mcv

Hi,Finally booked up the test after months of looking through this bloody workbook.Still struggling on cable selection and vd.Ive heard the examiner is very helpfull over in adelaide,so hopefuly sort it out there.

Anyone know the formula for working out the 'earth fault loop'? or can help with the ccc calcs or give any advice ,it wouold be much appreciated.


Anyone else going over on these dates???

Cheers Richard

Del-Jo

Zs = earth fault loop impedance
Uo = nominal phase voltage
Ia = current causing automatic operation

Zs = Uo/Ia

page 238 and 344 of the regs book

and check your answer on page 324 of the regs book.

hope this helps,

Del

mcv

Thanks for the formula,

How would I work out the answer to Question 6 section 1 worksheet E of the peer workbook.

A 230v single phase sub-circuit is protected by a 20A type C circuit breaker.
what shall be the maximum loop impedance of the circuit(use the formula)


any takers?

cheers Richard

Lee and Joanne

zs= Uo/Ia

230/20x7.5 =1.533

same as table 8.1

Lee and Joanne

clause B4.5 page343-344 for the x 7.5

Table8 page 324

Page no might be different on latest rules book

Lee and Joanne

Ia = current causing automatic operation of the protective device

Ia for circuit-breakers is the mean tripping current as follows:
Type B = 4 × rated current
Type C = 7.5 × rated current
Type D = 12.5 × rated current

Jockstar

How many questions are in the work book? How long did it take to work through? How many hours a day did/do you spend on it?