Underground cabling plays a crucial role in providing 24×7 reliable power supply. It offers a host of benefits such as resilience in severe weather conditions, ease of network expansion in densely populated areas and protection against theft. Underground cabling by distribution utilities is primarily being done under the government’s Integrated Power Development Scheme (IPDS). Meanwhile, underground cabling is important for network expansion in the transmission segment since these cables entail minimum right of way (RoW) and require fewer clearances. While underground power cabling is undoubtedly an expensive choice, demand continues to be driven by the need for reliable supply, safety and aesthetic considerations, and the availability of clearances. A key underground cabling system was completed in Varanasi, Uttar Pradesh, in 2018. The project entailed the conversion of overhead lines to underground cables, the establishment of two 33 kV substations, and the augmentation of 11 existing substations at an estimated cost of Rs 4.32 billion. Apart from this, underground cabling projects are under way at Kumarapalayam, Congress Nagar division, Hudkeshwar, Jaipur, Gorakhpur and Amravati.
Underground cables are less prone to damage caused by severe weather conditions such as lightning, hurricanes, cyclones, typhoons, tornados and freezing as they are not exposed to the environment. Besides, underground cables are protected against power theft, thereby reducing aggregate technical and commercial (AT&C) losses. In an underground cabling system, it is almost impossible to tap the conductor, thereby checking illegal connections. Another growth driver is network expansion. Underground cables require minimum RoW and other clearances such as wildlife and forest clearances, which often delay transmission projects. In the distribution segment, underground cables help in network expansion in densely populated areas. Since these cables are laid under the ground, they do not require physical ground space. They also add to the aesthetics of the area, as they do not obstruct the view.
At the distribution and sub-transmission levels, the majority of underground cable projects are being implemented under the IPDS. The scheme has earmarked Rs 20 billion for executing these projects. It envisages the implementation of underground cables aggregating 18,008 km across various states. Maharashtra has the highest target with 5,762 km, followed by Uttar Pradesh with 2,864 km and Rajasthan with 2,179 km. Underground cabling projects have also been proposed under the Smart Cities Mission to ensure reliable power supply and enhance aesthetics. Underground distribution cabling projects are also being implemented under other state and central government schemes for network improvements such as the Andhra Pradesh Disaster Recovery Project, the National Cyclone Risk Mitigation Programme, and the North Eastern Region Power System Improvement Project.
As per the Central Electricity Authority, the cost of an underground cabling system is three to four times that of an equivalent overhead system. The estimated cost of an 11 kV overhead single- circuit line with dog conductor is Rs 0.5 million-Rs 0.6 million per km while the estimated cost of a 3×300 square mm 11 kV underground cabling system is around Rs 2 million per km. The cost of the underground cabling system also depends on the cost of the road restoration work required.
Areas of concern
One of the key concerns for underground cabling is the damage caused to the cables from other underground activities. The uncoordinated underground development activities undertaken by multiple agencies and private contractors result in frequent cable cuts, leading to a depreciated life of the cable and an increase in operating costs. Besides, the cable insulation deteriorates over time owing to various loading cycles. Over time, the cable insulation weakens, which increases the potential for line faults. Besides, since these cables are below the ground, they require specialised techniques for fault detection and restoration, and the repair time is much longer. Also, it is difficult to modify underground lines once the cables have been laid.
Net, net, underground cabling is a boon for the transmission and distribution segment, as it helps in network expansion in densely populated areas, minimises power theft and requires minimum clearances. Undertaking underground cabling projects based on the specific needs and requirements of an area is essential for meeting the government’s goal of providing 24×7 reliable power supply.