POWER August 2014 - 18

3. Comparison of mean time between failures (MTBF). Increasing the number
of annual preventive maintenance visits, compared to no preventive maintenance, increases
the MTBF. Courtesy: Emerson Network Power
tion improves MTBF and another measure
of availability: mean time to repair. Power
plants can move away from the common
time-based maintenance cycles to a new
service model where there is faster notification
of an event, followed by the ability
to have remote system engineers analyze
data and diagnose the problem.
Not having a power distribution system or
Number of annual preventative maintenance visits
teries don't do their job, serious damage
and personal injury could result. Damaged
equipment could take months and
cost millions to repair, while lost power
production could be even more expensive
and lead to fines and penalties. A proper
maintenance program can help by yielding
the following benefits.
Increased Battery Life
Every emergency power system contains
life-limited components that should be
maintained, according to the manufacturer's
specifications and as required by
NERC, and batteries are no exception. In
the event of a power outage, a single bad
cell in a string of batteries could compromise
the entire backup system and leave a
plant without protection.
While UPS battery manufacturers may
market their batteries with a 10-year design
life or life span, the actual service life
of the battery will be much shorter due to
the external factors that cause degradation.
The reality is that batteries lose capacity in
as few as three years due to several factors,
including usage, operating environment,
and insufficient maintenance.
Because of the many factors that can
affect the useful life of a UPS battery, it
is important that-as soon as it is placed
into service-a battery should be maintained
with a program that identifies system
anomalies and provides information
that trends end of life (Figure 2). Through
this type of maintenance program, plant
owners and operators are able to get the
most out of their investment in these critical
assets.
Batteries that are beginning to fail
cause an imbalance that adversely affects
the life of other batteries in the string and
should be removed from service. And when
a UPS battery needs to be replaced, time
is of the essence, especially when considering
the staggering financial impact that
an extended or unplanned outage can
have on an organization.
18
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POWER | August 2014
Maximized System Reliability
To avoid UPS battery failure that leads to
downtime, the best practice is an approach
that includes integrated battery monitoring
and preventive maintenance (PM). In
Emerson Network Power's data analysis of
more than 450 million operating hours
for more than 24,000 strings of UPS batteries,
the effect that regular PM had on
reliability was clear. This analysis revealed
that the MTBF for units that received two
PM service visits a year is 23 times better
than a UPS with no PM visits (Figure 3).
Furthermore, those with battery-monitoring
systems installed at their site had
a reduced rate of outages due to bad batteries.
While outages did still occur, the
incidents were isolated to cases where customers
were either not watching their system
or they did not know how to properly
analyze the data provided by the monitor.
This brought to light the need for experts
to correctly monitor the alarm data and
properly maintain the systems.
Improved System Availability
The use of stationary battery monitors with
remote professional analyst services gives
power plant operators a way to collect
comprehensive battery data and receive
early warning of alarm or out-of-tolerance
conditions. Ultimately, using this combinaemergency
power system working properly is
problematic to many power plants and can
have a detrimental effect on an organization.
However, implementing the best practices
in upgrade and maintenance services
can help owners and operators realize many
benefits, including simplified maintenance,
easier regulatory compliance, improved
safety, and better overall availability. ■
-Wally Vahlstrom is director of technical
services for Emerson Network Power's
Electrical Reliability Services group.
Trackers Optimize Yield of
Utility-Scale Solar Plants
The utility-scale solar market is rapidly
growing in North America, representing a
large area of opportunity for project and
product developers alike. The market more
than doubled in size between 2012 and
2013 alone, propelling the solar racking
and tracking sector to revenue of $8 billion.
Analysts are projecting this strong
growth to continue in the coming years.
Solar trackers-motorized structures
that orient photovoltaic (PV) panels toward
the sun throughout the day-in
particular are an increasingly important
aspect of utility-scale project development
(Figure 1). With substantial research
and development advancements in recent
years, trackers are no longer cost prohibitive
due to high manufacturing or operations
and maintenance costs. For many
utility-scale projects, trackers can significantly
increase yield by optimizing the
angle of incidence between a module and
incoming solar rays.
1. The Langelé solar plant in France utilizes solar trackers. Solar trackers have
been proven to increase plant production compared to fixed-tilt systems. Courtesy: Exosun
Times better
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POWER August 2014

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