Zeitschrift für Elektrotechnik und Elektronik

A Microcontroller Based Protection of a Transformer from Transient and Permanent Faults Using Matlab/Simulink

Ezennaya SO and Enemuoh FO

This work presented a microcontroller based system that can be used in distribution transformer protection. The system checked the operating parameters of the transformer (current and voltage) and reported the quantity that was flowing through the transformer. The system was designed such that it was able to detect currents above the normal operating limits (transient currents) and isolated the power transformer from the distribution line. This isolation process was to ensure that the transformer is safe from any excess current (external fault). Excess current causes overheating of transformers and equipment which consequently gets damaged if not controlled. The scheme discussed in this work therefore gave a solution to this problem. It also provided the need to reduce cost of maintenance and ensure that supply of electricity to consumers is not interrupted for a long period. A SET-RESET (S-R) flip flop was used as an interfacing instrument between the power transformer and the circuit breaker emulating the operation of the PIC16F690 microcontroller. This was as a result of the inability of the software adopted to
incorporate the controller into the main model. A circuit breaker was used as the switching gears to isolate the transformer from the power system in case a fault. The Scope and Floating Scope of the Simulink model showed current waveforms and indicated the fault currents. It was observed that at a fault of 1.5MVA, the breaker operated at an interval of 0.05 seconds each of two settings of auto-reclosure. While the system returned back to normal after two shots of the reclosure for a transient fault. The auto-reclosure locked-out after exhausting the two setting time for permanent fault. The targeted objective of this project was the effective operation of the auto-reclosure during fault and was confirmed excellent.