Condition monitoring system for power transformers

The lifetime consumption of oil immersed power transformers mainly depends on its load. To take special attention on the behavior of power transformers, a monitoring system was developed. The system measures the current load, the voltage, some typical temperatures, the tap changer position and the state of fans and pumps of all cooling units. Additionally, the output signals of a gas-in-oil sensor and an oil humidity sensor are evaluated. This paper describes the both the hardware setup and the monitoring algorithms used in the system. In order to determine the winding temperature distribution with improved accuracy, a thermal model has been designed.