H2scan TM Catalog 2025 - Flipbook - Page 31
Because determining transformer life
expectancy is a complex task, online
monitoring can alert users to changes
in a transformer’s health so they can
focus on their most troubled units
of maintenance dollars spent. Therefore, the reliability of the
monitoring solution is key to ensuring the system provides the
most bene昀椀t for the life of the transformer. Solutions with low
or no maintenance are normally preferred.
The most widely used tool to understand the health of the
transformer is to measure the dissolved gases in the
transformer insulating 昀氀uid. When thermal and or arcing faults
occur inside the transformer, the insulating 昀氀uid and solid
insulation degrade and form gases in the 昀氀uid. By analyzing
these gases, the health of the transformer can be assessed. The
value of online monitoring solutions is that they alert operators
when fault gas levels are increasing inside the transformer.
The 2019 IEEE C57.104 not only provides information
on DGA (dissolved gas analysis) typical values but also
provides guidance on gas rate-of-change and sampling
recommendations up to and including daily sampling,
depending on the condition identi昀椀ed. Due to the di昀케culties
in managing such a task, online monitors can provide the
data without sending personnel to transformers that are at
high risk of failure. Of course, this is also a safety concern.
So, how do asset managers evaluate which of their
transformers will be the next to fail? While some critical
transformers may get multi-gas DGA, bushing monitoring,
partial discharge monitoring, and other forms of monitoring,
most utilities are in no position to deploy large monitoring
systems on all their transformers. They must choose a
strategy that will provide the most value for every dollar spent.
Transformer owners must pay not only to evaluate the up-front
costs of the monitoring solutions but also the maintenance
required to keep the solution working over the life of the
transformer. Most utilities in North America are incentivized
to spend capital dollars and want to minimize the amount
90000258
For over 40 years, online monitors have used the hydrogen
concentration in the insulating 昀氀uid as a primary indicator of a
change in transformer health. When signi昀椀cant issues occur
inside the transformer, the hydrogen concentration increases,
which is a key indicator that there may be something that needs
to be addressed urgently. When the hydrogen concentration
increases, operators can perform a manual DGA to understand
the severity of the issue. For large transformers where multi-gas
monitors are justi昀椀ed, these gases can be evaluated in near
real-time. For smaller transformers or large transformers with
no multi-gas DGA monitoring, hydrogen monitoring alerts
users that gases are being generated, and action can be taken
to understand the severity of the situation. Many utilities
deploy a strategy where hydrogen monitors alert them to
issues, and then a portable multi-gas monitor provides more
complete information when workers arrive on-site.
4. Conclusion
Because determining transformer life expectancy is a complex
task, online monitoring can alert users to changes in a
transformer’s health so they can focus on their most troubled
units. Depending on the transformer asset class, design, and
other factors, most utilities expect their transformers to last 40
to 60 years. Since the average age of a transformer in North
America is around 40 years old, asset managers must evaluate
how to manage their 昀氀eets best, given today’s challenges.
It is far more likely that a transformer can be repaired if faults
are detected prior to failure. With transformer shortages and
rapid grid expansion due to the integration of renewables and
electric vehicles, it is more important than ever to ensure every
transformer remains in service as long as possible. Any major
transformer failure will stress the grid if a spare transformer
strategy is not in place. Proper transformer asset management
allows utilities to meet customer expectations and keep the
power 昀氀owing.
pg.31
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