It is widely accepted that one of the most significant contaminants affecting the performance of liquid immersed transformers is moisture. Because of its importance, many standards and guides give various descriptions of the effects of moisture, various recommendations on the acceptable levels of moisture, recommendations for the determination of moisture and moisture mitigation techniques. This guide is intended to consolidate available state-of-the-art knowledge for moisture related parameters in liquid immersed transformers and to serve as a reference that other standards and guides can refer to.

This guide applies to liquid immersed transformers and reactors and addresses: * Moisture related phenomena and parameters in transformers and reactors * The theory of moisture dynamics in solid-liquid and solid-liquid-gas insulating physical complexes * Methods of assessment of moisture related parameters in solid-liquid and solid-liquid-gas insulating physical complexes * The effects of moisture on operating transformers and reactors, and the risks associated with these effects * The establishment of a baseline for each moisture related parameter * The tracking and interpreting of changes against the baselines throughout the life of the transformer or reactor

This guide recommends methods for: * the assessment of moisture and moisture related phenomena in liquid immersed transformers and reactors * the establishment of a baseline for each moisture related parameter * the tracking and interpreting of the changes against the baselines throughout the life of the unit