Impact of photovoltaic generation on the allowed revenue of the utilities considering the lifespan of transformers : a Brazilian case study.

Abstract

This paper investigates the effect of distributed photovoltaic (PV) generation on the aging of overhead dis- tribution transformers and on the allowed revenue of the utilities that defines tariff readjustments. A metho- dology based on the calculation of the depreciation rate of assets and replacement of transformers as a function

of transformers’ aging is proposed. Different penetration levels of PV generation are considered by means of a probabilistic load flow using the Monte Carlo simulation method. Randomness of the load, solar irradiation, location of the PV systems and ambient temperature are modeled. Three indexes are defined to represent the effects and conduct the discussion. The network hosting capacity is analyzed in relation to overvoltage and overcurrent impacts. A realistic case study based on representative feeders of a distribution utility in the southeast of Brazil is conducted by computer simulations. Results indicate that the effect of distributed PV of increasing revenue readjustments occurs at PV penetrations higher than 40%. Overvoltages can limit the amount of distributed PV only at very high penetration levels and overcurrents are not a major problem.