Neutral to be Earthed at 3 Phase UPS Output OK or Not?

Earthing the neutral of the UPS separately is OK until someone opens the connection and grabs hold of the neutral thereby forming the earth path through that individual's body, at which point one hopes that the facility's indemnity insurance policies are fully subscribed as the prospect is that individual having half-a-day-out with the Undertaker. Were the equipment to continue to operate while the 230V-N were connected to earth, then there is something seriously adrift with the circuit protective equipment further upstream, a major safety problem, and the prospect of it causing fire if left unchecked. Sort this problem out and the N-E voltage problem at the UPS will go away.

Don't piddle about any longer. Hire an experienced Electrical Engineer today/this morning/right now. Get this individual to chase through the upstream connections and eliminate the fault. Have this individual review and confirm the settings of the circuit protective equipment having removed the fault. Make sure the investigation and its outcome are recorded for future reference, just in case the problem arises again.

If you have a 3 phase UPS and uses only 3 phase voltage, then, the neutral should not be grounded to earth. The UPS itself provide its own neutral point for 230V. Only the body of the UPS is connected to earth.

If neutral of the UPS is connected to earth, then there will be a reverse flow of voltage to your UPS if there is a faults in the power distribution system where the leakage voltage will flow back to your UPS by the earth wire.

...if, indeed, the upstream circuit protection equipment failed to operate...

Hi,

There are many types of UPS out there. You need to know wether your UPS has a Bypass or output isolation transformer (Not the small rectifier transformer).

In UPS systems with bypass option, without output IT, you will not have a new neutral at the output, and the bypass neutral is taken as it is. Input neutral is not used. Hence we usually have a by-pass Isolation transformer / AVR ( delta-star) with newly derived neutral connected to UPS bypass. In any case, earthing the neutral again is not advisable, without additional IT.

Plz see this doc for exact implementations

http://www.apcmedia.com/salestools/COCR-8SYKH8_R0_EN.pdf

https://www.insight.com/content/dam/insight/en_US/pdfs/apc/apc-role-of-isolation-transformaers-in-data-center-ups-systems.pdf

Your electrical consultant takes a risk for safety. Technically it can be done but not safe. If you have earth fault protection / RCBO it will triggered by the current that flow through earth.

This is a repeat post.

In OP's UPS, the output is 3 Phase delta connected. However single phase loads needs to be connected to the output. The OP has connected single phase loads, supposedly balanced, in a floating neutral arrangement, which is very dangerous. OP was advised to provide 3 phase delta to star double wound isolation transformer with dedicated star point neutral earth connections. With this arrangement single phase loads can safely be connected to UPS.

".....Because of which all facility N-E voltage rises to 230V."

This is a dangerous situation with potentially disastrous consequences. You are living with a time bomb. Without wasting time, immediately arrange to provide the isolation transformer to mitigate the problem.

Pattahiraman is right, this is EXTREMEly Dangerous. must b fixed ASAP = immediately !!!

This is true as when the 4 pole upstream tripped all the UPS suppled RCBO tripped

so the IT is a must ......that soves my rpoblem and will consult with APC on this

thanks