Design of an Automatic Transfer Switch for Seamless Generator-to-Grid Changeover in Commercial Buildings in Kaduna

This project designs and implements an automatic transfer switch that provides seamless changeover between the public electricity supply and a standby diesel generator for commercial buildings in Kaduna State, North West Nigeria. Frequent and unannounced grid power outages in Kaduna cause data loss, equipment damage, and operational disruptions in commercial premises including offices, hospitals, and hotels that depend on continuous power. The designed system monitors the utility supply voltage and frequency using a precision sensing circuit. When grid voltage drops below 195V or grid frequency deviates beyond the 47.5 to 52.5 Hz band for more than three seconds, the system signals the generator to start and, after confirming stable generator output, activates a double-pole transfer contactor to connect the building load to the generator supply. Upon restoration of acceptable grid supply, the system waits a configurable settling period before transferring the load back and signalling the generator to cool down and shut off. The control logic is implemented on an ATmega2560 microcontroller with a real-time clock for event logging. Transfer time from grid failure to generator supply was measured at an average of 12 seconds, including generator cranking and settling. A manual override facility allows maintenance engineers to control the changeover independently. The prototype was installed and validated at a commercial office building in Kaduna, operating reliably through 47 changeover events over a four-week monitoring period. Keywords: automatic transfer switch, generator changeover, power outage, Kaduna, standby power.