Analysis of cross blocking method implementation for overcoming sympathetic inrush current phenomena

Abstract

This project present analysis and implementation of cross blocking feature as the solution for overcoming the mal-operation of the transformer differential relay in sympathetic inrush phenomena. The sympathetic inrush phenomena will occur to the transformers that connected in parallel. The inrush current will flow to the transformer that is already energized when energizing the second transformer on the power system. It will effect a voltage drop and this voltage drop caused the saturation to the already transformer in the negative direction. These phenomena caused the mal-operation of the relay that the main point of this project is to overcome it. The results obtained after designing 100MVA, 33/ 11kV three phase transformer by using PSCAD/ EMTDC simulation. As results, cross blocking method will operate as a block tripping and this method is useful to eliminate mal-operations that occur during the energization of the transformer due of the failure of harmonic restraint function in transformer differential relays. These analyses solve the problem of sympathetic inrush current phenomena.