Different Electric Vehicle Charging Strategies to avoid Reducing the Insulation Oil Lifetime of Distribution Transformers

The widespread presence of uncontrolled electric vehicles causes overloading of distribution network equipment. One of these equipments is distribution transformer, which should pay attention to overloading and reducing lifetime of this equipment due to charging of electric vehicles. First, strategies have been proposed to investigate the effect of electric vehicle penetration level and charging on network equipment. From these strategies, with the help of Monte Carlo simulation, electric vehicle charging models are obtained for 24 hours. The first strategy involves slow and fast uncontrolled charging modeling in the residential and work areas, and the second strategy is charging only in the workplace. In these models with having parameters such as number of cars, base load, trip information, and electric vehicle penetration coefficient, obtain load profile from summation of total normal load and electric vehicle charge. And then load profile will be given to thermal model of distribution transformer. The output of the thermal model is the transformer hot spot temperature. From the hot spot temperature of the distribution transformer, a reduction in the lifetime of the insulator is obtained, which indicates a reduction in the lifetime of the distribution transformer. The results show that to reduce the lifetime of distribution transformer, it is better to use electricity tariff to smooth the load profile. For simulations MATLAB software is used.