Hello everyone, I know this is operating outside of design but I’m curious to hear your advice. I’m currently testing these devices out in a 24/7 manufacturing facility, for 120/208 there’s no issues as we have plenty of outlets to plug into.
The issue comes with 480V panels. given the need to keep everything up and running, it’s not an option to take a panel down to install a transformer into the neutral and we are not keen do work on the panel live either. Is it possible to provide an “assumed” 480 signal to the device?
Our use case is more general diagnostic than super granular tracking so the loss of accuracy is acceptable- but as I understand the reference voltage also helps sync the device in some way. I’m a mechanical engineer by trade so the finer points of the electrical side fly way over my head.
There are options, but I don’t have enough information to make any recommendation.
First, if you have 480V it’s no doubt 277/480 where 277 is phase-neutral and 480 is phase-phase. Generally, the 480 is only used in delta connected devices like motors or transformers.
No doubt there are also one or more transformers converting the 277/480 to 120/208. Assuming that everything originates from the 277/480 supply, the 120/208 should be more-or-less in phase. I say more-or-less because there will be some phase-shift caused by the intermediate step-down transformer, but that should not be significant for your purposes.
You can use a reference transformer plugged into one of the 120V outlets and then scale it up to 277V using the calibration option in the VT setup. If you are only monitoring 277V/480V circuits, you can get by with just that one 120V VT scaled up to 277V. If you also want to monitor any 120V circuits, you would need a second 120V VT plugged into input 13 or 14.
Since you are not concerned with utmost accuracy, I would recommend using derived reference. It will require that you follow the instructions in the Docs. This can be complicated, and generalizing would only make it more confusing. If you provide a line drawing of the circuits that you want to measure, I can make specific recommendations.
This is exactly what I was looking for thank you! We’re currently identifying what panels we want to test this on but this should be enough to get started