Asymmetrical short-circuit current constant (r)
Asymmetrical short-circuit current constant (r)
(OP)
Hi!
I'm searching the equation for the short-circuit force on a substation busbar. I already find the equation in the IEEE Std 106-1998 (on page 16) (IEEE Guide for Design of Substation Rigid-Bus Structures) and I don't understand where does the constant (see Table 2), used in the equation, come from.
So, the second constant from table 2 (0.866) is (sqrt(3)/2) or cos (30), are the ieee editors use the line-line short-circuit current?
Pleas help!
rigidbar






RE: Asymmetrical short-circuit current constant (r)
For Metric units:
Fsc=(1.6*(r)*Isc^2)/((10^4)*(D))
For Imperial units:
Fsc=(43.2*(r)*Isc^2)/((10^7)*(D))
Where
Fsc=Fault current unit force, N/m [lbf/ft]
Isc=symmetrical rms fault current,A
D= conductor spacing center-to-center, cm [in]
(r)= constant base on type of fault and conductor location (see table)* ********THERE IS MY PROBLEM!!!!*********
type of short| CONFIG. | F. on cond. | ??(r)??| ____________________________________________
| Ph-to-ph | A---D---B | A or B | 1.00 | ?
___________________________________________
| 3 Ph | A -D- B -D- C | B | .866 | ?
___________________________________________
| 3 Ph | A -D- B -D- C | A or C | .808 | ?
___________________________________________
Where
A B C= are the 3 phases/conductors
D= distance between phase
I would like to know where does the (r) come from. Any documents or references would be appreciated!
So here is all the information I have, hope this can help.
Thanks a lot for your help!!!
rigidbar
RE: Asymmetrical short-circuit current constant (r)
RE: Asymmetrical short-circuit current constant (r)
type of SC| CONFIG. | F. on cond. | Γ|Inst Max F ________________________________________________________
| Ph-to-ph | A---D---B | A or B | 1.00 =43.2/43.2 | F=43.2K.I^2/10^7d _________________________________________________________________
| 3 Ph | A -D- B -D- C | B | .866 =37.4/43.2 | F=37.4K.I^2/10^7d
_________________________________________________________________
| 3 Ph | A -D- B -D- C | A or C | .808 =34.9/43.2| F=34.9K.I^2/10^7d
_________________________________________________________________
NOTE: F = lb/ft; d=Conductor Spacing (in), I = Current RMS Symmetrical
Additional inoformation could be found in the enclose link
h
RE: Asymmetrical short-circuit current constant (r)
Your info are very interesting and they confirm what I tought...
Thanks again!