Line constant measurements and loading current test in long-distance 275 kV GIL

This paper reports on the results of a loading current test and measurement s of the line constants of a long-distance gas-insulated transmission line (GIL) in a tunnel. The loading current test was carried out at 80% rated cu rrent, to verify the soundness of the thermal expansion and contraction of the GIL. As a result, the performance of the GIL was confirmed to be approp riate in terms of the thermal expansion and contraction. With respect to th e line constants and transient enclosure voltage, each of the measured valu es was found to be at an appropriate level presenting no problem for the se rvice operation of this line.