Cable Bus (CB)
16
16.1 Introduction
Cable bus connections have been in service for many decades in the USA. This concept was first developed and accepted by utilities in the United States. It was later adopted by Canada, Japan, Korea, Taiwan, Saudi-Arabia, and several other countries.
Cable bus was introduced in article 365 of the National Electrical Code in the year 1969 and later moved to article 370 in 2002. NEC 2011 describes Cable Bus as follows:
“Cable Bus is an approved assembly of insulated conductors with fittings and conductor terminations in a completely enclosed ventilated protective metal housing. Cable Bus is ordinarily assembled at the point of installation from the components furnished or specified by the manufacturer in accordance with instructions for the specific job. The assembly is designed to carry fault current and to withstand the magnetic forces of such current.”
Cross Section of a Cable Bus
(Figure – 16.1) Courtesy: MDF Cable Bus Systems
Cable bus is an organized method of spacing single-core cables of different phases and locating them inside a well-ventilated enclosure to meet the specification parameters of a connection.
Cable bus is manufactured for a wide range of installation up to a rated voltage of 72 kV and a rated current of 8 kA. Cable bus has been tested for a short time rating of 100 kA (r.m.s).
A single connection can have up to twenty-seven cables (nine per phase) sharing the load. It is the simplicity in design with the least number of accessories and robust construction that makes cable bus an extremely reliable product.