POWER September 2023 - 27

ELECTRICAL MAINTENANCE
the original braces were made of wood,
but several of them had been damaged
by weather exposure over
time. The
manufacturer of the braces was still in
business and able to supply new ones
made of high-density polyethylene with
a short turnaround. After that, Austin Energy's
network construction department
came to the site to cut, terminate, and
install all the new cable.
3. Cable damage as found. Courtesy: Austin
Energy
either partial or corona discharge and
required immediate replacement (Figure
4). The unit outage was extended by two
weeks to accommodate this.
There were 12 fittings in the top plate
of the breaker enclosure, each containing
four cables. That is four cables per phase,
three phases, a run between generator
and breaker plus a run from breaker to
transformer, and this arrangement exists
for each of the two units. Looking from
underneath the fittings, the cable damage
was even more severe than first thought.
Repair was not that straightforward.
The first hurdle was in getting the re4.
Cable damage from below. Courtesy: Austin
Energy
placement cable itself, which was 750
MCM (1,000s of circular mils) and estimated
at about 5,000 feet of length. Austin
Energy does not keep cable of this
gauge on hand. The only manufacturer
that responded to a request for quote
said that the lead time would be 40 to 44
weeks. Fortunately, a local distributor did
have this size and quantity available for
immediate delivery.
The next hurdle was that the cable
trays for these cables had braces every
few feet to keep the cables evenly
spaced through the tray. This arrangement
is called a cable bus. In this case,
Lessons Learned
Across the industry, cables are frequently
not considered after they are installed.
They don't have moving parts or pieces
that wear out. They carry currents back
and forth, and they just function. Unless
cables are mechanically damaged during
some sort of work, they are generally
thought of as permanent.
This set of experiences has shown
that, as with everything else, time tends
to wear down even something as simple
as a cable. Austin Energy is now planning
inspections and testing for the higherpowered
cables and will be vigilant for
future defects. ■
-Matt Kuffler, PE is the plant engineer for
Sand Hill Energy Center with
Austin Energy.
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September 2023 | POWER
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POWER September 2023

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