Cable size for 550kVA Standby Diesel Generator

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The required cable sizes are in the American NEC, which even if not mandatory in your country is still a useful guide to accepted good practice.

Alternatively consult the British IET regs, which also list cable sizes, again a guide to good practice even if not a local requirement.

You may need a larger cable than at first seems correct if a long run is involved, in order to limit voltage drop.
In tropical climates cables may also need upsizing due to the high ambient temperature.

In the absence or more detailed information, I would suggest that if UK type armoured cable is to be used, that two cables each 4 core 240mm be used in parralel.
That size cable is, normal ambient temperatures, suitable for from 409 amps to 445 amps depending on how installed.
Larger cables do exist but are less common and very expensive.

240mm can just about be handled manually, but is very heavy.
 
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broadgage said:
In the absence or more detailed information, I would suggest that if UK type armoured cable is to be used, that two cables each 4 core 240mm be used in parralel.
That size cable is, normal ambient temperatures, suitable for from 409 amps to 445 amps depending on how installed.
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XPLE is becoming more common.
Two parallel 185mm2 would do and if there are no abnormal ambients, then possibly even two 150 could handle it.
As you say, 240mm2 is big heavy cable.
 
Article 445 of the National Electrical Code contains rules for generators. The ampacity of the conductors from the generator terminals to the first distribution device containing overcurrent protection shall not be less than 115 percent of the nameplate current rating of the generator.
 
erickench said:
Article 445 of the National Electrical Code contains rules for generators. The ampacity of the conductors from the generator terminals to the first distribution device containing overcurrent protection shall not be less than 115 percent of the nameplate current rating of the generator.
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Typically that does not apply if the generator has a factory mounted over current protective device.

That section would apply when the generator is ordered without a OCPD and the windings are directly connected to flied wiring to a remote OCPD.
 
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