An electrical power distribution system ensures the safe and efficient delivery of electricity from the main source to various end-use points. SMDBs are integral components of every electrical power distribution system, enabling the sub-circuits to operate safely and efficiently. A properly SMDB setup requires Strategic planning, timely installation, and regular maintenance to keep faults, overloads, and other hazards at bay. In this guide, we elaborate on best practices for maintaining sub-main distribution boards to ensure efficiency, safety, and compliance with legislative thresholds and standards.   

What is an SMDB?   

SMDB's full form is the Sub-Main Distribution Board. It functions as an interlink with an intermediary panel between the main distribution board and the sub-distribution board or final circuits. SMDBs receive power from a Main Distribution Board (MDB) and further distribute it across a building/facility to different zones or loads.  

Significance Sub-Distribution Boards  

• Load segregation: SMDBs support apportioning the electrical load into various zones.  

• Fault isolation: Faults blocking one section do not jeopardise the entire system.  

• Localised inspection: Facilitates targeted repair work and maintenance. 

• Maintenance efficiency: Empowers Inspectable Unit components to be part-scoped, enabling simplified servicing.

Main Power Supply SMDB Primary Unit Components   

1. 1. Incoming Circuit Breaker (ICB): Protects the board from damage due to excessive current and short circuits.

2. 2. Outgoing Circuit Breakers or MCBs: Supply power to sub-circuits whilst simultaneously protecting each load.  

3. 3. Busbars: Provide distribution of power to different breakers, completing the metering and control functions efficiently.  

4. 4. Neutral and Earth Bars: Provide neutral and earth connections to ensure grounding.  

5. 5. Enclosure: All components are contained in a casing which can either be metal or insulated.  

Installations Best Practices for SMDB   

1. Planning and Assessed Loads 

Develop a strategy prior to installation, ensuring there is an all-encompassing analysis of the load. Be familiar with the electrical needs, possible future expansions, and all primary and secondary categorisations of loads. In order to avoid overloading, special care should be taken to study whether the system is designed for future expansion.

2. Location and Accessibility   

Position SMDBs in sites that are:

• Dry and well ventilated

• Free of any combustible materials

• Constructed so that routine maintenance can be performed easily and quickly

• Clearly marked for easy recognition.

3. Compliance with Standards 

No national and international proven milestones should be left out, such as:

• IEC 61439-1 & 2 on low voltage switchgear and control gear assemblies

• IS 8623 standard in India

• Anything from the Electrical Circuit locally (NEC, IS codes, etc)

4. Proper Sizing of Components 

Pay attention to every detail, including:

• Sizing of the circuit breakers as per load

• Busbars as per their current carrying abilities

• Cables on account of voltage drop, along with insulation on the cables

5. Busbar Arrangement and Insulation 

A busbar must be:

• Supplied with a proper attachment of rating level and insulation

• Fixed at an adequate distance from minimum spacing to avert short circuits

• Clearly marked for easy distinction between phases.

6. Earthing and Bonding 

Make certain that any metallic parts are connected to earth. It is expected that neutral and earth bars will be bolted to the building’s earth in a very firm manner.

7. Ventilation and Cooling 

Use appropriate ventilation or cooling systems for SMDBs that are expected to endure high electrical loads. Component overheating can cause damage, shorten lifespan, and result in failure.

8. Enclosure Protection (IP Rating) 

Please note rated use enclosures with appropriate IP ratings.

• IP43 for general indoor uses 

• Prefer using IP55 or better for dusty and moist environments.

Other Activities Involving Maintenance of Sub-Distribution Boards

1. Routine Inspection 

• Look out for any signs of overheating.

• Check all connections for corrosion or looseness.

• Ensure that labels are provided clearly and accurately.

2. Thermal Scanning 

Employ thermal imaging cameras to spot possible hot spots on busbars and breakers or terminations in the cables.

3. Inspection, Cleaning & Dust Removal 

Accumulation of dust results in non-economic arcing. Non-conductive tools should be used to clean the SMDB to mitigate poor insulation.

4. Torque Testing 

Loosening of connections induces overheating and arcing. All busbars and terminal joints shall be re-torqued in line with the set per the manufacturer's guidelines.

5. Functional Testing 

• Operate the circuit breaker to check functionality.

• Test insulation resistance with a megger.

• Conduct continuity tests of earth and neutral connections.  

Common Installation Mistakes to Avoid   

• Never overload the board past its maximum rated capacity.  

• Mixed neutral and earth segregation.  

• Utilisation of cable or busbar of smaller dimensions.  

• Omit labelling circuits and breakers.  

• Insufficient IP protection for the surrounding environment.  

Upgrades and Expansions 

When improving your previously set electrical installations, remember to:  

• Analyse current load compared to the capacity of the SMDB.  

• Use modular SMDBs that allow the addition of circuits easily.  

• Ensure all additional parts correspond with the latest requirements.  

Role of SMDBs in Energy Efficiency and Monitoring   

Because nowadays sub-main distribution boards can contain:  

• Digital energy meters to track consumption.

• Remote monitoring systems through IoT.  

• Power factor correction units.  

It minimises the wasting of energy, monitors the load balance, and maximises the efficiency.

SMDB vs Main Distribution Board (MDB) 

Also Read: Distribution Panel Board: Types, Sizes, Components, and Function

Conclusion  

Regardless of whether they are found in residential complexes, commercial spaces, or industrial environments, well-architected sub main distribution boards are vital for the optimal and dependable functionality of an electrical system. Using best practices in SMDB installation and maintenance aids in not only prolonging the life of the equipment but also tightening safety compliance with industry standards. With periodic inspections, correct load management, and upgrades to smart monitoring solutions, your SMDB can be designed for enduring reliability while effortlessly meeting future demands.