Synchronous generator negative sequence reactance
Synchronous generator negative sequence reactance
(OP)
Hi,
I have a small portable powergenerator:
350kVA, 280kW, 400V, 505A, 50Hz, PF=0,8 and 1500 rpm.
From data sheet
xd''=0.140 pu, saturated
x2 =0.140 pu (neg. seq.)
My question is now this x2, is it subtransient or what?
Can I use x2 (and xo, zero. seq.) for synchrounous generators for short circuit calculations?
Any comments or hints for books/www links are really needed!
Best Regards
John
I have a small portable powergenerator:
350kVA, 280kW, 400V, 505A, 50Hz, PF=0,8 and 1500 rpm.
From data sheet
xd''=0.140 pu, saturated
x2 =0.140 pu (neg. seq.)
My question is now this x2, is it subtransient or what?
Can I use x2 (and xo, zero. seq.) for synchrounous generators for short circuit calculations?
Any comments or hints for books/www links are really needed!
Best Regards
John






RE: Synchronous generator negative sequence reactance
Mike
RE: Synchronous generator negative sequence reactance
An x2'' ??
Best regards
RE: Synchronous generator negative sequence reactance
RE: Synchronous generator negative sequence reactance
Bung
Life is non-linear...
RE: Synchronous generator negative sequence reactance
Source: IEEE Orange Book - Recommended Practice for Emergency and Standby Power Systems
Mike Cole, mc5w@earthlink.net
RE: Synchronous generator negative sequence reactance
1st 5 cycles - use xd''
5 - 200 cycles - use xd'
above 200 cycles - use xd
Mike
RE: Synchronous generator negative sequence reactance
x2 is x2.. (no matter time)
I do not doubt you, but can you give me a short lecture why this is so, or maybe a good book to study these issues?
Best Regards
John
RE: Synchronous generator negative sequence reactance
Is it correct that the machine parameters (xd'', xd', xd Xq'' etc. and time constants) are unaffected by generator voltage and excitation level?
If I would like to do calculation on the generator transient respond to nearby motor starting, can I then use the machine parameters (xd'', xd', xd Xq'' etc. and time constants)? Or are the parameters only related to short circuits?
When the generator voltage is controlled by an AVR, can I calculate the Ik (steady state)?
Best Regards
John
RE: Synchronous generator negative sequence reactance
Direct Axis Synchronous Reactance, Xd(i):
Direct Axis Transient Reactance, X'd(i):
Direct Axis Sub-transient Reactance, X"d(i):
Quadrature Axis Synchronous Reactance, Xq(i):
Quadrature Axis Transient Reactance, X'q(i):
Quadrature Axis Sub-transient Reactance, X"q(i):
Stator Leakage Reactance, Xl:
Negative Sequence Reactance, X2(i):
Zero Sequence Reactance, X0:
Saturated Sub-transient Reactance, X"d(v) (on MVA Base):
Armature Resistance, Ra (on MVA Base):
RE: Synchronous generator negative sequence reactance
I am not sure if for small units this exercise can be justified because is time consuming and high cost associated with softwares to model the system.
Here are some of the answers for the original post.
QUESTION: … Is x2, is it subtransient or what?
ANSWER: X2 is the negative sequence reactance. Its value can be estimated as follow:
a) Turbine Generator with 2 or 4 poles
& salient pole generators w/o damper………………….. X2 ~ X”d.
b) Salient pole generator with damper …………..1.1X”d<X2<1.5X”d
QUESTION: Can I use x2 (and xo, zero. seq.) for synchrounous generators for short circuit calculations?
ANSWER:Yes, X2, Xo and X”d can be used in conjunction with the connection configuration to calculate the short circuit. As mpparent states above, Xo is smaller than X”d. This value could be expected between the following
c) Range expected for Xo:……………………….. 0.1X”d<Xo<0.7X”d
RE: Synchronous generator negative sequence reactance
That should explain everything you would ever want to know..
:)
Mike