Instrumentation & Controls

Since 1999, the Texas grid operator ERCOT has given plant owners economic incentives to upgrade and extend the life of their generating units. Lower Colorado River Authority has seized the opportunity to modernize the control systems of its 1970s-vintage Sim Gideon natural gas–fired steam plant. Sophisticated control schemes now calculate the toll taken by running units under severe service conditions—including the high ramp rates that a plant must execute to sell ancillary services.

On-line temperature monitoring of steam turbine rotors must be based on modeling thermodynamic processes—not direct temperature measurements. Good operating decisions can significantly extend the life of aging turbines, particularly those that are routinely cycled or operated at their maximum ramp rates.

Operators of combined-cycle plants that have been pressed into cycling service should make sure that the aqueous diet of their steam generators—especially heat-recovery steam generators—fits the plants’ more active lifestyle. Following are some tips for keeping your HRSGs’ water treatment regimen in tip-top shape. These prescriptions can keep the units vital longer and make them subject to fewer unexpected failures.

The state of interconnection standards for distributed generation plants remains disconcerting to many prospective owners of such plants. IEEE 1547 has been in place for several years and appears to be the best option in a field of competing standards. But IEEE 1547 is an imperfect standard; it holds at least six holes. Here are some suggestions for filling them.

Contrary to public belief, the most common electrical phenomenon produced by a power plant’s steam turbines, turbine-driven compressors, and pumps isn’t sparks or lightning bolts. It’s static electricity. The physical effects of static electricity—greater vibration and higher temperatures—can damage bearings, shaft journals, couplings, and gears enough to cause a forced outage. A few inexpensive instruments in the hands of a well-trained technician can prevent "frosting" and "worm tracks" in your babbitt bearings. We’ll start the training right now.

Arc flash is arguably the most deadly and least understood hazard faced daily by plant personnel. Research indicates that even the best safety plan, training regimen, and protective equipment may be no match for the heat and blast effects of an arc flash. Consider this article a wakeup call to retrofit every switchgear cubicle in your plant with a properly designed remote racking system. Forewarned is forearmed.

A quick and nimble boiler distributed control system can end up moving at the speed of molasses in winter after a low-NO_x retrofit. In one utility fleet, several units—despite being equipped with a modern DCS—were experiencing firing system time lags and degraded dynamic loading capability. Swinging steam pressures and opacity excursions were forcing operators to constantly remove the unit from the load dispatch. Read how a new boiler master design read the riot act to those unruly steam generators.

One expert has called it the "digital delta"—the seemingly endless challenges in refurbishing U.S. nuclear plants with digital instrumentation and controls. But it appears more like a deep ditch, where even those seeking to license new reactors could get stuck. Here’s the latest on the issues, experience, and results—plus recommendations for getting the industry out of the mud and back on the road.

The use of longer steam turbine last-stage blades (LSBs) reduces the number of low-pressure casings and, thus, a turbine’s total installed cost. In many cases longer blades extract more energy from low-pressure steam before it enters the condenser and improve a turbine’s overall thermodynamic efficiency. But creating longer blades requires forsaking conventional design techniques for complex aerodynamic analysis of stationary vanes and rotating blades. Has the market push for longer LSBs exceeded current technology limits? Does the industry conduct proper analysis to determine when using longer blades is beneficial or not?

Renewables require rethinking just about everything/Torque-splitting drive train improves wind turbine reliability/Waste gas–burning engines reach milestone/Hybrid power plant targets pipeline losses/Power from paint/Gulf Coast Power Association conference report/Pat Wood talks about the challenges facing ERCOT