On-site testing and PD diagnosis of cast-resin distribution transformers

Distribution transformers undergo routine and type tests in accordance with IEC 60076 [1, 2, 3]. Amongst others, these tests include induced voltage tests combined with partial discharge (PD) measurement as well as measurement of no-load losses, load losses and short-circuit impedance. During its operation, transformer experiences operational stress and ageing processes. To be able to assess the condition of the transformer and to estimate its remaining lifetime, on-site tests are a helpful tool for transformer manufacturers as well as Distribution System Operators (DSOs) and their respective service suppliers. This paper describes a modular test system to carry out these tasks properly taking into consideration the potentially narrow installation of the test object.