Methods for calculation of the marginal exploitation lifespan of power transformers 35 rV and higher based on the state indexAlexandr Nazarychev, Dmitriy Andreev, Alexey Tadjibaev, Svetlana Vysogorets and Ilia SulynenkovE3S Web Conf., 58 (2018) 02006DOI: https://doi.org/10.1051/e3sconf/20185802006