I'm trying to create a energy grid monitoring system using Arduino

Im attempting to use Arduino connected with a GSM shield connected to power grid.

The objective is to deploy the unit all over the city so that data can be received in almost real time so that power status can be known.

I need to understand what chip can I connect with my Arduino so that I can relay the status via gsm.

I've worked out what programming needs to be done but I'm not sure what should I be using to read logic '0" or on as power status.

Complete application of the unit is listed here.

I'm using Arduino Uno 3.

Thanks in advance.

So you just want to know if the power is on or off? Could do that with an optocoupler.

https://openenergymonitor.org/

People tend to notice whether the power is off. Have them use their phones to report it to your own web site, with the server on an uninterruptible power supply.

Have a small lamp connected to the power grid and an LDR attached to the Arduino to detect whether it is lighting. The Arduino will need battery backup.

Or, if the backup battery is trickle charged from the power grid the Arduino could monitor the low-voltage charge voltage to detect a power outage.

...R