Aerial LiDAR enters Indian Electricity Sector
A new approach to OHL design in India
By Paul Richardson An innovative aerial survey utilising LiDAR technology and PLS- CADD? software has been successfully deployed in the Indian electricity transmission sector for the optimisation of 1,900 circuit kilometres of 765 kV overhead lines (OHLs) that run across mountains, plains and urbanised areas. Network Mapping, a UK and US based aerial LiDAR service provider, performed the survey work as a consultant to Jabalpur Transmission (JTCL) and Bhopal ? Dhule Transmission (BDTCL), owned by Sterlite Grid Limited, an innovative Indian engineering firm at the forefront of the power transmission infrastructure sector. The purpose of the project was to assist with two 35-year Design-Build-Operate concessions by employing LiDAR technology to optimise route corridors for planned transmission lines to maximise load transfer capacity and reliability and minimise construction costs and delays. The project attracted commentary from the Chancellor in the UK and the Finance Minister of India as a demonstration of improving Anglo-Indian initiatives. This article describes the project, the unique challenges faced in India, and the results of the LiDAR and PLS-CADD? optimisation process.
New infrastructure for India
India is currently engaging in large scale investment in its transmission infrastructure with 109,000 circuit kilometres to be designed and constructed as part of the 12th 5-year plan (2012 to 2017). This level of investment is required to meet the huge increases in demand created by growth of the industrial and population bases together with rising living standards. Gross Domestic Product has increased by 7.7 percent between 2007 and 2011, and the population by 1.76 percent per year from 2001 to 2011. Black-outs and brown-outs are common; six hundred million people were left without power in July 2012 following the cascading failures of the northern, eastern, and north-eastern grids. The concessions for the new-build projects that form the topic of this article were comprised of five single circuit lines and one double circuit line at the 765 kV level. The six concessions crossed mountainous terrain, flat plains, and large rivers in five states of Central India. These States, from west to east, incorporated Gujarat, Maharashtra, Madhya Pradesh, Chattisgarh, and Jarkandh. Against this context it was crucial for JTCL and BDTCL to design new Over Head Lines (OHL) for their concessions that would provide extremely high levels of both utilisation and reliability in a cost effective solution. This necessitated deployment of the very latest technology. Aerial LiDAR survey techniques and PLS-CADD? software were chosen by Sterlite to fulfil these objectives. ?It is a matter of great pride that Sterlite Grid becomes the first organization in India to undertake and accomplish an aerial LiDAR survey as a part of the construction of its Transmission Line assets,? remarked Pratik Agarwal, Director, Sterlite Grid. ?All the tower spotting concerns are known prior to construction itself and resolved thereby helping in faster project implementation and lesser provision for contingencies.?
Capturing data using aerial LiDAR technology ? the benefits Aerial LiDAR technology is a rapid survey technique that has been employed extensively to assess electricity transmission infrastructure throughout the world. Digital 3D models are created by emitting laser points, generally from a helicopter acquisition platform. Only one technician is required to operate a base station within each 20 kilometre radius of the survey platform. The technique allows comprehensive data of a high resolution to be captured quickly, with typical point densities being in excess of 20 points per square metre. Provided there is adequate ground control, the absolute accuracy of a single point will be of a high level and the relative accuracy between points will be even greater still. The high resolution of survey points captured by the system allows the ground surface, man-made and natural features to be adequately mapped to ensure regulatory clearance is met for the new line design. The speed of data capture as compared to conventional surveying is one of the major benefits of a LiDAR survey. Typically, data capture progresses at a rate of 60 kilometres per day. For Sterlite?s survey, data for the entire 1,600 kilometres of transmission lines was captured in 20 days (a higher than average capture rate of 75 kilometres per day) and processing was completed within 3 months. The difficult terrain encountered would have posed significant obstacles to a traditional survey; due to the aerial nature of Network Mapping?s survey, however, this was much less of a problem. Conducting a survey from an aerial platform also avoided issues of inflated land compensation claims that can sometimes arise when ground surveyors have a prominent presence in an area. ElectricEnergy T&D MAGAZINE I JULY-AUGUST 2013 Issue 37