A resonant transformer for high voltage testing of generator stators

Abstract

A partial core transformer has been designed such that its magnetising reactance has been matched to a generator stator insulation capacitance. The reactive current drawn by the stator insulation is provided by the transformer magnetisation This means that the supply only has to provide the real power losses of the transformer and in practice any mismatch between the magnetisation current and the stator capacitance. A high voltage inductor was designed and used in the testing of a generator at a New Zealand power station. It supplied 115kVAr of reactive power compensation at 23kV. The inductor was turned into a resonant transformer by the addition of a low voltage primary. A laboratory test showed that the required high voltage of 23kV could be obtained from energising the primary at 285V at 60A or at a rating of about 1/7th the load. A further resonant transformer was then designed for a 334kVAr capacitor load to test generator stators at 31.5kV. This transformer was supplied from a nominal 400V supply and gave a gain in kVA of 16. The transformer has a finished weight of approximately 300kg.

Keywords:

• Resonant
• transformer
• high-voltage
• stator
• generator
• testing

Additional information

Notes on contributors

Pat Bodger

Pat Bodger

Pat Bodger completed his BE (Hons) and PhD degrees in electrical engineering from the University of Canterbury in 1972 and 1977 respectively. From 1977-1981 he worked for the Electricity Division, Ministry of Energy, New Zealand. He was appointed as Lecturer in the Department of Electrical Engineering, University of Canterbury in 1982. He is now Head of the Department of Electrical and Computer Engineering and is Professor of Electric Power Engineering. He is also Director of the Electric Power Engineering Centre.

Wade Enright

Wade Enright

Wade Enright completed his BE (Hons) and PhD degrees in electrical and electronic engineering from the University of Canterbury in 1992 and 1995 respectively. During 1996 he worked for the Manitoba HVdc Research Centre in Canada. He spent 1997 with the Electricity Corporation of New Zealand Ltd. In 1998 he returned to the University of Canterbury to continue Transformer Research. In 1999 Wade formed his own professional engineering company “Viva.” Through “Viva” he offers technical services to industry. Wade continues to lecture/research at the University of Canterbury.