Diesel Generator wire size

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ADS74, Typically we don't take a 3 conductor cable and use all three conductors for one phase. In each cable there is an A phase, B phase and C phase.

If I understand you, you want to use a total of (6) 3 conductor cables, where each conductor is 300mm^2. The understanding is that the ampacity of that cable (based on the rating of its insulation) is rated at 312 Amps.

This gives you a total ampacity of 312*6=1872 Amps. I suggest that you add another cable and have (7) all together. Just a thought.
 
DGrant041-

I think due to so many posting that i have done regarding this matter, confuses some of you guys. In my first post i mentioned of 3 sets of 3C x 300mm2 cable, simply means 1no of 3C x 300mm2 cable per phase, (take note that on my first post i did not gone all the details of what happen in the site, pls review the posting). After i have visited the site, detail of informations were gathered and concluded to use 2nos. of 3C x 300mm2 cable per phase, this means 6 cores cores of cable per phase. Please review the previous posting.


Plate-

what you said is abosutely correct about the termination arrangement of the cables ( each cable will have ph-A, ph-B, ph-C). I could use 3 nos. of 3C x 300mm2 cable/phase which means 7 core of cable on each phase, youre right, but the price of the copper had gone up this time, so im proposing the use 2nos. of 3C x 300mm2/phase, this will carry 80% of the load, the gen will not work more than 80% anyway. what you think of this? Thanks
 
ads74 said:
I have made some calculations for the replacement of the burned cables. For a Gen 1.7MVA, 440V, 2230A, 3ph. i will use 2 nos. of 3Cx300mm2 XLPE/Cu cable/phase with a current rating of 312A (applying all the rating factors), but this will carry only 80% of the load. If i use 3 nos. of 3Cx300mm2/phase it will cover the whole load. But the problem is the copper price have gone up. Is it feassible to use 2nos. instead of 3nos.? The generator will not be working more than 80% anyway. Need some advise, thanks!
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OK Plate,

Since you have the correct interpretation of the situation, could you translate PLEASE. I've looked up the fact that 300 mm2 is 600 MCM but what is this:

"2 nos. of 3Cx300mm2 XLPE/Cu cable/phase with a current rating of 312A"
 
dave_asdf said:
when the generator was originally hooked up were the cables connected to each phase? or one core per cable to each phase? ( i think i worded that right )
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Each conductor cable has three (3) core each of which has to be on each phase meaning 1st core=phaseA, 2nd core=phaseB, 3rd core=phaseC. The cable melted because the current capacity of the cable cannot handle the working load of the generator.
 
dave_asdf said:
just some things that i would take a look at when i get there are
1)are all the cables burned up or just a couple?
-If only a few what does this generator power? if it is not powering a delta transformer take a look at the size of the neutral and loading from phase to phase.
-obvious stuff, cam-lock fittings if temporary cable, tightness of connections, are these in the sun?
2)did the generator ouput breaker do it's job?
-if this was caused by high current your breaker should have tripped. Rate the cable to the size of the feeder breaker, not the generator. it's the CB's job to protect the cables. if you have a 2000A gen with a 3000A output breaker (for whatever reason...) you should have 3000A capable cables.
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Dear Dave,
I read all the correspondences related to this problem and was very interrested in your statement "-If only a few what does this generator power? if it is not powering a delta transformer take a look at the size of the neutral and loading from phase to phase".
I have similar problem where the loading is from phase to phase and the neutral is not connected to earth.
Do you think that connecting the neutral of the generator to earth could probably solve the problem?
Best regards
GabyKhoury
 
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