Electrical stress can cause several disturbance or failure on transformers. It can cause minor fault like tripping transformers or mayor fault like explotion of the transformers. Electrical stress can caused by external fault (distrubance) or internal fault. Some external fault which is causing electrical stress : overload, over current, under voltage, over voltage, ground fault, low power quality, and high electromagnetic pulse. This fault has been secured with protection system on transformers. So it can’t disturb transformers system. When transformers have this fault. e.g. : overcurrent, under voltage, or over voltage it generate heat in winding andincrease the possibility to arching fault. This two fault have highest possibility to transformers failure or transformer explotion.
The main parameter for insulation system in oil transformers is Breakdown Voltage (BDV). Breakdown voltage value indicate the power of oil to insulate or hold the electric charge Some electrical stress which is generated by internal fault is partial discharge and arching. Partial discharge and arching is generated when two spot have high potential (voltage) difference. So the electric charge move to lower potential (voltage) LV side or ground. when this electric charge can be hold by insulation system, generate corona effect. Arching like the partial discharge. But, when the insulation system can’t hold the electric charge. So the electric charge move continuously to the lower side ( LV side or Ground ) it generate short circuit in transformers system. Short circuit generate heat and failure on transformers system. When arching (short circuit) occur in long periode it can cause the transformers explotion.
Oil transformers function as insulation system on transformers. When the electric charge move to lower side (LV or ground ), it can be held by oil transformers. So the transformers system can avoid the arching or short circuit. The main parameter for insulation system in oil transformers is Breakdown Voltage (BDV). Breakdown voltage value indicate the power of oil to insulate or hold the electric charge. The oil like the isolation material for electricity, the higher BDV value so the higher isolation/insulation value. This is the main protection in insulation system oil transformers. PT. Petrolab Services analyze this parameter using IEC 60156 international standard.
The main parameter for insulation system in oil transformers is Breakdown Voltage (BDV). Breakdown voltage value indicate the power of oil to insulate or hold the electric charge
Refferences :
- https://www.electricaloilservices.com/?faqs=what-is-the-difference-between-uninhibited-and-inhibited-electrical-oils.9th July 2015
- Shkolnik, Andy. https://www.sdmyers.com/knowledge-vault/oxidation-inhibitor-and-reinhibiting-oil-filled-transformers/.16th July 2013