H2scan TM Catalog 2025 - Flipbook - Page 34
In order to compete, transformer manufacturers need to reduce costs. This
means reducing the amount of materials like copper, steel, paper, oil, and
components such as temperature gauges and pressure relief devices.
It also means that manufacturers must pay significantly more detail to
how each transformer is built. A small issue like a nick in a conductor, torn
paper, or a loose connection may not have caused a problem 50 years
ago because there was much more margin built into each transformer.
Today, those minor problems can cause major issues such as overheating,
partial discharge, and so forth.
Utility Transformer Management
Utility asset managers have slowly adopted certain monitoring over time.
When almost every transformer has temperature gauges and oil level
indicators, it is easy to see why the first electronic monitors provided the
ability for utilities to monitor those items remotely with their supervisory
control and data acquisition (SCADA) systems. While this data is important,
it does not necessarily warn the owner of an imminent failure.
As monitoring systems evolved, online dissolved gas analyzers (DGA)
became commonplace 10 to 20 years ago, with most utilities placing
DGA monitors on critical transformers. As more DGA monitors became
available, there was much excitement in the industry about the idea that
transformer owners could monitor all the critical gases in real time. While
this capability provides valuable information, it comes at a cost. The
installed cost of most online 8 to 10 gas monitors is in the US$60,000 to
US$80,000 range.
Most of those monitors will require significant maintenance within four
to eight years after installation and every four to eight years after that.
Figure 2. Significant diagnostic fault gases are generated in mineral when hot spot
Therefore, the maintenance costs of multi-gas monitors have become
temperatures reach 150°C. As the temperature increases above that level, hydrogen
a major issue for utilities who want the data, but do not have the
is generated at ever-increasing rates.
maintenance budget available to keep the monitors running. For utilities
with large transformer fleets, they have had to significantly limit the number
of installations because of the high installation and maintenance costs.
Hydrogen monitors have proven to be effective in warning transformer
owners of significant issues for more than 30 years. These monitors
Because of the high cost of multi-gas monitoring, it is reasonable to
typically update every hour to every second. The good news is that today
speculate that less than 1% of utility power transformers have working
there are maintenance-free hydrogen monitors available that use solid-
multi-gas monitors installed. Since maintenance budget is limited, many
state sensors with no need for maintenance or calibration for more than 10
utilities simply do not have the maintenance budgets to maintain their
years. The other great benefit of these monitors is that they typically cost
multi-gas monitors. This begs the question, “If a utility is only monitoring 1%
between US$5000 to US$8000 for base models.
of its transformers and the transformer failure rate is between 1% and 3%
per year, what is the likelihood a utility will catch a transformer failure with
an online monitor?”
Utility Accounting
Bene昀椀ts of Hydrogen Monitoring
As solid-state components drive down monitoring costs, it is easier to
justify adding monitors to smaller and smaller transformers. Most utilities
For asset managers, the big question is: “If I’m managing a fleet of power
have standardized on certain hydrogen monitors for certain classes of new
transformers, what’s the best way to accurately predict which ones will
transformers. On new transformers, the cost of the monitor is included as
be next to fail?” Since most transformer experts agree that DGA analysis
part of the transformer, so it is easy to justify. Installing large-scale retrofits
is the best answer, how can utilities effectively monitor real-time DGA on
on an existing transformer fleet is a much more difficult proposition.
a fleet of hundreds or thousands of transformers? The short answer is
hydrogen monitors.
In general, utilities are incented to spend capital because they earn a rate
of return on their capital investment. On the other hand, they typically do
Hydrogen is a key gas that is generated when significant issues like
not earn a rate of return on maintenance dollars spent, so dollars spent on
overheating, partial discharge, and arcing occur in transformers. While
maintenance simply reduces their earnings per share. Various accounting
some of these issues might persist for weeks, months, or years, these issues
rules have not previously allowed utilities to earn a rate of return on low-
can also lead to failure in minutes, hours, or days. Annual oil samples are
cost asset monitors.
not frequent enough to catch fast-evolving transformer faults.
90000258
pg.34
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