Enhancement of the Differential Relay Performance on Two Parallel Transformers Connected to the Unified Grid

Abstract

Summary: Power Grid is growing larger and larger. Power transformer is one of the main components in power grid that has new types of faults and problems that was rarely discussed before. This thesis is concerned about enhancing the behavior of the differential protection relays on power transformers to correctly deal with such relatively new faults and maintain selectivity of protection system against two types of faults. The first case is zero sequence current affecting power transformers in case of external fault occurrence. The second case is sympathetic inrush between two parallel transformers during energization of one of them.