Cable bus systems are used to transfer large amounts of power (very high current and voltage) between a power source and a load center. They are engineered systems that include cable trays, wireways, and conductors for connecting a power source to a machine. Unlike trays and wireways, cable bus systems are complete packages that include wiring or cabling.
Suppliers offer products in both standard and custom lengths, with special models available for specific applications. As electrical cable systems, specifications include ampacity, voltage, voltage drop, height, width, and the number of conductors per phase.
Types of Cable Bus System Components
Cable bus systems consist of various components including insulated power cables, non-magnetic support blocks, and a ventilated metal enclosure.
- Insulated power cables are single conductor cables used to carry power across the system and prevent electrical or heat flow outside the insulating sheath.
- Support blocks are designed to maintain proper cable spacing while providing short-circuit bracing.
- Metal housings are welded metal enclosures designed to withstand mechanical forces from short circuit currents. Materials of construction include aluminum and stainless steel.
Accessories include equipment connections, fire stops, flanges, terminal lugs, termination kits, wall entrance seals, neutral-phase conductors, and ground conductors. Neutral-phase conductors are insulated. Ground connectors are insulated, bare, or tin-plated. Additional components and accessories may include box connectors, tap boxes, water-tight seals for outdoor use, long-barrel compression lugs, shield grounding kits, and supports.
Applications and Standards for Cable Bus Systems
Some cable bus systems are designed for use with primary and secondary feeders or service entrance applications. Others are used to transfer large amounts of power from generators to transformers, generators to switchgear, transformers to switchgear, or switchgear to switchgear. Products for uninterruptible power supplies (UPS) are also available.
There are several major standards for cable bus systems. Load test guidelines include NEMA VE-1/CSA tray standards from the National Electrical Manufacturers Association (NEMA) and the Canadian Standards Association (CSA). The CSA, the National Electricity Code (NEC), and the Insulated Power Cable Engineers Association (IPCEA) provide standards for cable bus support and cable ampacity. Heat rise standards include ANSI C37.20 and C37.24 from the American National Standards Institute (ANSI).