Wireless ct clamp data

Hi ,

I've 2 deye single fase inverters . Both of them are installed in the shed. Where the electricity enters the house is around 30 meters away from on shed.
I'm looking for a way to send data of the clamps that came with the inverter to my inverter. Ct clamps need to be installed in the house. Sadly enough you can't make the ct clamps cables longer. That would solve all my problems. Saw solutions for one inverter . But i have 2 inverters . Anyone know how to solve this?

gohigher said:

Sadly enough you can't make the ct clamps cables longer.

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Why not?

The key is that you need to use twisted pair wires, the twisting protects the signals from external noise. My assessment is that should work electrically. Power frequency is so low the loss in the cable will be minimal. For example, the EG4 18KPV manual says the CTs can be extended 100 meters using Ethernet cable.

I would use a high grade Cat 6 network cable which provides 4 pairs. Run more cables if you need more CTs than 4.

Keep the leads twisted all the way from the inverter to the CTs.

You will want to pay attention to polarity so you don't reverse a CT hook up.

If you want to test this, put a CT on some load close to the inverter with a short cable, measure the current, then extend it with a network cable and verify the measurements are within acceptable tolerance. I predict it will be.

There is also shielded network cable if you want to go an extra step. Attached the shield to ground at the inverter end and NOT at the CT end. You don't want induced currents in the shield which might occur if you connected it at both ends.

Mike C.

This is great, but are there wireless options?

You could set up one esp32 as a server with the ct clamps attached to its analog input. Then also use another esp32 as a client connected to the two inverters through an analog output. You may need to adjust the voltage for/from the esp32 on both ends depending on what the ct and inverters are made to handle. The server can update a single number on every cycle through the program, and the client can read this number on every cycle. These two devices can be connected to Wi-Fi locally and should have very low latency (less than one millisecond if you have a decent network). The only hard part is understanding exactly what kind of signal to expect on each end. There are so many different types of cts that you will need to read up on all of the details of the cts. I have been considering this for a while, but it turns out my inverters can’t actually use cts.

Letmo said:

You could set up one esp32 as a server with the ct clamps attached to its analog input. Then also use another esp32 as a client connected to the two inverters through an analog output. You may need to adjust the voltage for/from the esp32 on both ends depending on what the ct and inverters are made to handle. The server can update a single number on every cycle through the program, and the client can read this number on every cycle. These two devices can be connected to Wi-Fi locally and should have very low latency (less than one millisecond if you have a decent network). The only hard part is understanding exactly what kind of signal to expect on each end. There are so many different types of cts that you will need to read up on all of the details of the cts. I have been considering this for a while, but it turns out my inverters can’t actually use cts.

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That will not work for an inverter configuration

A CT clamp measures the current flowing, but in order to determine the direction, power factor etc., the voltage also needs to be measured at the same time. A delay in the relaying of the current information will render the measurement useless.

The solution is either:-

a) if your inverter can only use a raw CT, then you will need to extend the wiring as detailed above.

or

b) if the inverter also supports a CT-based or shunt based meter, like an Acrel or Eastron, that outputs the processed power data over RS485 or similar, then you can extend that over Ethernet or potentially WiFi / LoRa.

For more info on that option, see this thread...