10.1 Introduction

The synthesization of flexible & thin insulation material with good temperature withstand capability (Class B and above) led to the development of the sandwich bus. It has enabled low voltage bus conductors to be pressed against each other with a thin insulating material between them, conducting heat across the insulation for efficient dissipation, and making the assembly extremely compact.

Presently, sandwich bus construction is limited to low voltage applications in AC and DC systems. There are low & medium voltage cast resin bus, where the thickness of the resin insulation is significant.

The main advantage of the Busway over Busduct are as follows:

• Extremely compact. The cross-sectional area, reduced to approximately 15% of the equivalent, Busduct.
• Low inductive reactance and hence low voltage drop.
• Have a minimum degree of protection of IP – 55.
• Lighter and hence low cost of the support structure and installation
• Easy to install and maintain as the number of fixings per set of joints is minimal.
• Much higher fault withstand capability. Claimed to be as high as 200 kA r.m.s and 450 kAp.
• With less sail area, it is subjected to much lower wind loads and solar radiation.
• The design lends itself to standardization and can be sold in the retail market.
• Meets fire safety standards as there is no path for the smoke to travel through the Busways.
• Ideally suited for high rise buildings, with tap-offs at each floor for power distribution.
• For a similar rating, it is cheaper than a Busduct.
• Fully encapsulated, hence conductors are not susceptible to corrosion.
• No requirement of anti-condensation heaters and drain plugs.
• No necessity of hot air blowing or dehumidifier for ensuring the integrity of the Insulation.
• Very low noise levels.
• Interphase capacitance is a welcome feature.
• Aesthetic look.