3M™ Aluminum Conductor Composite Reinforced (ACCR) is an all-aluminum composite overhead conductor with an all-aluminum composite core. It is an high-temperature low sag (HTLS) conductor that offers excellent mechanical and electrical properties. In this exclusive exchange, we have Khader Basha, Head of Electrical Markets Division, 3M India, giving insights on the technicalities of ACCR and how reconductoring of existing lines with ACCR can help utilities to increase power transmission capacity without additional right-of-way constraints.
What is the technical composition of Aluminium Conductor Composite Reinforced (ACCR) conductors?
3M Aluminum Conductor Composite Reinforced (ACCR) is a proven, high temperature, low sag (HTLS) overhead transmission conductor. Designed as a replacement for similar-sized ACSR and ACSS, it provides up to twice the ampacity with less thermal expansion (sag) while maintaining or improving mechanical loads, tensions and clearances on existing structures. Depending on the application, 3M ACCR can carry 2x or more current as compared to a standard conductor of comparable diameter. It has less weight and sag, but the same strength and can be installed to meet tension and clearance requirements. This allows maximization the capacity of transmission upgrade using existing structures and eliminating any challenges of ROW. As compared to greenfield projects, the upgrade can be done faster, efficiently and cost effectively.
How does ACCR conductor compare with the conventional ACSR conductor, in terms of efficiency?
3M ACCR has been installed at voltages ranging from 6kV to 500kV and can be used as an alternate to any standard ASCR conductor. It is typically used when large capacity increases are required, usually 50 per cent or higher, especially where thermal limits are an issue. Its thermal properties and strength-to-weight ratio can solve difficult challenges, including ampacity upgrades with clearance constraints, long spans or difficult terrain (rivers, canyons); extreme climatic conditions (corrosion or ice and wind loading); and environmentally or demographically sensitive areas (wetlands, dense population). It is also used on new lines over spans where shorter or fewer towers are important for siting and permitting.
In scenarios where corridor for lattice tower is not available, Installation of light-weight ACCR conductor on monopoles can be viable solution.
What about the cost of ACCR conductors vis-à-vis conventional ones. Please discuss the initial costs and the cost efficiency over the lifetime of the conductor.
ACCR is most viable solution in comparison to constructing new lines. Cost is a function of the revenue generation/loss that can be attributed in relation to the time taken to construct a new line to cater to the increasing demand. The benefits of choosing ACCR needs to be evaluated on a TCO (total cost of ownership) model and not on a conventional cost estimation process. The benefits on a TCO model clearly far out-weigh the capex and the payback period is shorter and higher revenues realized will prove to be a worthy investment.
Tata Power, as we recall, did significant re-conductoring of its overhead lines in Mumbai using ACCR conductors. Tell us more. Is 3M in talks with other utilities as well?
In cities like Mumbai, it is not possible to obtain new corridors for construction of transmission lines, due to scarcity of space available. It is also very difficult to augment and maintain the existing corridor due to development around the transmission lines by way of new buildings and encroachment on “right of way”. The feasible solution seemed to use existing towers and enhance the current carrying capacity.
Tata Power installed 125 miles (200 km) of 300 T-16 (150 mm²) 3M ACCR on two lines near Mumbai. The lines were upgraded just two years before from a single to a bundled ACSR, but it could not keep pace with the rapid demand growth in the area. In addition, residences had sprung up directly under the lines. Tata Power did not want to disturb them but did want to improve clearances over them. With ACCR, Tata Power met these goals, while increasing capacity enough to last for 10 years.
Tata Power has upgraded their two critical transmission line which consist of twin conductor and double circuit, In these two 110kV lines conductor were replaced from conventional ACSR to 3M ACCR to double the ampacity while keeping the same clearance and tower loads. Both the lines pass through densely populated slums, railway crossing, highway crossing and residential areas. The installation was completed in the planned time frame, without disruption or inconvenience to residents and transport services. The reels length was planned in such a way that not a single splice was used in both the circuits.
Apart from re-conductoring, is ACCR conductor also viable (economically) for greenfield overhead transmission lines?
Yes, in scenarios where corridor for lattice tower is not available, Installation of light-weight ACCR conductor on monopoles can be viable solution.
Considering the demand, pace of implementation, technical requirements and challenges of RoW, habitation, vegetation and geographic conditions on these transmission corridors we believe ACCR should be a solution of choice to transmission utilities.
3M also makes high-voltage accessories. How does ACCR conductor complement these?
3M offers a wide portfolio of products for HV transmission for both cables and conductors. The portfolio is distinct to the medium of HV transmission and completes customers’ requirements of using 3M solutions in either of their networks.
Do you face competition from other companies, mainly multinationals, that are offering energy-efficient conductors to India?
Customers have options to choose the right solutions that meet their requirements in all aspects—technical, commercial and economical—considering their specific implementation time lines and site conditions. “Efficient” is a loosely used term until it is subjected to stringent evaluation as per standards, customers specifications and long term sustained performance meeting targeted capacities and goals.
Globally, which countries or regions have been large markets for ACCR conductors?
The important markets are: US, Europe, parts of Asia and Latin America.
Given that India is investing significantly in its power T&D grid, how do you see the prospects for ACCR conductors?
India today is power surplus in terms of generation capacity and this has been possible due to the rapid growth of the renewable energy sector. However, inadequate or lack of power evacuation and transmission infrastructure has been a major bottleneck. Augmentation of transmission network is needed, and this is a capital-intensive sector. It is estimated that about $60–80 billion investment is needed over the next 5 years to meet the ever-growing power demands of India. Privatisation of this sector—with Sterlite and Adani being the major players—will help accelerate this investment. That said, environmental clearances pose a major challenge that can slow down or derail the pace.
Considering the demand, pace of implementation, technical requirements and challenges of RoW, habitation, vegetation and geographic conditions on these transmission corridors we believe ACCR should be a solution of choice to transmission utilities.
