Neutral Earth connection

Surely the simple fix is to reconfigure the tele-control to trip all outgoing ACB's on loss of mains, but leave the switchboard input breakers closed, then reclose the output ACB's once you are stable on the HV generation (there won't be load on the HV as the output ACB's are open)


That solves the shorter term problem  - then all you need to do is confirm the bus section is 4 pole and you can refit the N-E from the TX spill box to the switchboard (one half at a time) and swap out the 4P ACB's for 3P


That may well be a lot easier than retrofitting N-E contactors into an existing switchboard.


It sounds like a pretty normal dual fed system with HV generation - generally well executed, but flawed in your case by the introduction of 4P ACB's on the incommers.


As an aside - what's protecting the transformer unloading tails into the switchboard - or are you close coupled (ie Transformer switchboard)


Two feeds via the UPS bypass switchboard isn't that unusual if the board has a reasonable form of separation - it's not credible to lose both on single fault


I'm guessing this is Healthcare facility so ideally you should have duplicate A and B UPS anyway to feed into the duplicate IPS systems (HTM 06-01 will give you a good indication of what you are trying to achieve).


Like Mike - I would absolutely try to avoid solving this with N-E contactors (or mashing an MCCB to act as same), in favour of solving the N-E bonds at the switchboard and eliminating the 4P devices. Without knowing what ACB's you have, it's not that easy to say, but it's entirely possible you have a bit of minor copper reworking and have a 3P plug straight in (from the same range)


Regards


OMS

Surely the simple fix is to reconfigure the tele-control to trip all outgoing ACB's on loss of mains, but leave the switchboard input breakers closed, then reclose the output ACB's once you are stable on the HV generation (there won't be load on the HV as the output ACB's are open)


That solves the shorter term problem  - then all you need to do is confirm the bus section is 4 pole and you can refit the N-E from the TX spill box to the switchboard (one half at a time) and swap out the 4P ACB's for 3P


That may well be a lot easier than retrofitting N-E contactors into an existing switchboard.


It sounds like a pretty normal dual fed system with HV generation - generally well executed, but flawed in your case by the introduction of 4P ACB's on the incommers.


As an aside - what's protecting the transformer unloading tails into the switchboard - or are you close coupled (ie Transformer switchboard)


Two feeds via the UPS bypass switchboard isn't that unusual if the board has a reasonable form of separation - it's not credible to lose both on single fault


I'm guessing this is Healthcare facility so ideally you should have duplicate A and B UPS anyway to feed into the duplicate IPS systems (HTM 06-01 will give you a good indication of what you are trying to achieve).


Like Mike - I would absolutely try to avoid solving this with N-E contactors (or mashing an MCCB to act as same), in favour of solving the N-E bonds at the switchboard and eliminating the 4P devices. Without knowing what ACB's you have, it's not that easy to say, but it's entirely possible you have a bit of minor copper reworking and have a 3P plug straight in (from the same range)


Regards


OMS