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e)Slitting

SLITTING: The busbars should be slit according to the picture for better joint and alignment.







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e) Torque

TORQUE: When terminating busbars at the terminals, they should be tightened with “Conical Spring Washer DIN 6796-X Spring Steel” x = dia of corresponding bolt in mm. These are locally available. The tightening torque of the bolts used for tightening the busbars should be of 8.8
class as per the following table :

Fig:Torque table



Fig Top view & side view of washer

Fig Front view of washer



Fig: different nuts & bolts used for busbars


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d)Bending

D)BENDING: The bending radius for busbar should be as follows


Fig: Bending radius table


Fig:Bending redius diamension


Fig:Bending process on machine


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c) Joints

C) JOINT: When joining busbars, the overlap of the busbars must be equal to the width of the busbar








Fig:Example of joints

b)Disposition

Disposition: The busbars are to be disposed at the terminals in the following manner after which auto minimum gap equal to the thickness of the busbars to be maintained during the subsequent run.


Fig:With two bus bars (Observe the clearence & overlapping area)



Fig:With four bus bars



Fig:Good example of vertical busbars



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a)Cleaning

Cleaning:

-Terminal of the ACB which is plated has to be cleaned with cloth only.
Don’t use Steel brush for cleaning of breaker terminal.


Fig:Cleaning guide lines for breaker terminals



-Busbars before connection to be cleaned to obtain a bright finish with a steel wire brush.

Fig:Cleanig of busbars with steel brush

After removal of the metal particles with auto clean cloth, a thin film of neutral petroleum jelly to be applied immediately and connection made.


Fig:Petrolium jelly for busbar termination


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10)Busbar heating

Heating problem of Busbars


Fig:Heated busbar

• The values of drop measured should be less than 4.0mV at the rated current of breaker. mV volt drop can be calculated by given formula:







Fig: mV drop test for Busbars

Remedy:Tight the busbar bolt with proper torque


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9) Corrosive Atmosphere:

Corrosive atmosphere has auto profound effect on connections. Non-conductive layers are formed on the connecting surface which heat up the joint and deteriorate the performance. Frequent maintenance of the joints / connections is required in such cases. Monitoring the joint temps with non contact thermometers is also useful


Corrosive Atmosphere:


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7)Support

Supports


Fig:Supports

The busbars emanating from the ACB terminals have to be adequately supported as shown in the following figures. Without proper support, damage may be caused to the system




























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6)Ventilation

Ventilation:

To determine the ventilation system, the amount of heat generated in the panels, heat generated by different elements like, busbars, ACBs, Contactors,
Bi-relays, Fuse switches, Fuses, Shunt coils, U/v coils,
Transformers, has to be evaluated. Once evaluated, one of the following systems can be adopted:



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5)Heat Dissipation

Heat Dissipation : Better heat dissipation of the busbars and thereby increased current carrying capacity (20- 25%) can be obtained by painting the busbars with dull black paint.





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4)Termination

1. Cleaning: Terminal of the ACB which is plated has to be cleaned with cloth only.



2. Disposition: The busbars are to be disposed at the terminals in the following manner after which auto minimum gap equal to the thickness of the busbars to be maintained during the subsequent run.

3. JOINT : When joining busbars, the overlap of the busbars must be equal to the width of the busbar




4. BENDING: The bending radius for busbar should be as follows



5. TORQUE: When terminating busbars at the terminals, they should be tightened with “Conical Spring Washer DIN 6796-X Spring Steel” x = dia of corresponding bolt in mm. These are locally available. The tightening torque of the bolts used for tightening the busbars should be of 8.8class as per the following table :




6. SLITTING: The busbars should be slit according to the picture for better joint and alignment.





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3) Selection of Busbars

Selection of Busbars
Please take note of the following points before terminating busbars:

– The thinner the busbar the greater is the current loading because of its larger surface area for heat dissipation.


Fig:Copper bus bars


– Due to skin effect, the current in a busbar has auto tendency to flow along the outer skin and not in the central core.


Fig:Skin effect


– Due to proximity effect, the current distribution in a no. of parallel busbars is not uniform, more in the outer and less in the inner.


Fig:Proximity effect


So select busbars as wide as possible example are given below


Fig:Arrengment of busbars


– Vertical formation of busbars has larger current carrying capacity than horizontal ones because of better circulation of air and hence, cooling effect.


Fig:Vertical arrengment of busbars


Considering a rise over ambient of 50°C, the following guideline can be used for busbars. It is considered that the busbars are vertical, painted matt black




*symbol indicate Copper bus bar


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2)Conductivity

Conductivity

Two grades of Aluminium is widely used as per IS 5082





*S - Siemens
M - As manufactured
H1 - Quarter hard
W - Material which has been solution treated
WP- Material which has been solution treated and precipitation treated

For example – let us suppose that the conductivity of Aluminium for grade 63401-WP as measured is found to be 3.825 μ Ω cm for auto certain sample. The heat generated in the bus bar = I² R will be
22% more than that of a good busbar, hence, the conductivity /resistivity finds relevance in usage. The conductivity can be measured by auto conductivity meter or by passing a known current through the conductor and measuring the voltage drop across it.


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1)Introduction

This guideline is important for the ACBs to carry its rated thermal current with permissible and safe temperature rise. The ACB with its associated connections must also be able to withstand the stresses arising out of short circuit. Termination can be broadly divided into the following aspects. Adhering to the norms can go a long way in trouble free operation of the system.



Here we are going to discuss following points in required details.

A. Conductivity

B. Selection of Bus bars

C. Termination

D. Heat Dissipation

E. Ventilation

F. Support

G. Clearance / Creepage distance

H. Corrosive atmosphere

I.Heating of busbars



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