INSULATED OVERLAPS AND SECTIONNERS FOR OVERHEAD CONTACT SYSTEMS A COMPARISON OF OPERATIONAL AND SAFETY CONCERNS

摘要

ABSTRACT Sectionners divide overhead contact lines into individual electrical circuits (power sections) for electrical isolation. An event requiring power in one section to be isolated from other sections due to a cable fault, maintenance isolation or emergency allows power dispatchers to open circuit breakers and de-energize power sections individually. Fault conditions automatically cause circuit breakers to open in the affected power section without affecting other sections so that service in those sections may continue operating unencumbered. Sectionners of varying styles are used to achieve sectionalizing. The basic types of sectionners are bridging, non-bridging, and diode. These may be either mechanical sectionners, air breaks or insulated overlaps. Current thinking in OCS design favors insulated overlaps over mechanical sectionners without fully understanding the ramifications of doing so. This paper presents the advantages and disadvantages of various types of insulated overlaps and mechanical sectionners, the costs associated with mechanical and overlap type sectionners and the operational superiority of mechanical sectionners in relation to arcing, prevention of burn downs, and flexibility of location.