15.1 Introduction

Low voltage, high current open busbars are supported on insulators and carry current without a dedicated enclosure. They find application both outdoors & indoors and in AC & DC systems. High current open busbars can be broadly classified into two major categories based on the electrical system.

High Current DC Busbars

High Current AC Busbars

15.1.1 High Current DC Busbars

Low voltage high current DC busbars are installed in metal extraction plants such as Aluminium, Magnesium, Sodium, Potassium, Calcium, Lithium, and refining plants among many others. The magnitude of the current can be as high as 600 kiloamperes DC. The voltage at the rectifier terminal can be as high as 1650 volts DC. 
As an example, open busbars connections are explained (in brief) in the Aluminium extraction plant (Hall & Heroult Process) where the conductor material is Aluminium and base metal refining process, where the conductor material is Copper. 

15.1.2 High Current AC Busbars

Low voltage high current AC busbars are installed in electric arc furnaces (EAF) and Electric induction furnaces (EIF). Some of the very recent developments have DC voltage applied to the Electric Arc Furnace electrodes. 

(Open Busbars supported on medium voltage insulators had been used as connections between Generator and Generator Transformer in power plants, in early to middle of last century, before the development of isolated phase bus. This application is beyond the scope of the present discussion).

15.2 Description

In the design of the High current busbars, the following are the main criteria to be met:

Limiting Voltage Drop

Limiting Temperature Rise of Busbars

Limiting Losses in Busbars

Reducing Stray Magnetic Fields

Ease of Disconnection / Shorting

Resistance to Corrosive Atmosphere

 

Temperature rise, losses, and voltage drop are all inter-related. While higher magnitudes of these parameters will result in a low capital cost and higher running cost, lower magnitudes will result in a high capital cost and lower running cost. The optimization parameters will depend upon the nature of the industry and the cost of energy.