Patent ID: 6239959
Filing Date: 2001-05-29
Classification: H02H

Abstract:
A protective relay for protecting a phase of a polyphase electric power transmission system by generating a tripping signal in response to a fault between said phase and a ground, comprising:means for generating in respect to said phase of said polyphase system a quadrilateral reactance characteristic;means for generating in respect to said phase of said polyphase system a quadrilateral restrictive directional characteristic; andmeans for generating in respect to said phase of said polyphase system a quadrilateral resistive blinder characteristic,wherein inputs to said means for generating in respect to said phase of said polyphase system a quadrilateral reactance characteristic comprise:Operate: I.sub..PHI.' Z - V.sub..PHI. Pol. #1: I.sub.0 Z.sub.1 Pol. #2: I.sub.2 Z.sub.1 Pol. #3: I.sub.1F Z.sub.1Where:I.sub..phi. 'Z is the compensated IZ product,Z.sub.1 is the positive sequence replica impedance,V.sub..phi. is the phase to ground voltage,I.sub.0 is the zero sequence current component,I.sub.2 is the negative sequence current component, referenced to a proper phase, andI.sub.1F is the fault component of the positive sequence current component, referenced to the proper phase, with pre-fault load current removed.