Ze testing

[lugz89]

evening

i am fillling out my logbook and am asked what the purose of doing a Ze test is can anyone tell me please

thanks

 

[J@mes]

To ensure that the DNO supply earth system is operating within the correct tolerances for the type of system installed.

 

[lugz89]

someman thanks very much

 

[trebor]

It depends where the question is coming from, if you are talking initial verification for example the answer is as james correctly said to ensure that there is an external earth present at or less than the stated value for the system where supplied, but also to verify that the value is equal to or less than the designers figures.

 

[ELEKTRIC]

To ensure that there is an earth path present external to the installation.

 

[nick611]

to ensure that max permitted disconnection time can be achieved under fault conditions

 

[martysparky]

I recently was asked what is the most convenient method of obtaining Ze

a. measurement
b. calculation

I thought it depends on situation and who its convenient for ie. client or spark.

I would go with measurement for the above reasons.

 

[Risteard]

I recently was asked what is the most convenient method of obtaining Ze

a. measurement
b. calculation

I thought it depends on situation and who its convenient for ie. client or spark.

I would go with measurement for the above reasons.

Surely measurement or enquiry... How would you calculate?

 

[telectrix]

always get mine by measurement. it's cheaper and quicker than phoning DNO and listening to stupid automated multiple choices, why don't they include " press * for a human". followed by crappy music, where you get cut off before somebody decides to pick up the phone

 

[martysparky]

Surely measurement or enquiry... How would you calculate?

Well the GN3 states

Ze is determined by Measurement, Enquiry or calculation.

I suppose the remainder from Zs after subtraction.

Not sure if I would ever take that route though.

 

[Des 56]

Using a measured Pefc should give a reasonable calculation of Ze

 

[martysparky]

Would anyone agree that Measurement and Enquiry would be the best option. One to prove there is actually an earth and two, to prove the system is as designed.

I was also thinking how could you measure if it was not convenient to de-energize from the clients point of view and how could you get an accurate Ze from calculation not including parallel paths.

 

[brucelee]

yes mate agreed
measurment first option to give a accurate value and also to prove there is actually a earth present , enquiry second and calculation from measuring pefc as des has stated last option

but they are all acceptable as GN3 states

 

[martysparky]

I know and agreed, but you would have to disconnect the earth for pefc and if that was not an option was wondering how, if possible, an accurate Ze could be measured under those circumstances as pfc or Zs would include parallel paths from what I know.

 

[brucelee]

no mate when measuring Pefc or pscc to find pfc you dont disconnect the earthing conductor you only disconnect the earthing conductor when doing Ze

the earthing conductor has to be connected to carry out a pfc test