An improvement in protection coordination and criteria settings for Bhutanese power system

Abstract

Overcurrent and ground fault relay coordination have been studied for a pilot 132/33/11 kV Substation in Bhutan. The calculated settings as well as the existing settings have been simulated and the critical findings and recommendations are made. The methodology of overcurrent and ground fault relay coordination are also proposed.

Similarly, the criteria settings for differential relay have been discussed along with the compensation in respect of CT ratio, vector correction, magnetic inrush and zero sequence filtering. The pickup setting followed by 1st and 2nd slope biasing has been discussed.

Further, the distance relay setting has been analysed whereby the parameters and methodology for phase to phase and phase to ground resistive reach setting are elaborated. The field settings are compared with the calculated settings and simulations have been carried out for verifying the results. The distance relay setting calculations are developed through excel template taking into consideration the MiCOM P44x relays. Accordingly, the flow chart has been made in conformity with the guidelines.