DG induction machines were typically small—less than 500
KVA. These machines were restricted in size because their
excitation is provided by an external source of VARS. In recent
years however, power electronic-controlled capacitors are being
installed on the terminals of these units to provide a controlled
source of excitation. This has allowed induction generators to
increase in size to approximately 3.0 MW. Induction generators are
similar to induction motors and are started like a motor (no
synchronizing equipment needed). Induction generators are less
costly than synchronous generators because they have no field
windings. These machines can supply real power (Watts) to the
utility but require a source of reactive power (Vars), which in some
cases is provided by the utility system. These generators can
provide fault current for only a few cycles for faults on the utility
system. Interconnection protection associated with induction
generators typically requires only over/under voltage and
frequency relaying. Self-commutation is also possible with utility
pole-top capacitors and can result in non-sinusoidal waveforms and
overvoltage. This point is discussed later in this paper. Induction
generators are typically used in wind applications.