networking platform to meet the IEC61850 sampled value requirements
I think you are misunderstanding the requirements for IEC 61850 Sampled Value transmission. It is possible that you could create a configuration file which demands a sample rate of 1 MHz, for a dataset that approaches 1500 bytes - but this is clearly unrealistic in practice.

There is a suggested (but not standardised) format for SV, IEC 61850-9-2 "LE" (Lite Edition), which is used by several hardware vendors. This includes up to four voltage and four current samples, and ends with a packet size of about 126 bytes. It is suggested to sample at 80 samples per nominal cycle for protection applications, so for a 50 Hz power system this means 4000 packets per second.

This equates to about 4 Mbps, per SV stream. If you are simulating the packet contents, then time synchronisation is likely not important in this case, so you shouldn't even need a real-time platform - a PC should be capable to generating several SV streams fast enough.

If of any use, I created a program which can be used to generate mock SV data: https://github.com/stevenblair/rapid61850