Abstract:

Effective insulation and earthing systems are essential for ensuring the safety, reliability, and overvoltage protection of electrical distribution substations. Inadequate performance of these systems often results in equipment damage, power outages, and safety hazards. This project evaluates the performance of insulation and earthing systems in selected distribution substations within the Ilesa Road 11kV feeder with the objective of improving overvoltage protection and operational reliability. Field investigations and measurements were conducted to determine insulation resistance values, earth resistance levels, and the condition of earthing conductors and surge protection devices. The measured parameters were assessed against established IEEE and IEC standards to determine compliance and system adequacy. The results indicate that while some substations operate within acceptable limits, others exhibit elevated earth resistance and reduced insulation integrity, increasing their susceptibility to lightning-induced and switching overvoltages. Based on the findings, the study proposes practical improvement measures, including enhancement of earthing electrode configurations, regular insulation testing, and proper coordination of surge arresters. The outcomes of this project provide useful technical guidance for distribution network operators and contribute to improved substation safety, reduced overvoltage risks, and enhanced system performance in similar distribution environments.