Optical methodology for the health assessment of power transformers

Among the most critical components in the electric power system is the power transformer. As such, a significant body of research has been put forward to attempt to anticipate the needs for maintenance to be performed. Traditional health assessment has required sampling. of oil for submission to a laboratory for analysis, but this has been deemed undesirable in light of budgetary constraints on maintenance staffing., and new predicitve maintenance philosophies for substation equipment. A number of processes have been developed in recent years for online health assessment of transformers, most of which have focused on dissolved gas analysis. This paper describes a novel optical methodology for on-line transformer health assessment that utilizes an ultraviolet absorption measurement to identify the degradation of the transformer oil. An optical system was selected because of its immunity to the electromagnetic noise typical of substations, and because of the minimal impact that non-conducting materials have on the insulation system design of the transformer. The system is designed to identify deterioration and premature aging resulting from overheating; low level arcing or excessive exposure to atmospheric air. The system consists of a light source, filter, guide and detection components, and a very simple computational requirement. The measurements performed with the prototype system are validated with a high precision spectrophotometry measurement and an independent oil-testing laboratory.