Condition assessment and fault diagnosis of two load tap changers using dissolved gas analysis

Considering the objectives of "condition based preventative maintenance strategy", condition assessment was performed over two load tap changers of 125 MVA power transformers in 230/63 substations using dissolved gas analysis (DGA). The selected load tap changers were: (1) an MR M-type load tap changer and (2) an Elin load tap changer. Choosing load tap changers of 230/63 kV power transformers are quite reasonable since the mentioned power transformers are the most frequently being used power transformers in Iran. The oil samplings were performed according to ASTM D 3613 standard, in two stages and in a three-month interval. Furthermore, samples were analyzed for dissolved gases considering ASTM D 3612 standard.