I have a client who has a solar system that they wish to monitor that is connected to a subcircuit in a detached shed.  Is it possible to create a 'virtual' three phase meter ?

Hi:

The WEM3080T can work in both 3 phase or split phase(You can consider it as three single phase meter with same neutral line).

About how to use WEM3080T in solar pv monitoring , please refer to https://www.iammeter.com/applications/solar-pv-system-monitoring