The through fault current effect of 150/20 kV transformer to its insulation resistance and Tan Delta test in PT. PLN (Persero) TJBB APP Durikosambi

In 2014, PT. PLN (Persero) P3B Jawa Bali has 150/20 kV power transformers as much as 695 transformers. The average lifetime of 150/20 kV transformers is 14.55 years while it was designed for 40 years. The delayed of feeder protection on handling disturbance can cause through fault current of the transformer. The magnitude and duration of fault currents are of utmost importance in establishing a coordinated protection practice for transformers, as both the mechanical and thermal effects of fault currents should be considered. On IEEE Std. C57.109-1993 with no explicit mention that the withstand capability of the transformer is at maximum short circuit current with 2 s duration. Through fault current may have an impact on the decrease of transformer insulation. The transformer insulation diagnosis can be done by resistance test and dissipation factor test. Resistance test can reveal the obvious faulted transformer winding such as shorted turn or open winding. Dissipation factor test provides the characteristics of insulation have deteriorated or not. By comparing through fault current occurring on the transformer with insulation tests, the effect of through fault current to transformer insulation can be found. It is used to analyze, evaluate and provide appropriate treatment for the transformer. In this paper, the samples were taken from several substations in the scope of APP Durikosambi with a reference to substations that has several transformers with same specification. The results show that the through fault current affects insulation, increase CHG and CHL value of dissipation factor and does not affect the other values of dissipation factor. The increase of dissipation factor CHG and CHL is directly proportional to the frequency and magnitude of the through fault current on the transformer, while for the other dissipation factor is not affected by the through fault current of transformer. Therefore, the through fault current affects the transformer insulation in primary winding. This paper compares through fault current with the insulation resistance that shows through fault current doesn't affect insulation resistance.