184 Power System Transients
2.4.2.5 Transmission Line
Most transmission lines in Japan are of double-circuit vertical conguration
with two GWs and are thus composed of eight conductors. The use of a fre-
quency-dependent line model is recommended in a numerical simulation,
but a distributed line model with xed propagation velocity, attenuation,
and surge impedance, that is, the xed-parameter distributed line model
explained in Reference 23, is often used.
2.4.2.6 Substation
1. Gas-insulated bus and cable: A cable and a gas-insulated bus are rep-
resented either as three single-phase distributed lines with their
coaxial mode surge impedance and propagation velocity or as a
three phase distributed line system. As a gas-insulated substation ...