67V between earth and neutral terminals

[Guest rufuskes]

Hello all,

I am having a crisis in my Company.

 

After commisioning a proper earthing system I discovered that I still have a voltage of 67V between the earth and nuetral terminals. I do not want sensitve devices like switches and routers to be destroyed.

 

Please help me.

 

Thanks

 

Rufus

[marke]

Hi Rufus

 

Can you give any detail of what the 67V is? Is it a high frequency component, or is it line frequency. This is particularly relevent if a solution is to be found.

 

Best regards,

[Guest rufuskes]

Originally posted by marke

Hi Rufus

 

Can you give any detail of what the 67V is? Is it a high frequency component, or is it line frequency. This is particularly relevent if a solution is to be found.

 

Best regards,

 

Hi Mark,

 

Thanks for your time.

 

The 67V is the p.d betwen the neutral and the earth terminals at the Mounted panel box. We have a 4-wire three phase system from both the local power authorities and our Stand-by Generator. Both the transformer from the local authorities and the Generator are earthed separatedly. I have also earthed the Power Distribution Panel separately. The frequency of all equipments here is 50Hz. We have sensitive ICT hardware connected to the power system like Routers, Switches, modems and high end servers, in addition to over 40 client computer systems. they are all connected to the Panel with circuit breakers. The Panels are then connected to two Central APC 12kVA UPS. The UPSes get their input power supply from the mains of the building via two circuit breakers. I tried to isolate the earthing of the ICT hardware from that of the main building, yet I still get 67V between the nuetral and earth terminals.

 

Last weekend my PABX got one of its modular cards burnt. Also, a printer's network card and the corresponding network cable connected to the switch via a patch panel got burnt.

 

Also, sometimes either one of the circuit breakers trips off or is destroyed completely, prompting me to replace it.

 

Please I need help. What can I do to reduce this menacing NEV.

 

Regards,

 

Rufus

[RalphChristie]

I suppose your system is solidly earthed.

 

Somewhere between the panel box and your source one of your wires is off, either the neutral or the earth, most probably the earth.

[johnbose]

Looks like you have a UPS whose output is floating. If its floating try earthing the UPS output separately to your common earth . THis should help in reducing the voltage to near zero

[epsngr]

Looks like you have a UPS whose output is floating. If its floating try earthing the UPS output separately to your common earth . THis should help in reducing the voltage to near zero

 

 

How did u resolve this issue? I suppose that one earth system will be better that separate earth. A fault in a separate earth can cause fault current to flow through others.