Simulating analog

Is it possible to use digital tools to simulate an analog environment?

December 10, 2010

Dear Control Engineering: I was reading a story about a new simulator at a nuclear power plant. The photo included with the article shows an old-style analog control room. Is that still operating? How do you build a simulator for that?

The article you mention from November 16, discusses how Omaha Public Power District is updating the simulator at its Fort Calhoun nuclear plant. The photo with the story is not dated, but looks like it could go back to 1970. According to the folks at L-3 Mapps, who will be providing the simulator, that photo is about two years old, and is not an actual control room, but the simulator. Nuclear power plants typically built a duplicate control room to use for training. The photo is included here again, cropped a little tighter and larger so you can see more detail.

The control room of the plant reportedly does still look like that, so the simulator retains its accuracy. This brings up some interesting thoughts on implementing such a project. If you’re dealing with more modern digital control architecture with computer driven HMIs, it isn’t all that difficult to create a platform that looks just like the real thing. You can use all the same graphics to retain the look and feel. However, if you’re creating a simulator that has to drive analog meters, chart recorders, and panel annunciators as output devices, it’s a bit more complicated. Your system has to generate whatever kind of signal is required to get that device to display the correct values. That requires some interesting I/O capabilities. It’s sort of like having to build a robotic horse to pull an old wagon rather than simply replacing it with a truck.

Many of the devices that were common 30 or 40 years ago when these plants were being designed and built aren’t so easy to get any more. However, some companies continue to build specialty items that these legacy nuke plants depend on. For example, Invensys Operations Management recently announced a partnership with Curtiss-Wright Flow Controls to continue manufacturing the old Foxboro SPEC200N line of analog control system equipment. These products date back to 1976 but are still working in many power plants.

That’s not to say that all nuke plants are museum pieces. Many have updated their automation and control infrastructure, however there are many differences from location to location. Analog is still alive and well in many.

–Peter Welander,