TEST PROCEDURE
Sources of supply were made available at Hudson Avenue station, where the use of the feeder test busses and associated equipment afforded a con¬venient connection to the feeders leaving the station. Since virtually all of each cable under observation had steel binding tape, it was necessary to provide sufficient generator capacity to measure the zero sequence impedance at currents of approximately 200 amperes per conductor, preliminary calculations having indicated that at low currents complete saturation of the magnetic tape would not have been obtained. Two 60-cycle generators were available: one, a delta-connected 2,300-volt 6,000-kvamachine; the other, a 5-kva star-connected 120-volt generator. Positive sequence impedances were measured at approximately 250 amperes per phase. Phase differ¬ences between the voltages and currents were deter¬ mined through the use of an a-c potentiometer5 which afforded voltage and current readings to within 1 per cent, and phase differences to within 0.5 degree. Figure 2 is a schematic diagram of the test connec¬tions for the measurement of zero sequence im¬pedance.