POWER March 2015 - 47

COMBINED CYCLE GAS TURBINES
lation design, the drum is replaced by a thinwalled
external separator. The change allows
for higher temperature transients and simpler
chemistry control.
Rafael Santana, LEC maintenance manager,
said the number of problems has been
surprisingly small. " We did encounter some
minor hiccups with our HP turbine control
valve, " he said. " But it's not the fast-start
plant that caused that issue, but rather a manufacturing
defect, probably aggravated by the
number of starts. "
The gas turbine as well is performing
admirably.
" We have had multiple planned outages to
conduct inspections, and in the most recent inspection
of the turbine in November, all the components
looked pristine, so they were returned
back to operation instead of replacing them. "
Though greater demands are placed on
the plant with the additional cycling, the demands
on the plant staff are not unusual. " I
wouldn't say there is much difference, " Santana
said. " In terms of normal maintenance
and intervals of operation, it's the same. "
Minor Growing Pains
As with any plant, there was a learning curve.
Siemens provided remote monitoring of LEC
for the first year, using networked instrumentation
to track the operating parameters from
its service center in Orlando, Fla. This enabled
Siemens to give LEC feedback any time anything
wasn't operating in an optimal fashion.
" There were some growing pains in the
beginning, " Jeremy Lawson, LEC plant engineer
said, such as properly tuning the water
levels in the HRSG up to the bypass valves.
There were a few little hiccups with the
HRSG, with one of the lower acoustic baffles
coming loose due to the cycling regime and a
lack of support. There was also a minor leak
in one of the tube bundles in the #1 preheater
at the tube support a few months after operations
began. Both problems were corrected
and have not recurred.
The plant also encountered high-temperature
trips of the steam turbine (ST) across the
intermediate-pressure exhausts. This was resolved
through faster ST starting and loading.
DeBortoli's staff also found some ways to
reduce the plant's already low CO emissions.
Working with Siemens, the plant staff made adjustments
to the fuel flow and positioning of the
inlet guide vane (IGV). " We ended up keeping
our IGV closed until we got to 50 MW. "
These tweaks, plus boosting the ramp rate
to its 13.4 MW/minute maximum, helped cut
CO emissions by 350 pounds per start.
But all in all, these were minor challenges.
" Out of the box, there is just a little bit of dialing
in so the operators understand what works
and what doesn't, " Santana said, " but overall I
March 2015 | POWER
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think that we haven't really changed anything
major with the logic or the operation. "
DeBortoli concurred: " The overall process
is pretty much where we want it to be. Not
ongoing improvements from here on out, but
just really minor things. "
Moving On
With the uncertainty and changes in the California
energy market, particularly the drought
that is challenging hydroelectric generation,
DeBortoli said LEC expects to continue seeing
demand for its fast-ramping capabilities going
forward. " The market condition is very dynamic
right now, so we don't know what's going to
happen in the next couple of months. "
Last July, General Manager Ken Speer likened
NCPA's experience with LEC to " driving
a Ferrari rather than a Chevy. " LEC and
its sister unit in El Segundo appear to have hit
the ground running when it comes to meeting
the role they were intended for. ■
-Thomas W. Overton, JD is a POWER
associate editor.
Our technology. Your success.
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POWER March 2015

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