What Was Old Can Be New Again

Issue 10 and Volume 112.

By Steve Blankinship, Associate Editor

I&C upgrades for Procontrol P13 Systems can be done incrementally, depending on your need.

More than 600 ABB Procontrol P13 instrumentation control systems are operating worldwide—about 160 of them in the United States. The plants range from small 30 MW cogeneration facilities all the way up to utility-scale coal plants in the gigawatt-output range.

Many continue to function much as they did a decade or more ago because it had not been possible for asset owners to economically or incrementally upgrade those instrumentation systems to meet today’s market needs. In many instances, the inability to upgrade has meant running instrumentation based on DOS or Windows ’98 software platforms.

But existing P13 systems can be brought up to more current performance standards. A platform to do it for the power generation industry has been developed by Alstom Power Service and the upgrades can be implemented in increments ranging from small to comprehensive.

“In the United States alone there are all these old ABB P13 systems and this is the only way to replace as much or as little of the old system as you want,” said Mike Dost, vice president of instrumentation and controls for Alstom Power Service. “You can replace a few boards at a time if that’s all you can afford. The more at risk your plant is to poor performance, the more you can replace.”

All this came about in part due to ownership changes that took place as Alstom and ABB first merged and later separated. Alstom retained the machinery, meaning the ABB machines became Alstom turbines, while ABB maintained the electronics. In time, the electronics embedded in the Alstom turbines were eclipsed by newer technology.

P13 was one of the most widely used control system platforms in power plants built by Alstom (the turbines were originally ABB) between the mid 1980s and the late 1990s. With many of these systems nearing the end of their expected life, the replacement BlueLine series that has been developed offers what may be a cost-effective and relatively low-risk approach towards keeping these systems in service with modern performance. The modules also can offer significant cost reductions compared to the original P13 boards.

The initial drive that led to development of the BlueLine turbine control system platform was the need for a simple Modbus serial interface card that could be used between an operator station and a control system. For years, serial Modbus interface cards were expensive, difficult to configure and modify and hard to troubleshoot. The need existed to develop a new Modbus card that kept all desireable features of the old serial nterface card and also added a few new features.

The result was the BlueLine 70SI01 serial interface card that largely solved the obsolescence issues of the old P13 platform and added the ability to test and verify communications with a standard laptop. It was successfully installed in over 120 HMI systems at several plant locations. These installations run continuously and, to date, have experienced no failures. With that, the decision was made to expand the BlueLine series to include other standard I/O cards.

The replacement cards also provide flexible addressing, meaning they source several signals into the control system and can have non-sequential addresses. They can, therefore, assume unused channels while not taking up other valuable addresses. That approach can be useful for retrofits and upgrades.

“We are able to place eight high performance thermocouple measurements in a single BlueLine card,” said Dost. “Compare that to the OEM board with one thermocouple measurement multiplexed to eight channels.” He said the old card was three times wider and two orders of magnitude slower. And, the old analog I/O cards could only send and receive analog signals with 12-bit resolution. The BlueLine analog I/O cards send and receive analog signals with 15-bit resolution, he said.

Logic engineering and servicing software was developed to work with the new BlueLine 70CP01 processor. The software, named BlueLine Tools (BLT), uses object-based logic building for creating new control architecture or importing HEX target code already in use. Editing is easy due to an error-checking regimen built into the software. There cannot be a signal without a source, nor can there be a module without all supporting hardware behind it. As an additional safeguard, the 70CP01 processor will not go active when loaded with badly formed code.

The software combines both the logic editor and the servicing interface into one package, allowing information to be equally shared between the two and providing a better overall view of what’s happening while troubleshooting. This includes “on the page” monitoring and simulation capabilities, a missing/simulated/disturbed signal search and the ability to show raw values in various formats. Other notable utilities within the software are the recording and trending tool, and multiple report generators.

A Really Big Co-Gen Plant

Among the first major power plants to get the upgrade was the Midland Cogeneration Venture (MCV) in Midland, Mich. MCV is one of the largest cogeneration power plants in the United States and was at one time the world’s largest cogeneration facility. When producing at full capacity, MCV can send 1,500 MW to the Michigan grid and, as a steam host, supply 1.5 million pounds per hour of process steam.

The 12 Alstom GT11NM gas turbines are typical of the Alstom machines that relied solely on individual ABB control systems. Two years ago Midland’s owners bought upgrades for all of them. During a pre-planned outage in March, Unit 14 was upgraded with BlueLine controls. The old processors (9 ABB 70 PR03s and 2 ABB 70AS47 trip processors) were replaced with five much smaller Alstom BlueLine processors. The upgrade also changed the control system software. The replacement system is Windows-based and communication software uses function-block diagram logic that lets the plant follow signals and logic changes in a graphical environment. The system has Ethernet capabilities for service work, which is important to Midland because there are 12 gas turbines.

Profile of a BlueLine module installed at Midland
Click here to enlarge image

The single system replaced several groups of systems, including the main open loop, main closed loop, emergency open loop, emergency closed loop and trip protection. It replaced four ABB processors in the main loop with one unit. And because the replacement I&C equipment is state-of-the-art, it operates at lower temperatures using less power and should, therefore, have a longer life.

“Midland’s original system was hard to work with and maintain,” said Doug Comar, controls supervisor at the plant. “There were two types of processors (70PR03 and 70AS47). Paper documentation was required, so making and documenting logic changes was cumbersome. The DOS-based software was obsolete, as were the computers it ran on. Furthermore, direct processor connection was needed for service.”

Comar said it had become a reliability issue with lots of failures from the original processors. Each gas turbine had 11 processors due to the technology in the mid 1980s. With 12 machines there were a lot of possible failures. What’s more, the original equipment manufacturer had expressed concern that maintaining the older processors could be limited because IC chips were no longer being manufactured. “It made sense to upgrade,” Comar said.

He said the old system required removing erasable programmable read-only memory (EPROM) and burning new ones to adjust settings or change the logic. “You had to be at the machine to pull out a processor and insert the new EPROM. You could only communicate with the processor you were plugged into. Now, you can make all the minor tweaks you want and do them remotely.”

Comar said the new system has saved man-hours because instead of sending a technician to check or change something, it can be done remotely…all integrated through the plant network.

All of the plant’s processors were converted into 70CP01 units with all functionality, architecture and protection maintained. That meant that only a single type of processor had to be mastered. The new system’s logic programming methodology is graphical object based. Benefits include allowing the user to work in the easier-to-understand function block environment. Also, all documentation is generated by the BlueLine Tool so any changes are automatically updated.

The new software runs on a Windows OS computer with an onboard Ethernet port. Using a laptop for the engineering station made the most sense for Midland. “Being able to work with the user program on a standard computer made a difference in itself,” said Tom Douglas, Alstom senior control system engineer. “It is much easier to move, copy and store the user program with the added flexibility of modern networking and USB ports.”

Since the 70CP01 was designed with an Ethernet communication port as its service interface, it opened up an entire world for Midland. “Employees can now connect from a common point, and connect as needed to any unit or processor,” said Comar. “In the past, even if a small logic modification was needed, we had to visit each of the 12 units and replace the EPROM. With the new processors, they can just press the download button and the documented change is loaded.”

Project Engineering Phase

Because Midland was originally running a P13 hexadecimal control system, its logic and signal information had to be restructured to import into BlueLine Tools. Additional information was required from site. “These included the actual hexadecimal code running in the 70PR03’s, their plant signal list, and also their current hardware configurations. We combined installed 70AS47 trip processors with the Emergency Open and Closed Loop controllers,” said Tom Laird, business development manager for Alstom Power.

Laird explains that the original unit control set up included main open and closed loop, emergency open and closed, two trip channels and two processors exclusively for their HMI. Therefore, 11 original processors had to be replaced: nine of the old OEM’s 70PR03 processors and two 70AS47 processors. “Thanks to the 70CP01’s larger internal memory space and internal addressing capacity, we were able to combine the logic of several 70PR03s into one 70CP01, as well as combine the trip processors with the emergency loops, thus eliminating the issue of having multiple processor platforms,” he said.

Once all logic was imported into BlueLine, lab testing began. “We not only tested that the processors correctly executed logic, but also that they did it the same way the old 70PR03s did, so that the upgrade was more like a simple plug-and-play,” said Tom Douglas, Alstom senior control system engineer. A simulation was programmed to put signals onto the local bus and responses from both the 70CP01 and 70PR03s were recorded and compared. Minimum differences were found.

“We also built a turbine/generator simulator, so we could put the unit into different operating modes. This allowed us to perform trip tests as well,” said Douglas. Alstom and Midland performed multiple tests during the customer acceptance test. The tests covered all trip signals programmed into the system.

Smooth Commissioning

As with most commissionings, a few problems were encountered and quickly fixed. These included having to modify logic that was originally deleted per the customer’s request during the pre-engineering phase. The sheet and logic were replaced immediately and the processor reloaded. The output cards were satisfied and alarm lights cleared.

In addition to making a few logic tweaks, some new hardwiring was needed. Wires once attached to the other main open loop controllers could now be removed since they were condensed into a single 70CP01. Wiring for the emergency loops were moved to the controllers’ new location.

Alstom reloaded the Target code to the processors with the Midland personnel present and Midland personnel reloaded it several times as well. “This was to show them not only how to use the software, but the speed and ease in which it was done,” said Qui Nguyen, Alstom control system engineer. “Because communication between the servicing kit and the processor is now done solely by Ethernet, downloads and uploads take fractions of seconds, especially good when we ran into issues on site.”

Since commercial startup in mid-March, Unit 14 has been started and brought down multiple times without issue or incident. Midland has since upgraded two more of its gas turbines and expects to eventually have all 12 using the BlueLine upgrades. “I allowed two weeks for the first installation and it just took a week,” said Comar. The next upgrades were completed using only MCV technicians. The second upgrade took three days and the third one took a long day. “So from here on in,” Comar said, “I’d schedule two days for each upgrade.”