3.1 Different Types of Distribution Systems

[Audio] Hello Everyone!! This is a lecture for JFB32113 Building Maintenance and JFB32123 Building Maintenance And Services..

[Audio] We will continue subtopic 3.1 in the Chapter 3 Electrical Installation and Lighting System.

[Audio] In this chapter, we will study the anatomy of electrical distribution systems in buildings. Electrical distribution refers to the process of delivering electrical power from the main supply source to the equipment and appliances used inside a building. A building's electrical system is designed in a structured way so that electricity flows safely and efficiently from the main supply to the final devices such as lights, sockets, and machines. For example, when you turn on a lamp in your room, electricity travels through several stages in the building's distribution system before reaching that lamp..

[Audio] The distribution network connects the main power supply to the electrical loads inside the building. According to the diagram on this slide, the distribution system must achieve four important outcomes: Safe power delivery – electricity must be delivered safely without causing hazards. Reliable electrical supply – the power supply should be stable and continuous. Efficient power utilization – electricity should be distributed efficiently without unnecessary losses. Protection against electrical faults – the system must protect equipment and users from electrical faults. For instance, if a short circuit occurs in one part of a building, protection devices such as circuit breakers will disconnect the faulty section to prevent damage..

[Audio] Electrical distribution inside a building usually follows a three-tier hierarchy. The three levels are: Background Distribution – the connection between the building and the external power grid. Supply Distribution – the distribution of electricity to different floors or zones in the building. Local Distribution – the final delivery of electricity to equipment and appliances. This hierarchical structure helps organize the electrical system efficiently. Think of it like a road system: highways bring traffic into a city, main roads distribute traffic across districts, and small streets deliver traffic directly to houses..

[Audio] Background distribution is the main electrical gateway of the building. This level includes major components such as: Transformer – reduces high voltage from the external power grid to a usable level. Main switchboard – the main control point of the building's electrical system. Main distribution board – distributes electricity to different parts of the building. Busbars and main cables – carry high electrical current throughout the system. These components handle the largest amount of electrical power in the building. In a large shopping mall, the transformer receives high voltage electricity from the grid and steps it down before it enters the building system..

[Audio] After electricity passes through the main distribution board, it is sent to different zones of the building. This is known as supply distribution. At this stage, electricity is distributed to: Floor distribution boards Lighting distribution panels Power distribution boards This zoning system has several advantages: It reduces the total cable length. It improves load management. It allows easier maintenance in specific zones. For example, each floor of an office building may have its own distribution board that supplies electricity only to that floor..

[Audio] To improve efficiency, buildings often divide electrical systems into smaller zones called sub-zones. Instead of sending thousands of cables directly from the main switchboard to every room, electricity is first sent to floor distribution boards. From there, it is distributed to specific areas such as: Lighting zones Power zones HVAC zones This method helps simplify the electrical wiring system and makes it easier to manage. For instance, in a university building, one zone may handle lighting while another zone supplies electricity to air-conditioning systems..

[Audio] Local distribution is the final stage of the electrical distribution system. At this stage, electricity is delivered from sub-boards directly to the devices used by people. These devices may include: Lighting circuits Socket outlets Air conditioning units Electrical equipment This stage connects the electrical system directly to the end users. When you plug your phone charger into a socket outlet, you are using electricity from the local distribution system..

[Audio] This slide summarizes the distribution hierarchy using a table. The three levels are: Background Level Covers the entire building and grid interface. Uses equipment like transformers and main switchboards. Its objective is high-capacity power intake and central control. Supply Level Serves specific floors or building zones. Uses floor distribution boards and power panels. Helps manage electrical loads and reduce cable length. Local Level Serves individual rooms and appliances. Includes circuits, sockets, and end-user wiring. Delivers electricity directly to equipment. This structured system ensures electricity flows safely and efficiently..

[Audio] This diagram shows the complete journey of electricity through the building. Electricity enters the building at the background level through the main switchboard. It then moves upward through vertical distribution cables to the supply level, where floor distribution boards manage power for different areas. Finally, electricity reaches the local level, where it powers sockets, lighting, and appliances. This is similar to a water distribution system where water enters a building through a main pipe and is then distributed to different floors and rooms..

[Audio] One important advantage of hierarchical distribution is fault containment. If a fault occurs at the local level, such as a damaged socket outlet, the breaker in the supply level will trip. This isolates the problem to only one zone instead of shutting down the entire building. This system prevents large-scale electrical failures. For instance, if a faulty appliance causes a short circuit in one room, only that circuit will lose power while the rest of the building continues operating normally..

[Audio] To ensure electrical systems operate safely, regular inspection and maintenance are necessary. Important maintenance activities include: Inspection of distribution boards – ensures all components function properly. Monitoring electrical load balance – prevents circuits from being overloaded. Checking cable insulation – prevents electrical leakage and overheating. Tightening loose connections – improves safety and electrical efficiency. Proper maintenance helps prevent electrical faults, fire hazards, and equipment damage. Example If cable insulation becomes damaged, it may cause short circuits or overheating, which could lead to electrical fires..

[Audio] In summary, electrical distribution systems in buildings are organized into three levels: background distribution, supply distribution, and local distribution. This hierarchical structure allows electricity to be delivered safely, efficiently, and reliably from the main supply to the final electrical devices used by occupants. Understanding these systems helps engineers design electrical installations that are safe, easy to maintain, and capable of supporting modern building operations..

[Audio] That's all for now. See you in next class!! Have a good day everyone, Bye!.