What is Busbar:
Busbar is a node of power system, where incoming and outgoing circuits are connected. A busbar is a strip/bar/solid rod/hollow tube of copper/aluminum that conducts electricity within a switchboard, distribution board, substation, battery bank or other electrical apparatus.
Busbars are typically either flat strips or hollow tubes as these shapes allow heat dissipation more efficiently due to their high surface area to cross-sectional area ratio. Hollow busbar section has higher stiffness than a solid rod of equivalent current-carrying capacity, which allows a greater span between busbar supports in outdoor switch yards. Busbars may be connected to each other and to electrical apparatus by bolted, clamp or welded connections.
Different types of Busbar:
Different types of Busbar:
Phase power busbar:
Phase power bus bar may consists of two, three, four bar for 1-phase, 3-phase, 3-phase 4 wire system respectively. These power busbars are insulated from each other and metal earthed enclosure used to tap incoming and outgoing power supply.
Earth busbars:
Earth busbars are typically bare and bolted directly onto any metal chassis of their enclosure.
Current carrying capacity:
The current-carrying capacity of a busbar is usually determined by the maximum temperature at which the busbar is permitted to operate.
As per British Standard BS 159 stipulates a maximum temperature rise of 50°C above a 24 hour mean ambient temperature of up to 35°C and a peak ambient temperature of 40°C.
As per American Standard ANSI C37.20 alternatively permits a temperature rise of 65°C above a maximum ambient of 40°C, provided that silver-plated (or acceptable alternative) bolted terminations are used. If not, a temperature rise of 30°C is allowed.
A very approximate method of estimating the current carrying capacity of a copper busbar is to assume a current density of 1250 A/inch2 and that for Aluminum is 800A/inch2 in still air .
The more popular thumb rule being followed in India is to assume current density of 1.0 Amps / Sq.mm for Aluminum and 1.6 Amps/Sq.mm for Copper for any standard rectangular conductor profile.
Busways or Bus ducts:
Busways or bus ducts are long busbars with a protective cover, segregated phase bus, rather than branching the main supply at one location. They allow new circuits to branch off anywhere along the route of the busway.
Following are some advantages of Bus bar trunking system over normal cabling system:-
Busbar trunking has several key advantages over conventional forms of power distribution including: -
Following are some advantages of Bus bar trunking system over normal cabling system:-
- Installation time is less compared to wired systems leads to cost savings.
- It provides increased flexibility in design and versatility with regard to future modifications and expansion.
- Greater safety and peace of mind for users.
- Installed vertically the same systems can be used for rising-mains applications, with tap-offs feeding individual floors.
- Very compact so provides space savings.
- Where aesthetics have to be considered, busbar trunking can be installed.
Busbar trunking has several key advantages over conventional forms of power distribution including: -
- For higher ratings of power distribution we need to have multiple runs of cable. In such conditions unbalanced distribution of current may takes place and causing overheating of some cable. This is completely avoided in the Bus Bar Trunking systems.
- When multiple runs of cables are used it often leads to improper end connections thereby causing overheating of contacts, burning of cables ends and is a major cause of fire. This is completely avoided in Bus Bar Trunking systems.