The number of distribution poles and transmission towers within a 1-kilometer stretch of overhead lines varies significantly based on multiple factors, including voltage level, power line type, supporting structure, geographical location, local regulations, and specific grid requirements.
In urban areas, distribution utility poles are typically positioned at closer intervals, while in rural regions, they are spaced farther apart. Additionally, the use of taller structures for higher-voltage transmission and distribution reduces the overall number of towers and poles.
Power transmission towers are fewer in number than distribution poles within a 1-kilometer distance, as their height enables longer spans between structures.
Number of Distribution Poles per 1-Kilometer
As a general approximation, older distribution installations typically have around 11 utility poles per kilometer. These poles are spaced approximately 90 meters (300 feet) apart and support medium-voltage distribution systems (11kV to 14kV), often using wooden or pre-stressed concrete (PSC) poles for low-tension (LT) applications.
Number of Transmission Towers per 1-Kilometer Span
As a general guideline, transmission lines operating at 110kV to 115kV typically have 3.3 to 3.6 towers per kilometer. This corresponds to a spacing of 275 to 305 meters (approximately 900 to 1000 feet) between structures, optimized for voltage class and mechanical load requirements.
Number of Transmission Towers per 1-Kilometer Span
As a general guideline, transmission lines operating at 110kV to 115kV typically have 3.3 to 3.6 towers per kilometer. This corresponds to a spacing of 275 to 305 meters (approximately 900 to 1000 feet) between structures, optimized for voltage class and mechanical load requirements.
It should be noted that these are approximate values, and the actual number and spacing of poles and towers may vary depending on specific conditions, regulations, local environments, project requirements, and other factors affecting the electrical infrastructure in the area.
For instance, in rural regions, the spacing between 11kV to 14kV low-tension (LT) utility poles may exceed 30 meters (≈100 feet), typically ranging from 30 to 45 meters (≈100 to 150 feet), resulting in fewer poles per kilometer. In urban areas, pole spacing is often less than 30 meters (≈100 feet), leading to a higher density of poles. Additionally, high-voltage (HV) transmission lines generally have fewer structures per kilometer than distribution lines. For example, 33kV high-tension (HT) rail poles with a height of 13 meters are typically spaced 80 to 100 meters (≈260 to 330 feet) apart, while the span between 66kV HT lattice steel towers is approximately 200 meters (656 feet).
Span and Spacing of Transmission Towers and Distribution Poles
As previously mentioned, the spacing between HT transmission towers and LT distribution poles is determined by factors such as power line capacity, tower type and structure, geographical location, and local codes. The following are rough estimations of spans and distances for LT poles and HT towers:
- Distance between 11kV-14kV Utility Poles：30 – 45 meters (≈ 100 – 150 ft)
- Distance between 33kV Towers：80-100 meters (≈ 260 – 330 ft)
- Distance between 66kV Towers：200 meters (≈ 656 ft)
- Distance between 132kV Towers：250 – 300 Meters (≈ 820 – 985 ft)
- Distance between 220kV Towers：350 Meters (≈ 1150 ft)
- Distance between 400kV Towers：425 – 475 Meters (≈ 1400 – 1550 ft)
