How do i open circuit phase R. Line number 4 on the digram being phase R?
I'm not sure what you mean by 'How do i open circuit phase R'. If the impedance (resistor) in line 4 breaks or burns out it is open.
I suspect this is a question about an unbalanced Y.
ok so i should open circuit it by removing the load in line 4 correct and draw a direct line to the source?
An open circuit means the conduction has failed, i.e. it is broken. If one wants to model an open ciruit, one would have to add a switch, which then opens.
_______________ is closed
_________/ _____ is open
Separate names with a comma.