POWER December 2015 - 49

OPERATIONS & MAINTENANCE
Procure an Inventory of Spares. Maintaining
an inventory of spare motors for
critical machines allows non-emergency
maintenance of offline equipment. This can
be coupled with a predictive maintenance
system to ensure refurbishment is planned
and carried out at optimal intervals.
Conduct Periodic OEM Inspections.
It is important to have OEM engineers or
maintenance specialists inspect important
motors. The experts usually have a detailed
understanding of the design, access to a
vast historical database, the ability to recognize
problems based on experience with
like equipment, and they can identify what
performance and reliability improvements
have been added since the machine was
manufactured.
Operate within Design Specifications.
Confirming that equipment is being operated
within the original design expectations
can pay dividends. Damage to insulation and
components may not be immediately apparent,
but it is a proven fact that machines operated
beyond design conditions do not last
as long as machines run within operating parameters
defined by the OEM.
Maintain Adequate Cooling Airflow.
Motors and generators create a lot of heat
that must be dissipated to prevent damage to
machine components. Operators should ensure
that clean, uncontaminated air is flowing
through plant motors. In humid climates, the
air should be conditioned and space heaters
should always be turned on when machines
are turned off to prevent condensation. If
particulate concentration in the air is heavy,
proper filtration must be used and maintained.
For machines with totally enclosed
air-to-air cooling or totally enclosed waterto-air
cooling systems, the condition and
performance of the cooler must be monitored
and maintained. Contamination of the cooling
medium is a major cause of premature
motor failures.
Tracking Transformer Performance
The easiest way to determine how oil-filled
transformers are performing is to track oil
quality and gassing. When a transformer's
insulation system is overstressed, gases are
produced that dissolve in the oil. By analyzing
the dissolved gas in the oil, developing
faults can be identified. At a minimum, annual
oil sampling should be conducted for
this purpose. Most oil testing companies offer
trending services for their customers and
can point out potential trouble as it arises.
John Engstrom, senior product and sales
leader-transformer services for GE's Industrial
Solutions business, said that there
are monitoring systems available today with
the ability to measure moisture in oil, combustible
gases, loads, and temperatures. One
example is GE's Kelman TRANSFIX transformer
gas analyzer, which can measure nine
gasses and moisture; it also has sensors for
various other inputs. These systems can be
expensive ($40,000 or more), so they are
mainly installed on generator step-up or other
large, critical transformers.
Another example is Siemens' transformer
monitoring and diagnostic system (TMDS).
An expert from Siemens Asset Services business
told POWER that the TMDS system
combines a variety of engineering models
with advanced techniques of statistical learning
to go beyond simple condition measurements
with prefixed limits. The system
(Figure 1) turns the data into actionable information
by translating combustible dissolved
gas, bushing capacitance deviation, moisture,
and other sensor measured data into diagnostic
and prognostic messaging.
Smaller, less-complex systems are available
to monitor noncritical transformers.
GE offers the Intellix GLA100, which conYour
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December 2015 | POWER
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POWER December 2015

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