Difference of Earth Potential

[a1guvner]

Whats peoples view on this on i had a while back

Massive aircraft hanger which had various maintenance bays within it, we were constructing a new training facility for a college within one of the bay areas, Carried out our installation with no problems and airside in one of the bays they had a substantial panel board, where we were going to take our supply from, nice and straight forward till now, this supply was fed from a HV network (bit dated) which is just for the airport, readings all good and installation tested out fine, when we were looking at the overall installation of the hanger it was apparent they had another HV transformer (alot newer) up the other end of the hanger which also fed this building. so in effect we have 2 HV transformers feeding the same building although from different switchgear so what i believed should happen and was the opinion of the NICEIC was to provide a common bond between the two intake positions but then in reality the mechanics of trying to provide the bond over the tops of planes being worked on was a logistical nightmare so it was opted to use the steel frame of the building as a conductor.

Just wanted to see peoples views and opinions

 

[Deleted member 26818]

It used to be, that if the HV and LV earthing will conflict (resistance of 1Ω or less), you will have to ensure that both are bonded together.
Here is a link to some more up to date info: http://www.ukpowernetworks.co.uk/pr...istribution_Network_Earthing_Construction.pdf.
Using the frame of the building would normally be considered ideal, for bonding between two LV supplies.
Throwing in the HV bit muddies the water though, as it seems practices and opinions as to what is considered correct change every so often.

 

[a1guvner]

Cheers, looks like a good read, will have a better look later,

 

[Knobhead]

I’ve put in a quiet a few transformers and where possible they would be solidly bonded, but it wasn’t always possible. The structure of the building was then used.

 

[Engineer54]

Just a thought here, ...One of these TXs could be serving the 400Hz supply to this hanger. All aviation hangers will have such a supply for the aviation purposes..

 

[a1guvner]

Just a thought here, ...One of these TXs could be serving the 400Hz supply to this hanger. All aviation hangers will have such a supply for the aviation purposes..

There was definately some dedicated supplies to power the planes whilst being worked on