Editing Water turbine (section)

== Control systems ==
[[File:From Turbine to Line Shaft.webm|thumb|Operation of a [[flyball governor]] to control speeds of a water turbine]]

Different designs of [[Governor (device)|governors]] have been used since the mid-18th century to control the speeds of the water turbines. A variety of [[centrifugal governor|flyball]] systems, or first-generation governors, were used during the first 100 years of water turbine speed controls. In early flyball systems, the flyball component countered by a spring acted directly to the valve of the turbine or the wicket gate to control the amount of water that enters the turbines. Newer systems with mechanical governors started around 1880. An early mechanical governor is a [[servomechanism]] that comprises a series of gears that use the turbine's speed to drive the flyball and turbine's power to drive the control mechanism. The mechanical governors were continued to be enhanced in power amplification through the use of gears and the dynamic behavior. By 1930, the mechanical governors had many parameters that could be set on the feedback system for precise controls. In the later part of the twentieth century, electronic governors and digital systems started to replace the mechanical governors. In the electronic governors, also known as second-generation governors, the flyball was replaced by rotational speed [[sensor]] but the controls were still done through [[Analog device|analog]] systems. In the modern systems, also known as third-generation governors, the controls are performed digitally by [[algorithm]]s that are programmed to the computer of the governor.<ref>{{cite journal|last1=Fasol|first1=Karl Heinz|title=A Short History of Hydropower Control|journal=IEEE Control Systems Magazine|date=August 2002|volume=22|issue=4|pages=68–76|doi=10.1109/MCS.2002.1021646|url=http://ieeecss.org/CSM/library/2002/aug02/04-HistoricalPerspectives.pdf|access-date=29 January 2015|archive-date=6 November 2015|archive-url=https://web.archive.org/web/20151106083244/http://ieeecss.org/CSM/library/2002/aug02/04-HistoricalPerspectives.pdf|url-status=dead}}</ref>

===Wicket gate===
[[File:Francis Turbine High flow.jpg|thumb|Wicket gates (yellow) surrounding a [[Francis turbine|Francis type turbine]]. 
Varying their angle manages water flow, thereby regulating turbine speed and energy produced by it.]]

A '''wicket gate''', or '''guide vane''', is a ring of gates (or vanes) surrounding a water turbine which control the flow of water entering it; varying the aperture between them manages the rate of the turbine's spin, and thereby the amount of electricity generated.<ref>{{cite web|title=What Is a Wicket Gate? |url=http://www.wisegeek.com/what-is-a-wicket-gate.htm|publisher=wiseGEEK|access-date=29 January 2015}}</ref>