Hello everyone,
I'm wrestling with grouping factors for cables between a substation and LV feeder pillar. I'm limited with the number of parallel feeds as the sub will only take 4 conductors per phase. I have my cable depth to 0.5m and soil resistivity to 1.2K.m/W. The software I'm using only gives an option of up to 600mm distance between trefoils as does ERA 69-30 so my question is how do I show the correct derating factor above 600mm is there any guidance? I was thinking that if I was to specify a 0.9m gap I allow an extra 0.12% as the difference between 0.3m & 0.6m is 0.12. The cables are direct buried and it's AWA. I can only get the cables to be satisfactory if I get the Cg to 0.95 but I want to be able to justify this choice but cannot find anything to assist me with anything over 600mm spacing.
