The Contribution of Conductor Temperature and Sag Monitoring to Increased Ampacities of Overhead Lines (OHLs)


  • Viktor Lovrenčić
  • Marko Gabrovšek
  • Matej Kovač
  • Nenad Gubeljak
  • Zdravko Šojat
  • Zaviša Klobas


The electric utility industry is restructuring itself to operate in a competitive wholesale market. However, the transmission system remains a regulated entity that connects deregulated generation with the end consumer. In many countries, the pace of investment in OHLs has lagged behind the rate of load growth and generated additional capacities, due to public, regulatory, environmental and financial obstacles to the construction of new transmission facilities. Consequently, many OHLs reached critical values of ampacity and sag. Many renewable energy sources, especially hydro plants, solar or wind farms also require dynamic operation of the power grid. OTLM – Overhead Transmission Line Monitoring system is adding new dimensions to the operation of OHLs enables more efficient performance while at the same time enhances the safety of system operation. A maximum utilization of the OHL ampacity is only possible, if the operators have accurate data about the actual ground clearance, crossed lines, vegetation, instantaneous conductor temperature and current.
With the measurements captured and processed by OTLM, the operator of the transmission network can optimize and determine the operation mode of OHLs. Software solutions also provide the means for a short-term prediction of conductor temperature. Temperature data along with data gained by laser scanning or similar measurements and diagnostics of the OHLs is necessary to up-rate OHL projects. This paper is supported with case studies, which prove that temperature and sag monitoring is an essential part of the transmission smart-grid.


OHL, OHL monitoring, sag, dynamic thermal rating (DTR), ampacity

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Published Online


How to Cite

Lovrenčić, V., Gabrovšek, M., Kovač, M., Gubeljak, N., Šojat, Z., Klobas, Z. “The Contribution of Conductor Temperature and Sag Monitoring to Increased Ampacities of Overhead Lines (OHLs)”, Periodica Polytechnica Electrical Engineering and Computer Science, 59(3), pp. 70–77, 2015.