Publications

As the largest LNG Plant in Indonesia, PT Badak NGL (PTB) operates four out of eight units of process train with a total LNG production of 11.5 mtpa. Twelve power generators capable of generating 150 MW are supporting this production process. The electrical power is distributed through 34.5 kV ring bus as well as 13.8 kV, 4.16 kV, and 480 V secondary selective radial configuration. Since its commissioning in 1977, there were 7 unprecedented transformer failures in PTB plant in the period of 2011-2016. From those seven failed transformers, four of them were sudden failures. These failures led to transformer replacement, which could take up to one year of downgraded situation. Therefore, a method to determine the overall condition of PTB’s transformers needs to be developed. For this purpose, Health Index (HI) method is used. HI represents the general condition of transformers based on site testing, laboratory testing, and operational condition evaluation. In this paper, 16 parameters are used to calculate the HI. These parameters can be grouped into 5 categories which are winding insulation condition, insulating paper condition, dissolved gas analysis, transformer oil condition, as well as age and loading factor. The weighing factor is determined based on three different methods. Twenty transformers from a total of 99 transformers were evaluated. The age is varying from 3 to 41 years old. The evaluation results showed the scoring and ranking of assessed transformers. Moreover, it can be used to estimate the expected remaining life of transformers. This HI is very useful to develop a recommendation regarding the number of transformers that would likely require replacement within future time horizons. Keywords: transformer, failure, health index, assessment, maintenance strategy