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Unique requirements call for thoughtful analysis and reevaluation
Each turbine in a wind farm is equipped with a step-up transformer, which boosts (steps up) turbine generator output voltage from a few hundred volts to die collector system's medium voltage distribution levels. These wind turbine step-up transformers are failing at an alarming rate and developers and operators of utility scale wind farm projects are scrambling to identify die most likely causes for this widespread failure.
The root cause of die failure is not hard to find: conventional distribution transformers that typically are used simply cannot stand up to the severe duty requirements of a wind turbine stepup transformer. To guarantee die future reliability of this valuable renewable energy source, wind turbine step-up transformers must incorporate diese unique requirements, which include variable loading, harmonics and non-sinusoidal loads, transformer sizing and voltage variation, low voltage (LV) fault ride through, as well as protection and fire behavior, step-up duty, switching surges and transient over-voltages, loss evaluation and gassing.
Wind Power's Biggest Challenge
Wind turbines are distributed in an array in which ambient winds blow across fan blades connected to turbines that generate electrical energy. However, while wind always blows it does not blow according to any regular schedule or wind speed, so turbine output energy varies continually.
Alternating current (AC) electrical energy cannot be easily stored; wirb no "shelf life," wind energy must be consumed by the end user as soon as it is generated. Generation plants of all kinds typically scale back production when demand is light and ramp up production to meet the higher demand when consumers turn on the switch. Unfortunately, wind power is not well suited to this type of supply side control.
When the wind blows, turbines can provide power. When die wind speed is low, only a fraction of the designed power capacity is generated. Below a certain speed (approximately seven miles per hour), the turbines cannot generate power at all. Ironically, in very high winds the turbines must also be stopped to prevent damage. Timing becomes a critical issue because invariably when customer's demand is greatest, wind-generated electricity may not be available. Thus, utilities must use the wind generated power whenever it is available and control die supply demand by...