Simulation Study of the Siemens 7UT613 Differential Protection Relay for Power Transformer

Abstract

The transformer protection system includes many different types, in which differential protection is the main protection. Differential protection of the transformer must satisfy the criteria of both having high sensitivity to protect the transformer from incidents and ensuring selectivity to avoid erroneous impacts that cause power outages. This paper presents the research to establish a model and evaluate the working characteristics of Siemens digital relay 7UT613 to protect the three-phase transformer 220/110/35 kV based on Matlab/ Simulink. On that basis, it can be adjusted to improve the accurate and reliable operation of the transformer differential protection relay when a fault occurs inside the protection zone. The simulation is conducted in the cases of normal transformer operation, transformer surge, short circuits on the 220 kV, 110 kV, 35 kV sides and short circuits on the load side. The results of analysis and evaluation include the current of the high voltage, medium voltage and low voltage coils fed into the relay; differential current and braking current; signal from the harmonic block and the Trip block of the relay.