The transmission and distribution sector has been a key focus area for the government. With a move towards providing round-the-clock power, high voltage transmission lines are being developed. Technologies such as flexible alternating current transmission system (FACTS) and high voltage direct current (HVDC) are helping in ensuring the stability and security of the country’s complex grid system. These technologies reduce transmission losses, optimise the power flow, support grid integration of intermittent renewable energy sources and increase transmission capacity and system stability. In tandem with these developments, advancements in cables and conductors can help achieve a seamless high voltage power transmission system.
In order to build a better transmission network and improve power market dynamics, several initiatives and programmes have been taken by the government. These include an investment plan of Rs 2,600 billion for transmission system strengthening under the National Electricity Plan, 2016, for the period 2017-18 to 2021-22, the Ujwal Discom Assurance Yojana (UDAY), the Deendayal Upadhyaya Gram Jyoti Yojana (DDUGJY), the Integrated Power Development Scheme (IPDS) and the Pradhan Mantri Sahaj Bijli Har Ghar Yojana.
The wires and cables industry has transitioned from being an unorganised sector to an organised one over the years. Some of the notable industry players engaged in designing and manufacturing are Polycab, Finolex Cables, CMI, RR Kabel, Sterlite Technologies, KEI Industries and Havells India.
Comprising nearly 40 per cent of the electrical industry, the wires and cables market in India has been growing at about 15 per cent per annum over the past few years, with the exception of a slowdown in financial year 2019-20. The year saw a drop in the market for transmission line towers (TLTs), conductors, insulators and transmission equipment among other products. According to the Indian Electrical and Electronics Manufacturers’ Association (IEEMA), the electrical equipment industry registered a decline of 14 per cent during 2019-20 as compared to a growth in the same period of the previous year. In the quarter ended March 2020, the decline was particularly stark due to the impact of Covid-19. While the switchgear and cables segment has seen good growth in terms of exports, domestic demand has declined, especially for low voltage and house wiring.
However, the market for wires and cables remains highly attractive, and is expected to grow further in the coming years. India is seen as a potential market by international investors for high voltage (HV) and extra high voltage (EHV) cables. Some Indian manufacturers have even established themselves in the EHV space globally, either through technical collaboration or through joint ventures. Recently, foreign investors entered into technical collaboration with Indian cable manufacturers for the production of EHV cables up to 400 kV. The domestic power cable industry has matured, in terms of technology, especially for HV cables up to 220 kV. However, India still meets a significant part of its demand for cables and accessories of 33 kV and above voltage levels through imports.
Advancements in cable technology
Cable design and material have evolved over the years with dry extruded cables increasingly replacing 37 wet paper insulated ones. Cross-linked polyethylene (XLPE), high density polyethylene, aerial bunched cables and spacer cable systems are the most commonly used covered cables. Due to the risks associated with bare overhead cables, covered cables such as XLPE, high density polyethylene and aerial-bunched cables have gained traction in the market.
There is a new cable type called electron-beam or e-beam cable, which finds use in high temperature applications in the solar, railway and shipping segments. Further, gas-insulated transmission lines are another form of emerging cable technology. They are a safe and flexible alternative to overhead lines and take up much less space while providing the same power transmission.
With the growing demand for power in urban areas and industries, underground cable systems are also being deployed by utilities. Underground cabling provides greater safety against electrocution as compared to overhead cables, requires lower right of way (RoW) and is aesthetically better than overhead transmission lines. Even though underground cabling costs are much higher than overhead cables of the same voltage, the high initial cost can be offset by benefits such as low chances of developing faults and low maintenance costs.
Yet another emerging category of cables are solar cables, which can support the increasing penetration of renewable energy into the grid and high solar power targets. Designed to help evacuate solar energy from photovoltaic (PV) modules, these cables connect individual modules and the string combiner box. Solar direct current (DC) cables are of two types – module cables or string cables and DC main cable. Solar cables have a high thermal rating to withstand extreme temperatures, superior abrasion and notch resistance. They can be used across a range of temperatures and are generally laid outside. For solar panels with trackers, the cables need to be flexible as the panels keep moving along with the sun.
Advancements in conductor technology
In recent years, advanced conductor technologies such as high temperature low sag (HTLS) conductors, superconductors and EHV lines have found preference among transcos. With urbanisation on the rise, there is a need to make transmission lines more compact. The transmission conductor industry has witnessed a number of technological advancements that help in increasing the amount of power transmitted through conductors and minimising RoW requirements. Further, advanced conductor technologies are centred on efficiency, safety, reliability, ease of design and environmental friendliness.
Conductors are being developed and deployed for carrying higher currents, while allowing higher temperature ratings. The advancements have led to aluminium conductors completely replacing copper conductors. Aluminium conductors include aluminium conductor alloy reinforced (ACAR), aluminium conductor steel reinforced (ACSR) and aluminium conductor carbon fibre reinforced (ACFR). HTLS, gas-reinforced, and high-performance superconductors are some of the more advanced variants of conductors. Conventional conductors cannot be operated at temperatures higher than 100 ºCelsius and it is difficult to acquire RoW for new power lines using these conductors.
HTLS lines have found increasing acceptance among utilities as they can operate at higher temperature ranges (150 ºCelsius 250 ºCelsius) than ACSR aluminium conductor steel reinforced (<100 ºCelsius) lines, and experience low thermal expansion. A major application of HTLS conductors has been in reconductoring the existing lines to increase power transfer capacity up to two times in the existing corridors. It comes with the benefits of faster execution, no additional ground footprint and improved safety.
However, there are some challenges associated with HTLS conductors. These include extended execution period and the associated cost escalation; in the case of reconductoring, outages need to be carried out by utilities; and the requirement for specialists for line recovery in case of snapping of conductor or tower failures.
Advancements in transmission towers
Over the year, there have been significant improvements in transmission tower designs and these developments have reduced the RoW requirement, minimised the visual impact, enabled faster execution and provided ease of installation. With new designs it has become easier to expand the transmission network to far-flung areas.
There have also been technology upgrades in tower foundation designs and these are being carried out by utilities via multicircuit multivoltage solutions, wherein the line is upgraded with more than one voltage circuit on the same tower. For voltage upgrade, the line capacity is increased by changing the system voltage from a lower value to a higher value of the line in the same available corridor. The power transfer capacity can be increased by over four times using this technology. Moving forward, there is also a need for utilities to adopt tower designs that can withstand natural disasters such as emergency restoration system towers and monopoles with smaller spans in disaster-vulnerable areas.
The way forward
The government’s target to scale up renewable energy in the coming years and provide a variety of incentives to the solar and wind segments is a key demand driver for electrical wires and cables. Further, wiring will be needed to set up charging infrastructure for electric vehicles. Utilities need to not only expand and strengthen transmission networks but also ensure uninterrupted and efficient flow of power by adopting new and emerging technologies. With large-scale projects planned across the country, many of them located in distant regions, there is a rising demand for high capacity transmission infrastructure. The advancements in cables, conductors and transmission towers are expected to help the power sector meet this demand.
By Meghaa Gangahar