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can be ‘issues’ with kVArs. Electronic/
smart meters have several ways of
measuring this, giving a different power
factor to the one you would calculate
from the right-angle triangle.
THE ECONOMICS
By way of example, we will
concentrate on smaller installations, say
from 100A upwards.
These often have no restriction
on power factor, unlike so-called
contestable installations in which it
must be more than 0.9.
Let’s look at a 415V, 150A installation
with a power factor of 0.8 and a power
demand of 65kW.
Depending on the load diversity
factor, annual energy consumption is
200MWhr. This type of installation will
attract a kVA charge, typically about
$15 per kVA per month. Based on the
power factor of 0.8, the measure is
81.3kVA, or about $14,600 a year in
demand charges.
With the power factor increased to
0.95, the measure would be 68.4kVA
and annual savings on the demand tariff
would be about $2,300.
The figures with a power factor
varying between 0.6 and 0.8 based on
the same usable power as above (65kW)
give an average of 92.9 kVA. The savings
from improving the power factor to 0.95
are about $4,400.
The economics depend on a detailed
knowledge of tariffs, and we won’t
identify individual distributors.
However, the tariffs are public
documents and easily accessible,
although not necessarily easy to
interpret. Nevertheless it will pay off to
study them closely then go prospecting
among larger consumers, possibly
bearing a soft copy of your services.
REGIONAL DISTRIBUTION
Problems do occur with voltage
regulation, in particular on SWER lines.
Consumers connected to the
SWER distribution network can
encounter nasty problems with
motors stalling because of low voltage,
and solar inverters cutting out
because of low or high voltage
thresholds being exceeded.
Larger consumers, dairies for example,
will have standby diesel generators. Doing
a power quality test for these installations
is more than just a good idea.
Without solid data on the level of
voltage regulation and harmonics,
harmonic resonance of the converter of
a VSD with local capacitor power factor
correction on the SWER line can end
up damaging customer equipment and
cause metering problems.
SWER distribution has great
construction cost advantages but can be
tough on power quality.
ANALYSE FIRST
Power quality problems can
disadvantage consumers due to
higher bills and can drive up
maintenance costs.
Contractors can render a valuable
service by providing power quality
surveys. These should always be done
when considering capacitor bank power
factor correction, and also if harmonic
mitigation is planned.
Furthermore, the gathering of power
quality data is important when disputes
arise with distributors. Many companies
offer power quality analysers, and some
have rental options.
CONCLUSION
The distribution sector is generally
privatised, but it is highly regulated and
tariffs go up in accordance with capital
expenditure approvals by the Australian
Energy Regulator.
To a large extent the joy of electricity
cost reduction is found in technical
solutions. The largest individual
consumers have been aware of this for a
long time and have adopted sophisticated
demand response strategies.
The bulk of commercial and
industrial consumers are wide open
to your assistance as a qualified
electrical contractor.
E L EC TR I C AL CONNEC T I ON
SUMME R 20 1 6
Summer
Winter
20
25
30
35
40
Figure 1: Energy demand in peak gigawatts over the past 17 years.