Introduction to Superior Cable Bus
The Superior Cable Bus package by Medico Fabrication Inc. is the most reliable and economical electrical power feeder system available on the market today. Cable bus provides the method for efficiently transmitting large quantities of electricity between a power source and a primary load center, such as from a generator to transformer, transformer to switchgear or from switchgear to switchgear. Superior Bus can also be used as power feeders for large motors, machineries, as well as primary and secondary feeders in industrial plant electrical installations. The Superior Bus is an engineered cable management system that provides a safer, more cost effective alternative to bus duct, direct burial, and electrical conduit and wire power feeder/cable management systems.
System Overview
Superior Cable Bus is a completely engineered system consisting of fully continuous, insulated single conductor power cables mounted on nonmagnetic, self-extinguishing support
blocks within a ventilated enclosure. The Superior Bus is supplied with all the required accessories and fittings for a complete power feeder system. In addition to having
a high fault current carrying capacity, Superior Bus has the widest available range of ampere ratings and voltage classes for any made-to-measure power feeder system.
Electrical conducting cables carry currents of between 400 to 6000 amperes per phase at typical voltages of 600 volts to 35 kilovolts and higher.
Superior Bus is a cable bus system that maintains the free air rating by utilizing the only CSA certified ventilated enclosure available.
The all-welded metal enclosure is available in Aluminum Alloy, Stainless Steel or Galvanized (HDGAF) Steel.
All Superior Bus systems include the necessary equipment connections, entrance fittings, tap boxes, flanges, power cables, wall entrance seals, fire stops, elbows, terminal
lugs, termination kits, supporting structures and any miscellaneous parts that would be required for a complete power feeder system. Superior Bus comes in standard lengths
of 10 or 20 foot spans but custom lengths are an available option, with each piece being sized to fit for any installation. The Superior Bus system is suitable for both
indoor and outdoor use; with conductor spacing and ventilation being maintained throughout the entire system.
Superior Cable Bus: Conductors
The single conductor cables in a cable bus system are installed in a fully ventilated enclosure to keep the conductors within temperature limits. This engineered design allows for an excellent cooling of the conductors and a free air rating of the power conductors is achieved. In addition to eliminating hot spots in the conductors, the ventilated enclosure also protects the conductors from physical damage and guards the entry of foreign objects.
The fully insulated conductors are installed continuously in the field from the power source to the load thereby eliminating intermediate splices that could be potential weak points in the power system. These conductors are pulled in after the cable bus enclosure is installed. The only conductor connections are at the equipment terminations. Since connections are the cause of most electrical failures, minimizing the conductor connections substantially increases the system reliability.
All current carrying conductors have an insulation rating of 90 degrees centigrade for the specified ampacity and voltage. The conductor spacing and ventilation is maintained in the cable bus enclosure. These conductors are phased and supported with the support blocks to maintain low impedance and ensure the mechanical strength necessary to prevent the damage or movement of the conductors under short circuit conditions of up to 100,000 RMS symmetrical amperes. The phasing arrangements
of the conductors in the cable bus system result in low power loss and therefore lower operating cost.
Cable Bus systems having low impedance reduce the power consumption and minimize the voltage drop of the system. Conductors used may be made of copper or aluminum. The conductor insulation is usually cross-linked polyethylene (XLP) and for higher voltage the recommended insulation is ethylene-Propylene rubber (EPR).
Cable Bus manufacturers usually provide the standard cable termination hardware such as compression type cable connectors, terminal lugs and heat shrink or cold shrink termination kits for high voltage systems (5KV, 15 KV and higher).
Superior Cable Bus: Supports
The support blocks of a cable bus system are used to maintain conductor spacing and phasing arrangement. These are installed every 18" in vertical runs and a maximum of 36" in horizontal applications to ensure proper arrangement and bracing in the event of a short circuit. These support blocks are designed in segments to maintain a minimum of one conductor diameter in both the vertical and horizontal planes to attain the free air conductor rating. The bottom support blocks are factory pre-assembled in the bottom section of the housing assembly and the next layers of support blocks are then fastened using stainless steel bolts.
Superior Cable Bus: CSA Certified Ventilated Enclosure
The ventilated aluminum enclosure of the cable bus system is likewise designed to withstand the mechanical forces encountered from short circuit currents. Manufactured straight sections are factory cut in lengths of ten and twenty feet long. Just like a cable tray system, the cable bus system has fittings for use in directional changes such as horizontal elbows, vertical inside elbows and vertical outside elbows with bends for 90, 60, 45 and 30 degrees. Top covers are
removable while bottom covers are factory welded into place.
The cable bus enclosure is grounded at sufficient points for the purpose of preventing a potential above ground on the enclosure in the event of a fault. There are cable bus system enclosures that are made of aluminum alloy and that use high pressure splice joints which provide excellent ground continuity. This particular cable bus design eliminates the use of additional ground wire for most systems.
Cable bus enclosure made of stainless steel is also an option. However, due to the superior material properties of aluminum, it is highly recommended and suitable for cable bus systems intended for installation in extreme low temperature conditions.
Superior Cable Bus: Cost Efficiency
The cable Bus System has been proven to be the most cost effective power feeder. It can generate the following cost savings compared to the rigid bus bar duct system:
1. Lower Installation Cost
• Bus bar duct systems have pre-manufactured sections that need to be bolted in place and are usually heavy that require the use of heavy lift equipment that could add to the project cost.
• Cable Bus Systems are pre-cut to fit specific location. Sections are relatively light and its bottom cable support blocks are factory pre-installed. Sections can easily be handled by two men without the aid of heavy equipment such as booms, lifts or cranes.
2. Reduced Cost of Enclosure
• Outdoor type bus bar duct systems which are totally enclosed require larger bus bars due to derating because the exterior portion has insufficient cooling and anti-condensation devices like space heaters must be installed. These space heaters and larger enclosure add up to the project cost.
• Cable Bus Systems with its ventilated top and bottom covers can be installed both indoors and outdoors which allow the use of the free air rating of the single conductor cables.
Additionally, the Cable Bus Systems do not have to be precisely aligned with the bus bars in the switchgears or transformers which is necessary in the bus bar systems. Cable bus systems also do not require heater strips to keep moisture out of the system because it is designed to be ventilated for both outdoor and indoor conditions.
Superior Cable Bus: Accessories
The Superior Cable Bus offers the following standard accessories for their cable bus systems:
• Box Connectors - Box connectors are used to terminate cable bus at switchgear or other metal structures and are furnished with all the necessary hardware.
• Watertight Seals -These fittings are used to provide a weatherproof seal with walls and can also be used for floor penetrations that need to be watertight. Entrance fittings are furnished with all the necessary hardware.
• Tap Boxes - Tap boxes are necessary for intermediate load tapping. These are required to make taps from main bus runs to bus ties and intermediate loads.
• Cable Bus Supports - The Cable Bus Systems are supported according to NEMA standards and supports are installed typically 12 feet on center. Manufacturers supply a variety of structural and trapeze supports, including T-type, frame support, pedestal support and wall support.
• Horizontal and Vertical Elbows - These provide the ability to change the direction of the Superior Cable Bus in horizontal and vertical runs. Can achieve angular changes from 15 to 90 degrees.
Safety
• All welded rigid construction
• High pressure splice joints provide an excellent path to ground
• Workmen free of shock hazards no exposed bus elements, only insulated
conductors used
• Method of ventilation inhibits entry of foreign objects.
Introduction to Cable Bus Benefits of Cable Bus Quality Control Components and Accessories Cable Bus Sizing Cable Bus Technical Information AutoCAD Cable Bus Modeling Catalogue in PDF (English) Catalogue in PDF (French)
