"Load Power" anomalies ?

Hello,

I have two single phase meters: one between the grid and the load, and one beween PV inverter and the load (house).

Both of them have the firmare updated to: i.75.96 and have the uploadinterval set to "6".


But I am having some anomalies in the Power chart:



Shouldn't these have been fixed in the i.75.96 version ?

Let me know if you need more info.


Thank you!

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Hi Erceceus:

Yes, the reason is indeed as Maciej said. (Thanks Maciej  for your explanation😀)


The load power is calculated by this formula

Load Power = Inverter Power- Feedin Power 

For more details please refer to : Overview of Solar PV system monitoring


If you use two wem3080, one is used on the grid side while another is used on the inverter side.
The two energy meters can not sample totally synchronized.
Because the energy meter uploaded to IAMMETER every 1 min , there will be a maximum 1 min time difference in the sampling of the two energy meters.
This 1 min time difference would lead to the possibility of abnormal load calculation.
When the grid power and inverter power are nearly constant, this time difference will not affect the calculation of the load power.
But when the inverter power or grid power is varying a lot in a short time, the load power calculation will be not accurate (even exist a negative value).

The key problem is two single phase energy meter can not be synchronized in sampling.

If you use one three-phase energy meter (WEM3080T) , this problem will disappear. The WEM3080T supports split-phase usage,
so you can use any two phase of the WEM3080T to monitor the grid and the inverter.
Becasue they are the two phase of one energy meter, they will sample and upload totally synchronized.
So there will be no synchronized problem then.


Hello,I have two single phase meters: one between the grid and the load, and one beween PV inverter and the load (house).Both of them have the firmare updated to: i.75.96 and have the uploadinterval set to "6".But I am having some anomalies in the Power chart:Shouldn't these have been fixed in the i.75.96 version ?Let me know if you need more info.Thank you!

Hi,

The difference is due to the difference in recording time of both meters. 

This is when the weather is changeable sun / clouds.

Hello,I have two single phase meters: one between the grid and the load, and one beween PV inverter and the load (house).Both of them have the firmare updated to: i.75.96 and have the uploadinterval set to "6".But I am having some anomalies in the Power chart:Shouldn't these have been fixed in the i.75.96 version ?Let me know if you need more info.Thank you!

Thank you both Maciej and @laoliu for your explaination!

It make sense now.

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