Answer / kj

DG's are usually rated at 0.8 PF lagging. There is no
issues with running the DG at another higher or lower
lagging PF. Usually the output kw of the engine is set at
80% of the kva rating. For example a 100 kva DG will have
an engine rated at 80 kw. This will al;low for a full load
current of about 140 amps at 0.8 PF. Increasing the PF
towards unity the maximum load current must be reduced
until it is about 110 amps otherwise the engine will be
overloaded. If the PF is reduced below 0.8 PF the maximum
current must not exceed 140 amps. This means the kw of the
load must be reduced. This is to stop the windings in the
alternator being burnt.

Going to a leading PF will cause voltage instability and
can cause damage to the alternator.

Answer / k.prakashchandra

Keeping pf at 0.8 lag when running in parallel means the
terminal voltage of gen is higher than the system or busbar
voltage.But it results in higher gen & field currents which
cause unwanted heating of armature and also the field.If
you keep the pf at unity or -ve,the gen does not contribute
to system stability.The generator should also share the
reactive power of the system, which is usually
lagging.Anyway pf may be maintained at 0.9 to 0.95 lag.

Answer / meenakshi

if power factor goes beyond 0.8 (say 0.9), your dg will be
over loaded and may trip or call for frequent overhauls.

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