Comparison of transformer legacy protective functions and a dynamic state estimation-based approach

Abstract This paper presents a comparison of the legacy protective functions of commercial power transformer relays with a proposed dynamic state estimation (DSE) based approach. This DSE-based approach continuously monitors the health status of transformer by checking if all measurements match the dynamic model of the transformer. Any inconsistency between the measurement and model indicates a chance of internal fault. Unlike the traditional relays that require many complex settings and coordination, the DSE-based approach only needs to know minimal simple settings and the protection logic is purely based on the transformer health status. Therefore, it avoids many unnecessary failures caused by wrong settings or improper functions coordination. The proposed DSE-based protection approach has been tested on a 40 MVA, 115/35 kV three-phase transformer, along with a set of legacy protection functions. Laboratory implementation of the hardware-in-the-loop simulation is also presented in the paper. Extensive results validate the better performance of the DSE-based approach over the legacy functions.