Answer / 7anoter4

According to UL-1072 ch.57.5 insulation resistance of an
insulated conductor will be:
R=1000*K*log10(D/d)/L
D=insulated core diameter d=conductor diameter. L=cable
length.
The minimum permissible insulation resistance will be:
K=20000 Mohm/1000 ft. then L=cable length in ft. or K=6100
Mohm/km then L will be in m.
Let's say we have a 1*240 sqr.mm copper conductor 11 kV
XLPE insulated cable.
According to IEC 60502-2 [BS6622] insulation thickness=3.4
mm.
The conductor diameter is about 20 mm.
Then D=20+3.4*2=[approx.]27 mm.
R=1000*6100*log10(27/20)/m=7.95*10^5 Mohm/m or 795 Mohm/km.

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