Patent ID: 6529010
Filing Date: 2003-03-04
Classification: G01R

Abstract:
A method for location of a fault, and determination of a resultant fault resistance, occurring on a power transmission line which is series-compensated with capacitors, with a parallel-connected overvoltage protection device, between two stations (A) and (B), wherein distance to the fault from station (A) and the fault resistance are determined by means of values measured in station (A) of a voltage before (pre) and a voltage and a current after (post) the occurrence of the fault, wherein, if the fault occurred between the series capacitors and station B, the distance to the fault is determined by the steps of:solving the expression: x11=Im&it;(b_1)-Im&it;(b_1)&it;Im&it;(b_1)-4&it;Im&it;(a_1)&it;Im&it;(c_1)2&it;Im&it;(a_1)which represents a first distance-to-fault equation;solving the expression:a1x12âˆ’b1x1+c1âˆ’Rf1=0 for a, b and c, where a1, b1 and c1 designate complex coefficients and x1 represents the distance to the fault, and employing a first auxiliary vectorD1=(ZA+ZB+ZL)(IAâ€”postIAâ€”pre)+ZSCâ€”postIAâ€”postâˆ’ZSCâ€”preIAâ€”pre Or whereZA is a source impedance of a backward power network; ZB is a source impedance of a forward power network; ZL is an impedance of a power transmission line; Index, Post identifies a value after the occurrence of a fault; Index, Pre identifies a value before the occurrence of the fault; IA is a fault current; ZS is a complex impedance; and D1T, which designates a transpose matrix of D1, calculating a, b and c as follows: a_1=D1TD1T&it;D1&it;ZL&it;Kf&it;ZL&it;IA_postâ€ƒb_1=D1TD1T&it;D1&it;â€ƒ&it;(ZL&it;Kf&af;[VA_post+(ZL-ZSC_post)&it;IA_post]+ZB&it;Kf&it;ZL&it;IA_post)(12)c_1=D1TD1T&it;D1&it;(ZL+ZB)&it;(VA_post-ZSC_post&it;IA_post)&it;Kf(13)and where Im(a1), Im(b1) and Im(c1) are an imaginary part of the complex coefficients a, b1 and c, respectively, andthe fault resistance equalsRf1=Re(a1)x112âˆ’Re(b1)x11+Re(c1) where Re(a1), Re(b1) and Re(c1) are a real part of the coefficients a1, b1 and c1.