PM8000 residual current modbus register

[kantiarion]

Hello.

The current setup:

SE PM8240 SW 4.5.0 Standard, 4W-WYE, 4CT connected.

I want to read residual current calc value, and I suppose it is I5 (modbus register 3008) but the value is approximatively the same as I4. And if I do I4-I5 i obtain a value ~20mA so i supposes this is the residual current.

I read the modbus register map xlsx and I find "Residual current I0 sum" (modbus register 3094) but with wrong value(-4.591774807899561e-41). What is this register reading in fact?

It is a possibility to read residual current calculated directly from a modbus register?

[Charles_Murison]

Hello @kantiarion ,

The PM8000 does not have a Residual current I0 sum calculation. This specific register exists on the ION9000. I will forward this observation to the firmware team responsible for generating the modbus map file. For the PM8000, the Residual current calculation would indeed be I5. 

Regards,

Charles

[kantiarion]

Then something is not right with I5 calculation. The value of I5 is almost the same as measured value of I4 +-50mA I verify the connection again and nothing is wrong. The strange think is if I invert polarity of I4 the I5 is double I4. So how is calculated I5 current?

[Charles_Murison · Accepted solution]

Hello @kantiarion ,

Remember that when you are looking at currents from the web page or display etc. you are looking at 1 second RMS values. The calculated residual current you can think of the sample by sample summation of -(I1+I2+I3+I4). Then I5 as seen on web pages display etc. is the RMS of these calculate samples. You cannot look at the RMS currents and do math on those number expecting to be able to predict the value of I5. 

Regards,

Charles