HYDROPOWER GOVERNERS

What is a Governor?

• An attachment to a machine for automatic control or limitation of speed /A device giving automatic control (as of pressure or temperature or speed).
• A Governor is a device which controls the energy source to a prime mover to control its power for a specific purpose.
• Advanced governors are often referred to as Control Systems.
• Examples: Electronic Load Controller (ELC)and Induction generator controller (IGC) in water turbines.

What is a turbine governor?

• They are accessories for speed regulation of the turbines.
• It provides constant speed to the runner for fluctuating load.

Governing of impulse turbines

Spear regulation:

• In this method rate of flow is regulated by to and fro movement of spear inside the nozzle.
• It is used when fluctuation in load is small.

Deflector regulation:

• It is a plate connected between nozzle and buckets.
• It diverts the water away from runner and diverts it into tail race.

Governing of Reaction turbines

• In this type of turbine disharge is varied with the help of guide vanes.
• Greater energy is required to move gates as compared to spear in pelton.

LOAD CONTROLLER

• Electronics Load Control is an electronic governor that functions as a frequency and voltage regulator on a generator.
• Load control is suitable for a micro hydro power plant applied on rivers (with out a dam).

There are some advantages of load control:
1. Avoiding expensive mechanical tools.
2. Load control tools are relatively more simple and cheaper.
3. Load control is possible to accept very big load changes.
4. Simple maintenance.

WORKING PRINCIPLES

• To divert the excess power generated by the hydraulic turbines to dummy load,
• The frequency and the voltage of the system are maintained on safe range. 
• ELC works based on frequency signal.
• It will continuously checking the frequency every half cycle (10 ms), and take required action based on the frequency measured, if the measured frequency is above frequency set point it will trigger the thyristor at certain phase angle according to the error and continuously adjusted until set point is reached.

What does an ELC do?
Generating Power = Ballast Load + Main Load

IMAG, using induction motors as asynchronous generators

• Almost any induction motor can be used as a generator, as seen by studying its symmetric torque/slip diagram. 
• Slip<0 over-synchronous speed -> rotor is forced to turn faster than the magnetic field, mechanical power is transformed into electrical power. 
• IGC function as voltage regulator for power plan by asynchronous generator.

 Passive regulation with saturating inductance

• A capacitor bank must supply reactive power to the motor when used in stand-alone mode. 
• Terminal voltage will increase with capacitance, but is limited by iron saturation.

a) Passive regulation with saturating inductance



b) Voltage control by regulating solely the speed


c) Voltage control by regulating C




References
• A. Harvey, Micro-hydro Design Manual. Rugby: Intermediate Technology
   Publications, 2006.
• H. Ludens. (2010, Electronic Load Controller for microhydro system.
• Available: http://ludens.cl/
• Renerconsys, "Digital Load Controller for Synchronous Generator: Manual
• Instruction," 2010.
• D. Henderson, "An Advanced Electronic Load Governor for Control of
• Micro Hydroelectric Generation”, 1998
• Spirax Sarco, “Basic Control Theory”, 2010. 
• www.spiraxsarco.com