Short Answer:
The distribution system is divided into two parts — primary distribution and secondary distribution. The primary distribution network carries medium-voltage electricity (usually 11 kV to 33 kV) from the distribution substation to distribution transformers. The secondary distribution network carries low-voltage electricity (typically 230 V to 415 V) from these transformers to homes, shops, and small industries.
The primary network handles bulk power for a large area, while the secondary network delivers power to end users. Together, both networks ensure that electricity reaches consumers safely and efficiently at usable voltage levels.
Detailed Explanation:
Primary and secondary distribution networks
Introduction to Distribution Networks
The distribution system is the final stage in the delivery of electrical power. It ensures that electricity, after being stepped down from high transmission voltages, is further reduced and safely delivered to various consumers. This system is divided into two main parts: primary and secondary distribution networks. Both parts work together to transfer electrical energy from substations to the end users with reliability and safety.
Primary Distribution Network
The primary distribution network begins at the distribution substation, where high-voltage power from the transmission system is stepped down to medium voltage, typically between 11 kV and 33 kV.
Key Features:
- Carries electricity from substations to various distribution transformers.
- Covers wide areas such as towns, industrial parks, or sections of cities.
- Uses overhead or underground lines depending on the area.
- Supplies power to several transformers, which further reduce voltage for consumer use.
- Mostly three-phase and used for bulk distribution.
Purpose:
- To efficiently transfer medium-voltage electricity across a larger distance.
- To connect substation output to many smaller zones.
Secondary Distribution Network
The secondary distribution network begins at the distribution transformer, where medium voltage (11 kV or 6.6 kV) is stepped down to low voltage, usually 400 V (3-phase) or 230 V (single-phase).
Key Features:
- Delivers electricity directly to end users such as homes, shops, offices, and small industries.
- Covers smaller areas like streets, colonies, or buildings.
- Usually uses overhead lines in rural areas and underground cables in cities.
- Consists of shorter, more localized lines.
- Single-phase supply for domestic use and three-phase for small businesses.
Purpose:
- To provide usable voltage levels to consumers.
- To ensure safety and meet the needs of different types of electrical loads.
Difference Between Primary and Secondary Distribution
- Voltage Level:
- Primary: Medium voltage (11–33 kV)
- Secondary: Low voltage (230/400 V)
- Purpose:
- Primary: Transfers power to transformers
- Secondary: Supplies power to end users
- Area Coverage:
- Primary: Large areas
- Secondary: Localized small areas
- Consumer Connection:
- Primary: No direct connection to consumers
- Secondary: Directly connected to consumers
- Conductor Size:
- Primary: Larger conductors for high load
- Secondary: Smaller conductors for limited load
Importance of Both Networks
- Both networks are necessary for delivering power reliably and efficiently.
- Proper coordination between the two ensures voltage stability and prevents losses.
- Maintenance of both parts is essential to avoid outages and ensure power quality.
Conclusion
The primary and secondary distribution networks are vital components of the power delivery system. The primary network transports medium-voltage electricity from substations to transformers, and the secondary network distributes low-voltage electricity to end users. Each has its specific function and structure, but together they form a complete system that ensures electricity reaches consumers safely and in usable form. Understanding both networks is essential for planning, maintaining, and improving power distribution.