Why are high voltage transmission lines equipped with two power lines on each pole while low voltage distribution lines have only one?
High-voltage (HV) transmission lines often us to appear to have 2 sets of power lines on the same pole (or) tower while low-voltage (LV) distribution lines usually carry only one set.
The reason primarily depends on power capacity, reliability and system design.
1). Higher Power Transfer Capacity
Transmission lines carry electricity over long distances at very high voltages (110 kV, 220 kV, 400 kV and above).
To handle this large power flow utilities often use double-circuit lines
2 separate three-phase circuits mounted on the same tower.
This effectively doubles the power-carrying capacity without requiring an additional transmission corridor.
2). Improved Reliability
Having 2 circuits on one tower improves supply reliability.
If one circuit trips due to a fault (or) requires maintenance the other circuit can continue to supply power reducing the risk of the widespread outages.
3). Better Utilization of Infrastructure
Transmission towers and right-of-way land are expensive.
Installing two circuits on a single tower helps utilities optimize land use and construction costs while increasing system efficiency.
4). Lower Demand in Distribution Networks
Low-voltage (LV) and medium-voltage (MV) distribution lines (230 V, 415 V, 11 kV, 33 kV) supply smaller loads to the houses and local consumers.
A single circuit is usually sufficient to meet the required demand so only one set of lines is installed.
5). System Planning and Safety
High-voltage networks are part of the essential backbone of the grid so redundancy is essential.
Distribution systems on the other end prioritize simplicity and cost-effectiveness over redundancy.
High-voltage (HV) lines use two circuits per pole to carry more power and improve reliability while low-voltage (LV) lines usually need only one circuit because the load demand is lower.
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