Control systems earn higher profile at the 7F annual conference

The controls session at the 7F Users Group meeting has expanded in scope over the last couple of years to help owner/operators address multiple challenges—including diminished OEM support of legacy control systems and the need for tighter operational control to accommodate renewables, satisfy NERC CIP requirements, reduce emissions, etc. Several recent additions to the steering committee with controls experience have contributed significantly to the more robust program.

There were several user presenters in this portion of the 2013 conference. One focused on frequency response for combined cycles using the DCS. The speaker said the DCS emulates the governor and the preselected load set point is biased in proportion to the change in frequency. Critical to success is a high-resolution frequency measurement; the SFL1 in the Mark V or Mark VI via PI is not satisfactory. The solution here was to hard-wire a frequency meter to the DCS.

Another user presented on the value proposition of PI ProcessBook™, which makes it possible to efficiently display real-time and historical data residing in the PI system and other sources. He views ProcessBook as an efficient method for getting the most out of PI. Its advanced features are real simple to use, he said, and demonstrated this. Example: Scatter plots, good for identifying highly correlated items and for revealing when a process is off-track, are easier to build in ProcessBook than in Excel. If you’re unfamiliar with ProcessBook, there’s plenty of material up on the Web.

Control system upgrade, replacement. It seems that the most popular controls presentations at user group meetings concern system upgrades and replacements. One user presented on an HMI replacement for a combined cycle that began commercial operation in 2004. The original arrangement featured six GE HMIs and three screens in the control room. There was no HMI for use as an engineering work station (EWS). The new set-up features three of the OEM’s HMIs: two in the control room and one EWS. All machines are quad-monitor capable, the speaker said. There are still three monitors in the control room; the EWS has two monitors.

Another upgrade to the original system was the addition of a Wyse terminal (thin client) to the Packaged Electrical and Electronic Control Compartment for each gas turbine. The PEECC, sometimes shortened to PECC, is where the Mark VI and the motor control center for the GT reside. The inexpensive Wyse terminal is connected to the Ethernet loop for the HMI and Mark VI. The reconfigured and upgraded system has been in service for more than a year; no negatives were reported.

The replacement of Mark V control systems on two gas turbines serving a combined cycle that started up in mid-2005 was the subject of another presentation. Interestingly, the Mark V had reached end of life (EOL), according to the OEM, in March 2004—more than a year before plant’s commercial start; the announced end-of-service (EOS) date is March 2014. The owner felt compelled to upgrade. By way of background, the Mark V TMR system has four processors (referred to as cores) R, S, T, and C and a protective core P. It was initially provided with an IDOS <I> operator system and subsequently with a Windows/Cimplicity-based operator interface system and uses an ARCnet-based communications protocol to communicate with the operator interface system.

The owner’s engineers reviewed many options, including the following:

• Upgrade to Mark VI with its 32-bit computer system, Windows interface and better software tools, and Ethernet-based communications. However, this system reached EOL four years ago and EOS is expected in only six more years.

• Replace the Mark V with a Mark VIe. Advantages of the latter include (1) OEM’s current offering, (2) support expected until 2025 or beyond, (3) Windows HMI interface, and (4) Ethernet communications. Another benefit of a new Mark VIe is that it can be expanded to provide total plant control.

• Mark VIe migration (Mark V retrofit). This option involves installing a Mark VIe controller inside the Mark V cabinet and retrofitting it to the Mark V core. All boards are upgraded to supportable versions.

• Third-party DCS. The plant has Ovation™ for its balance-of-plant platform.

• Third-party solution with PLC-based controllers.

What to do? Perhaps the most obvious option would be to do nothing. Reasons include these: There are many Mark V systems operating in the electric power industry, the OEM will support the platform until parts run out, the OEM does offer field-service options (if you have the money, the OEM has a service team ready to support you), there is robust third-party support for control system components, and there’s access to support from other owner/operators via the 7F Users Group.

A replacement Mark VIe apparently was on the pricey side, although the speaker did not talk about dollars or contract terms and conditions, as is the rule at user-group meetings. One assumed cost was a concern because he said field I/O work was required for a new Mark VIe and outage time would be a week or two, possibly more.

Ovation was a serious consideration, but, in the end, the lack of experience of that platform on 7F engines was the deal breaker—this despite excellent reviews from the one customer based on two years of service. Little was said about the PLC-based option.

The preferred solution for this application was a Mark VIe migration because of the speed and economy of implementation, and OEM controls reliability and compatibility. Regarding the second point, minimal control system management was required, the OEM support network was already established, and there were multiple third-party options for control systems, automatic tuning, flame monitoring, etc.

Value of the vendor fair. The editors stopped by CSE Engineering Inc’s booth on the exhibition floor to ask what its team of experts would recommend to a critical generating facility having legacy Mark V controls on its GTs and then compare that solution with the one selected by the owner who had presented earlier in the day. Perfect question for Chairman Craig Corzine, a former GE employee having a deep background in Speedtronic® control systems and gas turbines, but he was out in the field. VP/GM Steve Morton was patrolling the company’s 8 x 10 ft territory. Like many 7F attendees, he had served in the US Navy and managed shore-side generation facilities.

Morton said CSE, which is celebrating its 20th anniversary this year, has decided not to develop a retrofit control system package for the gas turbines but continue development of CSE’s technology to extend the commercial viability of the existing Speedtronic control system with specific emphasis on the Mark Vs. Asked about CIP compliance, Morton said the concern with CIP standard compliancy is not related to the Mark V itself but to the HMI interfacing with the Mark V and it is one of the areas that the small California company has focused on.

Corzine was patched into the conversation by cell phone and he said that scrapping the Mark V on a controls refurbishment project was akin to throwing out the proverbial baby with the bathwater. If it was installed, commissioned, and has been maintained properly, it’s an exceptionally reliable system, the controls expert said. Spare parts and technical support are available and will be for several years to come. The only reasons to replace a Mark V in his view probably would be to accommodate a technological upgrade of the turbine—such as a DLN retrofit—or to transition to a fleet platform to reduce spare-parts inventory and to facilitate maintenance.

Corzine said CSE’s <ITC>® HMI is a CIP-compliant industrial monitoring and control software platform designed specifically to replace the functionality of the IDOS based Mark V <I> and Windows/Cimplicity-based Mark V HMI. The <ITC> system also is used to interface with the Mark IV and Mark V LM, and soon for the Mark VI and Mark VIe as well. The system communicates with the Mark IVs and Mark Vs using its native protocol over ARCnet and is provided with USB, PCI, PCIe, and Ethernet communications drivers. The system can support up to four individual ARCnet networks and can be used to integrate Mark IVs and Mark Vs within the same system.

For the Mark V, <ITC> incorporates all the functionality of the legacy <I> and current Cimplicity-based HMI systems, inclusive of Logic Forcing, Control Constant Editor, I/O Configuration, Control Sequence Editor, EEPROM Utilities, Diag_C, View Tools, and Auto-Calibrate. Additional features not available with the standard <I> or Cimplicity-based HMI system include Automatic F Drive Synchronization across all <ITC> systems, fully animated Real-Time Rung Display with sophisticated search and navigation tools, Multi-generator Tie-Line Control, Integrated Data Historian, Integrated Time-Sync Manager for all Mark Vs and balance-of-plant individual controllers, and integrated offsite remote monitoring and control.

Additionally, the <ITC> system is used extensively as a data historian and gateway between the Mark V and other computers or control systems, providing a direct read/write data exchange path between the devices for monitoring and control. Communications protocols include OSI PI, OPC (server and client), GE FANUC Series 90 (Serial and Ethernet), Allen-Bradley DF1 (Serial, DH+, and Ethernet), DNP 3.0 (Serial and Ethernet), Modbus (Serial, Ethernet TCP, Ethernet UDP, and Modbus Plus), Siemens S7-200, S7-300, and S7-400 (Serial and Ethernet), Westinghouse WDPF, and many more.

 

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