Phase identification with powerline line modulation (PLC) - Page 1
Forum section: electronics / projects

author: Lunasix
author_rank: Regular Contributor
timestamp: March 08, 2023, 07:54:50 pm
content: Hi,we want to be able to identify how are connected equipments on 3 phases power lines, in order to control current for each phase. Trying to do this with colors on cables is time consuming and not reliable when cabling is already made.So, I think to send a signal on the phase 1 at departure, and finding this signal at arrival (max 100m). Then, after verifying the phase rotation, we can identify the two remaining phases. We couls also send signals (different frequencies) on the other phases.I already have developped tester which provides FFT on power line (for harmonics test), up to 3 kHz with 25Hz resolution. I can add a high pass filter on 1 channel in order to reduce the 50Hz level and raise the input gain (I use MCP3903 with 16 to 24 bits resolution). Another solution on receiver side would be to use a FIR filter for the expected frequency, I don't know what is the best solution, FFT or FIR, but I can try. As I don't need to send data, a low frequency would be perfect to use these already available tester, but if higher frequency is necessary, I can easily (I think...) developp another receiver.My problem is rather for the sender : what would be the best solution to send this signal on power line ?I have done some research but I don't know really what to do : frequency, signal shape, coupling schematic (current or voltage, with or without transformer...). And I'am unable to do simulation as I don't know how to describe the powerline.So, if you have ideas....

author: johansen
author_rank: Super Contributor
timestamp: March 08, 2023, 09:45:44 pm
content: A 1Khz square wave generator (like a 555) driving a mosfet to switch a 9v battery capacitively coupled into a 100:1 current transformer, connected around your line.. should show up pretty clear at the end of the line.If the cables are all hooked up into transformer loads, the return current will be through the other two phases and will be half the magnitude of the cable the transformer is on.do you want to do this on energized equipment or not?if energized, you need a good sized capacitor and mosfet so that the capacitor can block the 1 amp of current at 100 amps load that a standard 100:1 ct will produce.or, you build a high pass filter that shorts out the current transformer at 60hz but lets the 1khz through.

author: Lunasix
author_rank: Regular Contributor
timestamp: March 09, 2023, 08:53:50 am
content: The equipment must be powered, it contains relays which must be closed to do the phase search.

author: johansen
author_rank: Super Contributor
timestamp: March 10, 2023, 10:23:07 pm
content: if you have capacitors connected line to ground at the end of the cable you are looking for, then you won't see any current on the return lines, you will only see it on the neutral and the power cable you've clamped the CT to. this should be pretty reliable to locate the cable.

author: stowwest
author_rank: Newbie
timestamp: March 27, 2023, 02:30:18 am
content: Quote from: Lunasix on March 09, 2023, 08:53:50 amI checked the power supply and there is indeed a problem there.

author: moffy
author_rank: Super Contributor
timestamp: July 15, 2023, 10:35:31 am
content: The site:https://www.homemade-circuits.com/remote-control-using-mains-power-line-communication/has a number of alternative circuits, one of which might be usefull.