CN101615785A - Electric transmission line longitudinal protection method based on shunt reactor - Google Patents

Abstract

The invention discloses electric transmission line longitudinal protection method based on shunt reactor; the present invention is based on the fault component network and set up transmission line internal fault model and external fault model; and be reduced to unified inductor models through conversion, by to the induction reactance X in the fault model _LDiscern, with X _LSize and symbol judge internal fault and external fault, solved externally under-sensitive problem when easy malfunction and high resistance earthing fault during fault of traditional differential protection, improved the performance of relaying protection largely and passed through simulating, verifying.

Description

Electric transmission line longitudinal protection method based on shunt reactor

Technical field

The present invention relates to the electric power line longitudinal coupling protection research field of both-end band shunt reactor, more specifically relate to a kind of electric transmission line longitudinal protection method based on parameter recognition.

Background technology

The ultra high voltage long-distance transmission line is generally all installed shunt reactor.It mainly acts on and being: one, compensation capacitive charge power, suppress system's overvoltage; Two, the light hours absorb capacitive power, control reactive power flow, stabilizing network working voltage.

Current differential protection is widely used in the high voltage power transmisson system as the main protection of transmission line, but the UHV transmission line capacitance current is big and the high characteristics of fault current harmonic content have influenced the performance of differential protection.Extra high voltage line parameter distributions and various compensation arrangement make and contain more low frequency component and aperiodic component in the fault current, and the ratio of line inductance and resistance is big, time constant is big, makes that low frequency amount, mark subharmonic and the aperiodic component decay in the fault current is slow.Aperiodic component, low frequency component and line distribution capacitance electric current by shunt reactor increase unsymmetrical current, have increased the risk of differential protection malfunction.

At present, taked some measures, but all there is defective in these measures at the current differential protection of ultra high voltage and extra high voltage network:

(1) improve protection and start setting value, this method has reduced the sensitivity of differential protection.

(2) utilize the phasor penalty method that capacitance current is compensated, this method can reduce protection and start setting value, but only limits to the power frequency amount, can not overcome the influence of low frequency component and aperiodic component, and the desired data window is longer.

(3) utilize the instantaneous value of voltage and current that capacitance current and reactor current are carried out time domain compensation, owing to can not determine the initial moment of fault, the electric current of shunt reactor can't accurately calculate, and compensation precision is restricted.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art part, a kind of electric transmission line longitudinal protection method based on shunt reactor is provided, this method can overcome capacitance current and fault current harmonic effects, and applicability is strong, the reliability height.

Principle of the present invention adopts the thought of parameter recognition.On the basis of fault additivity network, set up internal fault and external fault model, can be after the process conversion with the unified inductor models of two model simplifications for having same form, inductor models is equivalent to the system impedance at two ends during internal fault, is a less negative impedance; Inductor models is equivalent to the impedance of shunt reactor during external fault, is a bigger positive impedance.The present invention utilizes the principle of parameter recognition to calculate induction reactance in the fault model, differentiates internal fault and external fault by size and the symbol of relatively discerning induction reactance.

Technical scheme of the present invention is achieved in that

Concrete steps are as follows:

Fault additivity network model when 1) inside and outside fault being taken place for the transmission line of both-end band shunt reactor is unified to be inductor models: ${\mathrm{\Δu}}_{\mathrm{cd}}=L\frac{\mathrm{d\Δ}{i}_{\mathrm{cd}}}{\mathrm{dt}}+R{\mathrm{\Δi}}_{\mathrm{cd}},$ L wherein, R is respectively inductance and the resistance in the inductor models, Δ u _CdBe two ends busbar voltage sum, Δ i _CdBe differential current through the time-domain capacitive current compensation;

The internal fault model is: ${\mathrm{\Δu}}_{\mathrm{cd}}=-L_{\mathrm{seq}}\frac{\mathrm{d\Δ}{i}_{\mathrm{cd}}}{\mathrm{dt}}-R_{\mathrm{seq}}{\mathrm{\Δi}}_{\mathrm{cd}},$ Δ u _CdBe two ends busbar voltage sum, Δ i _CdBe the differential current through the time-domain capacitive current compensation, L _SeqAnd R _SeqEquivalent inductance and equivalent resistance for the two ends system impedance;

The external fault model is: ${\mathrm{\Δu}}_{\mathrm{cd}}=L_L\frac{\mathrm{d\Δ}{i}_{\mathrm{cd}}}{\mathrm{dt}}+R_L\mathrm{\Δ}{i}_{\mathrm{cd}},$ Δ u _CdBe two ends busbar voltage sum, Δ i _CdBe the differential current through the time-domain capacitive current compensation, L _LAnd R _LInductance and resistance for shunt reactor;

2) utilize least-squares algorithm that the inductance parameters L in the inductor models is calculated, definition identification induction reactance X _L=2 π fL, wherein f=50Hz is power system frequency, the inductance parameters in the L inductor models;

3) definition identification induction reactance setting value: X _Zd=k2 π fL _L, wherein k is a safety factor, and is desirable 0.5, f=50Hz is power system frequency, L _LInductance value for shunt reactor; If identification induction reactance X _LSatisfy: X _L＜0 or | X _L|＜X _Zd, then being judged to be internal fault, protective device sends trip signal, if identification induction reactance X _LSatisfy: X _L＞X _Zd, then being judged to be external fault, protective device sends block signal.

The present invention has the following advantages:

(1) this method has adopted parameter recognition, has made full use of the harmonic wave after the fault, is not subjected to the influence of aperiodic component and low frequency component.

(2) utilize size and the symbol decision internal fault and the external fault of identification parameter, discrimination is bigger, and protection has higher sensitivity.

(3) Temporal Data does not need time-delay to escape transient process after the employing fault, and it is short to calculate required data window, quick action.

Description of drawings

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

Fig. 2 internal fault additivity network model figure,

Fig. 3 external fault additivity network model figure,

Fig. 4 fault is unified inductor models figure;

Fig. 5 decision flow chart;

Figure 65 00kV both-end power supply electric line road EMTP analogue system figure;

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail, the invention belongs to the circuit Microcomputer Protection, the protective device that uses element of the present invention is equipped with in the circuit both sides.Protective device with the M side is an example; input variable is the electric current and voltage of this side electric current and voltage and N side; the electric current and voltage of this side is measured by current transformer TA and voltage transformer TV, and the electric current and voltage of N side is obtained by the communication device synchronous driving, and Fig. 1 has provided simple signal.

With reference to shown in Figure 1; the invention belongs to Microcomputer Protection; be made of data acquisition system (comprising that voltage transformer, current transformer, low-pass filtering, sampling keep and the A/D conversion portion), communication system, microcomputer main system (DSP), input-output system four parts, discriminating element core algorithm of the present invention is realized in microcomputer DSP main system by programming.A, B, the input of the analog quantity of C three-phase voltage and electric current through sampling keep and the A/D conversion after, deliver to the microcomputer main system, go out to discern induction reactance by corresponding algorithm computation, outside coming failure judgement to occur in still to distinguish in the district according to the size of identification induction reactance and symbol.

Shown in Fig. 2,3, be example with single-phase transmission line, the fault additivity network of internal fault and external fault, the positive direction of voltage is to point to earth point by bus, the positive direction of electric current is pointed to circuit for bus is arranged.Externally in the fault component network (Fig. 2), u _fBe the fault additional supply, m, n are the both sides system busbar, R _l, L _lBe line resistance and inductance; Δ u _m, Δ u _nBe respectively both sides fault component voltage, Δ i _Lm, Δ i _LnBe respectively the fault component electric current that flows through shunt reactor, the equation below they satisfy:

${\mathrm{\Δu}}_m=L_L\frac{\mathrm{d\Δ}{i}_{\mathrm{Lm}}}{\mathrm{dt}}+R_L\mathrm{\Δ}{i}_{\mathrm{Lm}}$

${\mathrm{\Δu}}_n=L_L\frac{\mathrm{d\Δ}{i}_{\mathrm{Ln}}}{\mathrm{dt}}+R_L\mathrm{\Δ}{i}_{\mathrm{Ln}}$

L wherein _L, R _LBe the inductance and the resistance of reactor, definition two ends fault component voltage sum is a differential voltage: Δ u _Cd=Δ u _m+ Δ u _n, the differential current of definition behind condenser current compensation:

Δi _cd＝(Δi _m+Δi _n)-(Δi _cm+Δi _cn)，

Δ i wherein _Cm, Δ i _CnCapacitance current for the transmission line two ends.Can obtain the external fault model is:

$\mathrm{\Δ}{u}_{\mathrm{cd}}=\mathrm{\Δ}{u}_m+{\mathrm{\Δu}}_n=L_L\frac{d(\mathrm{\Δ}{i}_{\mathrm{Lm}}+\mathrm{\Δ}{i}_{\mathrm{Ln}})}{\mathrm{dt}}+R_L({\mathrm{\Δi}}_{\mathrm{Lm}}+{\mathrm{\Δi}}_{\mathrm{Ln}})=L_L\frac{\mathrm{d\Δ}{i}_{\mathrm{cd}}}{\mathrm{dt}}+R_L{\mathrm{\Δi}}_{\mathrm{cd}}$

In internal fault model (Fig. 3), u _fBe the fault additional supply, m, n are the both sides system busbar; Equation below the voltage and current of two ends bus also satisfies respectively:

${\mathrm{\Δu}}_m=-R_{\mathrm{ms}}\·\mathrm{\Δ}{i}_m-L_{\mathrm{ms}}\·\frac{\mathrm{d\Δ}{i}_m}{\mathrm{dt}}$

${\mathrm{\Δu}}_n=-R_{\mathrm{ns}}\·\mathrm{\Δ}{i}_n-L_{\mathrm{ns}}\·\frac{\mathrm{d\Δ}{i}_n}{\mathrm{dt}}$

L wherein _Ms, R _Ms, L _Ns, R _NsBe respectively the resistance and the inductance of two end systems, top two formula additions can be obtained:

${\mathrm{\Δu}}_m+{\mathrm{\Δu}}_n=-(L_{\mathrm{ms}}\frac{d{\mathrm{\Δi}}_m}{\mathrm{dt}}+L_{\mathrm{ns}}\frac{d{\mathrm{\Δi}}_n}{\mathrm{dt}})-(R_{\mathrm{ms}}{\mathrm{\Δi}}_m+R_{\mathrm{ns}}{\mathrm{\Δi}}_n)$

$=-(L_{\mathrm{ms}}{k}_m+L_{\mathrm{ns}}{k}_n)\frac{d({\mathrm{\Δi}}_m+{\mathrm{\Δi}}_n)}{\mathrm{dt}}-(R_{\mathrm{ms}}{k}_m+R_{\mathrm{ns}}{k}_n)({\mathrm{\Δi}}_m+{\mathrm{\Δi}}_n)$

Wherein, $k_m=\frac{{\mathrm{\Δi}}_m}{{\mathrm{\Δi}}_m+{\mathrm{\Δi}}_n},$ $k_n=\frac{{\mathrm{\Δi}}_n}{{\mathrm{\Δi}}_m+{\mathrm{\Δi}}_n},$ In high-voltage fence, the breadth coefficient of fault component network is about real number, i.e. Δ i _m, Δ i _nBe approximately same-phase, so k _m, k _nBe real number, because the system impedance at two ends much smaller than the circuit capacitive reactance, can be ignored the influence of building-out capacitor electric current, the internal fault model can be written as simultaneously:

${\mathrm{\Δu}}_{\mathrm{cd}}=-L_{\mathrm{seq}}\frac{d({\mathrm{\Δi}}_m+{\mathrm{\Δi}}_n)}{\mathrm{dt}}-R_{\mathrm{seq}}({\mathrm{\Δi}}_m+{\mathrm{\Δi}}_n)\≈-L_{\mathrm{seq}}\frac{d{\mathrm{\Δi}}_{\mathrm{cd}}}{\mathrm{dt}}-R_{\mathrm{seq}}{\mathrm{\Δi}}_{\mathrm{cd}}$

Wherein, L _Seq=L _Msk _m+ L _Nsk _n, R _Seq=R _Msk _m+ R _Nsk _nRepresent equivalent inductance and equivalent resistance in the system impedance of both sides respectively.Compare internal fault model and external fault model, it is as follows to obtain unified fault model:

${\mathrm{\Δu}}_{\mathrm{cd}}=L\frac{\mathrm{d\Δ}{i}_{\mathrm{cd}}}{\mathrm{dt}}+R{\mathrm{\Δi}}_{\mathrm{cd}}$

The transmission line malfunction unified model as shown in Figure 4.When transmission line breaks down, can calculate parameters R and L by the fault unified model, and definition identification induction reactance X _LWith identification induction reactance setting value X _Zd,

X _L＝2πf·L

X _zd＝k·2πf·L _L

Wherein k is a safety factor, and is desirable 0.5, and f is a power system frequency, gets 50Hz.

The protection criterion is as follows:

Internal fault: X _L＜0 or | X _L|＜X _Zd

External fault: X _L＞X _Zd

With reference to protection judgment processing flow chart 5, concrete implementation step of the present invention is as follows:

(1) judge the fault initial time by starting component, and definite fault phase (with A is example mutually, down together), the phase voltage sequence u at transmission line two ends after the collection fault _AmAnd u _AnAnd phase current sequence i _Am, i _An, utilize memory voltage and memory electric current to calculate fault component voltage Δ u _Am, Δ u _AnWith fault component electric current Δ i _Am, Δ i _An, and data are sent to the opposite end.Utilize the electric current and voltage calculating differential voltage of this side electric current and voltage and offside and the differential current behind the building-out capacitor electric current:

Δu _cda(i)＝Δu _am(i)+Δu _an(i)

${\mathrm{\Δi}}_{\mathrm{cda}}\left(i\right)={\mathrm{\Δi}}_{\mathrm{am}}\left(i\right)+{\mathrm{\Δi}}_{\mathrm{an}}\left(i\right)-C_a\frac{({\mathrm{\Δu}}_{\mathrm{cda}}(i+1)-{\mathrm{\Δu}}_{\mathrm{cda}}(i-1))}{2\mathrm{\Δt}}$

Wherein, i is a sampled point, C _aBe transmission line A phase electric capacity, Δ t is the sampling interval.

(2) bring differential voltage and the differential current after compensation into the parameter recognition equation:

${\mathrm{\Δu}}_{\mathrm{cda}}=R\·{\mathrm{\Δi}}_{\mathrm{cda}}+L\·\frac{d{\mathrm{\Δi}}_{\mathrm{cda}}}{\mathrm{dt}},$ And utilize least square method that parameter L is discerned, calculate identification induction reactance X _LAccording to the least-squares parameter estimation method, the parameter recognition equation ${\mathrm{\Δu}}_{\mathrm{cd}}=R\·{\mathrm{\Δi}}_{\mathrm{cd}}+L\·\frac{d{\mathrm{\Δi}}_{\mathrm{cd}}}{\mathrm{dt}},$ Its general formula can be written as A ₁R+A ₂L=B, wherein: A ₁=Δ i _Cd, $A_2=\frac{d{\mathrm{\Δi}}_{\mathrm{cd}}}{\mathrm{dt}}=\frac{{\mathrm{\Δi}}_{\mathrm{cd}}(k+1)-{\mathrm{\Δi}}_{\mathrm{cd}}(k-1)}{2\mathrm{\Δt}}$ (adopt 3 differential formulas, Δ t is the sampling interval, and k is the image data sequence number, k=0,1,2,3 ...), B=Δ u _CdWith each sampling number according to substitution equation A ₁R+A ₂L=B can obtain an equation.Can form an equation group A with the substitution of multiple spot data _kR+A _kL=B (k=1,2 ..., m), m is a sampling number.

Make up matrix equation AX=B, wherein:

$A=\left[\begin{array}{cc}{A}_{11}& A_{12}\\ .& .\\ .& .\\ .& .\\ A_{m1}& A_{m2}\end{array}\right],$ $X=\left[\begin{array}{c}R\\ L\end{array}\right],$ $B=\left[\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="A2009100234820012H3.png"\; state="\{\{state\}\}">B</figure-callout>}}_1\\ .\\ .\\ .\\ B_m\end{array}\right]$

Can try to achieve X=[A _{2 * m}] ^-1B, i.e. Dui Ying resistance parameter R, inductance parameters L, and then obtain identification induction reactance.

(3) according to X _LThe size district in and the judgement of external area error; X _L＞X _Zd, to judge external fault takes place, block signal is sent in protection, otherwise, judge internal fault take place that trip signal is sent in protection.

According to above-mentioned embodiment the present invention has been carried out Computer Simulation, analogue system as shown in Figure 6, K ₁, K ₂, K ₃And K ₄Be 4 fault points that are provided with, total track length 342km, each parameter is provided with as follows in the model:

M side system impedance: X _1m=95.669 Ω, X _0m=199.20 Ω.

N side system impedance: X _1n=148.10 Ω, X _0n=45.947 Ω.

The shunt reactor parameter: $X_{L_L}=2017\mathrm{\&Omega;};$ $X_{L_N}=550\mathrm{\&Omega;}.$

Line parameter circuit value:

Z _l1＝0.027+0.3032Ω/km Z _l0＝0.1957+0.6945Ω/km

ωc ₁＝4.281×10 ^-6S/km ωc ₀＝2.859×10 ^-6S/km

The data sampling frequency is 2kHz in the emulation, calculates with 5ms data window after the fault.Identification induction reactance simulation result in different faults point different faults type sees Table 1, and the identification induction reactance simulation result of band transition resistance single phase ground fault sees Table 2. X wherein _LaX _LbX _LcBe respectively the identification induction reactance of three phase line, X _ZdBe identification induction reactance setting value.R _fBe transition resistance.

Identification induction reactance simulation result during table 1 metallicity fault

The EMTP simulation result of table 2 single-phase zone transition resistance earth fault

X during internal fault as can be seen from Table 1 _LBe negative value and less, and X during external fault _LFor on the occasion of and very big, can be according to X _LSize and symbol distinguish internal fault and external fault, and bigger nargin is arranged.Be not subjected to the influence of transition resistance as can be seen from Table 2 based on the line protection principle of shunt reactor, protection all can correct operation.

Claims (1)

1, based on the electric transmission line longitudinal protection method of shunt reactor, it is characterized in that:

Fault additivity network model when 1) inside and outside fault being taken place for the transmission line of both-end band shunt reactor is unified to be inductor models: $\mathrm{\&Delta;}{u}_{\mathrm{cd}}=L\frac{\mathrm{d\&Delta;}{i}_{\mathrm{cd}}}{\mathrm{dt}}+\mathrm{R\&Delta;}{i}_{\mathrm{cd}},$ L wherein, R is respectively inductance and the resistance in the inductor models, Δ u _CdBe two ends busbar voltage sum, Δ i _CdBe differential current through the time-domain capacitive current compensation;

The internal fault model is: ${\mathrm{\&Delta;u}}_{\mathrm{cd}}=-L_{\mathrm{seq}}\frac{\mathrm{d\&Delta;}{i}_{\mathrm{cd}}}{\mathrm{dt}}-R_{\mathrm{seq}}\mathrm{\&Delta;}{i}_{\mathrm{cd}},$ Δ u _CdBe two ends busbar voltage sum, Δ i _CdBe the differential current through the time-domain capacitive current compensation, L _SeqAnd R _SeqEquivalent inductance and equivalent resistance for the two ends system impedance;

The external fault model is: ${\mathrm{\&Delta;u}}_{\mathrm{cd}}=L_L\frac{\mathrm{d\&Delta;}{i}_{\mathrm{cd}}}{\mathrm{dt}}+R_L{\mathrm{\&Delta;i}}_{\mathrm{cd}},$ Δ u _CdBe two ends busbar voltage sum, Δ i _CdBe the differential current through the time-domain capacitive current compensation, L _LAnd R _LInductance and resistance for shunt reactor;

2) utilize least-squares algorithm that the inductance parameters L in the inductor models is calculated, definition identification induction reactance X _L=2 π fL, wherein f=50Hz is power system frequency, the inductance parameters in the L inductor models;

3) definition identification induction reactance setting value: X _Zd=k2 π fL _L, wherein k is a safety factor, and is desirable 0.5, f=50Hz is power system frequency, L _LInductance value for shunt reactor; If identification induction reactance X _LSatisfy: X _L＜0 or | X _L|＜X _Zd, then being judged to be internal fault, protective device sends trip signal, if identification induction reactance X _LSatisfy: X _L＞X _Zd, then being judged to be external fault, protective device sends block signal.

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