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r1 + r2 for 3 core 10mm XLPE

hertzal123 over 2 years ago

I,m trying to design a submain for an outbuilding.The circuit comprises 50m of 3 core 10mm xlpe

on a bs88 40A fuse.Have worked out R1+R2 for the cores as 50x3.66x1.2/1000 =0.0216 ohms

Can the armour be included in the calcs to lower ZS and how would it be done?The supply is TNS 0.8 ohms (understand we have to work on that value)

Thanks for any help,

Regards,Hz

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0 Chris Pearson over 2 years ago

You need to look up the manufacturer's specification, which will give you the CSA of the armour. Then you adjust for the resistivity of steel compared with copper.

That calculation seems very low. I have obtained 0.07 Ω (by calculation and measurement) for a 50 m drum of 25 mm² cable. Have you slipped a decimal place?
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0 Chris Pearson over 2 years ago

You need to look up the manufacturer's specification, which will give you the CSA of the armour. Then you adjust for the resistivity of steel compared with copper.

That calculation seems very low. I have obtained 0.07 Ω (by calculation and measurement) for a 50 m drum of 25 mm² cable. Have you slipped a decimal place?
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