Dear panneerrajangunasekaran,
I apologize for the delay, regarding to your question:
For neutral tampering, you need to measure not only current in phase but also neutral current.
Then meter can detect external connecting load to ground or reverse load wire connection.
If neutral is disconnected completely so the meter loses supply voltage then power meter electronics must use an internal battery and wakeup from time to time to check whether some current consumption is detected even under no presence of supply voltage on phase shunt resistor.
Please check the following application note: http://www.nxp.com/assets/documents/data/en/application-notes/AN4993.pdf
BR
Jonathan
