Transient Stability & Rotor Acceleration
Transient Stability & Rotor Acceleration
(OP)
Hi all,
I have just read something that has really confused me. I am researching transient stability of synchronous machines by reading "Power System Analysis" by Grainger and Stevenson.
Pg 718, describes a system where a generator supplies a bus with 3 transmission lines, two long and on short. All lines have CB's at each end. The short line has the CB at the remote end open and has a 3 phase fault close to the bus which is cleared by the CB at the near end.
The text then goes on to say: (I will summarise and not quote)
- There is a difference between mechanical and electrical power (Pm=unchanged (OK), Pe=0 (huh?)).
- This difference in power must be accounted for and is done so by acceleration of the rotor(if I accept the above I understand this).
Wouldn't an increase in load (like a short) act to slow down the rotor?
I have just read something that has really confused me. I am researching transient stability of synchronous machines by reading "Power System Analysis" by Grainger and Stevenson.
Pg 718, describes a system where a generator supplies a bus with 3 transmission lines, two long and on short. All lines have CB's at each end. The short line has the CB at the remote end open and has a 3 phase fault close to the bus which is cleared by the CB at the near end.
The text then goes on to say: (I will summarise and not quote)
- There is a difference between mechanical and electrical power (Pm=unchanged (OK), Pe=0 (huh?)).
- This difference in power must be accounted for and is done so by acceleration of the rotor(if I accept the above I understand this).
Wouldn't an increase in load (like a short) act to slow down the rotor?





RE: Transient Stability & Rotor Acceleration
Inductance is not capable of dissipating any real power. Generator power must go to zero.
Current will likely increase, but it is all reactive.
RE: Transient Stability & Rotor Acceleration
There are also second order effects - control, braking torque due to currents induced in rotor damping circuits etc.
RE: Transient Stability & Rotor Acceleration
L.L. Grigsby "The Electric Power Engineerng Handbook," CRC Press, IEEE Press, 2001, page 11-57, Figure 11.23.
Notice that Pe is a part of negative feedback and Pm is reference (constant)
Pe=E'V sin(delta)/X
Feedback, Pe, may be equal to zero while the error is equal to Pm.
RE: Transient Stability & Rotor Acceleration
Pe=E'V sin(delta)/X
V goes to zero for bolted short at terminal.
Therefore Pe goes to zero.
As avg mentioned. the turbine is slow to respond and Pmech originally stays constant, producing accelration.
RE: Transient Stability & Rotor Acceleration
This now makes good sense. Sometimes the old brain needs a prod in the right direction!
RE: Transient Stability & Rotor Acceleration