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Ian1981

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Need someone either confirming or someone to put me right!
Regulation 551.4.3.2.1
Protection by ADS shall not rely upon the connection to the earthed point of the system for distribution to the public when the generator is operating as a switched alternative.
A suitable means of earthing shall be provided.

To me this means when the generator becomes the main source of power to the installation, then the generator TNS earthing arrangement shall not be connected to the DNO supply authority earthing arrangement,say it’s pme arrangement.
Am I correct?
 
Yes, you must isolate the supply earth from the generator earth. Engineers working on the DNO network don't like back-feed from gennys, it makes their hair curl...
 
Yes, you must isolate the supply earth from the generator earth. Engineers working on the DNO network don't like back-feed from gennys, it makes their hair curl...
It’s just an argument I’m having with an ‘electrical designer/engineer ‘ on a job I’m on.
I say a link needs to disconnect the generator earthing from the dno arrangement when the changeover switch is utilised.
He says I am wrong.
 
As it says it shall not rely upon it rather than saying shall not be connected to it I interpret that as not necessarily requiring disconnection from it.
However you do need to provide adequate earthing for the generator supply so that it can operate independently of the DNO earth.
 
As it says it shall not rely upon it rather than saying shall not be connected to it I interpret that as not necessarily requiring disconnection from it.
However you do need to provide adequate earthing for the generator supply so that it can operate independently of the DNO earth.
That’s a fair point Dave.
Looks like I’ll have to go back with my tail between my legs :oops:
 
You need to be able to disconnect your earth electrode system so that it can be tested independently. But you probably don't need to disconnect it just because the genny is in operation.
 
Yes, you must isolate the supply earth from the generator earth. Engineers working on the DNO network don't like back-feed from gennys, it makes their hair curl...
If you had to disconnect the earth when changing over to generator supply then this would have to be incorporated into the changeover switch, all the changeover switches I have come across only switch the lines and neutral,
 
If you had to disconnect the earth when changing over to generator supply then this would have to be incorporated into the changeover switch, all the changeover switches I have come across only switch the lines and neutral,
Depends on the installation, I have seen both but the earth bar link was on a manually started genny.
 
I would assume this would then change the characteristics of the installation to a TT system while the DNO earth link was disengaged, and all TT regulations would be applicable at this stage
 
recommending that all earths should remain connected?.
Just for clarification
The earth bar has the following permanently connected:
equipotential bonding,
Generator earth spike
incoming earth from the DNO
 
recommending that all earths should remain connected?.
Just for clarification
The earth bar has the following permanently connected:
equipotential bonding,
Generator earth spike
incoming earth from the DNO
 
It’s just an argument I’m having with an ‘electrical designer/engineer ‘ on a job I’m on.
I say a link needs to disconnect the generator earthing from the dno arrangement when the changeover switch is utilised.
He says I am wrong.
I’m thinking it could be near impossible. consider 4 industrial units, all with a seperate DNO supply, common steel frame , all bonded ect ect , you have a backup generator how can you disconnect all there earthing connections
 
WPD are perfectly happy for us to leave the DNO earth connected when running on generators. HSE guidelines suggest connecting to true earth through an earthing point of an adjacent fixed installation. This I would think would it self be connected to the DNO earthing.
 

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