Use of gas concentration ratios to interpret LTC & OCB dissolved gas data

Dissolved gas analysis, DGA, has been universally accepted as the preeminent diagnostic tool for location of incipient faults in oil filled transformers. DGA has more recently been applied as a diagnostic tool for predictive maintenance on load tap changers, LTC's, and oil filled circuit breakers, OCB's. The savings in maintenance costs based on DGA diagnostics are significant. Data interpretation for OCB and LTC dissolved gas analysis is empirical in nature and significantly different than interpretation of DGA data for main tanks. Ratios of heating to arcing gases are informative for LTC and OCB dissolved gas analysis interpretation.