Implementation of a transformer monitoring solution per IEEE C57.91–1995 using an automation controller

Distribution network operation periodically exceeds the loading capabilities of a substation power transformer. This can result in accelerated insulation aging and, in some cases, failure due to complete deterioration of the insulation. The solution described in this paper allows users to monitor critical substation transformer assets with a comprehensive transformer thermal model per IEEE C57.91-1995. An automation controller calculates the transformer loading capability rating. The substation operator may initiate control action based on a warning or alarm that the transformer is overloaded and in danger of excessive insulation aging or loss-of-life. The hottest-spot temperature of the transformer core is used as a basis for calculating the insulation aging acceleration factor and loss-of-life quantities. CenterPoint Energy intends to use this information to better manage their transformer assets and further utilize the power transformer near its actual thermal limits.