How to trip a line in power flow using pssuserpf.py?

Anonymous

I have a line that I monitor. During normal power flow I want to trip it if its current exceeds a certain value. RAS and pssuserpf load correctly, but when I call pfcontrol functions inside post_iteration() i receive ierr=2, which means that

not called from allowable PCI automation function

My post_iteration() funtion in pssuserpf.py looks like this:

def post_iteration():
    _, flow = psspy.brnmsc(1, 2, "1", "AMPS")
    if flow > 50.0:
        print("MUST TRIP LINE")
        ierr1 = pfcontrol.pfbrchint(1, 2, "1", "STATUS", 0)
        ierr2 = pfcontrol.pfdscnbus(2)
        print(ierr1, ierr2)
        # both ierr1 and ierr2 are always 2. 
        return False
    else:
        return True

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As stated in POM, it is not allowed to call these functions from post_iteration(). I get: "DSCN not allowed from post_iteration power flow user exit. (006024)"