Hydropower Unit Inertia Requirement
Hydropower Unit Inertia Requirement
(OP)
I have been to help out with some info regarding a hydropower unit.
What are they talking about when they say inertia requirement in MWs/MVA in ton m2 for a hydropower unit?
What can one do in order to meet inertia requirement?
what is a reasonable value or a upper limit value and what kind of costs would be expected?
What is the mathematical relationship between tonm2 and MWs/MVR?
Thank you very much in advance!
What are they talking about when they say inertia requirement in MWs/MVA in ton m2 for a hydropower unit?
What can one do in order to meet inertia requirement?
what is a reasonable value or a upper limit value and what kind of costs would be expected?
What is the mathematical relationship between tonm2 and MWs/MVR?
Thank you very much in advance!






RE: Hydropower Unit Inertia Requirement
The stored kinetic energy is 1/2xJxWxW
J is moment of inertia in kg m(sqd)
W is rotational speed in rad/s
If you divide by the generator VA
Stored kinetic energy/VA = 1/2xJxW(sqd)/VA
When rotating at nominal frequency, the ratio of stored kinetic energy to VA on the left hand side is known as the generator inertia constant, H. For hydro, H is usually in the region 2-5. A lighter more efficient newer machine will have a lower H than an older machine.
Regards
Marmite
RE: Hydropower Unit Inertia Requirement
Regards
Marmite
RE: Hydropower Unit Inertia Requirement
So the H value is dependent on m,r and w of the machine. Would you normally add or reduce weight to the rotor or change the diameter of the rotor to adjust the H?
You say newer machines have a lower H but isn't it better to have a higher H value for system stablity?
I believe you but how do you go from kgm^2/s^2 to MWs - I missed something???
RE: Hydropower Unit Inertia Requirement
Volts= Joules/Coulomb
Amps=Coulombs per second
Watts= VxA = Joules per second
Watt seconds =Joules (same as kWh on your meter at home =energy)
Newer machines have lower H because advances in manufacturing technology mean there is less metal in them and they are more efficient. Bigger H is better for stability but worse for fault contribution as the machine can contribute more energy to a fault. Are you designing this thing from scratch?!
Regards
Marmite
RE: Hydropower Unit Inertia Requirement
Actually the owner was asking for options for differnt H values so they could consider using one or two lines for distribution. I was just asked to look into it.
Thanks again for your help.
RE: Hydropower Unit Inertia Requirement
I hope that Marmite is around or anyone else with comments.
I would like to get comments on the following:
It has been suggested that if the generator has a H=3.5 then we need 2 power lines for stability of the grid but if the generator has H=5 then we would only use 1 line.
Is it normal to adjust the inertia of the generator to meet grid requirements?
Do you see any problem with raising the H value?(lower efficiency, more stress on generator bearings or brackets)
I am guessing it would be cheaper to raise the H instead of building another line but what would you recommend in this situation?
RE: Hydropower Unit Inertia Requirement
While higher values of H will certainly help the transient stability of the network, they are not usually adjusted to meet network requirements. Factors such as the type of the excitation, system stabilizers, circuit-breakers reclosings, etc affect more the stability of the system following perturbations.
If data are provided, the system can be soundly designed with a standard transient stability program.
Bahram7
www.Simtech-Intl.com