Page 6 - Energize November 2021

COVER STORY

Best practices in distribution

transformer maintenance

and replacement

by Morné Bosch, ArmCoil

he importance of implementing effective asset
management plans to extend the operating
Tlife of electrical infrastructure equipment
is highlighted in best practices around the world.
However, from an asset management point of view,
these commonly practised maintenance strategies
are considered to hold excessive portions of
redundant costs. As such, many distribution power A proper understanding of these differences would lead to applying cost-effective, reliable
network users and owners apply strategies which and conditionally based maintenance policies and programmes. Having certain and
simply don’t produce the results they are searching comprehensive condition assessment of electrical equipment supports the selection of the
for, which ultimately leads to unplanned costs for appropriate maintenance plan.
corrective maintenance or replacement of the
distribution transformer. Analysing the situation in three steps
Subsequently, the question arises as to why ArmCoil advocates that distribution transformer users and owners investigate the current
these preventative maintenance policies or condition of their assets by using their existing suppliers or by means of ArmCoil’s On Site
programmes do not identify the corrective actions Condition Analysis (OSCA) team. An initial three-phase strategy used by ArmCoil’s OSCA
required ahead of schedule. The answer might programme assists in determining the needs of existing distribution transformers and
be that the necessary actions were identified at associated infrastructure.
a critical point and, due to a lack of skills, were This three-phase initial strategy may be used as phase dependent or as a holistic
not communicated properly; or the maintenance approach for proven long-term cost saving, which enhances preventative maintenance
required was delayed due to a decreased policies (see Table 1). Using this strategy has a beneficial impact on long-term cost
maintenance budget. At this point, it is relevant reduction and assists in early detection of transformer and associated infrastructure
to examine the difference between preventative replacement (and possibly a cost saving on insurance premiums), not to mention all the
maintenance, corrective maintenance, strategic benefits enjoyed from minimum environmental impact rewards.
maintenance and a replacement strategy.

Phase 1: Assessment of existing distribution transformer and associated infrastructure
In many instances, these are commonly mistaken
for preventative maintenance measures, which 1. Identification of required equipment and assets
unfortunately leads to flimsy maintenance 2. Condition assessment of required equipment and assets
practices. 3. Equipment and asset location identification
• Preventative maintenance: Sometimes referred 4. Capture of information for evaluation and strategic maintenance purposes
to as preventive maintenance, this is performed 5. Prioritisation schedule of critical vs. non-critical equipment and assets
regularly on equipment which is in good working 6. Client approval
order to lessen the likelihood of failure.
• Corrective maintenance: A task performed to Phase 2: Implementation of strategic maintenance schedule
identify, isolate and rectify a fault so that the failed
equipment, machine or system can be restored to 1. Identified critical vs. non-critical equipment and assets are prioritised for scheduled
an operational condition within the tolerances or maintenance
limits established for inservice operation. 2. Planning of strategic maintenance schedules
• Strategic maintenance: This defines the rules for 3. Client approval
the sequence of planned maintenance work. It
contains general scheduling information and can Phase 3: Condition monitoring and strategic replacement of the distribution
therefore be assigned to as many maintenance transformer and associated infrastructure
task lists and maintenance plans as required.
• Replacement strategy: An investment strategy 1. Pre-determined assessment and extended maintenance routines are proposed for
which attempts to mimic the returns of a certain equipment and assets derived from completed maintenance
asset or group of assets by using a combination 2. Strategic replacement proposals of aging equipment and assets are compiled
3. Preventative maintenance strategies are introduced and controlled by trained personnel
of different derivatives rather than buying the 4. Client approval
individual products in the market.

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