Static Bypass Switch in LV Busbar Repair

Thanks for the solid advice will do Sir

Are the neutrals from both transformers common to each other and earth/ground?

If so, there would be no difference of potential between the equipment ground and earth-ground so there would be no reason to switch or "bypass" the neutral inside the work zone.

If the transformer neutrals are not shared and/or not common to earth-ground, then the neutral should be disconnected on both sides of the repair work and bypassed using the fourth pole of the switch.

To be safe and properly protect all personnel working on the bus; Be sure to earth-ground all bus conductors and neutral conductors within the zone/area being worked on with bare copper conductors that are sized large enough to carry the maximum fault current available from the system.

The neutrals are not shared since the essential come from different source as well as the Normal supply

Since this is a temporary installation we will not use the remote control operation but basically the mechanical part of the custom built static bypass switch

My only concern is the protection on the downstream

the 630 A cb will supply to a max 300 A as we will shed load like chillers and small pumps

Once manually initiated , will it affect the Undervoltage setting at he receiving end

owing to the 20 nanosecond changeover

your above statements hold true .....

the contractor are asking for any standard since they are insisting that it is applicable only for UPS systems and not 2500 A busways

You have a wise contractor, he recognizes that a UPS system is not the same as a 2500A busway...and that 20ns changeover? That's an electronic, not mechanical, speed. The only thing in most ATS that's that fast is the speed of the solid state surge protection.

I suggest that you re-read the specs, most ATS have at least a 1 second delay to allow the larger motors' internal voltages to drop at least 50% to avoid closing in on a motor voltage that could be as high as twice normal if the connection takes place 180° out of phase with the incoming source.

For your own protection I hope that the contractor makes you sign a release and hold-harmless clause, then maybe you'll get a qualified consultant to guide you.

Totally agree

difference in application makes the project in limbo as it is intended for both UPS and busway repair application during the tender stage however they the contractor admitted that its only for UPS

As for the speed of no break its electronic as they are talking of SCR s

but will double check again the specs

as for the waiver, its the contractor telling us the other way around

So im opting for remedies as the unit had been delivered already

Simulation test with a dummy load

20 to 30 deg out of phase triggering of downstream cb protection ???

Contingency plan for downstream spare parts / upstream as well / including the new unit / since all scenarios must be considered

Catastrophic failure - how to return power to the old busway

Worst scenario is just connect a point to point cable in parallel to busway for the repair

and hire a consultant/ Supplier of such to assess the unit prior to execution

Thanks for the comments suggestions