Patent ID: 6397156
Filing Date: 2002-05-28
Classification: H02H

Abstract:
A protective relaying method for use in connection with a power system comprising electrical conductors carrying current and voltage waveforms, the method comprising the steps of:measuring a number (n) of current and voltage samples (Ik, Vk) representative of values of current and voltage waveforms, respectively, at successive instants of time on a conductor in the power system, wherein the number n is an integer greater than 1 and the index k takes on values of 1 to n; computing resistance (R) and inductance (L) values in accordance with an equation in which R and L are related to sums of differences in values of successive current and voltage samples; and performing a prescribed power system function based on the computed R and L values, wherein R and L are determined in accordance with the following equations: [RL]=(AT&it;A)-1&it;AT&it;b,withAT&it;A=[&Sum;k=1n&it;(Ik+Ik-1)22Î”&it;â€ƒ&it;t&CenterDot;&Sum;k=1n&it;(Ik-Ik-1)&CenterDot;(Ik+Ik-1)2Î”&it;â€ƒ&it;t&CenterDot;&Sum;k=1n&it;(Ik-Ik-1)&CenterDot;(Ik+Ik-1)(2Î”&it;â€ƒ&it;t)2&CenterDot;&Sum;k=1n&it;(Ik-Ik-1)2]AT&it;b=[&Sum;k=1n&it;(Ik+Ik-1)&CenterDot;(Vk+Vk-1)2Î”&it;â€ƒ&it;t&CenterDot;&Sum;k=1n&it;(Ik-Ik-1)&CenterDot;(Vk+Vk-1)].wherein &Dgr;t represents the time period separating successive samples.