OVATION USERS GROUP 2016: Low bidder may not be the vendor you want
One of the eye-opening presentations at the 2016 meeting of the Ovation Users Group, in Pittsburgh, July 25-28, involved a new coal-fired plant which experienced what can only be described as a failure by the original automation system supplier to design, deliver, and service a suitable system. It’s a lesson—no matter what type of generating facility—in the need for oversight of the automation platform in a day and age when it is, essentially, the brains of the plant.
The ultra-efficient unit was declared “commercial” in December 2011, but plant representatives elaborated after the presentation, stating the unit commissioning was never really completed. Three and a half years later, with Emerson Ovation taking over in summer 2014, the plant was finally operating with some semblance of normalcy by spring 2015.
The prior automation system vendor had anywhere from 10 to 25 control engineers onsite for the performance test, declared it passed, and then left one engineer behind. Twenty minutes after ownership was transferred, the boiler and turbine controls began ramping in opposite directions. The unit had to be tripped at an output dangerously above its gross capacity. Subsequently, say plant officials, “we experienced 200 GADS events in the first year.” Recall that GADS is the NERC Generation Availability Database System.
Apparently, the design and commissioning of the boiler and turbine controls coordination was not completed because of inconsistencies in operation, ancillary subsystems like fabric filters were inadequately addressed, and the plant was unable to change anything. Nothing was intuitive. “Over 100 separate DCS issues were identified,” officials noted, including the following:
- Inconsistent boiler/turbine coordinated control.
Operator workstation blackout.
Lack of bump-less transfer schemes.
Lack of balancing circuits to multiple control devices.
Inconsistent operation of HP steam bypass valve.
Inconsistent operation of lead/lag devices.
Lack of device permissive and first-out information to the operator.
Poor I/O partitioning of critical inputs.
Difficulty troubleshooting complex logic structures and hidden functions.
Low chance of survivability during a runback.
A more minor issue, at least in the scheme of things, was that overall control needed to be far more precise so that the plant could participate in the PJM regulation market.
Needless to say, Emerson came in and retrofitted Ovation concepts and standards while retaining what could be salvaged of the original software design. “We especially liked the open-access platform,” company officials said. Emerson retrofitted a system with 11,000 I/O points, 7000 logic files, and 280 graphics files, and developed standards which could work with the original system, according to the owner/operator presenter, all in six months.
Post rehab, online availability increased from a low of 73%, to more than 98%, capacity factor was raised from 68% to over 98%, forced outages were significantly reduced, 20-MW/min ramping was demonstrated, and startups became consistent. Another result: The number of alarmed points was reduced to 325 critical ones, from 24,000 previously!