CN104242262A - Rapid bus protection method based on fault component mean value product - Google Patents

Abstract

The invention discloses a rapid bus protection method based on a fault component mean value product. The rapid bus protection method particularly includes the steps of (1) collecting the voltages and the currents at the positions, where bus protection elements are located, of outgoing lines connected with a bus in real time; (2) conducting phase-mode transformation on the voltages and the currents of fault components, and extracting respective line mode components; (3) calculating the product of mean values of the line mode voltages and the line mode currents, wherein the plus or the minus of the product of the mean values serves as a basis for judging forward faults and backward faults, a judging result of the fault directions of all outgoing lines serves as a basis for judging whether the bus breaks down or not. According to the rapid bus protection method, the phase-mode transformation is adopted, a bus protection criteria is constructed through the characteristic of the product of the mean values of the line mode voltages of the fault components and the line mode currents of the fault components, and the rapid bus protection method has the advantages of being easy and convenient to use, high in sensitivity, high in motion speed and accurate in recognition, and enabling engineering to be easily realized.

Description

A kind of quick bus bar protecting method long-pending based on fault component average

Technical field

The present invention relates to a kind of quick bus bar protecting method long-pending based on fault component average.

Background technology

Build clean, safety, self-healing, economy, high-quality and interaction strong intelligent grid be developing direction and the inexorable trend of grid automation technology.The critical support point of transformer station as intelligent grid and the node of electric power networks, carry connection line, transmission of electric energy, change electric pressure, collect electric current, distribute electric current, control power flow, adjust the functions such as voltage.Therefore, the safe and reliable operation of electrical network depends on the reliability of substation equipment and system to a great extent.The substation bus bar connecting the equipment such as generator, transformer, transmission line and load, as one of the critical elements of electric power system, is the hinge of electric power system power transmission and distribution.If bus broken down, bus protection fast excision must connect all elements on it, and fault incidence is large, and protection equipment for busbar tripping or malfunction may cause serious consequence to whole electric power system.Along with the expanding day of electric power system scale and constantly increasing of electric pressure, configure bus protection that is quick, sensitive and high reliability and seem particularly important.

Divide according to structure, bus protection is mainly divided into two large classes: centralized protection and distributed protection.Divide according to protection philosophy, bus protection mainly contains the protection based on power frequency amount and the large class of the protection based on transient two.The bus protection extensively adopted at present is the current differential protection based on power frequency amount, but these class methods require the current sampling data stringent synchronization of each outlet.In addition, protective value is also subject to the impact of the factors such as CT is saturated and out of proportion.For eliminating the saturated impact of CT, improve responsiveness and the reliability of protection, Chinese scholars has carried out a series of research, and achieves some useful achievements.

" asynchronous method CT saturation differentiates new principle and application thereof " proposes the detection method of the CT saturation being applicable to PC bus protection; namely first cycle after fault occurs adopts first half-wave method for synchronously recognizing; and after fault occurs and differential protection does not have an action time, adopt harmonic braking locking identification.The program stands good to conversion hysteria fault and has been successfully applied to engineering reality, but operate time is no less than 20ms.

" the bus protection new principle based on transient current spectrum energy " proposes a kind of bus protection new principle based on transient current spectrum energy; this principle can realize effective differentiation of bus internal fault external fault by the spectrum energy of more each transient high frequency electric current in a timing window; the method quick action and not by the saturated impact of CT, but little initial angle fault will badly influence sensitivity and the reliability of this guard method.

" A busbar protection technique and its performance during CT saturation and CT ratio-mismatch " utilizes the quadrant at the phase angle place of the positive and negative sequence equiva lent impedance on bus corresponding to the power frequency fault component of each loop to distinguish bus internal fault external fault.Simulation result shows that the method is unsaturated by CT, the impact of CT ratio mismatch, and not by the impact of sample frequency, but responsiveness is slower.

" bus protection based on neural network model " proposes a kind of bus bar protecting method based on neural network model.The method can change and the situation of CT broken string by inconsistent, the bus running manner of adaptive CT characteristic, and identifies that internal fault external fault accuracy is higher, but neural network structure is complicated, need train in a large number, and greatly, practicality is not strong for operand.

" utilizing the decentralized bus protection of circuit transient state travelling wave power direction " utilizes the directional structure vectorical structure criterion of each circuit transient state travelling wave power; the method action fast and reliable; substantially not by the impact of fault type, fault resistance etc., but during voltage over zero generation single phase ground fault, protection can not correctly identify.

" the bus protection principle based on model and parameters identification " is passed through the identification of fault equivalence inductive circuit model parameter and the calculating of parameter discrete degree; accurately can judge inside and outside portion fault and the external fault CT saturation condition of bus, thus form the bus protection criterion with self adaptation braking characteristic.This principle does not need to arrange special CT saturation detection element, and without the need to filtering, responsiveness is very fast, but sensitivity decrease during bus troubles inside the sample space.

" A travelling-wave-based amplitude integral busbar protection technique " proposes a kind of row wave amplitude integration bus protection new principle; the differentiation of fault inside and outside bus is realized by the ratio relation calculating direct wave and returning wave amplitude; this principle is by the impact of the factors such as unsaturated, the fault initial angle of CT and fault earthing resistance; but this principle sample frequency is up to 100kHz; and the sample frequency of merge cells is generally 4kHz in intelligent substation, not easily Project Realization.

" the bus protection new method based on measuring wave impedance " proposes a kind of bus protection new method based on measuring wave impedance, and when there is bus troubles inside the sample space, the polarity of the measurement wave impedance of all circuits is negative, amplitude approximately equal; When outside bus generating region during line fault, the polarity of the measurement wave impedance of faulty line is just, and its amplitude is much smaller than the amplitude of the measurement wave impedance of non-fault line.The method has very high reliability and very strong adaptability, but the high and bus structure of sample frequency has a certain impact to measurement wave impedance tool.

As can be seen here, the existing research about bus protection, completely not economical and practical, quick action and highly sensitive method.

Summary of the invention

The present invention is in order to solve the problem; propose a kind of quick bus bar protecting method long-pending based on fault component average; the different characteristic that the method utilizes the average of fault component line mode voltage and fault component line mould electric current to amass when internal fault external fault builds bus protection criterion; have easy; highly sensitive; quick action, identifies accurately, is easy to the advantage of Project Realization.

To achieve these goals, the present invention adopts following technical scheme:

Based on the quick bus bar protecting method that fault component average is long-pending, comprise the following steps:

(1) voltage and current at each outlet bus protection component place that is connected with bus of Real-time Collection;

(2) by after the voltage and current filtering of collection, phase-model transformation is carried out to power frequency fault component voltage and current, extract the Aerial mode component of fault component voltage and current;

(3) product of line mode voltage average and line mould electric current average is calculated, using the positive and negative foundation as judging forward fault and reverse fault that average is amassed, differentiate that result is as the foundation judging bus whether fault using the fault direction of all outlets again, concrete differentiation comprises: if the modulus average product code detected by bus protection unit of certain outlet is negative, be then forward fault; If the modulus average product code detected by bus protection unit of certain outlet is just, be then reverse fault; If each branch road bus protection unit be connected with bus is all determined as reverse direction failure, be then busbar fault.

In described step (2), obtain power frequency fault component by after the full voltage collected and the first filtering load component of total current filtering high fdrequency component again.

In described step (2), the concrete mode of phase-model transformation is:

$\left(\begin{array}{c}{f}_0\\ f_1\\ f_2\end{array}\right)=\left(\begin{array}{ccc}1& 1& 1\\ 1& 2& -3\\ 1& -3& 2\end{array}\right)\left(\begin{array}{c}{f}_a\\ f_b\\ f_c\end{array}\right)---\left(1\right)$

In formula, f _a, f _band f _cfor fault component voltage or fault component electric current, convert the 1 mold component f obtained ₁with 2 mold component f ₂the all fault types of equal energy reflection, f ₀it is 0 mold component.

In described step (3), concrete basis for estimation is:

1) with the product S of the line mode voltage average of certain outlet and line mould electric current average _m=ave (Δ u _m(t)) × ave (Δ i _m(t)) positive and negative in identifying the criterion of fault direction, in formula, ave (Δ u _m(t)) and ave (Δ i _m(t)) be the line mode voltage of fault component after phase-model transformation and the average of line mould electric current of the m article of outlet be connected with bus respectively, S _mbe that the line mode voltage of m article of outlet and the average of line mould electric current are amassed, if S _mfor just, be then determined as reverse fault, if S _mbe negative, be then determined as forward fault;

2) calculate in formula, sign (S _m) be S _msymbol, regulation work as S _mduring >0, sign (S _m)=1; Work as S _mwhen=0, sign (S _m)=0; Work as S _mduring <0, sign (S _m)=-1, if formula set up, be then determined as busbar fault; Otherwise bus is normal, and n represents the total number of the outlet be connected with bus.

Described basis for estimation 2) in, the outlet be connected with bus comprises transformer branch and circuit.

In described step (3), fault positive direction is that bus points to outlet.

Beneficial effect of the present invention is:

(1) can reliably be suitable for single busbar connection and a complicated half breaker bus connection type, sample frequency is 4 kHz of Intelligent substation merging unit requirement, has stronger adaptability;

(2) under various fault initial condition, reliably, rapidly fault direction is identified, substantially not by the impact of the factors such as fault initial angle, fault earthing resistance, fault type, highly sensitive, quick action;

(3) when CT is saturated, protection can not malfunction, has very high reliability;

(4) recognition methods principle is simple, clear, identifies accurately, is easy to Project Realization.

Accompanying drawing explanation

Fig. 1 is simple substation bus bar structure failure schematic diagram;

Super-imposed networks when Fig. 2 is bus generation three-phase shortcircuit;

Fig. 3 (a) is protected location R during busbar fault ₁fault component when θ=0 ° being detected and average amass waveform;

Fig. 3 (b) is protected location R during busbar fault ₁fault component when θ=30 ° being detected and average amass waveform;

Fig. 3 (c) is protected location R during busbar fault ₁fault component when θ=90 ° being detected and average amass waveform;

Fig. 3 (d) is protected location R during busbar fault ₁fault component when θ=240 ° being detected and average amass waveform;

Fig. 4 is circuit l ₁upper f ₁there is super-imposed networks during three-phase shortcircuit in place;

Fig. 5 (a) is circuit l ₁r during fault ₁fault component when θ=0 ° being detected and average amass waveform;

Fig. 5 (b) is circuit l ₁r during fault ₁fault component when θ=30 ° being detected and average amass waveform;

Fig. 5 (c) is circuit l ₁r during fault ₁fault component when θ=90 ° being detected and average amass waveform;

Fig. 5 (d) is circuit l ₁r during fault ₁fault component when θ=240 ° being detected and average amass waveform;

Fig. 6 is bus internal fault external fault identification process block diagram;

Fig. 7 is 500 kV bus simulation models;

Fig. 8 (a) is l ₃i female CT during fault ₁the B phase current waveform figure of outlet;

Fig. 8 (b) is l ₃i female CT during fault ₃b phase current (saturated) oscillogram of outlet;

Fig. 8 (c) is l ₃i female CT during fault ₅the B phase current waveform figure of outlet;

Fig. 9 (a) is l ₃iI female CT during fault ₂b phase current (the CT of outlet ₃b phase saturated);

Fig. 9 (b) is l ₃iI female CT during fault ₄b phase current (the CT of outlet ₃b phase saturated);

Fig. 9 (c) is l ₃iI female CT during fault ₆b phase current (the CT of outlet ₃b phase saturated);

Figure 10 (a) is l ₃the A phase differential current (CT of mother I during fault ₃b phase saturated);

Figure 10 (b) is l ₃the B phase differential current (CT of mother I during fault ₃b phase saturated);

Figure 10 (c) is l ₃the C phase differential current (CT of mother I during fault ₃b phase saturated);

Figure 11 (a) is l ₃the A phase differential current (CT of mother II during fault ₃b phase saturated);

Figure 11 (b) is l ₃the B phase differential current (CT of mother II during fault ₃b phase saturated);

Figure 11 (c) is l ₃the C phase differential current (CT of mother II during fault ₃b phase saturated);

Figure 12 (a) is l ₃the line mode voltage component waveform figure (CT that during fault, each protected location of mother I detects ₃b phase saturated);

Figure 12 (b) is l ₃the line mould current component wave form figure (CT that during fault, each protected location of mother I detects ₃b phase saturated);

Figure 13 (a) is l ₃the line mode voltage component waveform figure (CT that during fault, each protected location of mother II detects ₃b phase saturated);

Figure 13 (b) is l ₃the line mould current component wave form figure (CT that during fault, each protected location of mother II detects ₃b phase saturated).

Embodiment:

Below in conjunction with accompanying drawing and embodiment, the invention will be further described.

As shown in Figure 6, a kind of quick bus bar protecting method long-pending based on fault component average, comprises the following steps:

(1) voltage and current at each outlet bus protection component place that is connected with bus of Real-time Collection;

(2) after filtering, phase-model transformation is carried out to power frequency fault component voltage and current, extract respective Aerial mode component;

(3) product of line mode voltage average and line mould electric current average is calculated; Using the positive and negative foundation as judging forward fault and reverse fault that average is amassed; Differentiate that result is as judging bus whether fault foundation using the fault direction of all outlets:

A: if the modulus average product code detected by bus protection unit of certain outlet is negative, be then forward fault;

B: if the modulus average product code detected by bus protection unit of certain outlet is just, be then reverse fault;

C: if each branch road bus protection unit be connected with bus is all determined as reverse direction failure, be then busbar fault;

In described step (3), concrete basis for estimation is:

1) S with the formula _m=ave (Δ u _m(t)) × ave (Δ i _m(t)) positive and negative in identifying the criterion of fault direction, in formula, ave (Δ u _m(t)) and ave (Δ i _m(t)) be the line mode voltage of fault component after phase-model transformation and the average of line mould electric current of the m article of outlet be connected with bus respectively, S _mbe that the line mode voltage of m article of outlet and the average of line mould electric current are amassed, if S _mfor just, be then determined as reverse fault, if S _mbe negative, be then determined as forward fault;

2) with the formula as judging the foundation whether bus breaks down, in formula, n represents the number of the outlet (comprising transformer branch and circuit) be connected with bus; In formula, sign (S _m) be S _msymbol, regulation work as S _mduring >0, sign (S _m)=1; Work as S _mwhen=0, sign (S _m)=0; Work as S _mduring <0, sign (S _m)=-1.If λ is n, be then determined as this busbar fault; Otherwise bus is normal.

Recognition principle of the present invention is:

1 accident analysis

No matter be that substation bus bar or the transmission line be attached thereto break down, from superposition theory, any fault is all equivalent to an additional voltage source in fault point, and the voltage and current produced by this voltage source is fault component.Thus can extract real-time fault component, thus realize the identification of bus internal fault external fault.Figure 1 shows that a simple substation bus bar structure failure schematic diagram, this bus has 3 outlets, is respectively l ₁to l ₃.R ₁, R ₂and R ₃for bus protection unit, respectively at bus B and l ₁on fault is set, for every bar circuit, the positive direction of regulation fault is that bus points to circuit.

1) busbar fault.If f on Fig. 1 median generatrix B ₁there is three phase short circuit fault in point, its super-imposed networks as shown in Figure 2.

In Fig. 2, assuming that each outlet is harmless circuit, L ₁, L ₂and L ₃it is the inductance of each circuit and equivalent power supply.From Circuit theory, super-imposed networks is all electromotive force of source zero setting in whole network, only has fault point electromotive force independent role and the network that formed, and this electromotive force is contrary with the voltage swing equal direction of this point before fault.If the voltage of fault prior fault point is V _f=U _msin (ω t+ θ), then protect installation place R ₁fault component voltage Δ u ₁(t) and fault component electric current Δ i ₁t () and average thereof amass S ₁computational process as follows:

Δu ₁(t)＝-U _msin(ωt+θ) (2)

$L_1\frac{\mathrm{d\&Delta;}{i}_1\left(t\right)}{\mathrm{dt}}=-V_F=-U_m\sin (\mathrm{\&omega;t}+\mathrm{\&theta;})---\left(3\right)$

$\mathrm{\&Delta;}{i}_1\left(t\right)=-\frac{U_m}{X_1}(\cos \mathrm{\&theta;}-\cos (\mathrm{\&omega;t}+\mathrm{\&theta;}))---\left(4\right)$

$\mathrm{ave}\left(\mathrm{\&Delta;}{u}_1\left(t\right)\right)=\frac{1}{T}{\&Integral;}_0^t\mathrm{\&Delta;}{u}_1\left(\mathrm{\&tau;}\right)\mathrm{d\&tau;}=\frac{-U_m}{2\mathrm{\&pi;}}[\cos \mathrm{\&theta;}-\cos (\mathrm{\&omega;t}+\mathrm{\&theta;})]---\left(5\right)$

$\mathrm{ave}\left(\mathrm{\&Delta;}{i}_1\left(t\right)\right)=\frac{1}{T}{\&Integral;}_0^t\mathrm{\&Delta;}{i}_1\left(\mathrm{\&tau;}\right)\mathrm{d\&tau;}=\frac{-U_m}{2\mathrm{\&pi;}{X}_1}[\mathrm{\&omega;}t\cos \mathrm{\&theta;}-\sin (\mathrm{\&omega;t}+\mathrm{\&theta;})+\sin \mathrm{\&theta;}]---\left(6\right)$

$S_1=\mathrm{ave}\left(\mathrm{\&Delta;}{u}_1\left(t\right)\right)\&times;\mathrm{ave}\left(\mathrm{\&Delta;}{i}_1\left(t\right)\right)=\frac{{U_m}^2}{4{\mathrm{\&pi;}}^2{X}_1}(\cos \mathrm{\&theta;}-\cos (\mathrm{\&omega;t}+\mathrm{\&theta;}))\&times;(\mathrm{\&omega;}t\cos \mathrm{\&theta;}+\sin \mathrm{\&theta;}-\sin (\mathrm{\&omega;t}+\mathrm{\&theta;}))---\left(7\right)$

In formula, X ₁=ω L ₁, θ is fault initial angle, ave (Δ u ₁(t)) and ave (Δ i ₁(t)) be respectively the average of fault component voltage and fault component electric current, S ₁for average is amassed.Utilize formula (2), (4) and (7), the waveform that fault component voltage, electric current and average thereof when can obtain several typical fault initial angle are long-pending, as shown in Fig. 3 (a)-Fig. 3 (d), in figure, each electric parameters is perunit value.

Fig. 3 (a)-Fig. 3 (d) shows, S ₁just be in special time after a failure.By calculating: when fault initial angle meets 0≤θ < π, at the S of 0<t<T (π-θ)/in the π time period ₁for just; When fault initial angle meets π≤θ <2 π, at 0<t<T (2 π-θ) S in the/π time period ₁for just, T is here being power frequency period, i.e. a 20ms.

Same analysis is known, R ₂and R ₃the average detected is amassed and R ₁the average detected is amassed has identical feature.It can thus be appreciated that during busbar fault, in specified time interval, the average product code of the fault component voltage that each outlet exit bus protection unit inspection arrives and fault component electric current is just all.

2) outlet fault.If the circuit l in Fig. 1 ₁upper f ₁there is three phase short circuit fault in point, its super-imposed networks as shown in Figure 4.In figure, L ₁₁and L ₁₂that bus B and the fault point inductance to line end is arrived in fault point respectively.

Similar busbar fault analysis, protected location R in Fig. 4 ₁the fault component voltage Δ u at place ₁(t) and fault component electric current Δ i ₁t () and average thereof amass S ₁result of calculation is as follows:

$\mathrm{\&Delta;}{u}_1\left(t\right)=-\frac{X_{2//3}{U}_m}{X^{\&prime;}}\sin (\mathrm{\&omega;t}+\mathrm{\&theta;})---\left(8\right)$

${\mathrm{\&Delta;i}}_1\left(t\right)=\frac{U_m}{X^{\&prime;}}(\cos \mathrm{\&theta;}-\cos (\mathrm{\&omega;t}+\mathrm{\&theta;}))---\left(9\right)$

$S_1=-\frac{X_{2//3}{U_m}^2}{4{\mathrm{\&pi;}}^2{X}^{\&prime;2}}(\cos \mathrm{\&theta;}-\cos (\mathrm{\&omega;t}+\mathrm{\&theta;}))\&times;(\mathrm{\&omega;}t\cos \mathrm{\&theta;}+\sin \mathrm{\&theta;}-\sin (\mathrm{\&omega;t}+\mathrm{\&theta;}))---\left(10\right)$

In formula, L _2//3=L ₂l ₃/ (L ₂+ L ₃), X ₁₁=ω L ₁₁, X _2//3=ω L _2//3, X '=X ₁₁+ X _2//3.Utilize above formula, can R be obtained ₁fault component voltage during several typical fault initial angle that place detects and fault component electric current and the long-pending waveform of average thereof, as shown in Fig. 5 (a)-Fig. 5 (d), in figure, each electric parameters is perunit value.

From Fig. 5 (a)-Fig. 5 (d), S ₁negative in special time after a failure.Simultaneously by can be calculated: as 0≤θ < π, at the S of 0<t<T (π-θ)/in the π time ₁be negative; As π≤θ <2 π, at 0<t<T (2 π-θ) S in the/π time ₁also be negative, T=0.02s herein.

Similar analysis is known: R ₂and R ₃the average of unit inspection is amassed and is had identical feature during busbar fault, i.e. S in special time after a failure ₁for just.Reach a conclusion thus, during any outlet fault, within the specific time interval, the fault component voltage on faulty line and the average of electric current are amassed as negative, and the average of non-fault line is amassed as just.

Bus protection does not need Fault Phase Selection, for reacting various fault type, the average of line mode voltage and line mould electric current can be adopted to amass to extract fault signature.Consider that the transformation matrixs such as existing Clarke exist the problem that single mode amount can not react all fault types, adopt a kind of new phase-model transformation, for this reason shown in (11):

$\left(\begin{array}{c}{f}_0\\ f_1\\ f_2\end{array}\right)=\left(\begin{array}{ccc}1& 1& 1\\ 1& 2& -3\\ 1& -3& 2\end{array}\right)\left(\begin{array}{c}{f}_a\\ f_b\\ f_c\end{array}\right)---\left(11\right)$

In formula, f _a, f _band f _ccan be fault component voltage or fault component electric current, through type (11) converts the modulus f obtained ₁and f ₂the all fault types of equal energy reflection.

The structure of 2 criterions

According to above-mentioned analysis, no matter be outlet fault or busbar fault, within the specific time period, can conclusion be obtained as follows:

(1) when the forward of certain outlet breaks down, the modulus average product code detected by the exit bus protection unit of this circuit is negative, and during reverse fault, symbol is just, this conclusion is adapted to any outlet.

(2) when bus breaks down, all circuits top (near bus bar side) bus protection unit inspection to modulus average product code be just.

For every bar outlet, the positive direction of failure definition is that bus points to this circuit, ave (Δ u _m) and ave (Δ i _m) be the average of line mode voltage after m article of outlet phase-model transformation and line mould electric current respectively, as follows:

$\mathrm{ave}\left(\mathrm{\&Delta;}{u}_m\right)=\frac{1}{N}\underset{k=1}{\overset{j}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;}{u}_m\left(k\right)---\left(12\right)$

$\mathrm{ave}\left(\mathrm{\&Delta;}{i}_m\right)=\frac{1}{N}\underset{k=1}{\overset{j}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;}{i}_m\left(k\right)---\left(13\right)$

In formula, j is the sampling number for calculating, and N is every cycle sampling number.Identify fault direction for convenience, structure criterion is as follows:

S _m＝ave(Δu _m)×ave(Δi _m) (14)

If S _mbe negative, be then determined as m article of outlet positive direction and break down; Otherwise fault occurs in the other direction.The fault direction of all circuits that comprehensive analysis is connected with bus, if fault is all direction, then judges busbar fault.For the bus having the outlet of n bar, structure bus criterion is as follows:

$\mathrm{\&lambda;}=\underset{m=1}{\overset{n}{\mathrm{\&Sigma;}}}\mathrm{sign}\left(S_m\right)---\left(14\right)$

In formula, sign (S _m) be S _msymbol, regulation work as S _mduring >0, sign (S _m)=1; Work as S _mwhen=0, sign (S _m)=0; Work as S _mduring <0, sign (S _m)=-1.If λ is n, be then determined as this busbar fault; Otherwise bus is normal.

Simulation analysis is carried out with the analogue system of Fig. 1:

1) Modling model

According to primary system structure and the relevant parameter of the actual 500 kV transformer stations in somewhere, PSCAD/EMTDC is utilized to construct bus simulation model, as shown in Figure 7.

Fig. 7 shows, and is connected, has 4 back into outlet, 2 times transformer branch between the female and II of I is female by 3 string switches.R _ibe decentralized bus protection unit, be loaded on the exit of each circuit.Wherein, R ₁, R ₃and R ₅form one group, extract CT respectively ₁, CT ₃and CT ₅electric current, be responsible for identifying the running status of mother I; R ₂, R ₄and R ₆form another group, extract CT respectively ₂, CT ₄and CT ₆electric current, be responsible for identifying the running status of mother II.C ₁and C ₂for the stray capacitance over the ground of bus, get 0.01 μ F.Transmission line adopts frequency dependent model, and evenly replaces, and as shown in Figure 7, for each bus protection unit, the positive direction of regulation fault is for point to each circuit by bus for the length of each circuit.Adopt low pass filter filtering high fdrequency component, then utilize Aerial mode component to calculate.In current intelligent substation, the sample frequency of merge cells is generally 80 points/every cycle, therefore sample frequency is set to 4 kHz, and the present invention adopts the data of 10 continuous sampling points to come Judging fault direction.

2) Adaptability Analysis of protection philosophy

By to single busbar connection analysis, propose based on the long-pending bus protection principle of modulus average, whether this Protection criteria of theory analysis can effectively break down by identification form bus.But for the bus structure of complexity, the half breaker bus mode of connection of 500 kV as shown in Figure 7, the circuit breaker between two buses is all in closure state when normal operation, and namely two buses are directly connected.Now, whether protection philosophy of carrying still adapts to, and theory analysis is as follows.

If bus breaks down (as the f on I bus ₁point), for each protected location of the female side of I, identical with single busbar connection situation, R ₁, R ₃and R ₅all differentiate and break down in the other direction, be comprehensively identified as the female troubles inside the sample space of I; For each protected location in the female side of II, analyze in theory and can obtain, R in specified time interval ₂, R ₄and R ₆modulus average amass as negative, therefore should all be judged to forward fault.But because I is female and II mother is directly connected and apart from very near, may all be judged to forward fault by not all protected location, but this does not affect the correct identification to fault, because only have when being all judged to reverse fault with the connected all protected locations of bus, be just judged to bus troubles inside the sample space; Otherwise, be then bus external area error.

If arbitrary line failure is (as circuit l ₂on f ₂point), R in specified time interval ₁and R ₂average is long-pending to be negative, and namely positive direction breaks down separately, and according to bus protection criterion, protection all differentiates that respective bus is normal.Other outlet is broken down, and is also like this.

In sum, put forward bus protection principle and should be able to be applicable to one-and-half breaker bus connection type in theory.

3) simulation and analysis of different faults initial condition

The performance of bus protection is easily subject to the impact of different faults initial condition, as fault initial angle, fault earthing resistance and fault type.In order to test the impact of different faults initial condition on proposed protection scheme, carry out following emulation.

The emulation testing of a, different faults initial angle.For investigating the adaptability of protection philosophy under different faults initial angle, f on I bus is set ₁there is B phase earth fault in point, fault initial angle is respectively 0 °, 120 ° and 330 °, and simulation result is in table 1.Circuit l is set ₂upper f ₂there is C phase earth fault in point, fault initial angle and corresponding simulation result are in table 2.

The emulated data of different faults initial angle during table 1 I mother fault

Table 2 circuit l ₂the emulated data of different faults initial angle during fault

From above two table emulated datas, for the bus internal fault external fault of different initial angle, protection all can correctly judge.During zero initial angle fault, average is long-pending to decrease, but does not affect the normal identification to bus whether fault, and criterion has sufficiently high reliability and sensitivity.

The emulation testing of b, different faults earth resistance.F on I bus is set ₁there is AB earth fault in point, earth resistance is respectively 50 Ω, 150 Ω and 300 Ω, and simulation result is in table 3.Circuit l is set ₂upper f ₂there is AC earth fault in point, earth resistance is respectively 0 Ω, 200 Ω and 300 Ω, and simulation result is in table 4.

The emulated data of different faults resistance during table 3 I mother fault

Table 4 circuit l ₂the emulated data of different faults resistance during fault

From table 3 and table 4 emulated data: no matter bus internal fault or external fault; along with the increase of fault resstance; the absolute value reduction that the average that each protected location calculates is long-pending; but almost do not affect criterion identification fault direction, the protected location of two buses all correctly can identify fault.

The emulation testing of c, different faults type.Respectively on II bus and circuit l ₃on the fault of different faults type is set, simulation result is respectively in table 5 and table 6.

The emulated data of different faults type during table 5 II mother fault

Table 6 circuit l ₃the emulated data of different faults type during fault

From above two table simulation results, during the bus district dissimilar fault of inside and outside generation, protection all can make accurate judgment.

4) emulation testing of string added time is considered.For longer-distance supertension line, sometimes improve transmission capacity by installing serial compensation capacitance, so the impact of serial compensation capacitance on protection need be considered.At l ₁upper near I mother place's installing series capacitance, string benefit degree is set to 40%.Respectively at f ₂, f ₄and f ₅(l ₁the female 80 km places of distance I) fault is set, simulation result is in table 7.

Table 7 adds the simulation result after string benefit

The data of table 7 go here and theres the data of added time and are carried out contrast and can obtain with not adding, add string mend after the long-pending change of average not quite, protection correctly reliably can identify fault.

5) the saturated impact analysis of CT

Easily malfunction is there is in traditional bus protection when external area error CT is saturated.In order to probe into the saturated impact on conventional busbars differential protection and institute's extracting method of CT, at l ₃on B phase earth fault is set, and CT ₃b phase occur saturated, then the B phase current of I mother and the female each outlet of II is respectively as shown in Fig. 8 (a)-Fig. 8 (c) He Fig. 9 (a)-Fig. 9 (c), and each phase differential current of corresponding I mother and mother II is as shown in Figure 10 (a)-Figure 10 (c) He Figure 11 (a)-Figure 11 (c).The waveform of Figure 12 (a), Figure 12 (b) and 13 (a), fault component line mode voltage that Figure 13 (b) is institute's extracting method and fault component line mould electric current, corresponding emulated data is as shown in table 8.

The simulation result that table 8 CT is saturated

As can be seen from Fig. 8 (a)-(c), 9 (a)-(c), 10 (a)-(c) and Figure 11 (a)-(c); the B phase current of circuit 3 after a failure 4.95ms reaches saturated; the differential current of the female B phase of I also increases to 4659A from 0, therefore the differential protection of mother I can malfunction.With table 8, Figure 12 (a), Figure 12 (b) and Figure 13 (a), Figure 13 (b) show that carried Protection criteria can correctly be judged as bus external area error when CT is saturated; this is because the method only utilizes the data window of 2.5ms after fault, before CT is saturated, judgement has just been made in protection.

The present invention first carries out phase-model transformation to fault component, and the product of the average of recycling line mode voltage and line mould electric current carries out Fault Identification, and this invention is used to identify whether bus breaks down.This invention does not need Fault Phase Selection and utilizes power frequency fault component to calculate, and sample frequency is low to moderate 4kHz, and traditional CT and CVT Transfer characteristic can meet the demands.In addition, this invention only needs the data window of 2.5ms to calculate, and amount of calculation is little, quick action.

By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.

Claims (7)

1., based on the quick bus bar protecting method that fault component average is long-pending, it is characterized in that: comprise the following steps:

(1) voltage and current at each outlet bus protection component place that is connected with bus of Real-time Collection;

(2) by after the voltage and current filtering of collection, phase-model transformation is carried out to power frequency fault component voltage and current, extract the Aerial mode component of fault component voltage and current;

(3) product of line mode voltage average and line mould electric current average is calculated, using the positive and negative foundation as judging forward fault and reverse fault that average is amassed, differentiate that result is as the foundation judging bus whether fault using the fault direction of all outlets again, concrete differentiation comprises: if the modulus average product code detected by bus protection unit of certain outlet is negative, be then forward fault; If the modulus average product code detected by bus protection unit of certain outlet is just, be then reverse fault; If each branch road bus protection unit be connected with bus is all determined as reverse direction failure, be then busbar fault.

2. a kind of quick bus bar protecting method long-pending based on fault component average as claimed in claim 1, it is characterized in that: in described step (2), the concrete mode of phase-model transformation is:

$\left(\begin{array}{c}{f}_0\\ f_1\\ f_2\end{array}\right)=\left(\begin{array}{ccc}1& 1& 1\\ 1& 2& -3\\ 1& -3& 2\end{array}\right)\left(\begin{array}{c}{f}_a\\ f_b\\ f_c\end{array}\right)---\left(16\right)$

In formula, f _a, f _band f _cfor fault component voltage or fault component electric current, convert the 1 mold component f obtained ₁with 2 mold component f ₂the all fault types of equal energy reflection.

3. a kind of quick bus bar protecting method long-pending based on fault component average as claimed in claim 1; it is characterized in that: in described step (2), obtain power frequency fault component by after the full voltage collected and the first filtering load component of total current filtering high fdrequency component again.

4. a kind of quick bus bar protecting method long-pending based on fault component average as claimed in claim 1, is characterized in that: in described step (3), concrete basis for estimation is: with the product S of the line mode voltage average of certain outlet and line mould electric current average _m=ave (Δ u _m(t)) × ave (Δ i _m(t)) positive and negative in identifying the criterion of fault direction, in formula, ave (Δ u _m(t)) and ave (Δ i _m(t)) be the line mode voltage of fault component after phase-model transformation and the average of line mould electric current of the m article of outlet be connected with bus respectively, S _mbe that the line mode voltage of m article of outlet and the average of line mould electric current are amassed, if S _mfor just, be then determined as reverse fault, if S _mbe negative, be then determined as forward fault.

5. a kind of quick bus bar protecting method long-pending based on fault component average as claimed in claim 1, is characterized in that: in described step (3), calculates in formula, sign (S _m) be S _msymbol, regulation work as S _mduring >0, sign (S _m)=1; Work as S _mwhen=0, sign (S _m)=0; Work as S _mduring <0, sign (S _m)=-1, if formula set up, be then determined as busbar fault; Otherwise bus is normal, and n represents the total number of the outlet be connected with bus.

6. a kind of quick bus bar protecting method long-pending based on fault component average as claimed in claim 5, is characterized in that: the outlet be connected with bus comprises transformer branch and circuit.

7. a kind of quick bus bar protecting method long-pending based on fault component average as claimed in claim 1, it is characterized in that: in described step (3), fault positive direction is that bus points to outlet.