Control System Upgrade Improves Pagbilao Power Plant Reliability, Availability

Issue 11 and Volume 110.

Pagbilao power station Units 1 and 2 recently completed a project to upgrade and unify combustion, turbine control and burner management systems with Emerson Process Management’s Ovation expert control system. The 750-MW plant, operated by Mirant Pagbilao Corp., is located in Quezon, Philippines.

Unifying the control systems has resulted in a number of operational and economic benefits for Mirant Pagbilao, including a greater than 1 percent increase in plant reliability; improvements in data acquisition, alarm monitoring and report management; and the prevention of forced outages and/or load restrictions that could have resulted in a potential energy loss of 16,800 MWh per day.

Prior to the upgrade, the control architecture at Pagbilao Units 1 and 2 consisted of two primary control systems-Emerson’s previous-generation Westinghouse Distributed Processing Family (WDPF) distributed control system for boiler and turbine control, and a Mitsubishi Heavy Industries DIASYS-UP system for burner management. Mirant considered two options for the controls upgrade: Replacing both of the existing systems with an entirely new control system or migrating the existing WDPF system to the Emerson Ovation expert control system and replacing the existing burner management controls with the new Ovation system. Mirant chose a WDPF-to-Ovation migration.

The Ovation system installed at Pagbilao includes embedded advanced control algorithms; an Ethernet network for high-speed communication of plant information; a controller with fast duty cycle to optimize plant performance; and analog, digital and special-purpose turbine and boiler I/O (input/output) modules.

From the beginning, Emerson designed the Ovation system to allow a straightforward migration path for users of its WDPF systems. Emerson’s migration path allowed Pagbilao to retain much of its investment by allowing it to keep existing I/O cards, field cabling, terminations and cabinets; as well as its system engineering investment in control logic, graphics and the database. This enabled the power plant to increase the functionality of its control systems in a cost-effective way.

“One of the many good things about the new Ovation system is that our operators have the opportunity to view and understand the SAMA-built control logic of individual operations,” said Juanito M. Sainz Jr., a Mirant Pagbilao power plant technical specialist. “This feature, when thoroughly used, can prevent a major outage that both directly and indirectly impacts operations and maintenance costs.”

In addition, the new Ovation Historian gives Pagbilao flexibility in the way data is presented and enables the plant to present process data in report format or communicate it to other plant systems via OPC-based connectivity (open connectivity via open standards). With the OPC Server, process data from the historian is sent to Mirant’s eDNA (data historian software from InStep Software) system which, in turn, broadcasts process data to remote stations and Mirant’s headquarters in Manila, Philippines, and Atlanta. The OPC server also exchanges information with the plant’s Bently Nevada system, which is used for the turbine vibration monitoring system. Finally, the OPC server is also connected to a Wonderware system, allowing data exchange between the Ovation system and Pagbilao’s sootblower system.

The new Ovation system has essentially centralized the functionality of several independent systems for data broadcasting, logging and reporting.

“Previously, data communication between the two control systems increased the level of risk involved in operation because of too many communication devices and protocols,” explained Sainz. “Now, operating the units is a lot easier. Nothing is better than having a single brand of control system.”

“We know that no two power plants are alike, and so we work closely with our customers to develop migration strategies tailored specifically to their operational and financial objectives,” said Bob Yeager, Emerson’s Power & Water Solutions division president. This is what Emerson did for the Pagbilao Power Station, resulting in an easy migration process and operational benefits.