COMPUTATIONALLY-EFFICIENT DISTANCE RELAY FOR POWER TRANSMISSION LINES

摘要

The relay includes means for obtaining current and voltage samples on the power transmission line for a particular possible fault type. The current sample is multiplied by the replica impedance of the power transmission line, while the voltage sample is multiplied by a polarizing voltage to provide a first complex expression having a real portion and an imaginary portion. The product of the current sample and the replica impedance is multiplied by the polarizing voltage to produce a second complex expression having a real portion and an imaginary portion. The real portion of the first complex expression is then divided by the real portion of the second complex expression to produce a scale value m which is compared against known reference scale values for each zone, so as to determine underimpedance conditions in any one of the zones.