Since I am new to this forum, I am not quite sure where to post my questions. Nevertheless, since, I think, that the basis of what I want to do reside with the emonTx, I have decided to post it to this topic.
I have a need to monitor the 3-phase 410-volt (phase-to-phase) 300kW AC supply in “near real-time” using WiFi over the Internet to upload the data to Emoncms, and I am wondering if someone else has done this before and if so, can he/she perhaps share their experiences with me.
I assume this is in industry. Our main user base is domestic, but, with appropriate c.t’s, there should not be a problem with 300 kW.
The main restriction faced by the emonTx is its single voltage input, which means that the voltage of phases 2 & 3 must be assumed to be the same when calculating power. That can be overcome by having one emonTx per phase.
If you want to use WiFi to send the data, then you need to add an ESP8266 module to an emonTx, or you may prefer an Arduino with a USB WiFi dongle and the emonTx Shield.
Hi Robert, yes it is for a shopping mall and yes, the assumption that voltage on phases two and three is the same as phase one does not really matter. We are trying to match the increases in power consumption to the demand of specific plant starting and stopping.
So you’re looking at 400 - 500 A c.t’s. There’s a good selection listed on our “Use in North America” page (because at 120 V, our UK 12 mm core diameter 100 A c.t’s won’t fit their aluminium incomers).
@Simsala has used a 3-phase sketch with favourable results on 3-phase installations in Germany, I think using the ESP8266 module. Hopefully, he’ll confirm the hardware that he’s using.
Yes @Robert.Wall is correct, I use the emontx with the WiFi-Adapter with @Robert.Wall’s new 3phase-firmware (which will hopefully soon be released) which is performing really great. I even used it with 3 x 1000 A CTs successfully (makes a whopping 690 kW :). They have 50 mA output and a 3,5 stereo jack, so it wasn’t even necessary to change the burden resistor. But the voltage measurement was always phase-to-neutral in my case.
Thank you both for the replies @Robert.Wall and @Simsala.
Looking at the long term, it may be a little more complicated than I originally made it out to be. Finally, I would like to monitor three sources of supply. Mains (municipal), Solar and Standby Generator supplies, meaning that I would either have to use three units or one with nine CT inputs. Because of this, I sent emails some of the major meter manufacturers asking them for possible solution, but I am not quite sure whether they would have something like that available, especially doing the readings in “near real-time”, say every 5 or 10 seconds.
Only a few three phase users as of now, but IoTaWatt accepts up to 14 inputs. Two can be used for voltage reference on phases B and C leaving 12 for CTs.
If derived phase reference is used, as in the EmonTX three phase sketch, only one voltage reference is used and all 14 inputs are used for CTs.
There are a couple of threads with discussion from some of the early users in Germany, Belgium and Australia. I’d be happy to answer any question you have.
The device supports any CT with up to 50ma output. The SCT019 sold in the OEM store are good for 200A with a 19mm hole. Should be easy to size a larger/higher amperage unit.