Electricity + Control August 2017

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12 Electricity + Control AUGUST 2017
While load shedding has currently been
suspended, the reality is that while you
are connected to the utility supply, you
are still susceptible to the vagaries of an unstable
power system in South Africa. In addition, to pos-
sible power outages, you are also exposed to volt-
age variations, sags, surges, spikes and harmonic
problems. Power assurance and power quality
solutions are necessary to protect sensitive equip-
ment from these problems.
An Uninterrupted Power Supply (UPS) is es-
sential to provide a failover system between utility
power and secondary systems such as a gener-
ator. They are also useful for providing sufficient
time to safely shut down equipment in the case
where secondary power is not available. However,
choosing the right UPS technology to suit your ap-
plication can be challenging.
The right solution for you
Determining what power solution is needed is a
science that requires careful consideration of sever-
al factors. Things such as the proposed installation
environment, the dynamics of the load, and wheth-
er the customer is looking for continuity of supply
only or complete power conditioning. The outcome
of this often not asked question will determine the
technology required and therefore the final cost of
the solution. If not properly planned, power condi-
tioning solutions can be less than effective and end
up costing businesses more than necessary.
It is vital that businesses, particularly those for
which quality of supply is critical, plan their solu-
tions properly. Before purchasing one or more
UPS, or any other power protection equipment, it
can be highly beneficial to conduct a power qual-
ity survey. This will enable organisations to gain a
sound understanding of the precise challenges of
their power environment which, in turn, makes it
possible for a tailored solution to be designed to
achieve the desired results.
Quality of Supply
Quality of supply problems can generally be cate-
gorised as follows:
• Surges: These are sustained over voltage con-
ditions, usually as the result of fault conditions
on the electrical network. Faulty neutral con-
nections and incorrectly tapped distribution
transformers can also result in a sustained
over voltage condition, resulting in damage to
sensitive electronic equipment
• Sags: These are generally as the result of poor
or ageing electrical distribution networks and too
large a load being switched in and out of a weak
network, resulting in a sustained under voltage
condition. Equipment such as electric motors and
refrigeration compressors are very sensitive to
these kinds of conditions and a continuation of
this condition can lead to overheating and perma-
nent failure of the motors. IT based equipment
tends to switch on and off under these conditions
leading to a disruption in the IT process through-
out the environment in which they are being used
• Spikes: These are very common during light-
ning season and are short duration high voltage
conditions. They can also result from network
switching and power factor correction compen-
sation. Depending on the frequency of these
spikes, they can result in data corruption of
process plants and IT networks and permanent
damage to sensitive electronic equipment
Is a UPS Alone Sufficient
for Your Power
Requirement?
Kevin Norris, Jasco Power
Experience and the results of many site surveys have shown that UPSs are not
completely effective on their own, and need to be supported by additional power
conditioning equipment.
ELECTRICAL PROTECTION + SAFETY
There are many factors
that influence the type
of UPS required.
UPSs are not completely
effective on their own.
Lightning protection
devices are necessary
on UPS installations to
protect the load and the
UPS from failure during
lightning activity.
Take Note!
abbreviations
1
2
3
IT – Information Technology
PFC – Power Factor Correction
UPS – Uninterrupted Power
Supply