Study of relaxation mechanism on a power network

An attempt was made to study the on-site relaxation mechanism of equipment in a power network consisting of a 30 MVA alternator, a transformer, underground cable and 66 kV SF₆ gas insulated switchgear (GIS). The objective of the study is to obtain a signature of the aging of the equipment. Toward this end, measurements were carried out before and after the treatment of the transformer oil, with and without the alternator connected to the transformer. Field difficulties encountered and observation from the tests are reported. The measured data was then used to identify the parameters of the extended Debye model. Furthermore, the validity of the frequency response analysis (FRA) on detecting transformer faults was investigated. It shows that the technique is very sensitive to fault occurrence and much information can be extracted from the test results