A new algorithm for coordination of relay and auto-reclosure in 220 kV transmission system

Majority of the faults on overhead lines are transient in nature and caused by lightning or temporary contact with natural objects like a bird, tree branch, etc. Successful re-energization of the line is achieved using auto-reclosing scheme as transient faults are going to clear after some time. This paper presents a new scheme for coordination of protective relay (R) and auto-reclosure (79). Fast Fourier Transform (FFT) filter is used to estimate the magnitude of three phase current and voltage signals of transmission line. Fault detection algorithm and auto reclosing scheme have been developed using PSCAD/EMTDC software package. To validate the proposed scheme, numerous computer simulations have been carried out by modeling 220 kV transmission systems. Different faults on transmission line such as transient and permanent are evaluated for the effectiveness of the proposed scheme. In relevance to the proposed relay/reclosing scheme, a control circuit has also been suggested with view point of practical implementation.