The figure below depicts a homogeneous power system in which the positive sequence impedance with module specified in p.u. have the same phase-angle. The transmission system consists of similar double circuit lines bussed at A, B and C. Calculate the impedance measured by distance relays installed at A for each circuit when a 30 fault occurs on: i. ii. iii. One circuit at a point 80% of the distance AB from A One circuit at a point 50% of the distance BC from B Taking E₁ = E2 = 1.0 p.u., discuss whether an indicated second zone impedance reach in excess of 1.0 p.u. is satisfactory for this system.
