Daily differences from cumulative value

[soldous]

Hello,

I have data about total cumulative consmuption of energy from 4 power sockets. The data are send every minute and when no energy is consume the value stay the same.  

I need to know daily differences from this cumulative values. 

Can anyone help me how to do it?

Thanks a lot.

Here is a sample of my data. 

[technolog]

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