Impact Study of Electric Vehicle Charging on Thimphu Distribution Network

Since the introduction of electric vehicles (EVs) in Bhutan in 2014, the number of EVs in the country has increased to 581 by 2023, according to the Bhutan Construction and Transport Authority (BCTA). This demand would pose challenges to power utility (BPC). It is therefore important to assess whether the existing low voltage (LV) distribution network can handle this additional load from EV charging stations. This paper evaluates the impact of EV loads to the LV distribution network of Thimphu, by modeling and simulating the LV networks using DIgSILENT PowerFactory. Using the one-year load data of 2023, the quasi-dynamic analysis is carried to investigate the daily, weekly, monthly and yearly variation of networks parameters and loading profiles with more focused to the networks connected with EV loads. Key factors considered were bus voltage profiles, transmission line and transformer loadings. The analysis from the seasonal variations in EV charging habits indicated that there is currently no significant impact of EV loads on the networks except Changedaphu substation and its interconnected lines and transformers tend to overload in winter especially during peak hours.