Ans: i) Insulated overlap: To isolate for operation and maintenance of OHE if two lengths of OHE belong to two elementary sections. Located at feeding posts, sub sectioning posts and booster sections.
ii) Un-insulated overlap: To rectify faults in one contact wire of two running in parallel wires without affecting power to OHE. Located at two adjacent sub-elementary sections.
iii) Neutral section: Passing of pantograph under insulated overlap will cause short circuit between two phases, damaging OHE & pantograph. To avoid this bridging a neutral section is inserted between them. Located between two substations.
iv) Section insulator: Section insulators are provided to insulate OHE of one elementary section from the OHE of another adjacent elementary section. Located at cross over from one track to other, from main line to siding.