Reliability evaluation of distribution transformers with high penetration of distributed generation

• The dynamic thermal aging of distribution transformer has been concerned.
• The reliability evaluation of distribution system in wide spread use of DGs is studied.
• This paper methodology has been applied to a realistic distribution system of Iran.

In this paper, a novel methodology is presented to evaluate the micro-grids reliability concerning the dynamic thermal aging failure of transformers. The widespread presence of distributed generation (DG) units reduces the loading passing through the distribution transformers and consequently improves the dynamic thermal failures. The system reliability is investigated for various penetrations of different scenarios from the view of DG technologies. The introduced method is applied to a realistic distribution system comprising different distribution transformers in Iran. The sensitivity analysis corresponding to adequacy indices such as expected energy not-supplied (EENS) based on DG penetrations is performed. By the use of the novel methodology proposed, it is possible to recognize how different DG technologies and penetrations can impact on the system reliability. The results demonstrate that the diesel generators and hybrid systems including diesel generators, photovoltaic units, and wind turbines are the most promising DG technologies to improve the transformer failures and the reliability of micro-grids compared with renewable DG units.