Earth rod and Zs values in farm. Help needed

[Deleted member 26818]

Sorry but where is the requirement that the SWA be insulated at the load end to be found?
Could you also explain how insulating at the load end would prevent the TNC-S earthing being exported to any point where the cable could be penetrated by a metallic object?

 

[ImpededLoop]

It's very thought provoking and good to think outside of the norm.

I think that 542.1.3.3 covers the earthing arrangement for the swa with TT at the load end.

Interesting debate.

 

[davesparks]

Sorry but where is the requirement that the SWA be insulated at the load end to be found?
Could you also explain how insulating at the load end would prevent the TNC-S earthing being exported to any point where the cable could be penetrated by a metallic object?

It'll be in guidance note 8 if it isn't in the BGB.

It won't be exported whatever you do to it, it is impossible to export an earthing system, unless you've found a way of shipping it to another country?
It can either be extended in to another part if the installation, or it could introduce an unwanted earth potential into part of the installation.

As we have already discussed if the SWA is penetrated by a metal object then the OCPD operates and cuts of the supply. This is a fault condition and not normal operating conditions for the installation.

What danger are you seeing from this metal object penetrating the cable?

 

[Deleted member 26818]

I think it is rather pointless continuing this discussion.
You are detailing the exact reasons why such a cable should not be connected to the TNC-S earthing, but seem unable to understand why those reasons make the practice unsafe.

I also find this practice of referring to non existing Regulations rather tedious.

 

[ImpededLoop]

I think it is rather pointless continuing this discussion.
You are detailing the exact reasons why such a cable should not be connected to the TNC-S earthing, but seem unable to understand why those reasons make the practice unsafe.

I also find this practice of referring to non existing Regulations rather tedious.

Hi Spin,

Just to help my understanding, why doesn't regulation 542.1.3.3 apply here?

I can understand your reasoning for thinking that the swa should be connected to the TT earthing system, but the above regulation clearly states that the swa is connected at the supply end of the cable.