Analysis Of Offshore Platform Current Transformer Failures

Abstract

Trip of a diesel generator (DG) differential protection relay in an offshore platform caused delays in remanning and production restoration after hurricane evacuation. This was the first DG differential protection trip since platform commissioning ~12 years back. Investigations revealed that current transformer (CT) casing had cracked to the extent of dislodging CT conductors resulting in differential protection trip.Damaged CTs were replaced by in-stock spare CTs. However, a couple of years later a similar differential trip occurred and was resolved by again replacing damaged CTs with in-stock spares. It became evident that a simple remediation of replacing damaged CTs will not help, as the trips started to happen more frequently only months apart.This paper analyses DG trip incidents, describes root cause failure analysis (RCFA), and presents remedies and learnings to mitigate the issue.