Diagnosis Of Withstand Test Power Transformer Based on Through Fault Current Disturbance

Transformers damage happened in Transmisi Jawa Bagian Tengah from 2008 until 2015 as much as 54 times. Active part damage, especially in winding, are the most major cases happened as much as 34 from 54 damage (63%), it was almost caused by Through Fault Current in seconday side of transformer (feeder). Diagnosis concept applied in PLN Transmisi Jawa Bagian Tengah considered into three (3) level assessment, there are health assessment, risk assesment (component level) and risk assessment (corporate level). The scope of this paper only discuss health assessment with condition index in each measurement for 21 unit step down power transformers which have been passed over withstand capability calculation. Measurement result grouped into condition index to see what is the dominant effect from through fault current and to correlate the relationship between one measurement with anothers. In conclusion, from all of type measurement were done, the worst effected by through fault current which produces high current in transformer winding and high mechanical stress caused by magnetic force resulting in obvious distortion at secondary side (low voltage) of transformer within deformation between main and tap winding and also dielectric stress resulting from high current impulse showed by Oil test (DGA) indicated that most of them were in thermal fault in oil (overheating) and thermal decomposition in paper, thermal effect on transformer to stand short circuit current and increasing the peak loading of transformer above 70% has significant impact on temperature rise oil/winding.