The Southern California Edison Company (SCE) operates a fleet of 285 HV and EHV substation power transformers. Failure of one of these banks can have a significant financial and operational impact. Online dissolved gas analyzers (DGA) and bushing monitors for power transformers
have become increasingly popular. The decision to apply online monitoring is usually driven by the criticality of the transformer and the consequence of an unplanned outage, whether lost production at a generator or industrial site or customer minutes lost within a utility network.
To reduce this risk, the strategic decision to equip the whole SCE fleet of EHV and HV transformers with online multi-gas, moisture, and bushing monitoring systems was made. This monitoring strategy is expected to result in:
• improved HV and EHV transformer reliability,
• reduced failure impacts,
• realization of complete transformer useful life, potentially several years beyond the nominal expected life,
• identification of units in urgent need of repair / replacement,
• early recognition of problems that the OEM’s warranty should cover,
• substantial reduction in overall transformer operating risks,
• improved accuracy of transformers health assessments.
Application of a comprehensive online DGA, moisture, and bushing monitoring strategy across Sothern California Edison’s (SCE’s) fleet of EHV and HV transformers provides both technical and operational benefits to all stakeholders. A detailed business case and financial model have been developed to show that SCE’s online DGA strategy is also economically prudent