Page 56 - North American Clean Energy March/April 2019 Issue

wind power
Reliable Insulation
System for Wind
Turbine Generators
by Jon Vaquerizo
Energy policies around the globe continue to focus on the increasing need for renewable energy, and the wind industry is at the lead of developing technologies. To remain competitive in the clean energy market, the Cost of Energy (CoE) must be considered, along with other main factors such as CAPEX, OPEX, reliability, and component lifetime.
Wind turbines include, in the nacelle, electric generators such as Doubly
Fed Induction Generators [DFIG], Squirrel Cage Induction Generators [SCIG], and Permanent Magnet Synchronous Generators [PMSG]). One speci c design has to perform under very di erent and demanding conditions in all kinds of environments: low/high temperature, standard/high altitudes, dust and desert conditions, low/high humidity levels, coastal areas with corrosion, and situations with chemical stressors. Even within the same wind farm, generators di er in performance depending on the power distribution layout. e life expectancy of components can be a ected by external factors such as over-voltages. Additional operating inconsistencies in the eld, like grid con guration, di erent frequency converter operation modes, and switching frequencies during synchronization/ grid disconnection, are not always part of the speci cation requirements or insulation system evaluation standards.
e Electrical Insulation System (EIS) is critical in designing a generator, and a key factor in the life span of the component. Unfortunately, 95 percent of repairs cannot be addressed up-tower, so reliability is a must. It’s always a trade-o when weighing the cost of the EIS against the need for safety and reliability. In order to reduce the time-to-market, EIS standardization is based on minimum requirements based on common standards such as IEC, MEMA, IEEE, and UL/ CSA. Again, many of these standards are developed under ideal conditions, and don’t account for all of the variables on site. is is where company experience comes into play, with the practice of total quality management (TQM), research and development (R&D) and continuous improvement (CI).
56
MARCH•APRIL2019 /// www.nacleanenergy.com
Image 1: Indar Electric 40kV and up to 300C equipment for EIS testing
A standard strategy is to reduce the CoE for an existing wind turbine by delivering
more power to the grid in various conditions. Generator and turbine manufacturers understand this; both work towards optimizing the all electrical system Average Energy Production (AEP). e generator always works harder under more demanding conditions,
so the electrical insulation system has a big impact on the generator’s lifetime, especially when considering today’s “new normal” expectation of a 25- year component lifespan.
Having an EIS certi ed by a 3rd party laboratory, such as UL, is normally required for a