Despite having been a part of the India power T&D for over 50 years, lack of awareness and expertise of utilities, have left monopoles as yet obscured.
Monopoles have been the latest advancement in transmission and distribution (T&D). Due to varied application and advantages and GoI's thrust on augmenting transmission capacity, monopoles have sought attention of the leading grid and distribution companies. However the market for monopoles has not got much traction due to lack of awareness and expertise of Indian utilities.
It has been more than 50 years since European and some Gulf countries have been using these steel structures in the T&D and telecom sectors. Monopoles were first introduced in India around 2008û09 by PowerGrid. Being a relatively new product for the Indian market, the market size is still developing and it would be difficult to place any number to it at the moment.
The major take-away is that monopoles have many advantages vis-a-vis, the lattice towers, the biggest being that they provide ease of erection where space is a constraint.
For a lattice tower four foundations are required for the tower legs that consumes land up to 100 square meters where as a monopole can be erected in a five sq meter area. Such monopoles are widely used in European Countries and are becoming popular here too.
'Riveted/angular towers have a much larger base ground coverage as compared to monopoles, which considering the lesser area requirement and several other advantages, are considered as replacement to the angular towers' states Devesh Bansal, Director, Skipper Limited.
Adds Sanjay Bhagat, VP & Head - TLT BU, Bajaj Electricals Limited, 'Monopoles have a number of benefits such as minimum space requirements, less number of elements and thus quick erection, short delivery time, an aerodynamic shape that ensures less resistance, protection against vandalism and an aesthetically pleasing design.'
Monopoles are used for a series of applications and are ideal for use when sufficient availability of land is restricted. They are the least intrusive and easiest towers to erect, making them one of the most popular tower types in the industry. There are a range of monopoles for the Indian market.
'We have been a pioneer in the industry and have global expertise in the power T&D industry. We manufacture power transmission monopoles from 33-400 kV, both single and double circuit lines and power distribution monopoles up to 33 kV,' shares Bansal. Adds Bhagat, 'BEL offers complete range for monopoles as per requirement of the customer. We design, manufacture and install monopoles from 11-400 kV, for single and double circuit power transmission lines. The company's present capacity for manufacturing transmission line structures is more than 30,000 tonne p.a. In fact, Bajaj's tower manufacturing facility has been approved by Powergrid and SEBs.'
Another player, Valmont Structures Pvt Ltd, India manufactures a range of steel power transmission poles from 11 kV-400 kV voltage grade, with multi-circuit designs and corrosion-resistant galvanized steel. The company also offers various designs - like tangent design, angle design, dead-end design - to meet specific needs.
Valmont India has type tested more than 10 transmission line monopoles of various voltage grades ranging from 66 kV-400 kV in different NABL accredited test facilities in India. The 11.2 km, 132 kV 'Muradnagar-DPH' transmission line under UPPTCL (commissioned in July, 2012), was constructed successfully in the existing 33 kV corridor with a sturdy monopole design.
The company's installation of 400 kV/220 kV multi-circuit monopoles for KPTCL at Bangalore have also been under successful operation for more than a year.
To minimise the adverse effects of high voltage electric power transmission lines, new technologies are forthcoming that when applied may be more acceptable. By judicious compacting of high voltage direct current (HVDC) and high voltage alternating current (HVAC) transmission systems, existing RoW can be utilised better.
A high-voltage, direct current (HVDC) electric power transmission system (also called a power super highway or an electrical super highway) uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current (AC) systems adopted at the distribution level in India.
For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. However, for shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be justified, due to other benefits of direct current links.
HVDC allows power transmission between unsynchronised AC transmission systems. Depending on voltage level and construction details, HVDC transmission losses are quoted as about 3.5 per cent per 1,000 km, which is 30 - 40 per cent less than with AC lines, at the same voltage levels. This is because direct current transfers only active power and thus, causes lower losses than alternating current, which transfers both active and reactive power.
The combined economic and technical benefits of HVDC transmission can make it a suitable choice for connecting electricity sources that are located far away from the main users.
The disadvantages of HVDC are in conversion, switching, control, availability and maintenance. Whether the transmission line is of DC/AC, they were being carried on overhead lattice towers till monopoles were introduced in India during the last decade. Another important aspect of power transmission/distribution monopoles are the carrying capacities, with Bhagat stating that there is no difference in carrying capacities. Monopoles can be used for all the voltage levels for AC as well as DC.
However, Bansal had a slightly separate view, 'The load carrying capacity of a lattice tower is up to 765 kV and higher, whereas for monopoles it is only up to 400 kV, with no major difference in the frequency level, adaptable to both AC/DC lines.'
Design & JVs
Commenting on their JVs, Bansal shares, 'Designing being a crucial aspect of our solutions, we have associated with world renowned designing company Rambol (Denmark) for designing the best monopoles, which very few companies can provide.'
While Bajaj doesn't have any JVs, their major clients Bhagat said include state and central electricity utilities, and private customers. On the design side, the company was among the first in India to have designed, type tested and supplied monopoles of 400 kV DC line with a height of 42 m - called monopole based transmission line - for Power Grid's Dadri-Ballabhgarh line.
Further adding on about the global and Indian standards that have evolved for monopole projects, Bhagat points out, 'monopoles are currently designed as per American Standard ASME 48; while the Indian standards for monopoles are under development.'
Bansal concurs, 'For monopoles we are currently using ASCE 48-05/48û11. The software that is used for designing poles is PLS Pole Software. However, unlike US and Europe, in India the BIS is yet to come up with global standards for manufacturing of monopoles.'
Another segment player, Transrail Lighting Limited, a Gammon Group company also presently uses ASCE 48-05 and ASCE 48-11 and the PLS Pole Software, which produces design in line with the American Standard specifications.
According to Kailash K Agarwal, Chief Executive Officer - Pole Division, Transrail Lighting Limited, 'The manual on Transmission Tower from CBIP (Central board for Irrigation and Power) also provides details for fabrication and design requirements of transmission monopoles.'
Higher weight and cost as compared to angular lattice towers, difficulty in transportation and installation especially in hilly areas, and manufacturing limitations for voltage range of 765 kV and above are some of the issues that pose challenges for monopoles.
But Bhagat explains, 'Present prices of monopoles are much higher than that of angular lattice structures mainly due to smaller market size and non-standardisation. With increase in market size, better availability of raw materials and manufacturing optimisation, prices of monopoles will surely get reduced, making it more attractive.' Also, among the most challenging issues India's transmission sector is facing today, are related to Right of Way (RoW), land acquisition, and regulatory and environmental clearances for transmission lines.
Observes Bansal, 'For many years transmission lines were constructed without major RoW issues, however with increased farmer and land owner awareness, reserved forest, bird sanctuaries, religious structures, etc., it has become increasingly difficult to get smooth and timely RoW clearances.'
Another primary challenge he feels the lack of awareness about monopoles, among utilities in our country. Bhagat agrees, 'At present, major obstacle is lack of awareness about monopoles and expertise with Indian utilities. As the market for monopoles has not yet fully evolved, there is no standardisation of specifications, designs or installation methodologies. With more monopole projects coming up in recent years, we can expect better standardisation in the years to come.'
'However, many prestigious utilities like UPPTCL, MPPTCL, KPTCL, MSETCL, and HVPNL are now considering implementation of monopoles for lines with RoW issues. In fact, PGCIL too has come out with tenders for monopole installations,'Bansal shares.
Nowadays most transmission utilities are facing problems in laying transmission lines in urban areas due to severe RoW problems. This is in view of non-availability of adequate land for installation of conventional lattice type towers.
To overcome these practical difficulties, monopoles are the latest alternative to overhead transmission lines, lattice type self-supporting towers, seeking only 1/16th the space sought by lattice towers for erection.
Feels Bansal, 'All locations wherever there are RoW issues, monopoles come out as tentative solution. However, considering the current scenario, monopoles will not completely take over the angular tower's market share any time soon.'
Concurs Bhagat, 'The monopole market is still at a nascent stage in India. However in last two-three years we have observed utilities are taking interest in such projects. Currently, these projects are mainly for new or diversion of existing limes in thickly populated areas near city centres where right of way (ROW) is a major issue.'
He adds, 'As per our estimation current market size is of around Rs.200-250 crore and we expect to increase it substantially with increasing issues in ROW for transmission lines and growing awareness on aesthetics for future projects near city centres.'
Bansal concludes, 'Till a decade further from now we expect both angular towers and monopoles to co-exist in mainstream power T&D. However, considering the potential of the product we do expect substantial growth in the number of projects in the coming few years.'