Claims
- 1. Method for automatically locating a fault (F) in a section of parallel A.C.transmission lines in a network comprising the steps of:
measuring currents and voltages of both lines at a measuring point arranged at one end (A) of the section, determining a fault distance (x) between the measuring point and the fault as a solution of an equation comprising the fault distance (x) as a variable and the fault resistance (Rf), wherein the equation isAx2Bx+C−Rf=0wherein parameters A, B, C, D comprise phase components of the locally measured currents and voltages and are obtained from calculating from the measuring point to the fault location along the both parallel lines, and wherein the equation is resolved into its real and imaginary parts:Real(A)x2−Real(B)x+Real(C)−Rf=0Imag(A)x2−Imag(B)x+Imag(C)=0,whereby the fault distance is derived from the imaginary part, asx=xa, if Imag(A)>0,x=xb, if Imag(A)<0,where: 22xa=Imag(B)-D2Imag(A)xb=Imag(B)+D2Imag(A)Δ=[Imag(B)]2-4Imag(A)Imag(C).
- 2. Method according to claim 1, wherein the parameters characterize a particular type of fault.
- 3. Method according to claim 2, including the step of determining a fault type matrix Kf for the particular type of fault by using a 3-phase general fault model.
- 4. Method according to claim 3, including the further step of:
using a matrix notation of said section taking into account mutual impedances between the lines, including the fault type matrix, and obtaining a matrix formulaAcx2+Bcx+Cc−Dc=0where Ac, Bc, Cc, Dc are 3*1 vectors, and multiplying both sides of the matrix formula with vector 23P=DDTDwhere DT is matrix transposed with respect to matrix D andAc=(Zm−ZLA)Kf(ZLAIAA+ZmIAB)CC=(Zm−ZLA)Kf(VA−ZV(|IAA|)IAA)Bc=Ac+CcD=(Zm−ZLA−Zv(|IAA|))IAA−(Zm−ZLB−Zv(|IAB|))IABDc=DRf
- 5. Method according to claim 2 wherein the fault type matrix Kf is expressed as
- 6. Method according to claim 1, including the step of series compensating the parallel transmission lines and representing the compensation in the calculating paths as equivalent resistance and reactance.
- 7. Method according to claim 6, wherein parallel connection of a series capacitor and a varistor constitutes a non-linear impedance (ZV) which is represented by the equivalent resistance and reactance (RV and XV) which are determined as a function of a traversing current of each phase, the method including the step of determining an actual value of the resistance and reactance with the actual currents, which, after the occurrence of the fault, flow through the impedance, whereby said non-linear impedance may be set in a matrix form.
- 8. Method according to claim 6 including the step of solving the equation for two cases; (1) when the fault is assumed behind the series compensation of the faulted line and (2) when the fault is assumed in front of the series compensation of the faulted line, as seen from the measuring point.
- 9. Method according to claim 6 including the step of determining a matrix of equivalent parameters for the series capacitors and metal oxide varistors of the faulted line in order to obtain the fundamental frequency equivalent.
- 10. Method according to claim 9, including the step of calculating the fault resistance Rf from the real part of the equation and including the matrix of the fundamental frequency.
- 11. Method according to claim 10, wherein the matrix of the fundamental frequency is expressed as
- 12. Method according to claim 10, including the step of selecting a lower calculated fault distance from said two cases, based on
estimated fault resistance of the two cases, and estimated amplitudes of healthy phases fault current, whereby lower estimated values support the calculated fault distance of a case.
- 13. Method according to claim 12, wherein the amplitudes of the phase currents for case (2) are obtained by iterative calculation.
- 14. Device for locating a fault (F) in a section of parallel transmission lines comprising calculating members arranged to automatically calculate, on the basis of current and voltage values measured adjacent to one end of said section and a known impedance of the lines, a distance between a measuring point and the fault, wherein the calculating members are arranged to determine, on the basis of information about the type of fault in question and complex quantities of the measured values and using a network model, the fault distance as the solution of an equation Ax2−Bx+C−Rf=0, wherein x is a variable fault distance and Rf is the measured fault resistance and
- 15. Use of a device according to claim 14 to determine the distance to fault in a parallel transmission line.
- 16. Use of a device according to claim 14 to record and signal currents and voltages associated with a fault at a distance (d) from a measuring station (A).
- 17. Computer program product selectively comprising computer code means and software code portions for automatically locating a fault (F) in a section of parallel A.C.transmission lines by making a computer or processor perform the steps of:
receiving values of currents and voltages of both the lines at a measuring point arranged at one end (A) of the section, calculating a fault distance x from the measuring point to the fault location along the both parallel lines as a solution of an equation Ax2−Bx+C−Rf=0, comprising the fault distance x as a variable and the fault resistance (Rf) and parameters A, B, C, D that depend on phase components of the locally measured currents and voltages, wherein the equation is resolved for the real parts and the imaginary parts respectively, and —reporting the fault distance x.
- 18. Computer program product according to claim 17 contained on/in, a computer readable medium.
RELATED APPLICATIONS
[0001] This is a continuation-in-part application of U.S. Ser. No. 09/745,161, filed on Dec. 20, 2000.
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09745161 |
Dec 2000 |
US |
Child |
09902863 |
Jul 2001 |
US |