LARGE TRANSFORMER FAILURE
Areas of expertise include electrical engineering, utility maintenance practices, evidence examination and tracking, common modes of failure involving large plant equipment, and cultural awareness in an international environment.
In north Jakarta, Java, Indonesia, a large power transformer at a combined-cycle power plant facility experienced a major failure involving extensive damage to upper exterior areas of the main tank, cooling fins, and one of the HV bushing turrets. The incident was further characterized by sustained burning around the affected areas for more than 30 minutes.
An engineer from ProNet Group was retained by the asset owner and insurance claims adjuster to investigate the incident and identify the root cause of damage. ProNet Group was also requested to identify potential countermeasures to protect against future incidents and brief the plant owner’s maintenance team accordingly.
Electrical Engineering – ProNet Group attended two site visits together with the insurance claim adjuster. During the first visit, ProNet’s engineer inspected the overall damaged unit which had remained in place since the incident occurred. The visit also included meetings, interviews and discussions with the plant owner’s on-site staff before and after the inspection. During the second visit, ProNet’s engineer inspected disassembled portions of the damaged unit including the HV bushing turrets which had been removed from the main tank. ProNet’s engineer also inspected exposed areas of the main tank made possible by the removal of the HV bushing turrets.
ProNet’s engineer was able to identify the root cause of failure as a defect which developed in one of the HV bushings as it approached a premature failure condition. Upon failure of the bushing, several incidents of arcing occurred between the HV Phase ‘T’ conductor inside the bushing and the nearby grounded transformer tank once conductive paths were established. The HV bushing failure was additionally evidenced by partial melting of the conductor and multiple arc strikes found on the inner wall surface of the Phase ‘T’ HV bushing turret. ProNet’s engineer also briefed the plant maintenance staff on suggested plant improvements, countermeasures and key maintenance activities for the HV bushings.