Maximum Distance between Busbar Supports

by Nuwan Bandara
Maximum Distance between Busbar Supports

Maximum  Distance between busbar supports determines the amount of current that can be passed through a busbar during short circuit condition. In general switchgear assemblies are designed for certain short circuits values. The. Key parameters that determine the distance between busbar supports is electromagnetic forces between busbars during short circuit incident. The Standard IEC 60865, “Short-circuit currents – Calculation of effects –Part 1: Definitions and calculation methods” has all the mathematical tools for calculating forces between busbars on short circuit condition. It has also provided a method to calculate effects on the support during short circuit. In this paper the calculation methods of IEC 60865 are used and computer simulations are used to verify the results

Index Terms- Busbar, Electromagnetic Forces, Short Circuit, IEC 60865, Main Conductors, Sub Conductors

I. PARAMETERS OF CALCULATING MAXIMUM DISTANCE BETWEEN BUSBAR SUPPORTS
There are bunch of parameters which determines the distance between busbar supports. To calculate electromagnetic forces due to
short circuit Short circuit level, Busbar size and shape and distances and conductor type are required. The support type and
material are also considered. In brief, parameters for calculating distance between busbar supports are listed below.
1. Short Circuit Level
2. Busbar Shape
3. Busbar Size
4. Distance between Sub Conductors
5. Distance between Main Conductors
6. Conductor Material
7. Support Type
8. Support Material

II. THEORY OF ELECTROMAGNETIC FORCE BETWEEN BUSBARS
Basic theories of calculating forces between busbars due to short circuit are Amperes law and
magnetic force expression.

???????? ????? ?? 1?? ???? ???? ???? 2(?) =?0?2/2??

I2 = Current in wire 2
μ0 = magnetic permeability
d = distance between 2 wires

????? ?? 1 ?? ???? (?) = ??1?

I1=Current in wire 1
L = length of the wire

????? ??????? ??? ????? =?0?1?2?/2??

 


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