Patent ID: 9270107
Filing Date: 2016-02-23
CPC Classification: H02H

Claim Text:
1. A method for supervising a condition of electrical equipment in an electrical power system which includes plural current transformers for multi-phase power equipment, the multi-phase power equipment being protected by a protection relay which can issue of a trip signal on occurrence of a fault in the electrical power system, the method comprising: a) measuring electrical parameters from the plural current transformers for the multi-phase power equipment; b) computing a fault indicative parameter for the multi-phase power equipment in the electrical power system from the measurements made with the plural current transformers; c) detecting a fault condition in at least one electrical measurement made from the plural current transformers, wherein a current transformer indicating a fault condition is a suspected faulty current transformer and remaining current transformers of the plural current transformers are considered to be healthy current transformers; d) detecting a change in the computed fault indicative parameter from the at least one electrical parameter measurement made from at least one of the healthy current transformers on detection of the fault condition in the suspected faulty current transformer; and e) comparing the detected change in the computed fault indicative parameter with a preset threshold value for the fault indicative parameter to determine a condition of at least one electrical equipment component in the electrical power system; wherein the computing of the fault indicative parameter includes computing a condition parameter selected from a group consisting of: a negative sequence current parameter computed from measurements made with at least one healthy current transformer, a phase angle difference parameter computed from measurements between current signals from any two of the healthy current transformers, and a combination parameter set based on the negative sequence current parameter and the phase angle difference parameter.