Not sure where the Pressure Relief Valve on a TC30 is. While it is true it should open and release pressure above a certain threshold, it is intended to open while deadheading, like pushing the joy stick one direction and holding it there after the rams have reached full extension. But the valve itself should be protecting against that, too.
I don't think it is your primary Pressure Relief Valve that caused the problem, there is something blocking your fluid flow. I would verify fluid can flow through the new line and that the filter was correctly installed.
Someone with a TC30 should be along soon to tell you the location of the valve.
You could also post in the New Holland subforum.