Turbine Selection for Hydro Power

Er, on the basis of the quantity of water and the head available, perhaps?

When the water level in the reservoir drops,hence drop,do you need to do adjustments to blade pitch or angle.

you mean low head and high volume and vice versa?yes turbines will differ .

I mentioned just some rough guidelines, there are more formal methods explained in many books and articles you can find online.

Also there are no hard and fast rules, especially when flow and head are in ranges where several turbine types are possible. In some cases for indentical flow and head you will find examples of two different hydropower plants, each of them using a different turbine type.

Here we talked about large turbines which always drive generators directly (i.e. turbine speed is the same as the generator speed) and all those generators are synchronous generators. In small hydro you can also sometimes find asynchronous generators as well various forms of speed increasing transmissions (belts, gears or whatever).

While more complex questions can't be answered by quickly googling, many basics can be found if spending a couple of minutes or hours searching online.

Dear Mr muthuk10,

High Velocity of Water will have HIGHER LEVEL OF KINETIC ENERGY, since the FORMULA is 1/2 x M x V^2, hence the Rotor of this Turbine will receieve Higher KINETIC ENERGY and run at HIGHER SPEED, and therefore the size of this Turbine will be SMALLER. As for as power is concerned (w x H)/75 X 1/EFFICIENCY in HORSE POWER. This H.P. multiplied by 0.75 is KW.

LESS VELOCITY will have LESSER KINETIC ENERGY, and hence the Rotor will run at LESSER SPEED, therefore the size of the Turbine will be bigger. For the same Power HIGH VOLUME of DISCHARGE is required. i.e., (W x h)/75 x 1/EFFICIENCY in H.P H.P. X 0.75 = KW.

In the Formula w = Less Quantity of Water, W = Large Quantity of Water, h = Less Head, H = High Head.

DHAYANANDHAN.S

Howmany types of speed governors are available for hydro turbines,on what basis (head,flow,inlet opening/closing etc)one is selected for a particular application.

Interesting question.

There are basically two families of digital turbine control systems (I don't talke about analogic as well as mechanical systems which are obsolete though still in use), I already mentioned it somewhere:

1) Specialized turbine controls which are typically based on proprietary hardware, also sometimes mixed with industrial PC and/or industrial PLC components (possibly with special I/O modules). Those controls also include a special software. They can be used for anything from a small Pelton to a large 1600 MW steam turbine and come as simple emodule to complete cabinets with touchscreens and redundant controls.

2) Turbine controls based on off-the-shelf components, usually built around one or more PLCs, also in combination with industrial PCs. In such case the hardware concept is nothing really special, the major taks is the software because turbine regulation is not that simple as it may look.

In any case availability an reliability play an important role. In some cases redundant systems are used. Some sub-systems of large turbine controls may be implemented with a 2oo3 (2 out of 3) voting.

AFAIK all major turbine manufacturers offer turbine regulators but you can also buy solutions by 3rd parties.

For water turbines, from a regulation POV there are basically two family of turbines:

1) Single regulated turbines (e.g. Pelton, Francis,...).

2) Dual regulated turbines (e.g. Kaplan though not all Kaplan are dual regulated).

Usually there are several regulation modes depending on operating conditions and operating modes and you can typically also switch bumpless between several modes (parallel tracking of regulators).

For example you can start a Pelton by accelerating at constant angular acceleration (or maybe pass faster resonance speeds zones) and than you can switch over to (nearly) constant speed before starting the sychronization process. Once synchronized you can regulate for constant active power (reactive power or cos phi regulation being handled by the digital excitation control (ACR) though generator active power defines the allowable reactive power range), in some cases you regulate the deflectors to handle quick load changes. In some low load cases you may use only a part of all injectors (nozzles) but you may require balance to protect bearings and reduce mechanical stress, etc. You can even run some turbines without water (maybe just cooling spray because the fan effect heats up the air around the turbine) for cos phi compensation.

For double regulation like large Kaplan it can be way more complex because you've to handle the cam electronically, in some case you go off-cam to optimize for power instead of efficiency, you may have to regulate to avoid overspeed, resonances, excessive turbulence or so.

Common to all large generators is that they're synchronous and therefore unless accidentally forced out-of-step (which must be avoided) they run at a given speed tied to the grid frequency.

There alre also pump-turbine groups. Even more complex stuff.

You could write a whole book about how to regulate water turbines. It also depends on the available instrumentation. For large turbines the efficiency is extremely important, so especially for double-regulated Kaplan you've to be very careful how you optimize you control laws. Also keep in mind that turbine data varies with time, so the optimal control law parameters when new are not necessarily the same as after a couple of years.

Usually the main factor is which flow you're allowed to use, from there you try to optimize its use.

The turbine and excitation controllers receive their control mode selection (for example constant active power and constant cos phi, as well as setpoint information (as absolute setpoint or as correction signals), it's a bit more complicated in real life because large groups can influence grid voltage and grid frequency. Interface can be discrete (digital and analog I/Os) and/or by digital communcation.