Abstract: A microprocessor-based transformer monitoring system to provide continuous on-line monitoring and analysis of transformer operation. The transformer monitoring system periodically monitors various parameters related to transformer load and condition. Maximum, minimum, and instantaneous values of the parameters are stored and analzyed. To perform the analysis, a hierarchy of thresholds is associated with each parameter. When a parameter exceeds any one of the thresholds, a response is produced by the transformer monitoring system. The type of response depends on the level of the exceeded threshold in the hierarchy. The range of response produced by the transformer monitoring system includes: continuing normal periodic data collection and analysis, increasing the rate of data collection and analysis, recommending an on-site physical check of the monitored transformer, reducing transformer load, and taking the transformer off line.

Abstract: A hot-spot temperature monitor for determining the hot-spot temperature of a transformer. The hot-spot temperature monitor determines the largest current flowing in the transformer and using this value calculates a temperature gradient. The temperature gradient represents the difference in temperature between the hot spot and the top-oil temperature. The top-oil temperature is also measured. The hot-spot temperature is calculated by adding the temperature gradient to the top-oil temperature. The hot-spot temperature sensor controls the transformer cooling units and can activate various alarms and indicators as desired.