Logical selectivity for medium voltage overcurrent protection and its verification via co-simulation tool for the responses of the power and communication network.

This thesis deals with the modelling and simulation of MV network overcurrent protection using EMTP. Transmission lines 25 Km in length for both radial and loop network with constant parameters operates at 50 Hz and 66 kV line to line voltages are simulated using EMTP. The first part of the thesis discusses the simulation of Radial network with unearthed neutral for analysing the behaviour of the fault current making the comparison with healthy feeder. Second part is to use a Radial network with compensated neutral, Petersen Coil (PC) is used for compensation of the short circuit current making the similar comparison. Third step is to design a 67N directional replay protection in EMTP to trip the circuit breaker in the fault situation. Then using both Radial and Loop network, a comparison and response of the 67N protection in both situations is analysed. Several simulations of Single Line to Ground Faults (SLGF) with different fault locations were carried out to verify the correct operation of the relay based on the developed protection scheme. The results of the simulation the operation of the relay based on its protection scheme and its response time based on the fault location. Finally, delay between the blocking signals are inserted to see the behaviour of the protection system under loop network configuration