:

If Y _diff>=KY _brak, there is bus troubles inside the sample space;

If Y _diff< KY _brak, there is bus external area error.

6. the bus bar protecting method based on parameter identification according to claim 5, is characterized in that, considers and escapes the impact that maximum imbalance current and bus troubles inside the sample space drain out electric current, and generally getting restraint coefficient K value is 0.6-0.8.