Calculating Subtransient Sequence Reactances

[turtlepokerman]

Hello Everyone,

I am trying to calculate the positive, negative, and zero sequence subtransient reactances for a generator. I asked the vendor for this information and was of course supplied with different information than I requested. Is there a way to calculate (pos,neg,zero) subtransient reactances if what was shown below was provided. I also requested X/R ratios and those were not provided either.

Xd(pu)
X'd(pu)
X''d(pu)
X2(pu)
X0(pu)
T'd(sec)
T''d(sec)
Tdc(sec)
Ta(sec)

All help is appreciated!

 

[waross]

Use the base KVA to convert the per unit (pu) reactance values to ohmic reactance values.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

All you're missing is the armature resistance; but if you're really clever you can calculate it from the time constants. X0 and X2 are what they are; no subtransient, transient, synchronous numbers.

 

[ijl]

As davidbeach observed, there is not such a thing as a negative or zero sequence subtransient reactance (let's call them X2" and X0"). The d-axis subtransient reactance X"d is used to calculate the initial short circuit current for a 3-phase fault. Similarly, the initial sequence currents for a phase-earth fault (for example) are calculated using the sum of Xd" and the negative (X2) and zero sequence (X0) reactances. Thus, Xd"+X2+X0 in a way serves as a subtransient reactance for sequence currents of the phase-earth fault. But not literally as these so called X2" or X0".