Airborne Lidar Helps Chinese Electric Utility Implement Smart Grid

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by Rick Gosalvez and Matti Syyrakki, Trimble

Work is underway to implement the smart grid in China. The world's largest electricity consumer, China gets 70 percent of its electricity from coal-fired power plants. Although its electricity consumption is expected to triple by 2035, China has committed to reduce its carbon emissions. The smart grid can play an essential part in meeting growing needs for electric power while increasing the amount of renewable energy used as a percentage of overall electricity consumption.

Building on the country's existing power grid infrastructure, China's new smart grid will address all aspects of electric power supply: generation, transmission, distribution, consumption and scheduling.

Measuring Existing Infrastructure

China's terrain has huge impacts on transmission corridor alignment and safety operations. Many corridors are far from cities, and some include blind areas that are remote or difficult to access. Traditional on-foot methods for maintenance and data collection make it slow and difficult to meet requirements for safety and smart grid development. The power industry needs safe, robust and efficient inspection methods.

Airborne lidar mapping technology provides a new approach for inspecting transmission lines. Airborne systems integrate laser ranging, digital imaging, Global Navigation Satellite System (GNSS) and inertial measurement units (IMUs) to collect geo-referenced point clouds and high-resolution aerial imagery. The data provides 3-D topography and precise locations of transmission corridors, as well as spatial information about objects within each corridor, including pylons, access points, wire sag, trees and buildings.

China's Power Providers Embrace Aerial Mapping

The State Grid Corp. of China and China Southern Power Grid Co. are working to implement smart grid technology. China Southern Power Grid is conducting infrastructure improvement projects with a total investment of some $3.2 million. One of the first steps was a project to develop accurate information on existing power lines and facilities. In addition to airborne lidar, the work included data processing and analysis to produce point clouds, orthophotos (a geometrically corrected aerial photograph), surface models and 3-D objects and vectors. The project covered 9,000 miles of corridors across Guangdong, Guangxi, Yunnan and Guizhou provinces, and 3-D data collection on all AC and DC transmission lines operating at 500 kV and higher, together with part of the network's 220-kV lines. The project objectives called for detailed ground information and high-resolution images.

The project contractor for the aerial mapping is Guangzhou Jiantong Surveying Technology Development Co. Ltd. As China's largest lidar technology application company, the organization carries the highest level of certification for surveying and mapping. Guangzhou Jiantong selected corridor mapping hardware and data processing and analysis software from Trimble's Geospatial Division to streamline the project work flow. Project deliverables included 3-D point clouds in combination with high-quality, geo-referenced orthographic images.

Guangzhou Jiantong used helicopters to collect data, although many predict future trends will include more cost-efficient unmanned aerial systems. Compared with fixed-wing aircraft, a helicopter is more flexible and can fly at a constant speed while maintaining low altitude. This minimizes flying time and helps ensure high-accuracy point clouds. The helicopters operated below the cloud cover, typically at 920 feet above ground level. During the two years of the project, the team conducted roughly 350 flight hours of observations. Because Trimble's geospatial corridor mapping systems include highly precise GNSS, the need for ground control was minimal. Pairs of points placed at 25-mile intervals were sufficient to produce accurate geo-referencing for the point clouds and orthophotos.

During data post-processing, technicians at Guangzhou Jiantong used processing software to classify objects within the 3-D point cloud, producing information on ground points, buildings, natural features, vegetation, power towers and power lines. The automated point cloud classification reduced the need for human interaction with the software and significantly improved engineering productivity by providing actionable intelligence from the geospatial data. The high-resolution images also helped technicians identify attributes of ground objects and attach true color to the 3-D models.

Guangzhou Jiantong developed an approach to use the lidar point clouds to develop 3-D models of pylons. The models ensured accurate positioning and allowed users to extract details of the power towers, including the location and number of insulators on the power lines at each tower. The results are maintained in a unified 3-D GIS management system tailored to electric power distribution and operations. Clients can log into the system to obtain information on power line facilities and surrounding environmental conditions.

Performance, Efficiency

The China Southern Power Grid EHV Transmission Line Data Collection Project is the first project to collect data over long distances and large geographic areas. It also is the first to implement a 3-D display of the entire line system, bringing economic benefits for transmission line management and maintenance. Managers can make decisions faster and with accurate knowledge of existing conditions.

In addition, the project promotes development of China Southern Power Grid. New information and methods for grid management have improved the capacity to identify and correct problems. The system allows real-time monitoring of regional power outages and provides overall improvement in monitoring accuracy.

As implementation of China's smart grid progresses, the need for accurate mapping will expand. By combining lidar, imaging and positioning with advanced software for processing and feature extraction, airborne corridor mapping will play an important role in bringing the smart grid to life.

Rick Gosalvez is Trimble's market manager for local government. He is responsible for global partnership and product solutions that address local government industry trends. Gosalvez previously worked in the U.S. with regional and local governments for land use development, advanced planning, policy analysis and mega infrastructure project planning. He is an active member of the American Planning Association and Urban Land Institute.

Matti Syyrakki is the business area director for Trimble Energy Division, which provides field, smart grid and asset management solutions to energy utilities. Syyrakki has a master's degree in geoinformatics from University of Helsinki and has been working with utility software since 1997.

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