The increasing power transmission capacity through thermal ratings is currently of great interest in electricity industry. This is mainly achieved by employing probabilistic thermal rating (PTR) or dynamic thermal rating (DTR) instead of implementing traditional static thermal rating (STR) methods.This thesis discusses the concepts of STR, DTR and PTR. The methodologies that used to calculate thermal rating of OHL in IEEE, CIGRE and IEC are compared. Furthermore, it extends to the comparison of recently developed DTR monitoring systems, CAT-1, Power Donut and Ampacimon, which are based on different operational principles. CAT-1 system directly measures the tension of OHL system and local weather. It uses the current loading from the network operator of the specific OHL as well as physical properties of the OHL. It calculates the ampacity without installing an instrument on the high voltage components of the OHL. Power Donut is directly installed on the OHL conductor to measure its surface temperature and inclination in order to calculate the ampacity. Ampacimon measures the conductor's vibration frequency and then implementing acoustic laws to derive the instantaneous ampacity. The accuracies and other characteristics of these calculation methods are compared for finding the optimal DTR monitoring method. Specific error analysis of these monitoring instruments is shown.The maximum difference between the three thermal ratings is the calculation of convection heat loss. When the wind speed is 0.5m/s, wind direction is 90°, ambient temperature is 40 ℃, the difference between the three thermal rating methods' results might be as high as 50%. The main reason is that the three models employ very different formulas to calculate convection heat loss in slow wind conditions.The errors of measurement devices used in DTR system were analysed. In normal condition and using IEEE DTR model, the total errors against the correct thermal rating value for CAT-1, Power Donut and Ampacimon are 1.842%, 0.755% and 6.6277% respectively. Tension, tilt angle and vibration measurement are the main sources for the three devices' error separately.
|Date of Award||31 Dec 2014|
- The University of Manchester
|Supervisor||Kostas Kopsidas (Supervisor) & Simon Rowland (Supervisor)|