Hazardous areas - control voltage transformer earthing -

[Cbuk2k2]

I've been in an ongoing debate regarding earthing of a control transformer and i'd like some other opinions.

690 primary, 120v secondary supplying control circuits (contactors/DC convertors etc), the neutral is tied to earth - My issue is the location that it is tied to Earth.

As far as I know the difference between a TN-S and a TN-C-S system is whether or not the neutral is connected to 'ground' at the source or further down the line.

60079-14 - 6.3.2 TN type of system earthing If a type of system earthing TN is used, it shall be type TN-S (with separate neutral N and protective conductor PE) in the hazardous area, i.e. the neutral and the protective conductor shall not be connected together, or combined in a single conductor, in the hazardous area. At any point of transition from TN-C to TN-S, the protective conductor shall be connected to the equipotential bonding system in the non-hazardous area.

Please see attached photo; The proposed design shows the point where the neutral is tied to earth (circled in blue) - this makes the highlighted section the 'C' in a TN-C-S system.

To create a TN-S system it would need to be where it is marked Red (taken directly off the transformer)

Also the highlighted cable is a line bushing from an Exd enclosure (which houses the transformer) to a close coupled Exe enclosure so this bushing cable would be combining the neutral and protective conductor.

Any thoughts agreeing/disagreeing? I can't seem to budge some peoples stance on it and to me it's black and white.

Cheers.

It’s fairly standard practice to be honest

 

[Pete999]

It’s fairly standard practice to be honest

I was brought up in the wrong era mate.

 

[Megawatt]

I've been in an ongoing debate regarding earthing of a control transformer and i'd like some other opinions.

690 primary, 120v secondary supplying control circuits (contactors/DC convertors etc), the neutral is tied to earth - My issue is the location that it is tied to Earth.

As far as I know the difference between a TN-S and a TN-C-S system is whether or not the neutral is connected to 'ground' at the source or further down the line.

60079-14 - 6.3.2 TN type of system earthing If a type of system earthing TN is used, it shall be type TN-S (with separate neutral N and protective conductor PE) in the hazardous area, i.e. the neutral and the protective conductor shall not be connected together, or combined in a single conductor, in the hazardous area. At any point of transition from TN-C to TN-S, the protective conductor shall be connected to the equipotential bonding system in the non-hazardous area.

Please see attached photo; The proposed design shows the point where the neutral is tied to earth (circled in blue) - this makes the highlighted section the 'C' in a TN-C-S system.

To create a TN-S system it would need to be where it is marked Red (taken directly off the transformer)

Also the highlighted cable is a line bushing from an Exd enclosure (which houses the transformer) to a close coupled Exe enclosure so this bushing cable would be combining the neutral and protective conductor.

Any thoughts agreeing/disagreeing? I can't seem to budge some peoples stance on it and to me it's black and white.

Cheers.

I don’t see a problem by bonding where you have circled in red. I have to agree with you why bond it again

 

[Bobster]

Well the most immediate problem I read is that you are using an Exe enclosure, with a supply that is not rated Exe.

So right off the bat this installation isn't going to comply.

At this voltage and power availability, Exd is the option you should be looking at.