In today's advanced communication, electronic and electrical technology, the used of Electromagnetic Interference (EMI) filter has almost become mandatory. Therefore it requires careful and high attention on the impact of this EMI filter installation. This paper discussed and explained the application of Earthing Current Signature Analysis (ECSA) as new developing technique in determining the earth leakage current contributed by the EMI filter installed in the Alternating Current (AC) Uninterruptible Power Supply (UPS) system in Oil and Gas industry.