Hydro Generator High Voltage Stator Windings: Part 1 – Essential Characteristics and Degradation Mechanisms

Abstract

About 17% of global electricity is generated from hydro power, which is still the only commercially viable renewable energy produced on a large scale (IEA, 2001). Only about 33% of Earth’s hydro potential has been developed so far, and given the increased environmental awareness and scrutiny, it is most unlikely that much of the available hydro potential will ever be utilised. The ageing Australian installed hydro generating capacity of approximately 7600 MW is mostly 30–60 years old and approaching its half-life refurbishment. Most of the generators of that vintage were generously sized by today’s standards, and offer an opportunity for uprating of their output as part of the refurbishment process. The understanding and correct specification of hydro generator high voltage (HV) stator windings is vital to the success of generator renewal process. The high voltage hydro generator stator windings are exposed to a variety of continuous and transient stresses, all having deleterious effect on the windings’ long-term durability. In general, HV winding life expectancy will depend on thermal degradation of insulation, electrical degradation of insulation, mechanical stresses and environmental winding contamination. Most often, the winding degradation occurs as a result of combined stresses, and is often referred to as multi-stress or multi-factor insulation ageing. The author has spent his working life designing and manufacturing high voltage stator windings, and is presenting a series of four informative papers on hydro generator HV stator windings as an Australian contribution aimed at the engineers involved with hydro generator refurbishment and uprates. This paper is the first in this series describing the essential characteristics of hydro generator stator windings and their degradation mechanisms.

Key Words:

• Hydro electric generators
• high voltage windings
• high voltage insulation
• power generation
• rotating machines
• synchronous generator

Additional information

Notes on contributors

M.M. Znidarich

Michael Znidarich graduated with Associate Diploma of Engineering (Electrical) in 1993, and Associate Diploma of Engineering (Mechanical) in 1995, both from TAFE in Perth, Western Australia. He received his BTech (Electrical), MTech (E&M), and ME (Electrical) degrees from Deakin University in Melbourne in 1999, 2001 and 2003, respectively. He is currently in the final stages of his PhD degree from University of Western Australia related to design of large synchronous electrical machines.

Michael was born in Croatia, where he completed his electrical apprenticeship in 1968. Since emigrating to Australia and for the past 32 years he has worked with TGE Energy Services in Perth, Western Australia. TGE Energy Services (formerly F. R. Tulk and Co) is a joint venture between Transfield Services Australia and GE Energy Services (Australia). In the early 1980s, Michael was instrumental in the establishment and development of a high voltage coil and bar manufacturing facility, which now has clients in 22 countries around the world. He is currently engineering manager for all three TGE Energy Services facilities (Perth and Bunbury in Western Australia, and Sydney in New South Wales). Michael’s current interests are focused on design of high voltage windings for large electrical machines, applied research on high voltage insulations for rotating electrical machines, and applied engineering for upgrades and uprates of hydro generators.

Michael is a corporate member of Engineers Australia and registered chartered professional engineer in Australia.