The state of power supply has been erratic for a long time and
many areas in the country are still struggling for a reliable source of
electricity. Especially the industries that need uninterrupted power supply for
economic sustainability have shown a tremendous rise in moving to diesel
generators as an important source of electricity and not just a temporary
arrangement. With the increase in usage and desirability of diesel generators
the need to find ways to improve their efficiency and power factor (PF) is also
on the rise.
What are the causes of low power factor?
Different load sizes that come with different power factor effects
is the primary cause for the overall reduction in the power factor of an electrical
layout. But various other reasons contribute to power factor output being low
and in a significant way. The reasons are primarily connected to the
fundamental limitations of a power generator.
A diesel power generator is a source of power that doesn’t
have a network of sources and loads to load it. Thus, it has a limited capacity
to fulfill sudden and large demands of reactive power. To build more on this
limitation, the below can be associated as reasons why there is lower power
factor in dg sets:
1. Over sized dg sets
Designers of a plant usually tend to oversize a dg set or limit its loading owing to a largely existent myth that
0.8 is the ‘designed’ PF for dg sets. This essentially leads to liberally sized
diesel guzzlers that do not deliver the full version of their economic
capability. The alternator of a dg set is same as its larger variants connected
to utility power turbines with scaled down proportions. Which means that it by
design has the capability to deliver the exact amount rated as its KVA (kilovolt-ampere).
So, 0.8 is not a design variable but it’s more like a thumb rule inferred from
the average power factor in any industrial electrical layout with a general set
of inductive - PF values .8 to .85, non-linear – Power Factor values .5 to .65
and linear (unity PF) - 0.80.
2.
Phase loading that’s unbalanced
Most of the industrial electrical layouts have loads that are
liberally connected on various power phase lines because physical limitations
of the process layouts are simpler to visualize when compared to the electrical
balancing on every line. This doesn’t seem to be a problem when it comes to the
grid connected situation where the primary connection of a phase maintains the
sync in the remaining from the utility side owing to a grid’s macro effect. But
in the case of a dg set that’s’ captive, syncing the phases
is not even a function built into its power electronics.
3.
The load of compensation
From various reports on the effect of different power factors
on dg sets and detecting safe zones it has become evident that close to unity Power
Factor is achievable and safer but low Power Factor for greater periods has
more negative impact.
This is part one of a two-part series. In the second part,
learn how to correct dg sets with low Power Factor.
