Economic benefit and risk evaluation of power transformer overloading

Power transformers have inherently some margin of overloading capability. The rated power of a unit is basically the load level that will result in internal temperatures that are below the limits set forth by standard producing bodies such as IEEE and IEC. The normal life expectancy is a conventional reference basis for continuous duty under normal ambient temperature and rated operating conditions. The risks associated with overloading can be drastically reduced if the transformer conditions are closely monitored throughout the overload period. This paper discusses the cost/benefit evaluation of transformer overloading. It appears that cost/benefit analysis of transformer overloading with on-line monitoring is feasible and that a consistent financial model can be produced to calculate the payback time. This calculation requires hypothesis on load magnitude and duration along with economic conditions prevailing during the overload period