The Tennessee Valley Authority´s (TVA´s) experience and action plans with freestanding oil-filled current transformers (CTs)

Historical background data are provided on current transformer (CT) failures, and some initial, unsuccessful attempts to correct the problem are discussed. Attempts to detect incipient failures by sampling the oil periodically revealed the weaknesses and hazards in the initial program. A task force was established to develop safety procedures that would minimize hazards to personnel working in the areas of suspect oil-filled CTs. The task force also developed an online monitoring device that detects incipient failures so that CTs can be removed from service before catastrophic failures occur