Some time ago, a case which led to some Interbus Transformer (IBT) or the existing power transformer substation explode in West Java. After investigation by the experts, the main cause resulting in the transformer exploding was the result of the huge load on the transformer which caused the Interbus Transformer (IBT) or Power Transformer work continuously at maximum capacity for too long. This is gave a negative impact on the condition and characteristics of the transformer and its own insulation. Due to the 100% usage for a long period, the transformer internal heat or hot-spot temperature rises and if left unchecked will cause degradation in the transformer insulation, especially in the form of a liquid insulating commonly referred to as the oil and transformer oil. Excessive temperatures can cause a transformer to heat and can reduce the reliability of the work of the transformer. The existence of isolation is very important because in addition to functioning as a separator between the transformer core, this isolation also serves as a cooling transformer so as to minimize the heat caused by the transformer. Because the transformer oil is in a state of heat for some time, then the oil will boil and produce steam-water vapor on the ceiling of the transformer. Later, the water vapors that arise earlier will fall into the transformer oil and will settle on the insulation between the core and also at the core itself. This of course will lead to the breakdown voltage of transformer oil will be reduced because the oil is not pure anymore.