Thermal monitoring on power transformers

Transformers are one of some important equipments on electricity network. Each utility, in this case PLN P3B Jawa-Bali, has to assure their reliability in order to maintain electrical power system stability by assessing transformer conditions. Once transformer condition attained, appropriate maintenance and operation strategy can be defined. Based on failure investigation, transformer conditions are influenced by its insulation condition. PLN P3B Jawa Bali has applied dissolved gas and oil characteristic diagnostics. Since the load grows faster than the network expansion, our transformers tend to be operated at their nominal value or even overloaded. We also find out that through fault current is one of transformers failure root causes. Therefore, we are developing on-line thermal monitoring and vibration in order. The oil and winding temperatures are dependant to load. As the load increases to its nominal value, risk due to transformer paper insulation damage caused by disturbances becomes higher. Subsequently the situation will accelerate the transformer to ageing. By recognizing the raise and fall function of these temperatures to load we can identify the thermal characteristics of the transformer. Other characteristic will be identified is dissolved gas increase caused by feeder faults. Based on these characteristics we are able to conduct some actions, for example: maintaining the temperatures in safe range by controlling cooling system (prohibiting ageing) or determining the condition status of the transformer at that particular time. In this paper we would like to describe our experience in developing the thermal statistic characteristics using load and temperature manual data acquisition, and dissolved gas produced by feeder faults.