Energy Efficiency and LV Switchboards


This seems to be a very odd topic of discussion as we never thought of Energy Efficiency for LV Switchboards. I have presented this in the 2nd Edition of EEETech organised by CII at IHC Delhi, which was a Technical Conference and exposition on Energy Efficiency, Environment and Technology. The theme of the exposition was ‘Mission of Zero Effect”. This thought came with the desire to think of something where I am deeply involved and relevant to the theme. Switchboard was an obvious choice for me as I spent my whole career around it.

We will understand the basic structure of the Power System with the help of below network diagram below. This will help us in further discussion on the topic.

Energy Efficiency - Power Supply System

Energy Efficiency and Electrical System

Just recall any of the discussions on energy efficiency where you were part of it. I hope you find professionals discussing the efficiency of Generation Equipment, Transmission losses, the efficiency of substation equipment like transformers etc. Please refer above diagram and think of a secondary distribution where the voltage is 400/230V but since the current is higher, I²R losses will also be higher. The Bureau of Energy Efficiency (BEE) recommends star-rated household equipments and energy-efficient industrial equipments for industries but the poor LV Switchboards which has the responsibility of distributing power safely to industrial establishments, commercial complexes and household never caught the imagination of energy professionals.

So I choose to discuss about Energy Efficiency in LV Switchboards. If we talk of energy efficiency in the secondary distribution system, then we must discuss the losses in the LV Switchboards and the ways to reduce them.

Losses in LV Switchboards

Why it is so important for the designers? Let us further deep dive further into the topic.

The main contributors to the losses in LV Switchboards are:

  • Bus bars
  • Circuit Breakers
  • Bus Joints
  • Connection Joints
  • Type of Enclosure

All the points have the potential of being a complete topic for engineering discussion. All these components have the potential to affect energy efficiency. Discussing all the points will make it very lengthy so we will restrict our discussion to the first factor. We will understand the losses in bus bars through an example as stated below.

We all know that bus bar selection is based on many engineering considerations like thermal rating, ambient temperature, conductivity, enclosure size, phase separation, no of bus bars per phase and fault level. All these factors reduce the bus bar utilization hence bus bar needs to be de-rated. But we have seen; that in the switchboard industry majority of manufacturers still follow the practice of selecting the bus bar with a current density of 1 amp/mm² or at best 0.8 amp/mm2 for Aluminium irrespective of its design and rating. This approach has a number of drawbacks but here we will restrict our discussion to energy efficiency only.

Let us consider two manufacturers “A” and “B” where A has selected the bus bar on engineering considerations and the second one has gone by the thumb rule of 1 Amp/mm². Assume both have designed and manufactured a 4000A-rated Power Control Centre (PCC) having an overall length of 15 meters. The maximum temperature of the Bus bar allowed at full load is 90˚C.    

Main Bus bar selected by manufacturer A: 2*3*150*6 mm².

Main Bus bar selected by manufacturer B: 4*100*10 mm². 

Consider an application for PCC with 24/7 operation for 365 days.

Total loss of energy (I²Rt) in Main Bus bar of Manufacturer A – 46925 kWh

Total loss of energy (I²Rt) in Main Bus bar of Manufacturer B – 63072 kWh

Considering the resistance of the aluminium bar at 90˚C.


PCC by manufacturer A is more efficient compared to B. Cost of PCC by Manufacturer B will be lesser compared to A as B has used less cross-section. Though the cost of PCC by A will be a little higher because of the use of more Aluminum but cost of energy consumed is lesser by 26% which will be a recurring shaving on a yearly basis. So operational cost is lower for PCC by A. It will also be more reliable in performance because of less heating. PCC by B is releasing more heat to the surroundings so it will have a higher carbon footprint which is not good for the environment.

Similarly, we can find out the loss contribution by other factors stated above. So, imagine if they put together what could be the combined loss of the switchboard. Though losses can’t be eliminated they can be kept as low as possible. Since giving the example of losses contributed by each factor will make the discussion very lengthy I am closing it here but would like to share the measures to be taken by engineers to design a low-loss switchboard.   

Design Approach for reduction of losses

  • Engineering considerations for Bus bar design like bus bar configuration, bus bar spacing and adequate enclosure size
  • Incorporation of switching devices as per manufacturer’s guidelines
  • Low-loss design for joints and connections with low contact resistance
  • Ventilated enclosure design for proper heat transfer
  • Panel design validation by type tests on a single prototype as per relevant Indian or International Standards.

Frequently Asked Questions

Q- Is it possible to calculate watt loss in a switchboard?

A- Yes. All the electrical components used in the switchboard have declared watt loss and can be found in the components sheet. For bus bars, joints and connections watt loss can be calculated from their resistance.

Q- How switchboard’s design validation is done?

A- By type testing the design at NABL accredited laboratory.

Q- Why energy efficiency of switchboards are important?

A- Switchboards work round the clock and even a 1000-watt reduction in losses can lead to a saving of 24 units of energy per day.

Q- What is the relevant reference International standard for LV Switchboards?

A- IEC 61439 Part -1 to Part-2

Q- What should be the conductivity of electrical bus bars suitable for switchboards?

A- For Aluminum it is a minimum of 56% while for copper it is 96%.

2 thoughts on “Energy Efficiency and LV Switchboards”

  1. This is an irony that we have yet not thinking labeling LV Switchboards on Energy Efficiency parameters. Engineers are invited to put their thought on the subject.


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