CpC half of phase?

[Dylboy]

Hello

Start off with hope all the KZN okes are doing ok and so sorry! Fortunately my folks in Balito are ok but the complex as a whole took a beating!

My question:

I have a chap stating that the CPC can not be less than half the phase C.S.A.

Now I am trying to find that reg to see for my self. He just says look at tables on 167 and page 304 but I can't figure it out.

Anyway I am not sure he is correct as then a 4mm˛ FTE has a 1.5mm˛ cpc then making that cable wrong which I doubt.

But keen to see what you all think and if the cpc half the phase is correct?

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[GCE]

Expand on the abbreviations CPC and CSA

You tend to come up with abbreviations that I struggle to work out

[Dylboy]

Apologies!

CPC, I got from UK stuff. It is Circuit protective conductor. Which here is the Earth cable.

C.S.A i shortened to Cross Sectinal Area.

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[GCE]

The regs actually state that it should be the same size as the phase conductor ( 6.12.1.1 e) but may be smaller if CB instantaneous tripping current is less than 10 ( 6.12.1.1 f )

If the earth wire forms part of the cable then it needs to comply to that spec ( 6.12.1.1 b ) - So in Twin and Earth , Armour cable ECC , surfix etc the earth is part of the cable and conforms to that standard.When the cable is manufactured/ designed it takes into account ( 6.12.1.1 d ) be able to carry the prospective fault current without excessive temperature rise of the conductor, within the disconnecting time,





6.12.1 Earth continuity conductors
6.12.1.1 An earth continuity conductor shall
a) consist of compatible conductors,
b) if it forms part of a cable other than a flexible cable, comply with the relevant
requirements of the standard for the cable,
c) if it forms part of a flexible cable, be of the same material as, and have a
nominal cross-sectional area at least equal to, that of the largest phase
conductor,
d) be able to carry the prospective fault current without excessive temperature
rise of the conductor, within the disconnecting time,
e) if it does not form part of a cable or flexible cable, have a nominal
cross-sectional area in accordance with table 6.25 and if it equals to the
phase conductor size refer to table 6.28(a), as follows:


f) using the same formulae above where the earth continuity conductor cross
sectional area is 50 % of the phase conductor, thus m = 2, table 6.28(b) for
the maximum length of copper earth continuity conductor for general
purpose circuit breaker apply.
Table 6.28(b) — Minimum size and maximum length of copper earth
contuinity conductors rated at 50 % of phase conductor diameter, for
general purpose circuit-breakers with instantaneous tripping current
Im = 10 × In

g) Where the proposed PE conductor with increased cross-section becomes
uneconomical, an earth-leakage protection device may be added or
deployed as additional protection, where the tripping threshold would be
substantially lower.
h) For aluminium conductors apply the formulae above with ρ = 37 × 10-3
ohm.mm2/metre

[Dylboy]

Hey GCE

Thank you!

For some reason i didnt get the notification !

The bit on the cable being manufacturerd was my example to him but he didnt care haha. If the adibitaic calcs prove good which they do then i am happy.

Intresting bit on the atuff mentioned before, thank you

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