We are currently wiring a few G.E. 15 kva xfmr's that have Electrostatic shield leads.The panels that the xfrm's are feeding are isolated ground panels.The tag on the leads instructs the installer to connect the leads to the newly established ground.What would be considered the proper newly established ground for this application
Electrostatic grounging
- Thread starter johnnyd
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Re: Electrostatic grounging
Depends on where you reference the grounded circuit conductor. The GEC can to to either the Xo, ot the isolated neutral bar in the first diconnecting means.
Normally shielded transformers have the GEC terminated to the Xo. So the shield would be terminated to the case where the bonding jumper is terminated.
If the grounded circuit conductor is bonded at the disconnect, then the shield is terminated on the ground bus in the disconnect. However this method defeats the purpose of the shield via long leads.
Most electrostatic transformers shields I have seen use a copper strap to the transformer case/enclosure where the bonding strap is located.
Depends on where you reference the grounded circuit conductor. The GEC can to to either the Xo, ot the isolated neutral bar in the first diconnecting means.
Normally shielded transformers have the GEC terminated to the Xo. So the shield would be terminated to the case where the bonding jumper is terminated.
If the grounded circuit conductor is bonded at the disconnect, then the shield is terminated on the ground bus in the disconnect. However this method defeats the purpose of the shield via long leads.
Most electrostatic transformers shields I have seen use a copper strap to the transformer case/enclosure where the bonding strap is located.
Re: Electrostatic grounging
Thank's for the input dereckbc.It just so happens that we received a sketch from the engineer today that shows the grounding just as you had suggested.I still don't see how this is a true isolated ground,the grounds are seperate in the panel but are bonded together in the xfmr.I would think that an EGC would be taken back to the water main atleast.
Thank's for the input dereckbc.It just so happens that we received a sketch from the engineer today that shows the grounding just as you had suggested.I still don't see how this is a true isolated ground,the grounds are seperate in the panel but are bonded together in the xfmr.I would think that an EGC would be taken back to the water main atleast.
Re: Electrostatic grounging
In any properly designed isolated ground system involving a transformer both the EGC and IG will originate from a common point such as the ground bus in the first disconnecting means. Some special transformers like shielded ones will contain a ground bus for the origination of the EGC and IG. To do otherwise would defeat the purpose.
No that would be a code violation. The GEC from the Xo might go to the water main if no other electrode were closer.
In any properly designed isolated ground system involving a transformer both the EGC and IG will originate from a common point such as the ground bus in the first disconnecting means. Some special transformers like shielded ones will contain a ground bus for the origination of the EGC and IG. To do otherwise would defeat the purpose.
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