The Indian power sector is witnessing an uptick in the adoption of advanced tower and structure technologies for expanding the network with minimum right of way (RoW), greater structural integrity, reduced maintenance costs, improved energy efficiency and better grid reliability. The deployment of tower designs such as monopoles and multi-circuit towers that meet these requirements are gaining traction. Besides, the deployment of emergency restoration towers is gaining momentum to restore power supply in minimum time in case of natural disasters and network failure. The use of advanced materials such as high-strength steel alloys and composite materials for the construction of power towers is also increasing. The adoption of these technologies may vary by region and depends on factors such as regulatory requirements, environmental conditions and specific needs of the power grid.
Monopoles
Transmitter tower alternatives include monopole towers. One main stem that is anchored to the ground makes up their entire structure. Since they can be built in a fraction of the space needed to create lattice towers and can reach heights of more than 50 metres, monopoles offer a practical option. The installation and delivery times of monopoles are also significantly shorter compared to other towers. Monopoles are also a greener option due to the benefit of a reduced base installation area, even when climbing higher than 40-50 metres.
Monopole towers play a crucial role in expanding and upgrading India’s transmission infrastructure. These are especially deployed in areas with high population density or areas where traditional lattice towers are not suitable due to space constraints. These are suitable for high voltage transmission lines in urban and suburban areas, and entail lower RoW requirements. Their sleek design allows them to blend into the surroundings and be less visually obtrusive, compared to traditional lattice towers. They can provide support to transformers, insulators and surge arresters, depending on the power grid’s requirement.
Monopoles are being extensively deployed at the transmission and distribution level in the country. Back in 2017, the Noida Sector 34-Electronic City route saw the installation of six monopole towers for Uttar Pradesh Power Transmission Corporation Limited by the Delhi Metro Rail Corporation (DMRC). Punjab State Power Corporation Limited has deployed towers at the 66 kV level network in Ludhiana. Madhya Pradesh Power Transmission Company Limited has constructed a line with multi-circuit, multi-voltage (2×220 kV+2×132 kV) monopole towers in the city of Indore.
Multi-circuit towers
Multi-circuit towers support multiple circuits of power lines and are designed to carry several sets of conductors, often at different voltage levels, in a single structure. They can optimise the use of the available land, minimise the environmental impact and reduce construction costs. In India, multi-circuit towers are commonly used in the power transmission sector. They are used to carry conductors at various voltage levels, such as 400 kV, 220 kV and 132 kV, depending on the requirements of the transmission line. These are particularly used in densely populated areas, where acquiring land for transmission line corridors is challenging. These towers contribute to a smaller footprint and fewer structures, which are important for preserving natural habitats.
Emergency restoration system
Emergency restoration system (ERS) towers, also known as rapid restoration towers, are designed to facilitate the rapid restoration of electrical power in the event of any damage or failure of high voltage transmission lines. ERS towers are not a permanent part of the power grid, but are strategically pre-positioned or quickly deployed to restore power during emergencies or outages. These towers often feature a modular design constructed from lightweight, yet sturdy materials, to facilitate transportation and assembly. These can be transported to the site and erected in a short time.
Utilities often have contingency plans in place and maintain a stockpile of ERS towers for rapid deployment. In June 2023, power supply to the coastal areas of Gujarat and Rajasthan was affected due to cyclone Biparjoy. All parties involved were given instructions by the power ministry to make preparations for an ERS to be stationed at key sites. Odisha, being on coastal line, frequently faces heavy winds and cyclones that can damage the transmission infrastructure. Odisha Power Transmission Company Limited has efficiently used ERS towers on multiple occasions during damage to multi-link networks and successfully restored power supply.
Other tower designs
Tower designs can be customised to meet the specific requirements of utilities. Compact guyed towers are a good fit for transmission networks over water bodies. A guyed tower is a slender structure comprising truss members, placed on the floors of waterbodies. Guyed towers are especially useful for deep and turbulent waterbodies and are a popular choice in the west. At the same time, compact chainette towers consist of masts, which are individually used to support two guys and ropes connected to the top of two masts. The insulator string and conductor bundles are suspended horizontally. Being narrow based, they are advantageous in steep and angular locations. Apart from this, transmission-cum-telecom towers and taller tower designs are helpful in densely populated areas. Winged circuit towers and shorter tower structures such as the triple-leg slope tower, which places all bundle conductors at the same level, can be used to protect the flora and fauna.
There are numerous other technologies that can be incorporated in transmission towers to optimise RoW, such as pilot jumpers, which are particularly helpful in narrow and high-altitude regions. Post insulators can be used for jumpers to reduce cross-arm projections, which, in turn, can decrease the RoW requirement. Higher voltages, coupled with DC substations, can also help optimise RoW. Further, existing towers are being upgraded with high thermal rating conductors. High temperature, low sag conductors are being deployed in very narrow transmission corridors. For instance, Powergrid has upgraded the 400 kV Siliguri-Purnea transmission line, which was facing RoW constraints.
Tower foundation
One of the measures to optimise the space requirement and maintain a robust network is to build a strong and durable tower foundation. Preferences are shifting from the archaic pad and chimney foundations to grillage foundations, which are more useful for ambient soil conditions, and precast foundations, which can survive extreme weather conditions and can even be set up in snow. Raft foundations, which are essentially large plan area foundations, are useful for lightly loaded structures on soft soil conditions. Meanwhile, driven piles or precast piles that are prefabricated off-site, can be installed in shallow trenches and have a high load-bearing capacity. They are cost-effective and easier to customise than other options.
More recently, helical and auger pile foundations have been gaining traction. Helical piles can support a variety of structures. They are deeply embedded in the ground and can thus support heavy tower designs. Meanwhile, auger pile foundations are embedded at a specific depth and are built to bear weight on both ends. They are friction based and are usually less expensive than helical piles.
The way forward
The country’s growing energy demands require a combination of technological advancements, regulatory reforms and strategic planning to enhance the reliability and efficiency of the power grid. The increased use of monopole towers should be encouraged, especially in urban areas, where aesthetics and space efficiency are essential. It can support the growth of urban transmission infrastructure without compromising the visual landscape. Besides, innovative solutions for RoW issues should be explored, such as the use of underground transmission lines and corridor optimisation to minimise land acquisition and environmental impact and support the integration of larger volumes of renewable energy sources into the grid.
Apart from this, utilities need to increasingly tap into digital solutions for the maintenance of towers and increase the availability of transmission infrastructure. The integration of sensors and monitoring systems into monopoles and other power structures enables predictive maintenance and allows for real-time data collection. Drones equipped with cameras and sensors are being used for the inspection of power structures and are a cost-effective and efficient solution to inspect structures in remote or hard-to-reach areas. These trends are shaping the future of power structures by enhancing their performance, safety and reliability.
