CN103812094B - The pilot protection system differential based on fault component virtual impedance and method thereof - Google Patents

Abstract

The invention discloses a kind of differential based on the fault component virtual impedance pilot protection system in Relay Protection Technology in Power System field and method thereof。System includes data reading module, protection computing module and the protection act module that order is connected；Method includes the current failure order components gathering line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and circuit both sides；Calculate the virtual sequence impedance of circuit；Virtual sequence impedance according to circuit midpoint judges whether to meet operating criterion, if meeting operating criterion, is then judged to troubles inside the sample space, and sends trip signal immediately；If being unsatisfactory for operating criterion, being then judged to external area error, not sending trip signal。The present invention can after breaking down failure judgement exactly, all kinds fault is respectively provided with higher sensitivity；Meanwhile, the present invention has higher reliability, when changing property fault, still has good selectivity。

Description

The pilot protection system differential based on fault component virtual impedance and method thereof

Technical field

The invention belongs to Relay Protection Technology in Power System field, particularly relate to a kind of pilot protection system differential based on fault component virtual impedance and method thereof。

Background technology

Traditional pilot protection in ultra-high-tension power transmission line mainly has Unit protection and current differential protection。Unit protection principle is simple, it is not necessary to two end data stringent synchronization, but it is subject to the impact of the factor such as high resistance ground, evolved fault, and may result in false protection when the sensitivity deficiency of circuit one end directional element。Current differential protection is highly sensitive; can adapt to the fault of various complexity and irregular operating state, but the synchronicity of metric data is required higher by it, and affected by capacitance current; when in district occur high resistance earthing fault time due to measured current in comprise load current, sensitivity it cannot be guaranteed that。

In consideration of it, experts and scholars are to how improving pilot protection sensitivity and reliability conducts in-depth research。Difference according to the electric parameters used; the research of pilot protection is broadly divided into 2 classes: first kind algorithm is based on the fault full dose information of electric parameters; as counted the steady-state quantity current differential protection algorithm of through current; eliminate the comprehensive impedance protection philosophy of line distribution capacitance impact; without the calculating power method differential relaying algorithm that line parameter circuit value compensates, the pilot protection algorithm etc. of reaction transition resistance active power。Equations of The Second Kind algorithm is based on the fault component information of electric parameters, such as the direction protection algorithm based on bucking voltage, based on the pilot protection algorithm of parameter identification, the zero-sequence voltage injection algorithm of improvement, the phase place correlation differential protection algorithm etc. that anti-transformer is saturated。

Requiring higher for tradition pilot protection synchronicity or be subject to the difficult problems such as the factor impact such as high resistance ground, evolved fault, the present invention proposes a kind of longitudinal differential protection system new principle differential based on fault component virtual impedance。Current/voltage fault component first with the current/voltage fault component information reckoning circuit midpoint that circuit two ends measure, the ratio calculating voltage and the current failure component obtained is defined as virtual impedance, again through two ends virtual impedance sum and virtual impedance smaller value structure ratio brake criterion。Then, by analyzing the different characteristic identification fault that this criterion presents under various failure conditions inside and outside district。Verify based on the simulation example of Matlab and PSCAD/EMTDC platform and show, this invention can after breaking down failure judgement exactly, all kinds fault is respectively provided with higher sensitivity；Meanwhile, not by abort situation, transition resistance, load current, the impact of distribution capacity and synchronizing information, there is higher reliability；When changing property fault, still there is good selectivity。

Summary of the invention

It is an object of the invention to, it is provided that a kind of pilot protection system differential based on fault component virtual impedance and method thereof, for solving the problem that tradition pilot protection synchronicity requirement is higher or is subject to the impact of the factor such as high resistance ground, evolved fault。

To achieve these goals, the technical scheme that the present invention proposes is, a kind of pilot protection system differential based on fault component virtual impedance, it is characterized in that described system includes data reading module, protection computing module and protection act module that order is connected；

Described data read in module for gathering the current failure order components of line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and circuit both sides, and send the data of collection to protecting computing module；

Described protection computing module for calculating the virtual sequence impedance of circuit according to line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and the current failure order components of circuit both sides, and sends the virtual sequence impedance of calculated circuit to protection act module；

Described protection act module is for the virtual sequence impedance according to circuit midpoint, it may be judged whether meet operating criterion；If meeting operating criterion, then it is judged to troubles inside the sample space, and sends trip signal immediately；If being unsatisfactory for operating criterion, being then judged to external area error, not sending trip signal。

A kind of longitudinal protection method differential based on fault component virtual impedance, is characterized in that described method includes:

Step 1: gather the current failure order components of line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and circuit both sides；

Step 2: calculate the virtual sequence impedance of circuit；

Step 3: judge whether to meet operating criterion according to the virtual sequence impedance at circuit midpoint, if meeting operating criterion, is then judged to troubles inside the sample space, and sends trip signal immediately；If being unsatisfactory for operating criterion, being then judged to external area error, not sending trip signal。

The virtual sequence impedance of described calculating circuit adopts formula:

$\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=Z_{\mathrm{ci}}\frac{\mathrm{\Δ}{U}_{\mathrm{mi}}\·\cosh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}\·Z_{\mathrm{ci}}\sinh (r_i\·\mathrm{dl})}{\mathrm{\Δ}{U}_{\mathrm{mi}}\·\sinh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}\·Z_{\mathrm{ci}}}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{{\mathrm{\ΔI}}_{\mathrm{ki}}^{\′\′}}=Z_{\mathrm{ci}}\frac{\mathrm{\Δ}{U}_{\mathrm{ni}}\·\cosh (r_i\·(1-d)l)-\mathrm{\Δ}{I}_{\mathrm{ni}}\·Z_{\mathrm{ci}}\sinh (r_i\·(1-d)l)}{\mathrm{\Δ}{U}_{\mathrm{ni}}\·\sinh (r_i\·(1-d)l)-\mathrm{\Δ}{I}_{\mathrm{ni}}\·Z_{\mathrm{ci}}\cosh (r_i\·(1-d)l)};\\ \end{array}$

Wherein, Δ I_miCurrent failure order components for circuit m side；

ΔU_miVoltage failure order components for circuit m side；

Δ′I_kiThe current failure order components of the k point for being obtained by circuit m thruster；

ΔU′_kiThe voltage failure order components of the k point for being obtained by circuit m thruster；

The virtual sequence impedance of the k point for being obtained by circuit m thruster；

ΔI_niCurrent failure order components for circuit n side；

ΔU_niVoltage failure order components for circuit n side；

ΔI′′_kiThe current failure order components of the k point for being obtained by circuit n thruster；

ΔU′′_kiThe voltage failure order components of the k point for being obtained by circuit n thruster；

The virtual sequence impedance of the k point for being obtained by circuit n thruster；

K is any point between circuit mn；

Z_ciFor line characteristic sequence impedance；

r_iFor circuit sequence propagation coefficient；

I=0,1 or 2；As i=0, represent zero-sequence component；As i=1, represent positive-sequence component；As i=2, represent negative sequence component；

L is the length of circuit mn；

D be on circuit mn k point to the distance percentage ratio of m side；

Cosh () is hyperbolic cosine function；

Sinh () is hyperbolic sine function。

Described operating criterion includes the operating criterion of the operating criterion of positive sequence fault component, the operating criterion of negative phase-sequence fault component and zero-sequence fault component。

The described virtual sequence impedance according to circuit midpoint judge whether to meet the operating criterion of positive sequence fault component particularly as follows: $\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=Z_{\mathrm{ci}}\frac{\mathrm{\Δ}{U}_{\mathrm{mi}}\·\cosh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}\·Z_{\mathrm{ci}}\sinh (r_i\·\mathrm{dl})}{\mathrm{\Δ}{U}_{\mathrm{mi}}\·\sinh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}\·Z_{\mathrm{ci}}}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{{\mathrm{\ΔI}}_{\mathrm{ki}}^{\′\′}}=Z_{\mathrm{ci}}\frac{\mathrm{\Δ}{U}_{\mathrm{ni}}\·\cosh (r_i\·(1-d)l)-\mathrm{\Δ}{I}_{\mathrm{ni}}\·Z_{\mathrm{ci}}\sinh (r_i\·(1-d)l)}{\mathrm{\Δ}{U}_{\mathrm{ni}}\·\sinh (r_i\·(1-d)l)-\mathrm{\Δ}{I}_{\mathrm{ni}}\·Z_{\mathrm{ci}}\cosh (r_i\·(1-d)l)};\\ \end{array}$

Wherein, k is the midpoint of circuit mn；

ΔI′_k1The current failure positive-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔI′′_k1The current failure positive-sequence component at the circuit midpoint for being obtained by circuit n thruster；

ΔU′_k1The voltage failure positive-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔU′′_k1The voltage failure positive-sequence component at the circuit midpoint for being obtained by circuit n thruster；

The virtual positive sequence impedance at the circuit midpoint for being obtained by circuit m thruster；

The virtual positive sequence impedance at the circuit midpoint for being obtained by circuit n thruster；

I_NRated current for circuit mn。

The described virtual sequence impedance according to circuit midpoint judge whether to meet the operating criterion of negative phase-sequence fault component particularly as follows:

$\left\{\begin{array}{c}\max (\mathrm{\Δ}{I}_{k2}^{\′\′},\mathrm{\Δ}{I}_{k2}^{\′})>0.1I_N\\ |\frac{\mathrm{\Δ}{U}_{k2}^{\′\′}}{\mathrm{\Δ}{I}_{k2}^{\′\′}}+\frac{\mathrm{\Δ}{U}_{k2}}{\mathrm{\Δ}{I}_{k2}^{\′}}|\≥\min \left\{\right|\frac{\mathrm{\Δ}{U}_{k2}^{\′\′}}{\mathrm{\Δ}{I}_{k2}^{\′\′}}|,|\frac{\mathrm{\Δ}{U}_{k2}^{\′}}{\mathrm{\Δ}{I}_{k2}^{\′}}\left|\right\}\end{array};\right.$

Wherein, k is the midpoint of circuit mn；

ΔI′_k2The current failure negative sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔI′′_k2The current failure negative sequence component at the circuit midpoint for being obtained by circuit n thruster；

ΔU′_k2The voltage failure negative sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔU′′_k2The voltage failure negative sequence component at the circuit midpoint for being obtained by circuit n thruster；

The virtual negative sequence impedance at the circuit midpoint for being obtained by circuit m thruster；

The virtual negative sequence impedance at the circuit midpoint for being obtained by circuit n thruster；

I_NRated current for circuit mn。

The described virtual sequence impedance according to circuit midpoint judge whether to meet the operating criterion of zero-sequence fault component particularly as follows:

$\left\{\begin{array}{c}\max (\mathrm{\Δ}{I}_{k0}^{\′\′},\mathrm{\Δ}{I}_{k0}^{\′})>0.1I_N\\ |\frac{\mathrm{\Δ}{U}_{k0}^{\′\′}}{\mathrm{\Δ}{I}_{k0}^{\′\′}}+\frac{\mathrm{\Δ}{U}_{k0}^{\′}}{\mathrm{\Δ}{I}_{k0}^{\′}}|\≥\min \left\{\right|\frac{\mathrm{\Δ}{U}_{k0}^{\′\′}}{\mathrm{\Δ}{I}_{k0}^{\′\′}}|,|\frac{\mathrm{\Δ}{U}_{k0}^{\′}}{\mathrm{\Δ}{I}_{k0}^{\′}}\left|\right\}\end{array};\right.$

Wherein, k is the midpoint of circuit mn；

ΔI′_k0The current failure zero-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔI′′_k0The current failure zero-sequence component at the circuit midpoint for being obtained by circuit n thruster；

ΔU′_k0The voltage failure zero-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔU′′_k0The voltage failure zero-sequence component at the circuit midpoint for being obtained by circuit n thruster；

The virtual zero sequence impedance at the circuit midpoint for being obtained by circuit m thruster；

The virtual zero sequence impedance at the circuit midpoint for being obtained by circuit n thruster；

I_NRated current for circuit mn。

The present invention can after breaking down failure judgement exactly, all kinds fault is respectively provided with higher sensitivity；Meanwhile, the present invention has higher reliability, when changing property fault, still has good selectivity。

Accompanying drawing explanation

Fig. 1 is the pilot protection system construction drawing differential based on fault component virtual impedance provided by the invention；

Fig. 2 is the sequence network figure of the system failure；Wherein, (a) is sequence network figure under external fault condition, and (b) is sequence network figure under internal fault condition；

Fig. 3 is protection cooperation logic relation picture；

Fig. 4 is phantom figure；

Criterion result table when Fig. 5 is external area error；

Result figure is differentiated when Fig. 6 is external area error；Wherein, (a) reversely exports negative phase-sequence criterion result figure during generation A phase short circuit grounding for N end, and (b) reversely exports positive sequence criterion result figure during generation three-phase shortcircuit ground connection for M end；

Criterion result table when Fig. 7 is troubles inside the sample space；

Result figure is differentiated when Fig. 8 is troubles inside the sample space；Wherein, when (a) N brings out mouth generation A phase short circuit grounding, negative phase-sequence criterion result figure, (b) M bring out positive sequence criterion result figure during mouth generation three-phase shortcircuit ground connection；

Criterion result table during each point generation single phase grounding fault when Fig. 9 is N end zero load；

When Figure 10 is N end zero load, M brings out negative phase-sequence criterion result figure during mouth generation single-phase short circuit ground connection；

Criterion result table when Figure 11 is that outside N lateral areas, Conversion fault becomes N lateral areas internal fault；

Figure 12 be N side reversely export generation A phase short circuit be converted to negative phase-sequence criterion result figure during AB phase short circuit grounding fault in N lateral areas；

Criterion result table when Figure 13 is N side outlet and reverse exit generation developing fault。

Detailed description of the invention

Below in conjunction with accompanying drawing, preferred embodiment is elaborated。It is emphasized that the description below is merely exemplary, rather than in order to limit the scope of the present invention and application thereof。

Embodiment 1

Fig. 1 is the pilot protection system construction drawing differential based on fault component virtual impedance provided by the invention。As it is shown in figure 1, the pilot protection system differential based on fault component virtual impedance provided by the invention includes data reading module, protection computing module and the protection act module that order is connected。

Data read in module for gathering the current failure order components of line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and circuit both sides, and send the data of collection to protecting computing module。

Protection computing module for calculating the virtual sequence impedance of circuit according to line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and the current failure order components of circuit both sides, and sends the virtual sequence impedance of calculated circuit to protection act module。

Protection act module is for the virtual sequence impedance according to circuit midpoint, it may be judged whether meet operating criterion。If meeting operating criterion, then it is judged to troubles inside the sample space, and sends trip signal immediately；If being unsatisfactory for operating criterion, being then judged to external area error, not sending trip signal。

For the Double-End Source system shown in Fig. 2, the operation principle of the pilot protection system differential based on fault component virtual impedance provided by the invention is:

Considering a strip adoption distributed parameter model both-end transmission line of electricity, the sequence network outside generating region and in troubles inside the sample space situation is respectively as shown in Fig. 2 (a) and Fig. 2 (b)。In figure, each parameter is order parameter, wherein Z_miIt is m side system sequence impedance, Z_niIt is n side system sequence impedance, Δ I_miWith Δ I_niIt is m and n side current failure order components respectively。Wherein i=0,1 or 2, as i=0, represent zero-sequence component；As i=1, represent positive-sequence component；As i=2, represent negative sequence component。I.e. Δ I_m1With Δ I_n1It is m side and n side current failure positive-sequence component, Δ I respectively_m2With Δ I_n2It is m side and n side current failure negative sequence component, Δ I respectively_m0With Δ I_n0It is m side and n side current failure zero-sequence component respectively。Hereafter in each amount, the implication of i is identical, no longer repeats one by one。Δ U_miWith Δ U_niIt is m and n side voltage failure order components respectively, Δ U_fiIt is fault point equivalent sequence voltage in super-imposed networks, Δ I '_kiWith Δ U '_kiIt is the electric current obtained by m thruster and voltage failure order components respectively, Δ I ' '_kiWith Δ U ' '_kiIt is the electric current obtained by n thruster and voltage failure order components respectively。

If line length is l, k point, to account for the ratio of total track length to the distance of m side be d, and line characteristic sequence impedance is Z_ci, circuit sequence propagation coefficient is r_i。Calculated the voltage and current fault sequence component of any point k in circuit by m side and n thruster respectively, can obtain:

$\left\{\begin{array}{c}\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}=\mathrm{\Δ}{U}_{\mathrm{mi}}\·\cosh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}\·Z_{\mathrm{ci}}\sinh (r_i\·\mathrm{dl})\\ \mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}=\frac{\mathrm{\Δ}{U}_{\mathrm{mi}}\·\sinh (r_i\·\mathrm{dl})}{Z_{\mathrm{ci}}}-\mathrm{\Δ}{I}_{\mathrm{mi}}\·\cosh (r_i\·(1-d)l)\\ \mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}=\mathrm{\Δ}{U}_{\mathrm{ni}}\·\cosh (r_i\·(1-d)l)-\mathrm{\Δ}{I}_{\mathrm{ni}}\·Z_{\mathrm{ci}}\sinh (r_i\·(1-d)l)\\ \mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}=\frac{\mathrm{\Δ}{U}_{\mathrm{ni}}\·\cosh (r_i\·(1-d)l)}{Z_{\mathrm{ci}}}-\mathrm{\Δ}{I}_{\mathrm{ni}}\·Z_{\mathrm{ci}}\sinh (r_i\·(1-d)l)\end{array}\right.---\left(1\right)$

When there is external area error, as shown in Fig. 2 (a), if trouble point is at the dorsal part (dorsal part in m side is in like manner) of circuit n side, owing to circuit self structure is not corrupted, therefore the voltage and current fault sequence component that to be no matter the voltage and current fault sequence component of the k point calculated by m thruster or obtained by n thruster be all this point is actual, satisfies condition:

$\left\{\begin{array}{c}\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}=-\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}\\ \mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}=\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}\end{array}\right.---\left(2\right)$

The ratio of definition voltage failure order components and current failure order components is virtual sequence impedance, has:

$\left\{\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=Z_{\mathrm{ci}}\·\frac{\mathrm{\Δ}{U}_{\mathrm{mi}}\cosh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}{Z}_{\mathrm{ci}}\sinh (r_i\·\mathrm{dl})}{\mathrm{\Δ}{U}_{\mathrm{mi}}\sinh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}{Z}_{\mathrm{ci}}\cosh (r_i\·\mathrm{dl})}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}=-Z_{\mathrm{ci}}\·\frac{\mathrm{\Δ}{U}_{\mathrm{mi}}\cosh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}{Z}_{\mathrm{ci}}\sinh (r_i\·\mathrm{dl})}{\mathrm{\Δ}{U}_{\mathrm{mi}}\sinh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}{Z}_{\mathrm{ci}}\cosh (r_i\·\mathrm{dl})}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}+\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}=0\end{array}\right.---\left(3\right)$

When generating region internal fault, circuit self structure is destroyed, and is equivalent to the fault point at super-imposed networks and increases an equivalent source, as shown in Fig. 2 (b)。If trouble point f between n and k (between m and k in like manner)。The actual value that voltage x current fault sequence component is this point of the k point obtained by m thruster；The voltage x current fault sequence component of the k point obtained by n thruster, owing to have passed through trouble point, will deviate considerably from actual value。Now virtual sequence impedance is:

$\left\{\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=Z_{\mathrm{ci}}\·\frac{\mathrm{\Δ}{U}_{\mathrm{mi}}\cosh (r_i\·\mathrm{dl})-\mathrm{\Δ}{I}_{\mathrm{mi}}{Z}_{\mathrm{ci}}\sinh (r_i\·\mathrm{dl})}{\mathrm{\Δ}}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}=Z_{\mathrm{ci}}\·\frac{\mathrm{\Δ}{U}_{\mathrm{ni}}\cosh (r_i\·(1-d)l)-\mathrm{\Δ}{I}_{\mathrm{ni}}{Z}_{\mathrm{ci}}\sinh (r_i\·(1-d)l)}{\mathrm{\Δ}{U}_{\mathrm{mi}}\sinh (r_i\·(1-d)l)-\mathrm{\Δ}{I}_{\mathrm{in}}{Z}_{\mathrm{ci}}\cosh (r_i\·(1-d)l)}\end{array}\right.---\left(4\right)$

Take k point for circuit midpoint, utilize and virtual sequence impedance presents during troubles inside the sample space different characteristic, structure criterion in the district outside:

$\left\{\begin{array}{c}\max (\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′},\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′})>0.1I_N\\ |\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}+\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}|\≥\min \left\{\right|\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}|,|\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}\left|\right\}\end{array}\right.---\left(5\right)$

In formula (5), the 1st formula is the fixing threshold portion of criterion, when detecting that either end starts when calculating the current value rated current more than 0.1 times。In formula (5), the 2nd formula is rate restraint criterion, the protection act when the absolute value of two ends virtual sequence impedance sum is more than the smaller value of virtual sequence impedance absolute value。Lower its protective value of surface analysis。

When there is external area error, by formula (3) it can be seen that actuating quantity theory should be 0, braking amount is then relevant with non-faulting side system impedance and line impedance, it is known that when non-faulting side system resistance value is 0, braking amount is minimum, assuming that trouble point is in m side, n side system impedance is 0, now has Δ U_ni=0, braking amount is:

$\left|\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}}{\mathrm{\Δ}{I}_{\mathrm{ki}}}\right|=\left|Z_{\mathrm{ci}}\tanh (r_i\·l_{\mathrm{nk}})\right|>\left|Z_{\mathrm{ci}}\sinh (r_i\·l_{\mathrm{nk}})\right|---\left(6\right)$

The result of formula (6) is about circuit sequence impedance half, can effective brake。

When generating region internal fault, it is contemplated that:

$\left\{\begin{array}{c}{Z}_{\mathrm{mi}}=-\frac{\mathrm{\Δ}{U}_{\mathrm{mi}}}{\mathrm{\Δ}{I}_{\mathrm{mi}}}\\ Z_{\mathrm{ni}}=-\frac{\mathrm{\Δ}{U}_{\mathrm{ni}}}{\mathrm{\Δ}{I}_{\mathrm{ni}}}\end{array}\right.---\left(7\right)$

If:

$\left\{\begin{array}{c}a=\left|\coth (r_i\·\frac{l}{2})\right|\\ b=\left|\frac{Z_{\mathrm{mi}}}{Z_{\mathrm{ci}}}\right|\\ c=\left|\frac{Z_{\mathrm{ni}}}{Z_{\mathrm{ci}}}\right|\end{array}\right.---\left(8\right)$

Considering that the impedance angle of system and circuit is all close to 90 °, in formula (8), a, b, c are each about arithmetic number, and wherein a is relevant with line length and line parameter circuit value, when line parameter circuit value is determined for constant；B, c represent the ratio of dorsal part system sequence impedance and line characteristic sequence impedance。

D in formula (4) is taken as 1/2, i.e. circuit midpoint, simultaneously molecule and denominator simultaneously divided byFormula (7) is substituted into formula (4), and this up-to-date style (4) can be expressed as:

$\left\{\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=Z_{\mathrm{ci}}\·\frac{-Z_{\mathrm{mi}}/Z_{\mathrm{ci}}\·\coth (r_i\·l/2)-1}{-Z_{\mathrm{mi}}/Z_{\mathrm{ci}}-\coth (r_i\·l/2)}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}=Z_{\mathrm{ci}}\·\frac{-Z_{\mathrm{ni}}/Z_{\mathrm{ci}}\·\coth (r_i\·l/2)-1}{-Z_{\mathrm{ni}}/Z_{\mathrm{ci}}-\coth (r_i\·l/2)}\end{array}\right.---\left(9\right)$

Due to hyperbolic cotangent coth (r_iL/2) it is a negative imaginary number；And consider that the impedance angle of system and circuit is all close to 90 degree, Z_miBe a positive imaginary number, then above formula can be expressed as:

$\left\{\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=Z_{\mathrm{ci}}\·\frac{(-j\·|Z_{\mathrm{mi}}\left|\right)/Z_{\mathrm{ci}}\·(-j\·|\coth (r_i\·l/2|)-1}{(-j\·|Z_{\mathrm{mi}}\left|\right)/Z_{\mathrm{ci}}-(-j\·|\coth (r_i\·l/2|)}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}=Z_{\mathrm{ci}}\·\frac{(-j\·|Z_{\mathrm{ni}}\left|\right)/Z_{\mathrm{ci}}\·(-j|\coth (r_i\·l/2|)-1}{-Z_{\mathrm{ni}}/Z_{\mathrm{ci}}-j\·|c\mathrm{oth}(r_i\·l/2|)}\end{array}\right.---\left(10\right)$

Abbreviation can obtain:

$\left\{\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=j{Z}_{\mathrm{ci}}\·\frac{\left|Z_{\mathrm{mi}}\right|/Z_{\mathrm{ci}}\·\left|\coth (r_i\·l/2)\right|+1}{\left|Z_{\mathrm{mi}}\right|/Z_{\mathrm{ci}}-|\coth (r_i\·l/2)}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}=j{Z}_{\mathrm{ci}}\·\frac{\left|Z_{\mathrm{ni}}\right|/Z_{\mathrm{ci}}\·|\coth (r_i\·l/2)+1}{\left|Z_{\mathrm{ni}}\right|/Z_{\mathrm{ci}}-|\coth (r_i\·l/2)}\end{array}\right.---\left(11\right)$

Formula (8) is substituted into formula (11), can obtain:

$\left\{\begin{array}{c}\frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′}}=j{Z}_{\mathrm{ci}}\frac{\mathrm{ab}+1}{a-b}\\ \frac{\mathrm{\Δ}{U}_{\mathrm{ki}}^{\′\′}}{\mathrm{\Δ}{I}_{\mathrm{ki}}^{\′\′}}=j{Z}_{\mathrm{ci}}\frac{\mathrm{ac}+1}{a-c}\end{array}\right.---\left(12\right)$

By formula (12) it can be seen that virtual sequence resistance value is relevant with the value of b and c, a point situation is analyzed below。

(1) a, b, c satisfy condition a > b and a > c time, substituted into formula (12), it is known that calculated that the span of virtual sequence resistance value obtained is by circuit two ends respectivelyThe phase place of virtual sequence impedance is identical。Due to the sum that actuating quantity is negative phase-sequence virtual impedance value, braking amount is the smaller value of negative phase-sequence virtual impedance value, and actuating quantity is more than braking amount, it is possible to correctly identify fault。

(2) a, b, c meet a>b and a<c or a<b and a>During c, an end system is weak feedback side, for m end for weak feedback side, has a<b and a>C, is substituted into formula (9), it is known thatSpan be (-∞ ,-jaZ_ci],Span beDocument (Suo Nanjiale; Liu Kai; the little China of foxtail millet; Deng. based on the electric power line longitudinal coupling protection [J] of fault component comprehensive impedance. Proceedings of the CSEE, 2008,28 (31): 54-61) point out; when one end is weak feedback side; the impedance of the other end is much smaller than circuit capacitive reactance, it is believed that the c size much smaller than a, c is aboutA value reduces along with the increase of line length and the lifting of electric pressure, circuit even for 500kV, when line length is less than 400km, the value of a is nor less than 3, thus calculated the absolute value obtaining virtual sequence impedance by m thruster more than being calculated the absolute value obtaining virtual sequence impedance by n thruster, now braking amount isActuating quantity is worked asTime take minima, b=∞, m side is unloaded, and actuating quantity and braking amount are respectively as follows:

$\left\{\begin{array}{c}|\frac{\mathrm{\&Delta;}{U}_{\mathrm{ki}}^{\&prime;}}{\mathrm{\&Delta;}{I}_{\mathrm{ki}}^{\&prime;}}+\frac{\mathrm{\&Delta;}{U}_{\mathrm{ki}}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{\mathrm{ki}}^{\&prime;\&prime;}}|=\left|(a-\frac{1}{a})Z_{\mathrm{ci}}\right|\\ \min \left\{\right|\frac{\mathrm{\&Delta;}{U}_{\mathrm{ki}}^{\&prime;}}{\mathrm{\&Delta;}{I}_{\mathrm{ki}}^{\&prime;}}|,|\frac{\mathrm{\&Delta;}{U}_{\mathrm{ki}}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{\mathrm{ki}}^{\&prime;\&prime;}}\left|\right\}=\left|\frac{1}{a}{Z}_{\mathrm{ci}}\right|\end{array}\right.---\left(13\right)$

Considering a span, actuating quantity is more than braking amount, and algorithm still can correctly identify fault when a side system is weak feedback side。

(3) a, b, c satisfy condition a <b and a < during c, by the analysis in (2) it can be seen that the size of the system sequence impedance of both sides can not meet above-mentioned condition simultaneously, it is not necessary to the reliability of algorithm in this situation is discussed。

Formula (5) is launched into respectively the operating criterion of positive sequence, negative phase-sequence and zero-sequence fault component, has:

$\left\{\begin{array}{c}\max (\mathrm{\&Delta;}{I}_{k1}^{\&prime;\&prime;},\mathrm{\&Delta;}{I}_{k1}^{\&prime;})>0.1I_N\\ |\frac{\mathrm{\&Delta;}{U}_{k1}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{k1}^{\&prime;\&prime;}}+\frac{\mathrm{\&Delta;}{U}_{k1}^{\&prime;}}{\mathrm{\&Delta;}{I}_{k1}^{\&prime;}}|\&GreaterEqual;\min \left\{\right|\frac{\mathrm{\&Delta;}{U}_{k1}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{k1}^{\&prime;\&prime;}}|,|\frac{\mathrm{\&Delta;}{U}_{k1}^{\&prime;}}{\mathrm{\&Delta;}{I}_{k1}^{\&prime;}}\left|\right\}\end{array}\right.---\left(14\right)$

$\left\{\begin{array}{c}\max (\mathrm{\&Delta;}{I}_{k2}^{\&prime;\&prime;},\mathrm{\&Delta;}{I}_{k2}^{\&prime;})>0.1I_N\\ |\frac{\mathrm{\&Delta;}{U}_{k2}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{k2}^{\&prime;\&prime;}}+\frac{\mathrm{\&Delta;}{U}_{k2}}{\mathrm{\&Delta;}{I}_{k2}^{\&prime;}}|\&GreaterEqual;\min \left\{\right|\frac{\mathrm{\&Delta;}{U}_{k2}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{k2}^{\&prime;\&prime;}}|,|\frac{\mathrm{\&Delta;}{U}_{k2}^{\&prime;}}{\mathrm{\&Delta;}{I}_{k2}^{\&prime;}}\left|\right\}\end{array}\right.---\left(15\right)$

$\left\{\begin{array}{c}\max (\mathrm{\&Delta;}{I}_{k0}^{\&prime;\&prime;},\mathrm{\&Delta;}{I}_{k0}^{\&prime;})>0.1I_N\\ |\frac{\mathrm{\&Delta;}{U}_{k0}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{k0}^{\&prime;\&prime;}}+\frac{\mathrm{\&Delta;}{U}_{k0}^{\&prime;}}{\mathrm{\&Delta;}{I}_{k0}^{\&prime;}}|\&GreaterEqual;\min \left\{\right|\frac{\mathrm{\&Delta;}{U}_{k0}^{\&prime;\&prime;}}{\mathrm{\&Delta;}{I}_{k0}^{\&prime;\&prime;}}|,|\frac{\mathrm{\&Delta;}{U}_{k0}^{\&prime;}}{\mathrm{\&Delta;}{I}_{k0}^{\&prime;}}\left|\right\}\end{array}\right.---\left(16\right)$

Formula (14), formula (15) and (16) three criterions of formula cooperate, and as the main protection of transmission line of electricity, matching relationship is as shown in Figure 3。Wherein, negative phase-sequence and zero-sequence fault component criterion can react various types of unbalanced fault, as long as and this criterion of fault sustainable existence just continue to set up；Although positive sequence fault component criterion can react all types of short circuits, but it is limited by Sudden Changing Rate memory time, and there is set of time is 60ms。To sum up, when fixing threshold portion negative phase-sequence or zero sequence criterion being detected starts, the differentiation result identification fault of negative phase-sequence or zero sequence criterion is utilized；When the fixing threshold only having positive sequence criterion starts, utilize positive sequence fault component criterion identification fault。

According to above-mentioned principle, the longitudinal protection method differential based on fault component virtual impedance includes:

Step 1: gather data, including line characteristic sequence impedance, sequence propagation coefficient, the voltage and current fault sequence component of protection installation place。

Step 2: calculate virtual sequence impedance。

Step 3: judge whether to meet operating criterion according to the virtual sequence impedance at circuit midpoint, if meeting operating criterion, is then judged to troubles inside the sample space, and sends trip signal immediately；If being unsatisfactory for operating criterion, being then judged to external area error, not sending trip signal。

Operating criterion includes the operating criterion of the operating criterion of positive sequence fault component, the operating criterion of negative phase-sequence fault component and zero-sequence fault component。

Virtual sequence impedance according to circuit midpoint judges whether to meet the operating criterion of positive sequence fault component as shown in Equation (14), virtual sequence impedance according to circuit midpoint judges whether to meet the operating criterion of negative phase-sequence fault component as shown in Equation (15), judges whether to meet the operating criterion of zero-sequence fault component as shown in Equation (16) according to the virtual sequence impedance at circuit midpoint。

Embodiment 2

Correctness and the reasonability of said system and method is verified below by way of simulation process。Fig. 4 is Beijing-Tianjin-Tangshan 500kV extra high voltage system figure, based on the system shown in Fig. 4 of building in PSCAD/EMTDC as phantom。

Phantom line length is 400km, and its parameter is: r₁=0.02083 Ω/km, l₁=0.8948H/km, C₁=0.0129 μ F/km, r₀=0.1148 Ω/km, l₀=2.2886H/km, C₀=0.00523 μ F/km。M side system:, Z_m=7.14+j101.54 Ω, Zero sequence parameter is identical with positive sequence；N side system:, Z_n=1.428+j20.308 Ω, Zero sequence parameter is identical with positive sequence。Emulation duration is 0.8s, and fault occurs when 0.5s, and sample frequency is 6kHz, and the making time of positive sequence criterion is after positive sequence criterion starts in 60ms。

In the present embodiment, the ratio of definition sequence actuating quantity and braking amount is K_i(i=1,2,0, represent positive sequence, negative phase-sequence and zero sequence respectively)。Fetching protection action threshold is 1, namely works as K_iWhen >=1, it is determined that for troubles inside the sample space, send trip signal to protection。

A external area error

Fig. 5 is that M side and N side reversely export the differentiation result of criterion when there is various short trouble。When there is external area error, circuit self structure does not change, and as can be seen from the table, each actuating quantity of order components criterion started is close to 0 with the ratio of braking amount, much smaller than action threshold value, is reliably failure to actuate。Fig. 6 (a) and (b) respectively M side and N side reversely export the differentiation result that symmetrical and unbalanced fault sequential occur。In figure, dotted line is the protection act threshold in rate restraint criterion; solid line represents each sequence actuating quantity and the ratio of braking amount (lower same); this figure shows; impact by filtering algorithm and the DC component of decay; starting criterion result in the later cycle in fault to tend towards stability, after stable, ratio is much smaller than action threshold。

B troubles inside the sample space

Troubles inside the sample space is divided into single phase grounding fault, and single-phase short circuit is through high resistance earthing fault, line to line fault earth fault, line to line fault phase to phase fault and three phase short circuit fault。Trouble point is arranged on distance M end 0%, 30%, 50%, 70% and 100% place。When generating region internal fault, circuit self structure is destroyed, the action situation of criterion under various short-circuit conditions is there is in Tu7Wei district, this method ratio of the actuating quantity of order components criterion and braking amount under all kinds fault is all higher than 1 as seen from table, and have very big nargin, meanwhile, criterion, all can action message when internal fault not by the impact of position of failure point and transition resistance。

Differentiation result when symmetrical and unbalanced fault occurs in Tu8Wei district respectively, and this figure shows, no matter the position of trouble point and fault type, and criterion all can correctly identify fault after fault starts in very short time, have higher sensitivity simultaneously。

Break down during the zero load of C one end

Unloaded and the circuit generation single-phase earthing fault for N end, trouble point is set for distance M end 0%, 30%, 50%, 70% and 100% place, table 3 and Fig. 7 are the judged result when zero load of N end and generation single-phase short circuit, from Fig. 9 and Figure 10, criterion is not by the impact of system impedance, regardless of position of failure point, and all can correct response fault。

D conversion type fault

Reversely export generation A phase short circuit grounding with N side, and convert through 0.02s that all kinds of fault occurs in N lateral areas is example to, the feasibility of this method is described。Figure 11 and Figure 12 is differentiation result in above-mentioned situation。

As can be seen from Table 5, owing to, in the process of Conversion fault, the self structure of circuit there occurs destruction, each order components criterion all can correctly identify fault。Figure 12 shows, after the type fault that changes, criterion can judge fault in a short period of time, has the ability of very strong reaction self structure change。

The development-oriented fault of E

A phase ground connection is there is respectively with N side outlet and reverse exit; this AB phase ground connection is developed into and ABC three-phase ground is example through 0.02s; the action situation of criterion is described; if the differentiation that Figure 13 is sequence criterion in above-mentioned situation is results, it can be seen that there occurs troubles inside the sample space; owing to this body structure of circuit is unsound; even if there is other types fault again, structure is still unsound, and protection can action message；If there occurs external area error, after there is development-oriented fault, line construction destroys not yet, and protection is reliably failure to actuate。

The above; being only the present invention preferably detailed description of the invention, but protection scope of the present invention is not limited thereto, any those familiar with the art is in the technical scope that the invention discloses; the change that can readily occur in or replacement, all should be encompassed within protection scope of the present invention。Therefore, protection scope of the present invention should be as the criterion with scope of the claims。

Claims (6)

1., based on the pilot protection system that fault component virtual impedance is differential, it is characterized in that described system includes data reading module, protection computing module and protection act module that order is connected；

Described data read in module for gathering the current failure order components of line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and circuit both sides, and send the data of collection to protecting computing module；

Described protection computing module for calculating the virtual sequence impedance of circuit according to line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and the current failure order components of circuit both sides, and sends the virtual sequence impedance of calculated circuit to protection act module；

Described protection act module is for the virtual sequence impedance according to circuit midpoint, it may be judged whether meet operating criterion；If meeting operating criterion, then it is judged to troubles inside the sample space, and sends trip signal immediately；If being unsatisfactory for operating criterion, being then judged to external area error, not sending trip signal；

The virtual sequence impedance of described calculating circuit adopts formula:

$\left\{\begin{array}{c}\frac{{\mathrm{\&Delta;U}}_{ki}^{\&prime;}}{{\mathrm{\&Delta;I}}_{ki}^{\&prime;}}=Z_{ci}\frac{{\mathrm{\&Delta;U}}_{mi}\&CenterDot;\cosh (r_i\&CenterDot;dl)-{\mathrm{\&Delta;I}}_{mi}\&CenterDot;Z_{ci}\sinh (r_i\&CenterDot;dl)}{{\mathrm{\&Delta;U}}_{mi}\&CenterDot;\sinh (r_i\&CenterDot;dl)-{\mathrm{\&Delta;I}}_{mi}\&CenterDot;Z_{ci}\cosh (r_i\&CenterDot;dl)}\\ \frac{{\mathrm{\&Delta;U}}_{ki}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{ki}^{\&prime;\&prime;}}=Z_{ci}\frac{{\mathrm{\&Delta;U}}_{ni}\&CenterDot;\cosh (r_i\&CenterDot;(1-d)l)-{\mathrm{\&Delta;I}}_{ni}\&CenterDot;Z_{ci}\sinh (r_i\&CenterDot;(1-d\left)l\right)}{{\mathrm{\&Delta;U}}_{ni}\&CenterDot;\sinh (r_i\&CenterDot;(1-d)l)-{\mathrm{\&Delta;I}}_{ni}\&CenterDot;Z_{ci}\cosh (r_i\&CenterDot;(1-d\left)l\right)}\end{array}\right.;$

Wherein, Δ I_miCurrent failure order components for circuit m side；

ΔU_miVoltage failure order components for circuit m side；

ΔI′_kiThe current failure order components of the k point for being obtained by circuit m thruster；

ΔU′_kiThe voltage failure order components of the k point for being obtained by circuit m thruster；

The virtual sequence impedance of the k point for being obtained by circuit m thruster；

ΔI_niCurrent failure order components for circuit n side；

ΔU_niVoltage failure order components for circuit n side；

ΔI″_kiThe current failure order components of the k point for being obtained by circuit n thruster；

ΔU″_kiThe voltage failure order components of the k point for being obtained by circuit n thruster；

The virtual sequence impedance of the k point for being obtained by circuit n thruster；

K is any point between circuit mn；

Z_ciFor line characteristic sequence impedance；

r_iFor circuit sequence propagation coefficient；

I=0,1 or 2；As i=0, represent zero-sequence component；As i=1, represent positive-sequence component；As i=2, represent negative sequence component；

L is the length of circuit mn；

D be on circuit mn k point to the distance percentage ratio of m side；

Cosh () is hyperbolic cosine function；

Sinh () is hyperbolic sine function。

2., based on the longitudinal protection method that fault component virtual impedance is differential, it is characterized in that described method includes:

Step 1: gather the current failure order components of line characteristic sequence impedance, circuit sequence propagation coefficient, the voltage failure order components of circuit both sides and circuit both sides；

Step 2: calculate the virtual sequence impedance of circuit；

Step 3: judge whether to meet operating criterion according to the virtual sequence impedance at circuit midpoint, if meeting operating criterion, is then judged to troubles inside the sample space, and sends trip signal immediately；If being unsatisfactory for operating criterion, being then judged to external area error, not sending trip signal；The virtual sequence impedance of described calculating circuit adopts formula:

$\left\{\begin{array}{c}\frac{{\mathrm{\&Delta;U}}_{ki}^{\&prime;}}{{\mathrm{\&Delta;I}}_{ki}^{\&prime;}}=Z_{ci}\frac{{\mathrm{\&Delta;U}}_{mi}\&CenterDot;\cosh (r_i\&CenterDot;dl)-{\mathrm{\&Delta;I}}_{mi}\&CenterDot;Z_{ci}\sinh (r_i\&CenterDot;dl)}{{\mathrm{\&Delta;U}}_{mi}\&CenterDot;\sinh (r_i\&CenterDot;dl)-{\mathrm{\&Delta;I}}_{mi}\&CenterDot;Z_{ci}\cosh (r_i\&CenterDot;dl)}\\ \frac{{\mathrm{\&Delta;U}}_{ki}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{ki}^{\&prime;\&prime;}}=Z_{ci}\frac{{\mathrm{\&Delta;U}}_{ni}\&CenterDot;\cosh (r_i\&CenterDot;(1-d)l)-{\mathrm{\&Delta;I}}_{ni}\&CenterDot;Z_{ci}\sinh (r_i\&CenterDot;(1-d\left)l\right)}{{\mathrm{\&Delta;U}}_{ni}\&CenterDot;\sinh (r_i\&CenterDot;(1-d)l)-{\mathrm{\&Delta;I}}_{ni}\&CenterDot;Z_{ci}\cosh (r_i\&CenterDot;(1-d\left)l\right)}\end{array}\right.;$

Wherein, Δ I_miCurrent failure order components for circuit m side；

ΔU_miVoltage failure order components for circuit m side；

ΔI′_kiThe current failure order components of the k point for being obtained by circuit m thruster；

ΔU′_kiThe voltage failure order components of the k point for being obtained by circuit m thruster；

The virtual sequence impedance of the k point for being obtained by circuit m thruster；

ΔI_niCurrent failure order components for circuit n side；

ΔU_niVoltage failure order components for circuit n side；

ΔI″_kiThe current failure order components of the k point for being obtained by circuit n thruster；

ΔU″_kiThe voltage failure order components of the k point for being obtained by circuit n thruster；

The virtual sequence impedance of the k point for being obtained by circuit n thruster；

K is any point between circuit mn；

Z_ciFor line characteristic sequence impedance；

r_iFor circuit sequence propagation coefficient；

I=0,1 or 2；As i=0, represent zero-sequence component；As i=1, represent positive-sequence component；As i=2, represent negative sequence component；

L is the length of circuit mn；

D be on circuit mn k point to the distance percentage ratio of m side；

Cosh () is hyperbolic cosine function；

Sinh () is hyperbolic sine function。

3. method according to claim 2, is characterized in that described operating criterion includes the operating criterion of the operating criterion of positive sequence fault component, the operating criterion of negative phase-sequence fault component and zero-sequence fault component。

4. method according to claim 3, it is characterized in that the described virtual sequence impedance according to circuit midpoint judge whether to meet positive sequence fault component operating criterion particularly as follows:

$\left\{\begin{array}{c}\max ({\mathrm{\&Delta;I}}_{k1}^{\&prime;\&prime;},{\mathrm{\&Delta;I}}_{k1}^{\&prime;})>0.1I_N\\ \left|\frac{{\mathrm{\&Delta;U}}_{k1}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{k1}^{\&prime;\&prime;}}+\frac{{\mathrm{\&Delta;U}}_{k1}^{\&prime;}}{{\mathrm{\&Delta;I}}_{k1}^{\&prime;}}\right|\&GreaterEqual;\min \left\{\left|\frac{{\mathrm{\&Delta;U}}_{k1}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{k1}^{\&prime;\&prime;}},\frac{{\mathrm{\&Delta;U}}_{k1}^{\&prime;}}{{\mathrm{\&Delta;I}}_{k1}^{\&prime;}}\right|\right\}\end{array}\right.;$

Wherein, k is the midpoint of circuit mn；

ΔI′_k1The current failure positive-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔI″_k1The current failure positive-sequence component at the circuit midpoint for being obtained by circuit n thruster；

ΔU′_k1The voltage failure positive-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔU″_k1The voltage failure positive-sequence component at the circuit midpoint for being obtained by circuit n thruster；

The virtual positive sequence impedance at the circuit midpoint for being obtained by circuit m thruster；

The virtual positive sequence impedance at the circuit midpoint for being obtained by circuit n thruster；

I_NRated current for circuit mn。

5. method according to claim 3, it is characterized in that the described virtual sequence impedance according to circuit midpoint judge whether to meet negative phase-sequence fault component operating criterion particularly as follows:

$\left\{\begin{array}{c}\max ({\mathrm{\&Delta;I}}_{k2}^{\&prime;\&prime;},{\mathrm{\&Delta;I}}_{k2}^{\&prime;})>0.1I_N\\ \left|\frac{{\mathrm{\&Delta;U}}_{k2}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{k2}^{\&prime;\&prime;}}+\frac{{\mathrm{\&Delta;U}}_{k2}^{\&prime;}}{{\mathrm{\&Delta;I}}_{k2}^{\&prime;}}\right|\&GreaterEqual;\min \left\{\left|\frac{{\mathrm{\&Delta;U}}_{k2}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{k2}^{\&prime;\&prime;}},\frac{{\mathrm{\&Delta;U}}_{k2}^{\&prime;}}{{\mathrm{\&Delta;I}}_{k2}^{\&prime;}}\right|\right\}\end{array}\right.;$

Wherein, k is the midpoint of circuit mn；

ΔI′_k2The current failure negative sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔI″_k2The current failure negative sequence component at the circuit midpoint for being obtained by circuit n thruster；

ΔU′_k2The voltage failure negative sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔU″_k2The voltage failure negative sequence component at the circuit midpoint for being obtained by circuit n thruster；

The virtual negative sequence impedance at the circuit midpoint for being obtained by circuit m thruster；

The virtual negative sequence impedance at the circuit midpoint for being obtained by circuit n thruster；

I_NRated current for circuit mn。

6. method according to claim 3, it is characterized in that the described virtual sequence impedance according to circuit midpoint judge whether to meet zero-sequence fault component operating criterion particularly as follows:

$\left\{\begin{array}{c}\max ({\mathrm{\&Delta;I}}_{k0}^{\&prime;\&prime;},{\mathrm{\&Delta;I}}_{k0}^{\&prime;})>0.1I_N\\ \left|\frac{{\mathrm{\&Delta;U}}_{k0}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{k0}^{\&prime;\&prime;}}+\frac{{\mathrm{\&Delta;U}}_{k0}^{\&prime;}}{{\mathrm{\&Delta;I}}_{k0}^{\&prime;}}\right|\&GreaterEqual;\min \left\{\left|\frac{{\mathrm{\&Delta;U}}_{k0}^{\&prime;\&prime;}}{{\mathrm{\&Delta;I}}_{k0}^{\&prime;\&prime;}},\frac{{\mathrm{\&Delta;U}}_{k0}^{\&prime;}}{{\mathrm{\&Delta;I}}_{k0}^{\&prime;}}\right|\right\}\end{array}\right.;$

Wherein, k is the midpoint of circuit mn；

ΔI′_k0The current failure zero-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔI″_k0The current failure zero-sequence component at the circuit midpoint for being obtained by circuit n thruster；

ΔU′_k0The voltage failure zero-sequence component at the circuit midpoint for being obtained by circuit m thruster；

ΔU″_k0The voltage failure zero-sequence component at the circuit midpoint for being obtained by circuit n thruster；

The virtual zero sequence impedance at the circuit midpoint for being obtained by circuit m thruster；

The virtual zero sequence impedance at the circuit midpoint for being obtained by circuit n thruster；

I_NRated current for circuit mn。