Abstract:
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 relays have 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.