Design, Reliability and Operational Consideration of Wind Turbine Generator Transformer

In present context, wind power is currently one of the most popular renewable power origins for producing power. To meet the growing energy demand, the volume of the wind energy farm is constantly growing. Due to development of large utility scale wind energy farm, reduction in LCOE (Levelized Cost of Energy) and demand for enhanced reliability of energy supply has been marked. In wind energy farm, wind turbine generator (WTG) transformers are among the most important parts and are utilized in vast quantities in bigger wind energy farms.

Depending on available wind charecteristics like velocity, direction etc., power output from wind energy farm is inherently intermittent. Accordingly, WTG transformers have variable loading charecteristics. These transformers operate only at part load for majority of the time. Hence, selection of design parameters judiciously may be allowed, this not only lowers the transformer’s initial cost but also aids in life cycle cost optimization and enhancement of reliability of operation.

Project timelines of wind energy projects are very stringent, and these projects are located at remote areas. New areas of emphasis are project cost reduction measures, lowering the high maintenance cost due to difficulty in approach to the remote location installations (offshore & onshore), decrease of aux power consumption along with enhancement of reliability of operation with the observation of very low tariff for the forthcoming projects.

This paper presents architecture of wind energy farm with its components details, Energy generation profile of wind turbine annually and wind turbine generator transformer loading cycle calculation, Analysis of estimation and comparisons of transformer losses, lifespan, and potential of cost savings for WTG transformer presently employed design & operational practices and that with the proposed concept. Choosing an appropriate short-circuit impedance of WTG transformers with varying ratings of wind turbine generator and converter based on techno-economical consideration. Adoptation of methodology for WTG transformers ONAN ratings consideration and their proposed operation in ONAF mode, frequent switching-on operation along with probable mitigation of switching surges over voltages, frequent intermittent loading operation consideration along with probable mitigation of partial discharge (PD), probable mitigation of harmonics affect, probable enhanced over-voltage capability consideration in these transformers to mitigate any over speed of wind turbine generator, probable enhanced thermal and dynamic capability requirement consideration to meet the low voltage fault ride through capability during any through fault condition, dry type transformers located at nacelle specially for offshore installations design & reliability enhancement to mitigate probable surrounding harsh climatic condition, operating environment & fire protection and high vibration. Simulation of software, mathematical computation, and analysis of techno-economic aspects will be presented in detail.