Obscure Cable Geometry Question: ABB T&D Book, Geometric Factor
Obscure Cable Geometry Question: ABB T&D Book, Geometric Factor
(OP)
Hello,
My problem is to determine the shunt capacitive reactance of a 3/C, 500MCM, non-shielded, 5kV cable...
This question is mostly for those familiar with the ABB/Westinghouse T&D Book, Chapter 4, Electrical characteristics of cables, or those familiar with cable geometry.
The cable geometric factor "G" I have seen cited as G = 2.303*log_10(2*r_i/d) where r_i = inner sheath radius and d = conductor diameter.
Does anyone know how this is derived? This appears in the T&D book with little derivation.
Can anyone say if this is also the same formula used for 3/C cables as well (see Figure 10 of this chapter)?
Thanks for your help.
My problem is to determine the shunt capacitive reactance of a 3/C, 500MCM, non-shielded, 5kV cable...
This question is mostly for those familiar with the ABB/Westinghouse T&D Book, Chapter 4, Electrical characteristics of cables, or those familiar with cable geometry.
The cable geometric factor "G" I have seen cited as G = 2.303*log_10(2*r_i/d) where r_i = inner sheath radius and d = conductor diameter.
Does anyone know how this is derived? This appears in the T&D book with little derivation.
Can anyone say if this is also the same formula used for 3/C cables as well (see Figure 10 of this chapter)?
Thanks for your help.






RE: Obscure Cable Geometry Question: ABB T&D Book, Geometric Factor
I'm looking at my copy of the Westinghouse T&D book and the curves for 3-conductor cables are based on shielded cable also.
RE: Obscure Cable Geometry Question: ABB T&D Book, Geometric Factor
Regards
Marmite
RE: Obscure Cable Geometry Question: ABB T&D Book, Geometric Factor
It seems that the values given on figure 10 (Westinghouse, page 36) are valid for 60Hz frequency.
Would anyone have an equivalent table which can be used for the calculation of GMR in applications where the frequecy is 50Hz?
Many thanks.
RE: Obscure Cable Geometry Question: ABB T&D Book, Geometric Factor
My cable is unshielded but using the cable model of Figure 9 should be conservative for calculating shunt capacitance.