Improvement of transmission line ground circuit current carrying limit after system interconnections

摘要

When one or more transmission lines are added to an existing transmission system, the intensity of the fault currents flowing along the ground wires near the substations may exceed the ground wire thermal limit. In such cases, it is generally preferred to improve the existing ground wire conductivity by replacing say a steel groundwire with an ACSR ground wire along the first spans near the substation. Generally, this procedure requires that the transmission line be de-energized, what may sometimes be considered unacceptable. This paper deals with optional procedures which can be implemented in the first line kilometers near the substations keeping the existing lines energized. Such procedures include sectionalizing of groundwires, use of continuous counterpoise and use of additional overhead ground wires installed below the conductors. This paper introduces also a technique known as "tower foot resistance adjustment", which complements the corrective effects of the aforementioned procedures.