Page 48 - Energize March 2022

TECHNICAL

their operational limits, there are serious safety implications to be considered too – and a bathtub curve,” he explains. “When
associated cost impacts. Ultimately, the risk of transformer explosions will rise without a transformers are brand new, they’re more
significant increase in the pervasiveness of testing, Wills warns. “That is the risk that exists if likely to experience teething issues. Then,
a user doesn’t know anything about the condition of a transformer,” he emphasises. “And it’s over the next 20 or 30 years, problems
worth remembering that an explosion might not just impact the transformer unit itself, but and faults are less common, and towards
the environment around it and potentially an entire substation.” the end of a unit’s life failure is expected
The financial costs of disruption, of putting in place temporary generation, rebuilding at some point. As such, similar to other
part of the network and incurring customer minutes lost in the event of a catastrophic network equipment, more thorough
transformer failure, would be significant. Looking at regulatory penalties alone, fines from testing at the beginning and the end of life
the regulator for interruptions could stretch into the millions. Indeed, between 2014 and is advisable.”
2018, distribution network operators paid the regulator £29 million (over R600-million) To identify transformer deterioration,
in fines for failing to meet guaranteed supply reliability standards for gas and electricity some test result diagnosis relies on
distribution. comparisons with previous measurements,
Wills adds. “A reference test performed
What does ‘good’ look like when it comes transformer testing? during routine maintenance can provide
A good testing regime offers both breadth and visibility across as many tests as are useful information at a later date,
deemed necessary. Thorough testing, feeding into an informed maintenance plan can especially if the data is not available from
have a fundamental impact on transformer lifespan – at least 40 years according to the a factory acceptance test.” The challenge
global power engineering community CIGRE – as well as the asset’s reliability. A holistic for asset management leaders is that
testing approach should include tests conducted both online – when the asset can remain there’s not a lot of information available to
operational – and offline, requiring planned downtime. In the case of the latter, it’s help guide the selection of which tests are
important to make sure that as many tests as possible are conducted within a single window right for specific assets or how test results
of opportunity in order that an asset’s time out of service is minimised. should inform maintenance decisions,
A rounded approach to testing should also consider which tests are required for according to Wills. The experience of
predictive maintenance and issue prevention, and which tests should be conducted in a seasoned asset management professionals
diagnostic scenario when faults occur, suggests Wills. Setting the regularity of testing for has guided the approaches and standards
different transformer units can be tricky, he acknowledges, because of their volume and used in most networks for years. But many
varying ages and locations – essentially, it’s not easy to standardise or make generalisations of those experienced minds have now
about which tests should be conducted or how often. retired or are approaching retirement.
There are some general rules around asset age however, which Wills says provide a Furthermore, products and equipment are
rule of thumb for creating sound maintenance plans. “Typically, chance of failure follows changing. Simply put, there are new ways

Megger transformer test equipment

energize | March 2022 | 46