There are three questions here. As you are in Germany, I assume you have a 4-wire electricity supply - three phases and neutral.
As the ‘Learn’ page about 3-phase supplies says, to measure 3-phase power you need one less wattmeter than the number of wires, so in your case, 3. For “wattmeter” you can use 3 × emonTx, or one emonTx using 3 current inputs. If you use 3 × emonTx, you will measure voltage and current of one phase in each emonTx, then you add the 3 power values to give the total. This is the most costly and the most accurate method.
If you have one emonTx, it has only one voltage input, so you must assume that the remaining two phases have the same voltage, otherwise there is an error. But it will measure the 3 phase currents accurately, and give a good estimate of the total real power.
The voltage you measure is totally dependent on the transformer (a.c. adapter) that you use. If you have a 380 V transformer connected line - line, then you can use that. You must not use our Euro a.c. adapter at 380 V.
The voltage rating for the YHDC SCT-013-000 refers to the insulation between the main cable and the secondary winding that is connected to the low voltage electronics. It is a safety standard. The value on the official YHDC data sheet is the transformer has been tested to 1 kV for 1 minute. You must not use this c.t. on a bare cable or busbar, therefore you will also have the insulation on the cable that is the primary winding.
(Seeedstudio has published wrong data in the past, so use their information with caution.)
Nice to see this topic. I have a similar situation in Germany where I want to measure 3 phases in one location, and two solar outputs in another.
I assume I will therefore need two EmonTX units, both running the 3 phase firmware? As I assume the two solar arrays will be connected two different phases.
I’ve read the guide 3-Phase Power — OpenEnergyMonitor 0.0.1 documentation and also the github site. Does the 3 phase firmware report signed current flow (i.e. import and export)? (In which case, out of curiosity, how does it know which is phase 2 and which is phase 3, assuming it assumes phase 1 is where the voltage reading is).
I gather that the actual billing meters aggregate phases, so that if you are exporting 2KW on one phase, and importing 3KW on another phase, the meter will assume 1KW of imports net.
Does anyone have feedback from installing and using the 3 phase firmware? The help file says:
Because of the additional power required for continuous operation, a 5 V USB power supply is likely to be required, even if only the on-board RFM69CW radio is used.
You tell it - the installation instructions have the details.
No. Not all have the required connection to reset the Atmel ATMega 328P at the appropriate moment to put it into programming mode.
That is true for a mechanical (Ferraris) meter, but it might or might not be true if it’s an electronic meter. It depends on how your energy supplier has instructed the manufacturer to program it.
It is especially the case if you have a low voltage 220 V supply. The danger is, when the supply voltage dips and that coincides with a radio transmission, the internal 3.3 V supply will fail momentarily, causing the processor to reset. The current drawn from the a.c. adapter is deliberately limited so that it causes minimal distortion to the voltage you are measuring. By using a separate 5 V d.c. supply that is likely to have a much wider range of input voltages, you are removing that distortion and removing the danger of the processor resetting if the voltage dips.
I have a good experience with the EmonPi working in the UK on a single phase supply. In Germany things are a bit more complicated needing not only two units, running the non standard firmware, but also a certified electrician to access the wiring. (At German rates, and they need to be booked way in advance).
Then I might even find its forbidden to clamp before the meter (taking unmetered energy), so I might end up having to clamp the wiring (pulled out of the consumer unit?). This probably needs discussing with the electrician first.
Am I right in assuming the solar measurement, from two arrays, will also need to be put on the 3 phase firmware? (Assuming they are on different phases and the plug might be on a different phase as well.
While that is strictly accurate, by comparing readings with the c.t. before and after the meter, the energy extracted by the c.t. would not be measurable. At maximum current it is 50 mA @ 1.1 V approx measured on the secondary side, i.e. not greater than 55 mW, and proportional to your load current squared (it’s constant resistance, P ∝ I²). Your supplier’s meter is unlikely to register consumption below approx 5 W. Quote from the manual for Siemens single-phase meter: “Creep inhibit circuit operating … at approximately 40mA” (i.e. it ignores less than 40 mA - about 9.2 W, so it will never see power extracted by the c.t., so anybody using that argument is not in possession of the facts.)
That depends on the inverters. If they are 3-phase, then yes, you will need a 3-phase measurement for those. If single phase (feeding at 220/230 V) then if the total current is less than 16 A, you can use the 4th c.t. channel of the emonTx. If the current is more than 16 A, you can still do that if you reduce the value of the burden resistor inside the emonTx, or you add a second burden in parallel externally.