2391 sample Question

[elephant]

hey guys,

if anyone really bored.... maybe they can try this and avoid any more confusion for me!

thanks,

A seven year old 400/230 V three-phase electrical installation within a small commercial

unit forms part of a TN-S system with a measured value of external earth loop impedance

(Ze) Of 0.22 Ὠ

The existing metal-clad TP-N distribution board contains BS EN 60898 type B & C circuit

breakers. The existing wiring system is 70

 

[spinlondon]

0.946ohms.

 

[rugbymacc]

come on spin...... show your cals

---------- Post Auto-Merged at 18:59 ---------- Previous post was made at 18:56 ----------

12.10/1000 = 0.0121 x 30meters = 0.363

0.363 x 2 (line and cpc) = 0.726 + ze

= Spin's Answer

 

[elephant]

thanks spin,

i knew i was doing it wrong- the resistance per metre 12.10 mὨ/m is for 20

 

[Chr!s]

i knew i was doing it wrong- the resistance per metre 12.10 mὨ/m is for 20

 

[elephant]

so plumber, u think spins answer is wrong?

thanks.

 

[spinlondon]

I'm assuming the question is asking for the expected measured values, obtained during testing.

 

[elephant]

ok thanks spin