Hi Ruki.
You have 2 S120 VFDs connected directly to the TP1200, without a PLC ?
Not sure if that can work. I have never tried it.
If you can have a lifebit or continously incrementing counter from each VFD then you can do this:
Have 2 internal tags for "connection_1_ok" and "connection_2_ok".
On system event 140001 set both "connection_1_ok" and "connection_2_ok" to 0.
On the lifebit or counter from the VFD 1, add the OnChange event and the function Setbit "connection_1_ok".
On the lifebit or counter from the VFD 2, add the OnChange event and the function Setbit "connection_2_ok".
If one of the VFDs goes offline, both "connection_1_ok" and "connection_2_ok" will go off, followed by the one that is still online going on again.