The insulation coordination for UHV lines (above 500 kV) is done based on

Due to skin effect

Skin Effect:
tendency of the current to crowd near the conductor surface.

Skin effect is proportional to frequency, conductor diameter and permiability.
Skin effect increases effective resistance of conductor.
In DC, no skin effect.

DC series motors are best suited for traction work because

Torque in d.c motor = k* φ * Ia
In series motor φ α Ia
Tα I²
N α 1/φ
N α 1/T

Ybus used in power flow studies and Zbus used in short circuit studies

Different computers are connected to a LAN by a cable and a

Under operating conditions, the secondary of a current transformer is always short ciruited because