SELF-DAMPING MEASUREMENTS AND ASSESSMENT OF HIGH-TEMPERATURE LOW-SAG (HTLS) CONDUCTORS

This project aimed to provide a better understanding of how self-damping measurement is conducted for high-temperature low-sag (HTLS) conductors and how Aeolian vibration assessment can be used to determine a better damping protection system for these types of conductors. This report describes how the self-damping characteristics of HTLS conductors are determined and measured based on work developed by the CIGRE Working Group B2-58 on the modelling of Aeolian vibration in HTLS conductors and includes recommendations for laboratory tests of conductors and fittings. For this CEATI project, self-damping measurement studies were conducted on two types of HTLS conductors of interest to CEATI members: a GAP conductor currently used in CEATI members’ utility systems, and an aluminum conductor steel supported with trapezoidal wires (ACSS/TW) conductor that has been on the market since the mid 1970s. A survey and interviews were conducted with utilities and conductor manufacturers to gather information on the assessment of the self-damping of HTLS conductors and how this assessment is used to design an effective damper protection system. Measurement data from laboratory tests performed at the Department of Mechanics of Politecnico di Milano (POLIMI) and the data from the testing done in this study were used to develop conductor self-damping empirical formulae similar to those already available for standard conductors, such as aluminum conductor steel reinforced (ACSR). These formulae allow the assessment of HTLS conductors’ Aeolian vibration levels using the energy balance principle (EBP), which is widely used for such assessments in standard conductors. Finally, a series of field measurement datasets from two overhead transmission lines (OHTL) equipped with two types of GAP conductors and dampers at the extremities were made available by CEATI and used to compare Aeolian vibration levels assessed through vibration recorder measurements with Aeolian vibration level predicted using the self-damping empirical formulae developed in this study. The predicted Aeolian vibration levels obtained using the GAP conductors’ self-damping regression model designed in this research were very close to the OHTL field measurement data provided by CEATI. The range of Aeolian vibration frequencies was also well captured by the prediction, showing the effectiveness of the proposed methodology.