Impact of Electric Vehicle Charging Loads on Distribution Transformers: A Case Study for Sri Lanka (Residential Areas)

Abstract

Electric vehicle (EV) adoption in Sri Lanka is accelerating rapidly, with a large number of new registrations in 2025 alone. This surge poses significant challenges to residential distribution networks, particularly in high density areas. Uncoordinated home charging stresses distribution transformers through increased peak loads and accelerated thermal aging. This paper investigates these impacts using operational data from Lanka Electricity Company (Pvt) Ltd and regional registration statistics. We find that unmanaged charging during evening peaks leads to frequent overloading and reduced asset reliability. To mitigate this, we propose a Smart Home Charging Management System (SHCMS) featuring weekly energy quotas, dynamic load based pricing, and automated rate throttling. Simulation results demonstrate that the SHCMS can successfully flatten load profiles and extend transformer insulation life. This work provides a scalable framework to enhance EV hosting capacity in developing power grids without immediate infrastructure upgrades.