depending on the desired option, the  variant 7  configuration either measures the three phase currents and one differential current (87n), or it measures the three phase differential currents only. the main functions are the high impedance differential function (1 or 3 phase) with its ct supervision counterpart (both described in the high impedance differential protection technical guide ). note that the additional functions (50, 50n, 51, 51n, 60, 68) are avaliable only...