Degree of polymerization estimation of insulation papers in power transformers based on load and temperature histories in Java-Bali Region of Indonesia National Electric company

Degree of polymerization (DP) is thought to be a good index to determined deterioration level of insulation paper in power transformers. In practical conditon, using this method is complicated and expensive due to the necessity of disasembling the transformer. Therefore an alternative method has been expected. In this paper a new method to estimate DP from load and temperature histories is proposed. The exsistence of moisture also considered. Mechanical strength of insulation paper of power transformers in Java Bali Region is assesed using the estimated DP based on the real load and temperature data. Furthermore failure probability of those transformers is considered based on the design stresses in a transformer winding generated by fault currents. Finally the estimated DP values are compared with those from furfural test.