POWER April 2023 - 18

GAS POWER
Optimizing Combined Cycle
Power Plant Operations
Courtesy: Cogentrix Energy
Cogentrix Energy and Siemens Energy have partnered to optimize 8000H-class gas
turbine reliability and outage planning. Under Cogentrix's management, the Patriot
site successfully upgraded one of its combustion turbine rotors in 2021, and the
Liberty plant achieved a continuous operations record for H-class 60-Hz machines
at 206 days.
Mike Straubmuller
P
atriot and Liberty (together known
as the " Hamilton " portfolio) are
two natural gas-fired combined
cycle projects in Pennsylvania. Both
projects utilize Siemens Energy's worldclass
8000H technology and started
commercial operations in 2016. Cogentrix
took over management of the facilities
from previous owners in June 2020,
and the operational performance of both
plants has improved significantly since
that time.
Cogentrix is a private independent
power producer that provides best-inclass
technical, operational, financial,
and commercial capabilities. Cogentrix
has 40 years of experience operating
combined cycle gas turbine (CCGT) power
plants, including many equipped with
Siemens Energy's technology. Today, Cogentrix
operates a diverse fleet of natural
gas-fired projects with more than 9 GW
of capacity spread across the PJM Interconnection,
ISO-New England, Electric
Reliability Council of Texas (ERCOT), and
SERC Reliability Corporation markets.
Cogentrix operational excellence is exemplified
by its CCGT fleet's low Equivalent
Forced Outage Rate - demand
(EFORd) figures of 0.52% in 2020 and
1.01% in 2021, which compare favorably
with the North American Electric
18
Reliability Corporation (NERC) averages
of 4.26% and 5.07% in the same periods.
In 2022, Patriot and Liberty had a
combined EFORd of less than 0.4%,
representing the best year of operations
under Cogentrix management.
Plant Designs
The Patriot (shown above) and Liberty
plants each consist of two units, each a
single-shaft clutched configuration, two
Siemens Energy SGT6-8000H combustion
turbines
(CTs)
with
Emergency
diesel generators (EDGs)
dry-low-NOx
combustors and evaporative coolers.
Each combustion and steam turbine
combination is connected to a 462-MVA,
23-kV generator equipped with a static
excitation system. The steam turbine
generators are two Siemens Energy
SST6-5000 tandem-compound reheat
type with cooling provided by air-cooled
condensers. The heat recovery steam
generators are two Vogt, three-pressurelevel
with superheat and reheat systems,
and supplemental duct firing capabilities.
Both plants utilize 100% reverse osmosis/electro-deionization
trains with ultrafiltration
(UF) pre-filters and chemical
treatment. The water treatment systems
at both plants include a 635,000-gallon
storage tank for feedwater and the fire systems.
Wastewater systems at both plants
are served by the local municipal system.
www.powermag.com
are 1,000 kW connected to two essential
services motor control centers. The
Siemens Energy SGT6-8000H turbines
short startup times, low heat rate, and
high operational flexibility help achieve
long and sustained run-times. In fact,
Cogentrix was able to achieve a 206-consecutive-day
run time record at Liberty,
which is considered the longest of a Siemens
Energy SGT6-8000H unit. Modern
blade design and optimized packaging
promote high reliability while keeping operations
and maintenance (O&M) costs
and outage risk low.
Operational Improvements
Cogentrix has a very strong relationship
with Siemens Energy, which manufactured
the SGT6-8000H units and provides
maintenance services under long-term
service agreements (LTSAs). Together,
Cogentrix and Siemens Energy were
able to reduce ongoing maintenance
costs while incorporating financially
beneficial performance upgrades for the
gas turbines, including planned rotor upgrades
at both Liberty and Patriot.
Cogentrix has a strong track record
of improving plant performance and
embedding a reliability-focused maintenance
philosophy to ensure sustained
performance. As previously mentioned,
POWER | April 2023
http://www.powermag.com
POWER April 2023

Table of Contents for the Digital Edition of POWER April 2023
