The second generation of smart meters are known as SMETS 2. Full form of SMET is Smart Metering Equipment Technical Specifications. It is with the previous generation known as SMETS 1. SMETS 2 smart meters were introduced in 2018.
A form of AC testing that applies voltage and measures the leakage/loss current of electrical insulation. It is a type of insulation testing used to evaluate the integrity of electrical insulation.
For the given circuit shown in figure, D1 is forward bias mode - On state D2 is in reverse bias mode - off state D3 is in reverse bias mode - off state.