3 Quick Questions – Hydro Governors

Hydro-governors have already made an impact in the water industry, but how are they moving forward?

Learn about ABB solutions and projects for the Water Industry: http://new.abb.com/water

What is a hydro-governor?

Hydro-governor is just a big word for a speed controller. Its typical application is to prime movers such as the steam engine, turbine, diesel engine and many other types of prime movers. To understand the basics of a governor, you must first know a little bit of history. Years ago during the industrial revolution, Thomas Mead, a mechanic and miller, invented the first centrifugal governor for a windmill that would lower a millstone onto grain only when the stone’s speed was sufficient. The centrifugal governor regulated the speed output but not the millstone power. With this concept, a fellow mechanical engineer, James Watt was able to adapt Mead’s centrifugal governor for the steam engine. James Watt and Matthew Boulton were then able to patent a combined engine and governor with remarkable success. For the next 100 years, this uniquely mechanical governor would be largely applied to steam engines of all types.
Despite the success of the flyweight governor in the world of steam engines, the purely mechanical governor did not have the same degree of success on hydraulic turbines. The control needs of a steam valve on a steam engine proved to be much simpler then controlling the opening of the wicket gates of the water based hydro units. Many engineers came up with variations of the mechanical governor with little success. Around 1860, hydraulic servomotors emerged in steering devices of large deep sea ships. The combination of hydraulic relay valves and servos with the flyweight governors ended up being the perfect contraption needed for hydro-electric turbines. These devices became known as mechanical hydraulic governors, or MHGs. Many of these original mechanical marvels are still in operation today. By the 1960s, electronic components slowly replaced governor components and further reduced the mechanical complexity. The hydro world began to see the emergence of the electro-hydraulic governors, or EHGs. EHGs are still in operation today and will continue to operate for years to come. Slowly, EHGs have been replaced with microprocessor based controllers. Due to the incredible reliability of both the MHG and the EHG governor, all of these technologies are able to coexist today.

What are the advantages of upgrading a mechanical-hydraulic hydro-governor to an electrical-hydraulic hydro-governor?

Microprocessor based governing systems are much easier to adapt and maintain for specific customer requirements. But more importantly, it greatly increases the level of automation in a plant. Hydroelectric power plants can easily be transitioned to be completely unmanned. The result is huge cost savings. With microprocessor based EHGs, it is easier to achieve higher levels of automation and operate the plant more efficiently, such as the use of water minimization programs and better integration with joint-plant control and unit commitment algorithms.

When should you start thinking about upgrading your mechanical-hydraulic hydro-governor?

Due to the extreme reliability of the former MHG and EHG, it is difficult to decide when to upgrade or replace them. There are companies that provide custom made replacement parts and reaffirm that “No Governor is Obsolete.” This statement is not absolutely true for all hydroelectric power plants. A good indicator is maintenance cost reductions usually done by increasing the automation level of the entire plant. This is likely to require upgrades outside of the governing system, e.g. the unit control (sequences), protection systems and communications todispatch centers.

Author:

Reid Boutot
Systems Integrator, ABB inc.