Mitigation of power outages in Rwanda

Abstract

Power outages in Rwanda severely affected most of the Western and Northern grids of Rwanda in 2018, 2019, and 2020. This paper studied the causes and mechanism of power outages and developed the methods and techniques to mitigate the power outages. Two operational elucidations such as a balanced steady state control system and an optimal overcurrent relay settings model for operational HV substation relay coordination have been proposed and developed. The sustainable synchronism between Rwanda Power system regions was becoming difficult over time due to load disturbances/changes. The under and over frequency, and under and over voltage load shedding techniques have been taken to reduce and mitigate the system outages. However, in order to minimize power outages in emergency regions, these systems have been extended in different regions such as Western and Northern grids which need to be maintained. The PID controllers for enhancing and mitigating the power outages have been developed in single and two area power systems. The load disturbance injection of 50MW has been created. Matlab/Simulink 2017a have been used to simulate the frequency load control, overcurrent relay, and power system models. The relay coordination and settings for a 110/15kV substation with a 17156.48A and 13987.10A of maximum and minimum fault currents, plug setting (PS), and actual operating time of the different relay have been ascertained and modeled. The simulation results have been compared with and without PID controller installation in the power system and it has been shown that the frequency response characteristics for single and two area networks in western and northern grids have been minimized to 0.0 Hz, 0.0 Hz, and 2.5 sec for overshoots, steady state errors, and settling times after cascade outages respectively.The overcurrent substation relayshave been coordinated with the expected times of 0.0924–0.0622sec, 0.0949–0.0720 sec, and 0.0764–0.0661sec for extremely, very, and standard inverse relay characteristics, respectively.