Sympathetic Inrush Identification Based on Features of Exponential Component in Differential Current

When the core of a power transformer enters saturation region, inrush will occur and result in results in the increase of differential current and may cause protection relay to malfunction. In order to prevent transformer protection relay from malfunctioning, this paper proposes a method for sympathetic inrush identification based on the trend of the exponential component extracted by using morphological transform (MT). Simulation studies is conducted using PSCAD/EMTDC to verify the feasibility of the proposed method. Simulation results show that the proposed method is adaptable to different conditions even if current transformer (CT) is severely saturated.

I. INTRODUCTION

Transformer is a very important primary equipment in power systems. When energizing a no-load transformer, inrush current may occur due to saturation of the core. The protection relay of power transformer may malfunction as a result of the large amplitude of the inrush current, which threats the stable operation of power system. In order to prevent the protection relay of transformer from being disturbed, researchers have done a lot of work on how to effectively distinguish internal fault from inrush current. However, many studies consider only a single transformer and ignore the sympathetic interaction between transformers in parallel or series operation.