Orlando, Fla., March 31, 2011 — Siemens Energy, Inc. recently and successfully commissioned its pad-mount transformers at the Flat Water Wind Farm.
The transformers, rated at 1,750 kVA, three-phase at 60 Hz, are connected to wind turbines and are used as generation step-up transformers.
They are meeting three unique wind farm electrical requirements that affect the usage of pad-mounted transformers: operation as a step-up transformer, over-excitation requirements and the need for enhanced insulation with greater basic impulse insulation level BIL. Siemens was responsible for design, manufacturing, delivery and commissioning.
Located in southern Nebraska's Richardson County and Kansas' Nemaha County, the 60-MW Flat Water Wind Farm comprises 40 1.5-MW wind turbines and has the capacity to power more than 16,000 homes with clean, renewable energy.
The project is owned by Flat Water Wind Farm, LLC, which is a partnership between Gestamp Wind North America, a subsidiary of Gestamp Renewables, and Banco Santander, S.A. Siemens was sub-contracted by Renewable Energy Systems Americas, the balance of plant construction contractor.
The peak elevation for the installation is 3,280 feet with a maximum ambient temperature of 40 degrees Celsius. The pad-mount transformer is compartmental type, self-cooled, as well as tamper- and weather-resistant, and it conforms to the enclosure security requirements of ANSI Standard C57.12.28 (Pad-Mounted Equipment-Enclosure Integrity).
Step-up transformers for wind farms require a different design than typical distribution pad-mount usage. Due to generator harmonics, wind farm transformer designs will be subjected to generator-related duties not seen in typical four-wire utility applications.
Siemens anticipates the possibility of over-excitation when wind gusts create turbine over-speed beyond rated range, thus sustained overvoltage is automatically incorporated in its wind farm pad-mount transformer designs.
Because wind farms are frequently sited on ridges and in isolated areas where lightning strikes are fairly common, another wind farm pad-mount development is "reinforced" insulation rated at 200 kV BIL for superior insulation safety margin.