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P
and profits are a few economic drivers
forcing operators to use more intelligent
power management strategies. Indeed,
today’s power management architectures
can cut energy consumption and fixed
utility charges as well as support power factor analysis and
record time stamped power quality data.
Real-time measurements of electrical parameters, such
as voltage disturbances or distortions,canalso be generated
and then transmitted via wireless networks to operators,
warning of breaches in threshold limits. And, the power
quality information provided by these systems can help to
improve on-siteefficiency and ease negotiations with utility
companies and energy authorities. So how does an operator
go about installing such a system?
of power analyserswill identify energy intensive processes
so that non-critical processes can then be relegated to offpeak demand hours.
By building up a detailed energy profile for a site or
enterprise in this way, operators can then determine the
best rate schedules. Meanwhile analysingthe profile by the
hour, day, week or month, means operators can also
aggregate loads and so negotiate more favourable terms
with the utility company
Real time power consumption monitoring also allows a
site manager to anticipate overload conditionsthat would,
for example, trip a circuit breaker. Alarm thresholds can
be set to warn managers if preset limits are reached, and
armed with the adequate system loading and status
information, he or she has time to organise remedial
action.
For starters, several utility meters or power analysers
should be located at the service entrance and at strategic
points throughout the site. Data can be transmitted to a host
PC over, sax a R W or RS485 linkthat supports multidrop
capability and high signal integrity in electrically noisy
industrial environments. Meanwhile, the latest energy
management software can be used to import real-time data
from more than 250 networked nodes.
But before this is possible, the operator must first
establish a power profile. Large commercial or industrial
electricity consumers have to deal with fixed energy
charges related to the power demand of one or more sites
as well as the charge per unit of energy consumed. If the
business exceeds the agreed power demand or “installed
power” then it is forced to pay extra costs.
To make matters worse, utilities can also impose higher
installed power tariffs that often represent up to 60% of a
commercial consumer’s total utility charge. So clearly, a
small mistake that leads to a brief excess power demand
can cost many thousands of pounds.
The good news for consumers is that even a basic energy
management system will provide information so that
operators can identify consumption trends and take
corrective action. Alternativelya more extensive network
42
IEE Power Engineer I ADril/May 2004
POWER PROBLEMS
Once a power profile has been established, power factor
control can be applied to a site. Indeed, software is now
massive manpower savings
POWER DISTORTIONS AND
UNPLANNED DEMAND ARE
JUST TWO PROBLEMS THAT
LEAD TO UNEXPECTED TARIFFS
FOR INDUSTRIAL FACILITIES.
NICEL RALF EXPLAINS HOW
TODAY'S POWER MANAGEMENT
available that allows managers to prioritise power factor
correction. Power factor correctedmachinery typically rnns
more efficiently, and if applied to cables and switchgear,
ratings can be reduced.
The latest power management architectures can also be
used to monitor power quality and address fluctuations in
the power supplied to a site or a piece of electrical
equipment. By detecting and measuring short term
variations, site owners can minimise the impact of low
voltages, voltage sags, harmonic distortion, or wiring and
grounding faults.Recording and timestamping these power
disturbances also means a business can later investigate its
equipment and processes, and assign responsibility for
equipment damage or lost output.
One such example is identifying a voltage transient.
These disturbances can take place when power factor
capacitor banks are switched or from the arcing of a loose
phase conductor
Harmonic distortion is another example. This can cause
significant problems to utilities if introduced to the local
supply or grid, perhaps hy overheating in transformer or
motor windings, or the failure of capacitor banks.
However, power management systems can analyse the
magnitude and direction of harmonics, which helps a
facility manager to identify whether the source is internal
or external to the site. For example, the harmonic footprint
of a 3-phase,fuu~waverectifier, is significantly different to
that of the single-phase switching power supply of a PC.
Using software to look at this information graphicall3
allows harmonic effects to be easily identified and quickly
rectified before equipment replacement costs or even
settlements with neighbouring businesses or utilities are
incurred.
Automated data collection has also moved on from the
days of using a handheld power analyser. Today, huge
volumes of data an?collected in real time from any number
of lccations acruss m y sites.This not only makes massive
manpower savings, but the higher data sampling rates save
time while human error is removed from the data logging
process.
IN PRACTe
The arrival o
:
EN50160 standard,which outlines the l i t s
for permissible harmonic distortion, has driven many
European industrial and commercial operators to install
power management equipment :and software at their
businesses. This approach is proving popular as it removes
the need for fflters - which are expensiveto design and build
to counteract any internally generated harmonics. Indeed
examples range from owners of shopping centres wishing
to optimise billing to petrochemical installation managers
wanting to bwst operating margins (fg1).
One example is a plastic moulding manufacturer with a
diverse range of products. These include automotive
mouldings that cost up to €30 to produce, to commodity
parts, costing only a few cents.
In this instance, the manufacturer wanted to calculate
the true energy cost of making the various product, for two
reasons. First the market for comhodity components was
very price-sensitive. And second, making the high value
mouldings consumed significantly more energy than the
lower-valuecomponents.
The manufacturer found that simply dividing the
total energy costs equally - to determine a price for
each different component made the commodity parts
uncompetitive. And at the same time, the company would
be charging less than was appropriate for the higher value
components.
To solve this dilemma, the manufacturer installed a
power analyser at each machine in the facility to monitor
the energy consumed for each process. The data was then
used to develop a pricing strategy for all products. Gleaming
additional information, such as the power factor at each
machine, also allowed the manufacturer to ininduce extra
efficiency measures and cut energy costs.
So the next time you are faced with unexpected energy
tariffs, unplanned downtime or power interruptions,
perhaps automated power management canhelp.
~
Nigel Ralf is the general manager at Carlo Gavaui UK
IEE Power Engineer I ApriVMay 2W4
43
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