Isolation of standy generator earthing system 2

[peterpylon]

Please what is the safest and most cost effective way to keep a 3ph & N + E generator supply isolated (including the generator earthing system) when not in use via the 4* pole c/o contactor? I want a seperate earth and neutral wire to the installation from the earth/neutral star point on the set. I will be installing a separate generator earthing pit.

 

[avishai]

I do not understand why you want to isolate also the N and E but if you insist then you have to use a 5 pin socket that will disconnect all conductors when N & E are disconnected .
Try to convince me why you should do so as after designing tens of systems with one or more gen systems I never had this problem ( except mobile houses). A.Rash BScEE & PE
a_rash@bigfoot.com

 

[peterpylon]

The standby generator in question is on a large telecomms site, is 200KVA and for the clients reasons needs to be so. It doesn't "plug in" it is hard wired.

 

[avishai]

If it is hard wired then the only thing to do is to use a draw out 4 pole breaker the earth wire in any case you do not disconnect . Only check your local regulations about special requests for cases you install a 4 pole breaker (like special signs you have to place to caution about this kind of breakers). A.Rash BScEE & PE
a_rash@bigfoot.com

 

[dydt]

hi..
i will use a 4 pole contactor but i won't split the earth wire. i did 3 or 4 installations like this for data/computer center with back-up UPS and never had any problems.

dydt (toronto)

 

[fb599]

Hi Peter Pylon !

I always tend to have a 4 pole mechanically and electrically isolated changeover arrangement in my experience for standby pruposes and have a seperate manually disconnectable earth link arrangement mounted nearby. Merlin Gerin do the breaker set up and Furse Earthing do the link system. The reason for this arrangement is if the earthing of the installation is PME then the supply Co's earth can become severed in a cable fault when the generator may be required for long periods. In this case you could end up having no Earth at the installation! Best to parrallel earths if possible and have a suitable earth system with the genny if you get this problem. Hope this helps....