Cable Sizing

ok it is suggested by dg vendor that every phase and neutral will connect through a separate cable. i understand the current capacity of DG and cable, naturally it is not possible to connect all the cable in a cable alley. then what is ur suggestion

i understand ur points, it is dg vendor suggestion, he suggest 3.5 C,300sqmm copper cable for R,Y,B and neutral. the distance of DG and panel is 100 Mtr. what is ur suggestion

Do you mean the undermentioned arrangement?

R, Y & B Cores of Cable-1 will get terminated to Terminal "R" of the generator,

R, Y & B Cores of Cable-2 will get terminated to Terminal "Y" of the generator,

R, Y & B Cores of Cable-3 will get terminated to Terminal "B" of the generator,

and the Black cores of all the three cables can be bent & terminated to the "N" terminal of the generator.

Is it your idea?

If so, I strongly suggest against it, because, in such a case, there will be severe heating of the armour of each cable and the cable insulation might damage sooner than later.

Better go for bus bars.

Else, if cables are unavoidable go for spreader links & a cable adaptor box.

No, the proposal is as under:

R, Y , B & N Cores of Cable-1 will get terminated to Terminal "R" of the generator,

R, Y , B & N Cores of Cable-2 will get terminated to Terminal "Y" of the generator,

R, Y , B & N Cores of Cable-3 will get terminated to Terminal "B" of the generator,

R, Y , B & N Cores of Cable-4 will get terminated to Terminal "N" of the generator,

I may go for bus bar what the distance between DG and Panel is 100Mtr.Approx

Lets suggest

That means 1050 sq.mm of copper conductor each for the three phases and for the neutral too. Still, the phase conductor cross section is a weebit undersized, I feel, what with three/four conductors grouped together.

Moreover, why should the neutral require 1050 sq.mm? Is it not a waste of money?

If the distance is 100M it is all the more reason to go for bus bar, because the voltage drop in cable might be more than that in a bus for the same distance.

If due to some other reason, you cannot go for bus bar, then I suggest that you go for Copper Spreader Links emanating from the generator terminal box connnected to a more voluminous Cable Adapter Box, and connect as below:

R cores of Cables 1 to 4 to terminal R

Y cores of Cables 1 to 4 to terminal Y

B cores of Cables 1 to 4 to terminal B

Blk. cores of Cables 1 to 4 to terminal N

Please care to have enough splitting & bending space in the adapter box.

i will go with expert 65. enough allowance has been made for distance and installation factor

My opinion is max. current carrying capacity of 300mm.square is 559A CU/XLPE/PVC/SWA direct laid in the ground derating factor is 0.82(as adoptable in Saudi Electric Co-SCECO. KSA). In most stand-by power plants here in our area we do not recommend multi-cores conductor power cables either installed in cable trays or in cable trench. Power Plants or MV 132/13.80 Kv sub-distribution substations, we recommend the power cables between the gen-sets via ATS/MTS to MDB are single core cables. The advantage is easy to terminate, cable heat is minimal compare to multi-core cables. So your cable size is okey as you determined in your calculation to be 1,043amp. therefore 559x0.82 = 458amp net capacity of 300mm.sq XLPE cable. Then you need 3x300mm.sq to hook up in three terminals of gen.set as RYB or you can use neutral at full-size + 95mm.sq earthing. Then allow 25% for inrush/transient current will be 1,043ampx1.25=1,304 amp so your cable is 458x3= 1,374 amp greater than 1,304 amp(cables is safe)