Tl;dr: is my attempt at protective impedance on neutral going to render my system inoperable or unsafe?
I'm looking for some feedback on a modification I am planning to incorporate into a design based off of the TI MSP430F MCU. I am looking to monitor utility power, and the reference designs all have neutral essentially tied to analog and digital ground. Without getting too much into the topic of multiple grounds, I am planning to utilize a single ground in this system, not split analog and digital.
The real area of concern I have is that neutral has no isolation in all of the reference material. I want to add protective impedance to limit current to the rest of the system and also to provide additional protection in the event that line and neutral become swapped due to installation error.
The TI datasheet shows the simplified monitoring circuitry with direct connections between utility neutral and ground within the rest of the design.
I have performed some simulations and lab tests with the following changes, namely ~2MΩ between neutral and my system ground. I have not been able to perform this in a full representative system, only with a multimeter acting as the ΣΔ modulator within the MSP IC.
The schematic shown here is a simplified representation of a portion of my schematic. I will have galvanic isolation from utility power via the flyback transformer, but that isolation will be rendered somewhat useless by the rest of the system design.
Does my attempt at adding protective impedance on neutral gain me the safety benefits that I think it does? Do you see any issues with my implementation of this analog front-end modification from the TI block diagram reference?
