POWER September 2023 - 15

FOCUS ON O&M
Examples in Renewable Energy
Installations
The following three snapshots are examples
of ester transformer fluids being
used in today's demanding green
energy world.
Ester Fluid in Offshore Wind Substations.
Substations provide the vital
link between wind turbines and the electrical
grid. As wind farms move farther
offshore, substations are positioned on
purpose-built platforms, bringing challenges
that include transformer fire
safety and maintenance costs. In 2017
and 2018, Siemens delivered two newly
developed offshore wind substations for
the 588-MW Beatrice wind farm (Figure
1) in Scotland. They featured synthetic
ester-filled transformers and a shunt
reactor that supported a revolutionary
new design that was more environmentally
friendly and fire-safe compared to
mineral oil, and 30% to 40% lower cost
with much lower risks.
Offshore transformer risks include
fires that are difficult to combat and
could result in the wind farm being
shut down. Filling a system with synthetic
ester fluid instead of mineral oil
increases fire safety because the ester
has a much higher fire point (greater
than 300C) and a 100% fire safety record.
Furthermore, the specification of
synthetic ester fluid has enabled the innovative
design of significantly smaller
offshore substations, removing the
need for complicated (and expensive)
transformer fire suppression as well as
extra containment systems for the fire
suppression liquid collection. A smaller
substation also requires a smaller crane
to do the lift on to the bottom set of
piles, saving money and time spent
waiting for the handful of super large
and expensive offshore cranes.
In offshore substations, a transformer's
performance is just as important as
its fire safety. If the transformer fails to
withstand the challenging environment,
it will need to undergo expensive unplanned
maintenance. Thus, specifying a
synthetic ester fluid that is extremely robust,
oxygen stable, and proven to work
means greater assurance for operators.
Ester Fluid in Floating Solar Farms.
National Thermal Power Corporation, or
NTPC, India's largest energy conglomerate,
recently unveiled a 75-MW floating
solar PV installation in Kayamkulam,
Kerala, using 16 free-breathing transformers.
Floating solar is a relatively new
development in the renewable energy
world. The immediate advantages are
clear-floating solar uses less costly real
estate, allowing the surrounding land to
be used for agriculture. It also can reduce
evaporation, which for most reservoirs is
beneficial. In addition, the water can provide
a cooling effect around the panels
that improves PV panel performance.
However, exposing components such
as transformers to water and humid environments
increases the risk of corrosion
and rust, leading to the transformer insulating
fluid being potentially exposed to
air. Synthetic ester fluid was used in NTPC's
solar farm transformers because of
its proven performance in free-breathing
transformers (with its high oxidation stability)
and environmental risk reductions
(biodegradable status and non-toxicity to
aquatic life if any leaks were to occur).
Ester Fluid in a Hydroelectric Power
Plant. Swedish utility Vattenfall identified
the need for a new transformer for
the
Stalon
underground
hydropower
1. The Beatrice wind farm off the coast of
Scotland features substations that use synthetic
ester-filled transformers, considered
more friendly to the environment and less of
a fire risk. Courtesy: SSE Renewables
September 2023 | POWER
station in northern Sweden (Figure 2).
It was decided that a mineral oil transformer
would not be appropriate in this
instance. First, the 238-kV transformer
was to be placed underground, making
fire safety a critical requirement. Second,
though just as important, the power station
was located in an environmentally
sensitive area, where spillage of mineral
oil could cause serious and long-lasting
damage in addition to risking highly expensive
cleanup operations. A synthetic
ester fluid was deployed as the cooling
fluid because of its fire safety, non-toxicity
to fish, and biodegradability, further
endorsing the credentials of ester fluids
in renewable energy.
Ester transformer fluids have become
an important component of clean, rewww.powermag.com
2.
The Stalon hydropower station in Sweden,
with much of its operation underground,
uses synthetic ester fluid in its new transformer.
The fluid is used for purposes of fire
safety, along with its non-toxicity to fish and
its biodegradability. Courtesy: Vattenfall
newable, and green energy systems.
Their superior fire resistance, biodegradability,
and high dielectric strength make
them a safer and more sustainable option
than typical transformer fluids. They
also allow design engineers to create
innovative and cost-saving approaches
to substations and the entire system
where transformers are used. Ester
transformer fluids are now used in mainstream
applications by utilities, heavy
industry, and transformer manufacturers
worldwide, and are proven in transformers
from distribution units to power units
of more than 400 kV.
-Anthony Coker is executive vice president
for M&I Materials Inc.
Planning Is Key to
Successful Nuclear
Refueling Outages
U.S. nuclear power plants typically refuel
every 18 to 24 months. Refueling outages
normally occur in the spring and fall
of the year when demand for electricity
is at its lowest. The Energy Information
Administration (EIA) tracks U.S. nuclear
plant outages and provides the information
on a webpage that is updated daily
based on Nuclear Regulatory Commission
(NRC) data. From 2018 through 2023,
spring outages have peaked in mid-April
with the average total nuclear power capacity
out of service in the U.S. ranging
from about 15 GW to slightly more than
23 GW. Fall outages, meanwhile, peak in
late October with about the same capacity
offline for maintenance and refueling
as in the spring (Figure 3).
Safety is always a priority whether a
nuclear plant is in operation or conducting
a refueling outage (Figure 4). During
a refueling outage, plants typically optimize
downtime by scheduling facility upgrades,
repairs, and other maintenance
work while the nuclear reactor is offline.
15
http://www.powermag.com
POWER September 2023

Table of Contents for the Digital Edition of POWER September 2023
