Power transformers
Power transformers convert electrical energy between voltage levels all the way from power production to the end user consumption. A transformer consists of at least two windings on an iron core mounted in a tank. Conventional oil- and paper insulation is completely dominating. The challenges of the business sector are to manage an ageing transformer population, having a potential long life, and assuring that new units maintain correct quality. Related to this condition monitoring and test methods are important aspects.
Internally, aspects like ageing of materials, width-stand strength, transient behaviour, short circuit capacities and thermal design are all important for a the transformer’s quality. Externally, the transformer interacts with the power system which stresses it with overvoltages and over-currents, and the transformer stresses the system back with inrush currents. SINTEF and NTNU are co-operating in research in all these areas.
Topics covered are:
- Ageing of transformers; oil and cellulose insulation
- Maintenance; oil reclamation and drying
- Diagnosis of oil and paper samples; evaluation of moisture and contamination
- Formation of copper sulphide as a failure mode
- Measurement of partial discharges for fault localization and type testing
- Calculations and testing of thermal conditions
- Properties and testing of new insulation materials
- Continuous monitoring
- Insulation co-ordination
- Measurement and modelling of inrush currents
Post-mortem investigation of winding
