CN100576682C - Band serial compensation capacitance transmission line distance protecting method based on Model Identification - Google Patents

Abstract

The present invention relates to be with serial compensation capacitance transmission line distance protecting research field, specifically disclose a kind of band serial compensation capacitance transmission line distance protecting method based on Model Identification.The present invention has adopted the Model Identification technology; set up serial compensation capacitance prior fault model; electric current, this model of voltage sample value substitution of protection installation place are carried out parameter Estimation; error of calculation coefficient EF then; the position of putting relative serial compensation capacitance according to the error coefficient and the magnitude relationship failure judgement of definite value; and the combined impedance element, whether judge has fault to exist in the protection range, thus the action of control protective device.The fault point cooperated with impedance component with respect to the position of serial compensation capacitance when the present invention can judge the serial supplementary line single phase ground fault, can overcome the influence that serial compensation capacitance is adjusted the distance and protected, the sensitivity that has improved protective device.

Description

Band serial compensation capacitance transmission line distance protecting method based on Model Identification

Technical field

The present invention relates to serial supplementary line distance protection research field, more specifically relate to a kind of band serial compensation capacitance transmission line distance protecting method based on Model Identification.

Background technology

Series capacitor compensation is to improve the effective means of transmission line economy and reliability, and it mainly acts on and being: improve the conveying capacity of electric power system by the control trend; Improve the stability of electric power system; Improve quality of voltage and reactive power equilibrium; The line loss of minimizing system improves the circuit transmission capacity.It also has the effect that improves power system transient stability, optimizes transmission line trend and reduction system loss.

But series compensation capacitance has destroyed the linear relationship of transmission line impedance and distance, and traditional distance protection is applied to must consider in the serial supplementary line capacitive reactance Z of serial compensation capacitance _C, by all fronts impedance Z _LWith the serial compensation capacitance capacitive reactance sum Z that adjusts _Zd=(0.8～0.9) (Z _L+ Z _C), protection sensitivity is very low when the capacitive reactance of serial compensation capacitance is big.

Summary of the invention

The object of the present invention is to provide a kind of band serial compensation capacitance transmission line distance protecting method based on Model Identification; the fault point was with respect to the position of serial compensation capacitance when it can judge the serial supplementary line single phase ground fault; cooperate with impedance component; by all fronts impedance setting; can overcome the influence that serial compensation capacitance is adjusted the distance and protected, the sensitivity that has improved protective device.

Principle of the present invention is: set up serial compensation capacitance prior fault model, will protect electric current, this model of voltage sample value substitution of installation place to carry out parameter Estimation, then error of calculation coefficient E _F, the position of putting relative serial compensation capacitance according to the error coefficient and the magnitude relationship failure judgement of definite value, and combined impedance element, whether judge has fault to exist in the protection range, thus the action of control protective device.

Technical scheme of the present invention is achieved in that

Step 1: by protective device sampling circuit head end three-phase voltage value u _Am, u _Bm, u _CmWith current value i _Am, i _Bm, i _Cm, calculate zero-sequence current i _M0, computational scheme head end three-phase voltage phasor And electric current phasor

Determine the fault phase of single phase ground fault

Step 2: the parameter recognition equation of setting up the serial compensation capacitance prior fault

Wherein,

Be respectively the voltage and current of fault phase head end, $i_{m0}=\frac{1}{3}(i_{\mathrm{Am}}+i_{\mathrm{Bm}}+i_{\mathrm{Cm}}),$ k _L=(L ₀-L ₁)/L ₁, k _R=(R ₀-R ₁)/R ₁, L ₀, R ₀Be the zero sequence inductance and the resistance value of circuit unit length, L ₁, R ₁Be circuit unit length positive sequence inductance and resistance value, utilize the least-squares estimation method to calculate line resistance R, line inductance L and transition resistance R ' _F

Step 3: according to voltage, electric current and the zero-sequence current of fault phase head end, error of calculation coefficient E _F,

Step 4: according to error coefficient E _FSize judge: if E _F＜E _Set, then determine to break down before the serial compensation capacitance protective device action, wherein E _SetBe the error coefficient definite value, the principle of adjusting is: E _Set=(1.1～1.2) E _R1max, E _R1maxWorst error coefficient for the serial compensation capacitance prior fault;

Otherwise, determine to break down behind the serial compensation capacitance, if E _F＞E _Set, and | Z _J-Z _C|＜| Z _Set|, then further to determine to have fault in the protection range, if the protective device action is E _F＞E _Set, and | Z _J-Z _C|＞| Z _Set|, determine further that then protection range breaks down outward, protective device is failure to actuate, wherein Z _JBe the measurement impedance,

$k_Z=\frac{Z_0-Z_1}{{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="C2008100176620011H3.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1},$ Z ₁, Z ₀Be positive sequence, the zero sequence impedance of unit length,

Be the fault phase

Voltage phasor,

Be the fault phase

Electric current phasor,

Be zero-sequence current phasor, Z _CBe serial compensation capacitance capacitive reactance, Z _SetBe the impedance definite value, by all fronts impedance setting, Z _Set=(0.8～0.9) Z _L, Z _LBe all fronts impedance.

Described E _SetBe the error coefficient definite value, the principle of adjusting is: E _Set=(1.1～1.2) E _R1max, E _R1maxBe the worst error coefficient of serial compensation capacitance prior fault, can determine by emulation.The worst error coefficient E of described serial compensation capacitance prior fault _R1max, its acquiring method is: choose the different faults point and carry out emulation before serial compensation capacitance, choose the error coefficient maximum of each time emulation.

The present invention is based on the Model Identification principle, constructed error coefficient E _F, by error of calculation coefficient, distinguish string according to the magnitude relationship of error coefficient and mend the front and back fault, the combined impedance element judges whether there is fault in the protection range again.The invention has the advantages that the position that the energy failure judgement is put relative serial compensation capacitance cooperates with impedance component, can overcome the influence that serial compensation capacitance is adjusted the distance and protected,, improve protective device sensitivity by all fronts impedance setting.

Description of drawings

Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.

Fig. 1 is the hardware block diagram of circuit Microcomputer Protection;

Fig. 2 serial compensation capacitance prior fault illustraton of model;

Fault model figure behind Fig. 3 serial compensation capacitance;

The decision flow chart of Fig. 4 guard method of the present invention;

Fig. 5 750kV series compensated transmission line fault simulation schematic diagram.

Embodiment

With reference to Fig. 1; be provided with protective device at circuit M end; this protective device is by the three-phase voltage and the electric current of voltage transformer TV summation current transformer TA measurement circuitry M end; behind analog measurement process low pass filter, sampling holder and A/D converter; deliver to computer processor (DSP); send result of determination to relay by photoisolator by computer processor, carry out corresponding protection action.

With reference to Fig. 2, be serial compensation capacitance prior fault illustraton of model, for single-phase (is example mutually with A) earth fault equation is arranged $u_{\mathrm{Am}}=R(i_{\mathrm{Am}}+k_R{i}_{m0})+L\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}+R_F^{\&prime;}{i}_{m0}$ Set up, wherein u _Am, i _AmBe respectively the voltage and current of m end A phase, i _M0Be zero-sequence current.With reference to Fig. 3,, equation is arranged for single phase ground fault for fault model figure behind the serial compensation capacitance $u_{\mathrm{Am}}=R(i_{\mathrm{Am}}+k_R{i}_{m0})+L\frac{d(i_{\mathrm{Am}}+k_l{i}_{m0})}{\mathrm{dt}}+\frac{1}{C}\&Integral;i_{\mathrm{Am}}\mathrm{dt}+R_F^{\&prime;}{i}_{m0}$ Set up.

Model Identification is exactly that object and master pattern that needs are discerned are compared, thereby sorts out, discerns.The present invention is a standard with serial compensation capacitance prior fault model, the error coefficient E of structure reflection model similarity degree _F, $E_F={\&Integral;}_0^T|u_{\mathrm{Am}}-R(i_{\mathrm{Am}}+k_R{i}_{m0})-L\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}-R_F^{\&prime;}{i}_{m0}|\mathrm{dt},$ Wherein, R, L and R ' _FIt is the parameter that goes out with serial compensation capacitance prior fault Model Identification.If the serial compensation capacitance prior fault, identifying object conforms to master pattern, and error coefficient is less; If fault behind the serial compensation capacitance, identifying object and master pattern are not inconsistent, and error coefficient is bigger.So, can be relatively and the position of serial compensation capacitance according to the big or small failure judgement point of error coefficient.

Match with above-mentioned principle, impedance component can be by all fronts impedance setting, and needn't consider the capacitive reactance of serial compensation capacitance, improves sensitivity.If be judged to be the serial compensation capacitance prior fault, then protective device action; If be judged to be fault behind the serial compensation capacitance, then will measure the capacitive reactance Z that impedance deducts serial compensation capacitance _J-Z _C, then with the impedance Z of adjusting _SetRelatively, judge whether protective device moves.

With reference to Fig. 4, distance protecting method idiographic flow of the present invention is as follows:

At first, by the three-phase voltage and the electric current of voltage transformer summation current transformer measurement circuitry head end, analog quantity through behind low pass filter, sampling holder and the A/D converter, is obtained circuit head end three-phase voltage sampled value u _Am, u _Bm, u _Cm, and three-phase current sampled value i _Am, i _Bm, i _Cm, calculate zero-sequence current value i _M0, calculate the three-phase voltage phasor

And electric current phasor

Determine the fault phase of single phase ground fault

Secondly, make up serial compensation capacitance prior fault model equation $u_{\mathrm{Am}}=R(i_{\mathrm{Am}}+k_R{i}_{m0})+L\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}+R_F^{\&prime;}{i}_{m0},$ Utilize least square method substitution voltage, current sampling data, calculate model parameter R, L and R ' _F

According to the least-squares parameter estimation method, the parameter recognition equation

$u_{\mathrm{Am}}=R(i_{\mathrm{Am}}+k_R{i}_{m0})+L\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}+R_F^{\&prime;}{i}_{m0},$ Its general formula can be written as A ₁R+A ₂L+A ₃R ' _F=B, wherein:

A ₁＝(i _Am+k _Ri _m0)，

$A_2=\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}=\frac{i_{\mathrm{Am}}(k+1)+k_L{i}_{m0}(k+1)-i_{\mathrm{Am}}(k-1)-k_L{i}_{m0}(k-1)}{2\mathrm{\&Delta;t}}$ (adopt 3 differential formulas, Δ t is the sampling interval, and k is the image data sequence number),

A ₃＝i _m0，

B＝u _Am。

With each sampling number according to substitution equation A ₁R+A ₂L+A ₃R ' _F=B can obtain an equation.Can form an equation group A with the substitution of multiple spot data _1kR+A _2kL+A _3kR ' _F=B _k(k=1,2 ..., m), m is a sampling number.

Make up matrix equation AX=B, wherein:

$A=\left[\begin{array}{ccc}{A}_{11}& A_{12}& A_{13}\\ A_{21}& A_{22}& A_{23}\\ \&CenterDot;& \&CenterDot;& \&CenterDot;\\ \&CenterDot;& \&CenterDot;& \&CenterDot;\\ \&CenterDot;& \&CenterDot;& \&CenterDot;\\ A_{m1}& A_{m2}& A_{m3}\end{array}\right],$ $X=\left[\begin{array}{c}R\\ L\\ R_F^{\&prime;}\end{array}\right],$ $B=\left[\begin{array}{c}{B}_1\\ B_2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ B_m\end{array}\right]$

Can try to achieve X=[A _{3 * m}] ^-1B, i.e. corresponding parameters R, L and R ' _F

The 3rd, error of calculation coefficient $E_F={\&Integral;}_0^T|u_{\mathrm{Am}}-R(i_{\mathrm{Am}}+k_R{i}_{m0})-L\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}-R_F^{\&prime;}{i}_{m0}|\mathrm{dt}.$

Differential adopts 3 differential formulas in the calculating

$\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}=\frac{i_{\mathrm{Am}}(k+1)+k_L{i}_{m0}(k+1)-i_{\mathrm{Am}}(k-1)-k_L{i}_{m0}(k-1)}{2\mathrm{\&Delta;t}},$

Integration adopts the trapezoidal integration formula, ${\left[{\&Integral;}_0^t{e}_F\mathrm{dt}\right]}_{t=\mathrm{n\&Delta;t}}=\frac{\mathrm{\&Delta;t}}{2}[e_F\left(0\right)+e_F\left(n\right)+2\underset{k=2}{\overset{n-1}{\mathrm{\&Sigma;}}}{e}_F\left(k\right)],$ Wherein, $e_F=|u_{\mathrm{Am}}-R(i_{\mathrm{Am}}+k_R{i}_{m0})-L\frac{d(i_{\mathrm{Am}}+k_L{i}_{m0})}{\mathrm{dt}}-R_F^{\&prime;}{i}_{m0}|.$

At last, according to error coefficient E _FSize judge: if E _F＜E _Set, then to determine to break down before the serial compensation capacitance, trip command is sent in the protective device action; Otherwise, determine to break down behind the serial compensation capacitance, whether combined impedance element decision protective device moves again.Wherein, E _SetBe the error coefficient definite value, the principle of adjusting is: E _Set=(1.1～1.2) E _R1max, E _R1maxBe the worst error coefficient of serial compensation capacitance prior fault, its acquiring method is: choose the different faults point and carry out a large amount of emulation before serial compensation capacitance, obtain the error coefficient of each time emulation, get maximum wherein.

Determine to break down behind the serial compensation capacitance, the concrete decision method whether combined impedance element decision protective device moves is:

If E _F＞E _Set, and | Z _J-Z _C|＜| Z _Set|, then further to determine to have fault in the protection range, trip command is sent in the protective device action; If E _F＞E _Set, and | Z _J-Z _C|＞| Z _Set|, determine further that then protection range breaks down outward, protective device is failure to actuate.Z wherein _JBe the measurement impedance, $k_Z=\frac{Z_0-Z_1}{{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="C2008100176620011H3.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1},$ Z ₁, Z ₀Be positive sequence, the zero sequence impedance of unit length,

Be the fault phase

Voltage phasor,

Be the fault phase

Electric current phasor, Be zero-sequence current phasor, Z _CBe serial compensation capacitance capacitive reactance, Z _SetBe the impedance definite value, by all fronts impedance setting, Z _Set=(0.8～0.9) Z _L, Z _LBe all fronts impedance.

Provided the result of electromagnetic transient simulation program of the present invention (EMTP) below.As shown in Figure 5, the system voltage grade is 750kV, and circuit adopts distributed parameter model.The positive sequence parameter Z ₁=0.01217+j0.268 Ω/km, C ₁=0.01367uF/km; Zero sequence parameter Z ₀=0.27293+j0.84 Ω/km, C ₀=0.0093 μ F/km.Line length is 300km, and M, N side positive sequence and zero sequence system impedance are respectively Z _M1=0.7792+j6.744 Ω, Z _M0=0.4469+j15.709 Ω, Z _N1=0.8088+j6.3077 Ω, Z _N0=1.8527+j16.5808 Ω.

Serial compensation capacitance is installed in circuit 150km place, and compensativity is 50%.MOV protection voltage levvl is 2.3 times of electric capacity rated voltage peak value.

The data sampling frequency is 10kHz in the emulation, calculates with the data of a cycle after the fault.

Choose the different faults point and carry out a large amount of emulation before serial compensation capacitance, table 1 has been listed the error coefficient result of calculation when before serial compensation capacitance single phase ground fault taking place.

Table 1

Error coefficient maximum wherein is 157.8140, and then the error coefficient definite value is E _Set=1.1E _R1max=173.58.

Behind serial compensation capacitance, get K1, K2, three points of K3; respectively at these three some simulation metallicity single phase ground faults and band transition resistance single phase ground fault; K1 is positioned at the serial compensation capacitance rear side; K2 is positioned at protection range; K3 is positioned at outside the protection range, and table 2 has been listed the error coefficient result of calculation when metallicity single phase ground fault and band transition resistance single phase ground fault take place for K1, K2,3 of K3.

Table 2

As seen from Table 2, the error coefficient of three points is all greater than definite value E _SetBy table 1, table 2 as seen, the present invention can correctly distinguish the forward and backward fault of serial compensation capacitance.

Claims (2)

1, based on the band serial compensation capacitance transmission line distance protecting method of Model Identification, it is characterized in that,

Step 1: by protective device sampling circuit head end three-phase voltage value u _Am, u _Bm, u _CmWith current value i _Am, i _Bm, i _Cm, calculate zero-sequence current i _M0, computational scheme head end three-phase voltage phasor

And electric current phasor

Determine the fault phase of single phase ground fault

Step 2: the parameter recognition equation of setting up the serial compensation capacitance prior fault

Wherein,

Be respectively the voltage and current of fault phase head end, $i_{m0}=\frac{1}{3}(i_{\mathrm{Am}}+i_{\mathrm{Bm}}+i_{\mathrm{Cm}}),$ k _L=(L ₀-L ₁)/L ₁, k _R=(R ₀-R ₁)/R ₁, L ₀, R ₀Be the zero sequence inductance and the resistance value of circuit unit length, L ₁, R ₁Be circuit unit length positive sequence inductance and resistance value, utilize the least-squares estimation method to calculate line resistance R, line inductance L and transition resistance R ' _F

Step 3: according to voltage, electric current and the zero-sequence current of fault phase head end, error of calculation coefficient E _F,

Step 4: according to error coefficient E _FSize judge: if E _F＜E _Set, then determine to break down before the serial compensation capacitance protective device action, wherein E _SetBe the error coefficient definite value, the principle of adjusting is: E _Set=(1.1～1.2) E _R1max, E _R1maxWorst error coefficient for the serial compensation capacitance prior fault;

Otherwise, determine to break down behind the serial compensation capacitance, if E _F＞E _Set, and | Z _J-Z _C|＜| Z _Set|, then further to determine to have fault in the protection range, if the protective device action is E _F＞E _Set, and | Z _J-Z _C|＞| Z _Set|, determine further that then protection range breaks down outward, protective device is failure to actuate, wherein Z _JBe the measurement impedance,

$k_Z=\frac{Z_0-Z_1}{Z_1},$ Z ₁, Z ₀Be positive sequence, the zero sequence impedance of unit length,

Be the fault phase

Voltage phasor,

Be the fault phase Electric current phasor,

Be zero-sequence current phasor, Z _CBe serial compensation capacitance capacitive reactance, Z _SetBe the impedance definite value, by all fronts impedance setting, Z _Set=(0.8～0.9) Z _L, Z _LBe all fronts impedance.

2, according to the described band serial compensation capacitance transmission line distance protecting method of claim 1, it is characterized in that the worst error coefficient E of described serial compensation capacitance prior fault based on Model Identification _R1max, its acquiring method is: choose the different faults point and carry out emulation before serial compensation capacitance, choose the error coefficient maximum of each time emulation.

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