Public Service Electric and Gas Co. (PSE&G; Newark, New Jersey, U.S.), the oldest and largest publicly owned utility in the state of New Jersey, is in the middle of a 10-year plan to upgrade and enhance its electrical system. In 2003, when PSE&G, a subsidiary of Public Service Enterprise Group, celebrated its 100th year in business, plans were announced to invest US$1.4 billion in upgrades and enhancements to its electric system, which was already ranked among the most reliable in the nation.

The challenge for PSE&G, and most utilities with older lines, is that transmission line records are typically outdated or, in extreme cases, do not exist. Because PSE&G’s system has such a long history, when it comes to upgrades, drawings and maps are few and far between, making it difficult to plan without conducting a full line survey. To document location and condition of its grid, PSE&G used light detection and ranging (LiDAR) technology, flying over the transmission line corridor via helicopter using a scanning methodology that integrates infrared laser signal data and a global positioning system (GPS).

November Survey

In November 2004, W.I.R.E. Services (Winnipeg, Manitoba, Canada) was commissioned to perform the LiDAR surveys on a 213-km (132-mile) section of PSE&G’s single- and double-circuit transmission lines. W.I.R.E. Services is a combined initiative between Manitoba Hydro (Canada’s fourth largest utility) and LiDAR Services International (LSI; Calgary, Canada), which provides aerial LiDAR data for transmission line analysis to the North American utility market.

The LiDAR system scans with laser pulses at 14,000 Hz and develops a highly accurate survey profile of the transmission lines and terrain. The survey data is collected at 55 to 60 mph and has an absolute accuracy of 10 to 15 cm (4 to 6 inches). The data gathered from the survey can also generate information in map format to help the utility assess right-of-way clearance issues. Engineers will use the survey as the basis for designing new circuits that need replacement.

During five days in late November, manpower and equipment were mobilized into the New Jersey area to fly over a total of 14 single- and double-circuit transmission line corridors. During the flights, LiDAR data was collected together with downward digital color imagery and a forward digital video. The vast quantity of data captured was stored on the onboard computer systems.

The survey operation was coordinated with a ground team that set up GPS ground-control base stations and portable meteorological recording stations that monitored and recorded weather conditions during the flights. This data, combined with the load flow data, is necessary to calculate the actual wire temperature during data collection and, ultimately, for line modeling.

Useful Data

Combining the collected data, W.I.R.E. Services began creating PLS-CADD line models from Power Line Systems Inc. (Madison, Wisconsin, U.S.) and conducting a thermal rating analysis of each circuit, including an analysis of the vegetation conditions within and outside the line corridor.

PSE&G has pioneered other similar initiatives, investing $26.5 million in an integrated outage management and geographic information system (GIS) designed to model the utility’s electric system, identify outages, dispatch work crews and restore service to customers in record time. Another large investment has been for the design and development of a work management system that uses desktop and mobile data terminals to dispatch and track work. The $35-million project integrates the company’s enterprise IT network with several technologies, including wireless and interactive systems that enable the company to respond immediately to system alerts.

PSE&G has completed more than 70 major capital improvement projects along its 1931 km (1200 miles) of high-voltage transmission lines since the 10-year enhancement and improvement plan began. The utility’s commitment to technology has proven to be cost effective and is enabling design engineers to achieve below-budget, on-time completion of many of the major improvement projects. l