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Ze external earth loop impedance

Discuss Ze external earth loop impedance in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

S

Simon Hall

Hi I've done a Ze test on a TNS system and it's come back as 0.14 ohms is this reading ok as the max is 0.8 is there not a min amount you can have thanks
 
reading is fine. there is no minimum specified. damn good earth. i frequently get around 0.2.
 
ArseyDee said:
Am always a little suspicious when questions like this pop up from new members during one of Glen's bans! :)
Click to expand...

He isn't banned again is he!
 
Simon Hall said:
Hi I've done a Ze test on a TNS system and it's come back as 0.14 ohms is this reading ok as the max is 0.8 is there not a min amount you can have thanks
Click to expand...

Just means your damn near a local DNO distribution substation... lol!! Start worrying when you're getting values 00.4 ohms!! lol!!
 
And, just to point out something else.... there's not really such a thing as a maximum Ze value, either, as they don't officially exist. Neither BS7671 nor ESQCR contain the mythical figures of .35 and .8 for TN systems so the DNO's are quite at liberty to deliver as they wish. The only which IS set in stone is that circuit max Zs figures have to be achieved.
 
Rockingit said:
And, just to point out something else.... there's not really such a thing as a maximum Ze value, either, as they don't officially exist. Neither BS7671 nor ESQCR contain the mythical figures of .35 and .8 for TN systems so the DNO's are quite at liberty to deliver as they wish. The only which IS set in stone is that circuit max Zs figures have to be achieved.
Click to expand...

Your right to a point, though take PME, their is a legal limit with regards volts. So Tx set to 250 V and a 100 amp supply PME 0.35. So 100 x .35 = 35 V

250-35 = 215 V, very close to the 216.2 V minimum(230-6%)
 
Chr!s said:
Your right to a point, though take PME, their is a legal limit with regards volts. So Tx set to 250 V and a 100 amp supply PME 0.35. So 100 x .35 = 35 V

250-35 = 215 V, very close to the 216.2 V minimum(230-6%)
Click to expand...

Eh???? I think you need to have a think about that.
 

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