Help with the following Questions :-)

[Stirzy]

Hi All

can you please help in answering the following questions??

The value of resistance of an earth electrode used on a TT system is to be measured using an earth loop impedance test instrument!
A)State why it is necessary to isolate the installation before testing?
This would be classed as dead testing, & also to prevent the chance of electric shock

B) What action needs to be taken with the earthling conductor before testing and why?
The earthing conductor need to be disconnected from the consumer unit, only testing the electrode and not creating parallel paths.

C) Why the earth loop reading can be recorded as the electrode value?
??

thanks in advance :smilewinkgrin:

 

[happyhippy68]

Lazy! Please go and read Guidance Note 3 in the college library specifically section 2.17.3 page 48 onwards and you should be able to answer your homework.:joker:

 

[Richard Burns]

You are getting there but do need to think slightly more about the nature of the test you are doing.

A) This live test requires you to disconnect the earth connection from the installation which would leave it with no protection in case of a fault.
B) Disconnect the earthing conductor from the installation to avoid including measurement of any parallel paths
C) In a TT installation protected by an RCD precision of the value of Ra is not required and the Earth fault loop impedance test gives an suitable approximation of Ra. The loop resistance is an insignificant proportion of the resistance compared to the earth electrode resistance.

 

[Stirzy]

Thanks Guys clearly know more than me lol

is more the correct terminology i struggle with:thinking:

thanks all the same.......