History and Evolution of Electric Power Distribution
– Electricity distribution became necessary in the 1880s with the introduction of power stations
– Power-distribution systems were initially used for lighting, replacing gas lighting systems
– Arc lighting used high-voltage AC or DC, while incandescent lighting used low-voltage DC
– Arc lighting allowed for long strings of lights, while DC systems had limited transmission distance
– Functional transformers in the mid-1880s enabled AC power transmission at higher voltages
– Transmitting electricity over longer distances was a challenge in electric power distribution
– Functional transformers allowed for AC power to be stepped up for transmission and stepped down near the end user
– AC power transmission was cheaper and had greater economies of scale compared to DC
– Thomas Edison’s propaganda campaign against AC was short-lived, and his company switched to AC in 1892
– AC became the dominant form of power transmission with innovations in electric motor designs
– Distribution systems have transitioned from simple distribution lines to integrated networks
– Modern distribution systems, also known as microgrids, rely on renewable energy sources
– The evolution of distribution systems has been influenced by advancements in technology and the integration of renewable energy
Generation and Transmission
– Electric power starts at a generating station with a potential difference of up to 33,000 volts
– AC is commonly used, but some systems use rectifiers to derive DC power
– High-voltage DC can be advantageous for isolating AC systems or controlling electricity transmission
– Step-up transformers increase the voltage to a suitable level for transmission
– Electricity from different generating stations is combined in the transmission system
Primary Distribution
– Primary distribution voltages range from 4kV to 35kV phase-to-phase
– Large consumers are directly fed from distribution voltages
– Most utility customers are connected to transformers that reduce the voltage to the utilization voltage
– Utilization voltage is used for lighting and interior wiring systems
– Primary distribution serves as the initial step in delivering electricity to customers
Network Configurations
– Distribution networks can be radial or network systems
– Radial systems have one source of supply for each customer, resembling a tree structure
– Network systems have multiple sources of supply operating in parallel
– Spot networks are used for specific areas or critical installations
– Distribution substations play a crucial role in network configurations
Challenges and Future Trends in Distribution Systems
– Balancing the supply-demand relationship in distribution networks is a complex task
– The integration of renewable energy sources adds further complexity to distribution system operation
– Technological and operational means, such as optimization tools, are required to manage distribution systems effectively
– Microgrids face unique challenges due to their independence from transmission networks
– Ensuring reliability and stability in distribution systems is a key challenge
– Distribution systems operate at lower voltage levels compared to transmission networks
– Primary distribution voltage levels vary depending on the region and system design
– Distribution networks consist of substations, transformers, and distribution lines
– The infrastructure of distribution systems is designed to deliver electricity to end-users efficiently
– The configuration of distribution networks can be optimized to minimize power losses and improve reliability
– Distributed generation resources, such as solar energy and wind energy, are integrated into distribution systems
– This integration reduces dependence on transmission networks and promotes local generation
– Distributed generation resources require proper management and coordination to maintain system stability
– The integration of distributed generation contributes to the decarbonization of the electricity sector
– The future of distribution systems includes advancements in smart grid technologies
– Smart grid technologies enable real-time monitoring and control of distribution networks
– Energy storage systems play a crucial role in the future of distribution systems
– The integration of electric vehicles into distribution systems is a growing trend
– Distribution system planning and operation will continue to evolve to meet the changing energy landscape Source: https://en.wikipedia.org/wiki/Electric_power_distribution
Electric power distribution is the final stage in the delivery of electricity. Electricity is carried from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2 kV and 33 kV with the use of transformers. Primary distribution lines carry this medium voltage power to distribution transformers located near the customer's premises. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through secondary distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level.
The transition from transmission to distribution happens in a power substation, which has the following functions:
- Circuit breakers and switches enable the substation to be disconnected from the transmission grid or for distribution lines to be disconnected.
- Transformers step down transmission voltages, 35 kV or more, down to primary distribution voltages. These are medium voltage circuits, usually 600–35000 V.
- From the transformer, power goes to the busbar that can split the distribution power off in multiple directions. The bus distributes power to distribution lines, which fan out to customers.
Urban distribution is mainly underground, sometimes in common utility ducts. Rural distribution is mostly above ground with utility poles, and suburban distribution is a mix. Closer to the customer, a distribution transformer steps the primary distribution power down to a low-voltage secondary circuit, usually 120/240 V in the US for residential customers. The power comes to the customer via a service drop and an electricity meter. The final circuit in an urban system may be less than 15 metres (50 ft), but may be over 91 metres (300 ft) for a rural customer.
