Grid Fed Inverter Electrocuting lines men?

[johnnyfp]

How does a grid fed inverter check if it needs to shut of power to the grid if, for example the grid is down due to work or maintenance?

Does it stop producing and Poll for a voltage every x ms or does it use something cleverer (<-And is that even a word?)?

[bilko]

A grid tie inverter has to synchronise its output to the AC on the grid else the grid will send the smoke out of the inverter.   

[IanB]

Also if you are wise and you want to ensure your safety, you will place a short (a "crowbar") across the circuit you are working on after you have de-energized it and checked for no voltage. Then if anyone or anything tries to energize the circuit without permission it will trip the overload cutout.

[johnnyfp]

Makes sense.

How often does it sync up with the mains? (I know it's dependent on the model but they should all be similar, in the sense is it ever milliseconds or every minutes?).

[dr.diesel]

At least for Duke Energy, the largest utility in the States, you are in no danger with a grid tie inverter or generator.  All line work is done with all 3 phases shorted with heavy gauge wire.  Also remember, anything attempting to backfeed would also be feeding whatever portion of the grid it's still connected to, likely a huge load.

[gxti]

https://en.wikipedia.org/wiki/Islanding#Islanding_detection_methods

[johnnyfp]

Thanks! I didn't know it was called Islanding, but useful bit of information.

[bilko]

Makes sense.

How often does it sync up with the mains? (I know it's dependent on the model but they should all be similar, in the sense is it ever milliseconds or every minutes?).

Not sure, I would say at least every cycle.

[G7PSK]

I would also expect that after the grid has gone down any inverter on line would see the grid load as a short and shut down or burn up, most people will just leave everything on that was on went the power failed.

[Jeroen3]

If there is no grid, there is nothing to sync to.
You probably need to manually restart it, after opening your grid circuit breaker. (you don't want to power the neighbors do you?)

It must make sure there is synchronisation. If it loses that, energy might want to go back in the inverter.