Very strange IR fault - any one seen this before?

[Redline8400]

Evening all,

Went round to a clients house and did some tests on an outdoor socket. At the junction (in an IP rated wiska box) between the cable coming in from the house and the SWA running to a single outdoor double socket down the garden, the IR test between L-E fails at 0.05 Mohms. When the ends of both cables are disconnected from each other, and the IR tests are done on each cable separately (L-N, L-E, N-E), everything passes! It's only when I test between the earth coming from the house and the line of the SWA that I get the 0.05Mohms. The SWA is being supplied by an FCU inside the house off of a kitchen ring. Supply is TN-C-S.

Any advise much appreciated!

Red

 

[Pretty Mouth]

Evening all,

Went round to a clients house and did some tests on an outdoor socket. At the junction (in an IP rated wiska box) between the cable coming in from the house and the SWA running to a single outdoor double socket down the garden, the IR test between L-E fails at 0.05 Mohms. When the ends of both cables are disconnected from each other, and the IR tests are done on each cable separately (L-N, L-E, N-E), everything passes! It's only when I test between the earth coming from the house and the line of the SWA that I get the 0.05Mohms. The SWA is being supplied by an FCU inside the house off of a kitchen ring. Supply is TN-C-S.

Any advise much appreciated!

Red

The fault is not between L and the CPC then, it is between L and true earth. Is the armour of the SWA connected to the CPC at either end?

 

[Redline8400]

The fault is not between L and the CPC then, it is between L and true earth. Is the armour of the SWA connected to the CPC at either end?

This could indeed be the culprit. I'll double check the earthing of the armour and report back.

 

[Redline8400]

This is now solved. Armour of SWA wasn't connected to CPC on either end, and upon further testing found that there was continuity between L and armour of SWA. Turns out L and SWA armour were acting as a path to earth, hence the reading between L of swa and cpc of cable from the house. Turns out @Pretty Mouth was right. Thanks for the help.

 

[timhoward]

This is now solved. Armour of SWA wasn't connected to CPC on either end, and upon further testing found that there was continuity between L and armour of SWA. Turns out L and SWA armour were acting as a path to earth, hence the reading between L of swa and cpc of cable from the house. Turns out @Pretty Mouth was right. Thanks for the help.

Well done. Out of interest, how/where was L touching armour?

 

[Redline8400]

Well done. Out of interest, how/where was L touching armour?

There were at least 3 different spots on the cable where it had been punctured by a sharp object. Possibly a spade or some sharp garden implement.

 

[DPG]

Somebody was very lucky then!