Or take a look in the consumer box, the inverter breaker will be either a single or triple breaker.
See PZEM-017 DC Energy Monitor, i cannot speak for it’s quality or safety, I just noticed it and noted it here on the forum. It would involve interupting the DC lines to add a shunt and you would require 2, 1 for each array. But you should speak to an electrician if you are not 110% sure of what you are doing, the DC can be notably more dangerous than AC on domestic PV inverters.
I can help you with talking to this device, but the DC side is not typically DIY.
[edit]
As Robert states it might be easier (and safer) to communicate with the inverter, what inverter make and model is it?
[edit2]
Just realised you are not in the UK, I’m not fluent in Norwegian electrical standards so there may be other options, a photo would probably let us work it out,