> CASE STUDY
America’s Third-Largest Public Power Utility
Quells Nuisance Alarms
> BENEFITS
• Freed operators to concentrate on improving plant performance.
• Reduced alarm rate decreased possibility of operator missing an alarm.
• At Santan Station, plant startup used to two operators up to four hours,
now takes one operator less than two hours.
• Reduced configured alarms for six units at Santan Station, deleting
39.8% and reprioritizing remaining according to EEMUA Guideline 191.
• Reduced configured alarms at Navajo Generating Station Unit 1 by 44%
and reprioritized remaining according to EEMUA Guideline 191.
> CUSTOMER CHALLENGE
Performance Services
The Invensys Performance Services helps
customers improve plant performance
and safety, addressing a wide range
of operational areas including alarm
management, cyber security, wireless
solutions, control management, advanced
process control, optimization, and asset
management. Each offering embodies
our global experience and track record in
delivering these high value solutions to
customers in asset intensive process
industries.
The Performance Services offerings are
one of the core components of the
Invensys suite of services which also
includes Consulting Services, Project
Services, Customer Services, and Learning
Services. The combination of these
services, a comprehensive set of world
class technologies and our unique
InFusion technology platform is at the
heart of Invensys Process Systems’ ability
to deliver true Asset Performance
Management.
While process alarms are critical to the safe and profitable operation of a power
plant, too many and too frequent alarms can have the opposite effect. To reduce
alarm floods that seemed to be occurring with increasing frequency at the nation’s
third-largest publicly owned power producer, Arizona’s Salt River Project (SRP)
implemented a very effective alarm management solution at two of its generating
stations, Navajo and Santan.
SRP began consolidating aging analog plant controls at these stations into a single,
modern digital control system in 1990, based on the I/A Series® distributed control
system from Invensys Process Systems. In 2006 the I/A Series system was
incorporated into the newly installed Santan units. The I/A Series system now
encompasses more than 40,000 SRP I/O points, including coordinated control of
turbines, burners, plant logic, scrubbers, data acquisition, and performance
monitoring. The benefits of switching to digital control have been dramatic and
were evidenced almost from the start.
“Dispatchers could not believe what they saw when the unit took a 400 MW
runback at an average of 200 MW/Min. The boiler and turbine parameters were
not only in line, they were ‘flat line.’ Anyone with any experience operating a
once-through unit knows that this is remarkable,” said SRP dispatchers,
commenting on the startup progress at the Navajo plant.
One benefit of such a powerful control system is the ability to generate alarms
notifying operations of condition changes, but it wasn’t long before the number
and frequency of those alarms threatened to overwhelm operators.
“We were getting alarm horns all the time - at startup, shutdown, and during dayto-day operation. In one 18-hour period, operators were confronted with 5,000
alarms, every one of which required intervention of some sort and 98% were
designated top priority. The plant had to designate an operator just for alarm
management,” said Ron Bewsey, I&E supervisor and I/A administrator, commenting
on the extent to which the lack of alarm management was jeopardizing the
efficiency of the entire plant.
SRP has now met that challenge with an alarm management solution from
Invensys. SRP has already implemented this at all of Santan’s nine units, is ready
to go live on one more Navajo unit, and has a proven execution strategy to apply
the solution across both plants.
“We were getting alarm horns all the time — at startup, shutdown, and during
day-to-day operation. In one 18-hour period, operators were confronted with
5,000 alarms, every one of which required intervention of some sort and 98
percent were designated top priority. The plant had to designate an operator
just for alarm management.”
— Ron Bewsey, I&E Supervisor and I/A Administrator, Salt River”
“Now we have valid alarms that mean something to operators so they can respond appropriately. This
increases efficiency and reliability. Operators now see the alarm system as a tool they appreciate,
instead of a necessary annoyance,” said Bewsey.
> IPS SOLUTION
Starting with the two units at the Santan station, SRP assigned an
I&C specialist and a seasoned control room operator to work with two
Invensys engineers full time on implementing a three-phase alarm
management solution. In the first phase, the Santan/Invensys team
studied alarm system performance in depth and produced a report,
which defined baseline alarm system performance, established
performance targets based on EEMUA (Engineering Equipment and
Materials Users Association) best practices, and described the
system improvement methodology.
The second phase focused on system performance improvement.
This phase included development of an alarm system philosophy,
alarm rationalization, execution of alarm system changes, and a
human machine interface (HMI) that enables plant personnel to
visualize alarm system performance and history.
Related documentation described the causes of each alarm, consequences if the alarm is ignored, necessary corrective actions, and
rationale for each. The documentation also detailed work processes that guide the activities of operators,
technicians, and engineers. The design and rationalization process included a review of all alarms
against an alarm philosophy within the plant.
SRP’s alarm management team prioritized the alarms on the basis of economics, safety, and environment severities, as well as on the time needed to respond. Those in priorities one, two, and three would
be sent to the operator. Those coded as priority four would be sent to maintenance for diagnoses and
repair. The priority fives would just go to the historian for recording purposes; but not to the operator,
in accordance with SRP’s new alarm philosophy.
Prior to the documentation and rationalization process, 98% of the alarms were assigned priority 1,
with 2% spread across the rest of the priorities. After the documentation and rationalization, only 11%
were at priority 1, 14% at priority 2, and 75% priority 3. The new priorities are programmed into the
I/A Series system, which manages the routing of alarms to the appropriate location.
> RESULTS
Implementing the alarm system design at the nine Santan units has dramatically reduced the frequency
of alarms. Where plant startup had previously taken two people up to four hours, now one operator can
start up in less than two hours.
“We can now attend to each alarm instead of just hitting the ‘acknowledge’ button and we also have
more time to concentrate on improving the performance of the units rather than just trying to stop the
noise,” said Rees Scott, control room operator.
In addition to making things “a whole lot quieter,” eliminating nuisance alarms freed operators to
take actions to affect the efficiency of the plant in positive ways. In addition to signaling problems,
alarms might also be used to notify an operator of an opportunity to increase the plant efficiency,
for example, by decreasing heat rate.
At the Navajo Station, results may be even more dramatic. The alarm management team rationalized
and reprioritized Unit 1 alarms according to EEMUA standards and the Plant alarm philosophy
resulting in a 44% reduction of configured alarms. The rationalized alarms were implemented in
SRP Navajo’s SimSci-Esscor® plant simulator. Navajo is taking advantage of the simulator to train
operators on the new alarm system and plant alarm philosophy. The simulator models operation of
the plant in real-time enabling a prediction of the impact of the new alarm system design before
the changes are committed. Actual implementation is scheduled in the running system for Fall of
2007. Once the Unit 1 project is complete, the process will be repeated on the other two units and
the scrubbers as well.
The third phase will continue to optimize the alarm system and will cut alarms even more. Phase
2 will be completed by implementing advanced alarming which will “focus on reducing alarm
floods,” said the SRP alarm management team.
> HEADQUARTERS LOCATION
Invensys Process Systems
5601 Granite Parkway III, Suite 1000
Plano, Texas 75024 USA
O 1.469.365.6400
F 1.469.365.6400
www.ips.invensys.com
Contact Support
O 1.508.548.2424
> ABOUT SALT RIVER PROJECT
Salt River Project, based in Phoenix, AZ, was established in 1903 as the nation’s first multipurpose
reclamation project authorized under the National Reclamation Act. It is the nation’s third largest
public power utility, providing up to 6,500 megawatts (MW) of power to more than 900,000
customers throughout a 2,900-square-mile service territory in central Arizona. Revenues for 2006
were approximately $2.5B. In 2004, Electric, Light, & Power named SRP “Utility of the Year.”
SRP operates or participates in ten power generation plants. Its Navajo Generating Station on the
Navajo Indian reservation near Page, AZ, operates three 800 MW coalfired generating units. Its
Santan Station in Gilbert runs nine combined cycle units, providing a combined total of about 1100
MW. Its Kyrene station, located 15 miles away in Tempe, generates an additional 430 MW from one
combined cycle and three simple cycle units.
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