Synchronous reactance

[nawao]

Could somebody explain what is the meaning of the Synchronous Reactance, and the Sub Transient Reactance of a Generating Set.

 

[cuky2000]

During a short-circuit current and the reactance of the machine is a time-varying function such as

I(t)= (Em/Z).[Sin(wt+a-Q)-Sin(a-Q).e^-RT/L]
Z= SQRT[(R²+W²L²)]


To facilitate the analysis, the reactance is approximated in a stepwise fashion in three time zones denoted the substarnsient (2<cycles<5), transient (<5 cycles<30) and steady state (>30 cycles).

There are standard procedures for factory test of those parameters. For constant voltage the value of those parameters are as follows:

1- Subtransient: X’’_d = E/I”

2- Transient X’_d = E/I’

3- Steady-State X_d = E/I

See the enclose site to illustrate this concept.

http://xnet.rrc.mb.ca/janaj/1_3_1_transient_circuit_model.htm