potential transformer in metering circuit-Is it necessary?

[garimella]

I have to develop a low cost compact metering circuit. Inputs are from CT and PT. Inputs from PT (field side) is 3 phase 415V. Now should I use step down transformer in metering PCB or can I directly use voltage divider and isolator to sense the input voltage? What is the standard practice?

 

[FvM]

You can refer to application circuits of energy meter devices, e.g. from Analog Devices. Measurement transformers that can keep with the device accuracy (and metering standards) are very bulky and cost a high multiple of the electronic components. Isolation - if required - is implemented in the digital domain.

 

[garimella]

Hi FvM
I did refer to TI and AD tech notes before posting. I did not see any PT being used in the PCB for further stepping down. I could see just the voltage divider.

 

[FvM]

Yes, they don't use transformers.