关键词: 电动汽车充电负荷；配电变压器；寿命损耗；故障率；蒙特卡洛模拟

Abstract: With the rapid growth in the number of electric vehicle (EV) in use, the large-scale integration of EVs into the distribution network for charging poses new challenges to the power system. As the core equipment of the distribution network, the operational safety and lifetime loss of distribution transformers are more significantly affected by EV charging loads. Considering residential travel and charging behaviors, this paper establishes an EV load model that takes into account both users' fast-charging probability and charging decisions. It employs the Monte Carlo random simulation method to calculate the charging load characteristics of typical residential areas under different EV penetration rates. In accordance with the IEC 60076-7 standard, a transformer capacity assessment model is built, focusing on analyzing the mechanism by which EV charging impacts the hot-spot temperature, lifetime loss, and failure rate of transformers under two scenarios: uncoordinated charging and load leveling optimization.The results show that: for every 20% increase in EV penetration rate, the daily average lifetime loss of transformers can increase by 1.8 to 2.5 times; under the high penetration scenario of 75%, the peak failure rate of transformers is 62.3% higher than that under the base load scenario; after load leveling optimization, the lifetime loss of transformers can be reduced by 81.2%, and the failure rate drops to the level when no EV are connected to the grid. The research in this paper can provide theoretical support for the assessment of connecting charging piles to distribution transformers in old residential communities and the dispatch of ordered EV charging.

Key words: electric vehicle charging load; distribution transformer; lifetime loss; failure rate; Monte Carlo simulation