In the United States, hydroelectric power generation technology is over a century old. Then, during the first half of the 20th century, demand for electricity grew explosively. Since hydro generating plants (hydro plants) provide power generation, flood control and irrigation, the US government approved and funded the construction of many large hydroelectric dams such as the Hoover and Grand Coulee.
However, as a result of obsolescence and a growing inability to obtain suitable OEM replacement parts, the rationale of continuing to run a hydro plant with legacy mechanical governors is being called into question. Therefore, many engineers are weighing the advantages of digital governors in their hydro plants.
Continuing to run a hydro plant with aging mechanical turbine governors is fraught with multiple problems:
- They are less likely to respond stably to load disturbance
- Identifying the cause of a fault or, in some instances, recognizing that a fault is occurring is difficult until there is a significant failure
- Minor load variations can send a governor into unrecoverable oscillations
- Obtaining OEM parts is frustrating because they are harder to find and costly
- Needle sequencing is difficult because needle control is indirect, there is no ability to individually position the deflector or needle, and operators must manually link and unlink the nozzles
- Mechanical governors cannot sustain rapid load acceptance, which means a system cannot be rebuilt efficiently after an outage. In such cases, many power companies must co-opt off-site diesel plants turbines to increase system stability, resulting in additional operating costs. In fact, diesel generation represents the single most costly resource while using mechanical governors.
A digital governor solution provides many benefits, including improved response characteristics and performance.
- Digital governors designed around commercially available components allow flexible operation of the system. They allow for a reduced parts count and fewer spare parts, and offer better reliability because there are fewer fail points. They provide superior needle sequencing by controlling the deflector and needle servomotors virtually independent of each other. Independent control allows the deflectors to move rapidly in response to load changes while maintaining stable, controlled operation without manual intervention.
- They offer automatic under frequency detection, isochronous load sharing, water waste mode capability, the rapid load rejection management and integrated automatic synchronization. Advanced modes in the control algorithm can include provisions for speed sensing, regulation, and stabilization of the governor system via the algorithm and electronics that provide signals to control the turbines. An automatic synchronizing algorithm can even put the turbines online automatically.
- Digital governors mitigate the need to operate expensive diesel generators, which, in some cases, have saved up to US $150 million in diesel fuel costs over 30 years.
- Repair time for problems is also shorter with a digital governor system because it utilizes built-in diagnostic tools and alarms allowing maintenance personnel to quickly and easily determine where a fault has occurred. Admittedly, replacing a single electronic plug-and-play component is far easier than coping with a mechanical oil blowout or coupling.