Simplified approach to reduce transient overvoltages on insulation regarding compaction of 400‐kV overhead transmission lines

Abstract

The paper presents a methodology with a new simplified approach, as a set of procedures, aiming to optimize the insulation level when compacting 400-kV overhead transmission lines (OTLs) in order to increase their operational reliability. The procedure initiates from presupposed requirements for compaction, as it is becoming increasingly more difficult to carry out reconstruction, revitalization, or construction of new OTLs while keeping the original design criteria. The main purpose of this approach is to reduce transients on the insulation, which are caused by direct lightning strikes to the tower top, and influence switching overvoltages using an additional shield wire on OTLs. The insulation leader progression model E 50% and the dynamic ionization model E ion for grounding with the constant ratio between the tower grounding resistance R g and specific ground resistivity ρ g are used to evaluate the lightning transients. For the analysis, the switching overvoltages phase domain transmission line model is used, where OTLs are divided into a number of short segments. For the purpose of this investigation, a mathematical model of a double-circuit compact OTL is implemented.