Creep in Hydro Turbines

Creep is the situation in which there is slow rotataion (below 20 rpm) due to leakage of water through wicket gates which is always there. Creep situation is totally unwanted and undesirable for the m/c life. To know its presence we usually apply an instrument known as Creep Indicator. This assembly consists of solenoid and brushes. In ususal case when unit is not runing brush has contact with shaft and for any movement of shaft, brush tilts actuating a micro switch which give an alarm signal. Creep inidcator is designed such that it remains insensitive during Start Up, Running and Stopping. During this period solenoid get energised and removes the brush contact from the shaft.