Meter PM5340 Current reading problem

[Youssef-asec]

I have three meters from same bus 

1-PV solar 

2-Grid 

3-Outgoing

Three meters connected on ethernet switch then i am reading values through plc 

the problem is when I am reading current phase A which is Register 3000

SUM OF Current for PV Grid and Grid incomer is not equal to outgoing

so what can be the reason for that 

[Jesus_Diaz]

Hello @Youssef-asec,

Have you measured the current of each meter using a clamp meter or multimeter and compared it to the values shown on the meters?

There could be wiring issues such as CT polarity, incorrect phase order, or an incorrectly configured CT ratio. Please ensure the installation follows the instructions provided in the installation sheet.

Additionally, verify that all meters are measuring the same phase consistently and that there are no loose connections or grounding issues that could affect accuracy.

Regards,

JD

[Youssef-asec]

Hello@Jesus_Diaz

thanks for your support 

CT polarity checked
phase order checked

all meters measuring the same phase 
I notice that during night when we feed from grid only everything is good

I notice also increase in harmonics of voltage when PV start feeding 
voltage harmonics is up to 20%
but when grid feed only without PV harmonics is 4% 

[Jesus_Diaz]

Hi @Youssef-asec,

What is the difference between the summation and the value? is it consistent over time?

Aside from that difference, are other measurements expected—such as power, energy, etc.?

Also, what is the firmware version on these meters?

@rohith-s @Sidharthan do you have any additional comments on this?

Regards,
JD

[Charles_Murison]

Hello @Youssef-asec ,

What kind of tolerances doe your system have? What is the differences in readings. 

Let us say for example that the CTs are 1% accurate and meter is 0.1%, this means meter could be as much as 1.1% off and still be within rated accuracy. Now lets say that the 2 meters are 1.1% in one direction and the other meter is 1.1% in the opposite direction. this means the current could be different by 3.3% and still be within stated accuracy. 

The numbers are just an example and different CTs have different ratings and some will have ratings that differ depending on the current through the CT. The math is also the simplified example the math for tolerances gets a little more complex but a 3% plus difference is not unexpected.

There is also how are you collecting the data, latencies in communication, screen update rates and the often second by second variation of current makes trying to compare real time values very very difficult. A better test could be to have all meters be time sync'd, then integrate or average the current over a set period of time and compare the combined results.

Regards,

Charles