It was desired also to determine the positive sequence impedance of the 2 sizes (350,000 and 500,000 circular mils) of 3-conductor shielded cable most commonly used on the system. Figure 1 shows the routes of the feeders selected for test. The short circuit and ground points, designated in the figure by X, were established by closing the network transformer grounding switches, except in the 2 cases where feeders were grounded in substations.