Generator H-Constant and Inertia

[Cainraider]

Sorry, hit some send button prematurely.

Question #2. I've read an exerpt from a System Operator describing "inertial response".

"Conventional machines give an inertial response – this is a temporary surge in electrical output as the stored rotational energy of the machine is converted into electrical energy as the machine slows down."

From the swing equation and rotor dynamics, mechanical and electrical torque is positive so decelerating the generator wil decrease MW output. Am I missing something?

 

[Cainraider]

Another question on H-Constant. I heard H-constant described as follows:

For a synchronous generator with an H-constant of 4-sec. If 1 P.U. decelerating torque is applied to the generator running at synchronous speed, it will take the generator 4 seconds to decelerate to 0.5 P.U. synchronous speed.

Has anyone come across this charaterization? It's a good explanation for the lay person as opposed to tryinh to explain the ratio of MJ/MVA.