Abstract
Accurate calculation of temperature, stress, sag, and critical current (corresponding to critical temperature) of operational overhead conductors is important for ensuring the strength and sag safety of overhead lines. Based on 2D steady-state heat transfer equations, this article studies the temperature fields of the cross section of typical electrified conductors and establishes numerical simulation methods for calculating the layered stress, sag, and critical temperature. Using the algorithm, the relationship between the critical temperature and characteristics of conductors (e.g., the sag and tensile force) is studied. The results are verified by a comparison with the test results for heat-resistant aluminum alloy conductors JNRLH1/G1A-400/65 and JNRLH1/G1A-630/55. Finally, the paper studies the relationship between the critical temperature of the conductor and its most sensitive factors.
Highlights
During peak times, it is often necessary to dynamically increase the current of overhead lines to meet the power supply demands
The stress at different layers of strands and the sag are generally affected by the temperature fields on the conductor cross sections
Due to the uneven thermal expansion in different layers during operation, the mechanical properties of the conductor’s cross section will greatly change at definite temperature which is defined as the critical temperature (CT) [2, 3]
Summary
It is often necessary to dynamically increase the current of overhead lines to meet the power supply demands. Step 1.2: call the submodule 2 to calculate the layered stress of the conductor and the resultant force Pa on aluminum strands (see equation (27)). E calculation of temperature field is performed with fixed point iteration, and the calculative process is as follows: Step 1: set the initial values of allowed maximum number of iterations Itmax, allowed error tol, coefficient of thermal conductivity ks for steel core and ka for aluminum strands, current I, ambient temperature Tc, and wind speed vw, respectively. 5. Comparison of Experimental and Numerical Results is section provides comparative analyses of the results from experiments and numerical simulation, including those for (1) cross-section temperature of ACSR JL/G1A630/55 [25]; (2) layered stress of ACSR JL/G1A-400/35; and (3) temperature-sag and temperature-tensile force characteristics of heat-resistant aluminum alloy strands JNRLH1/ G1A-400/65 and JNRLH1/G1A-630/55 with a span of 60m. It should be noted that the critical point cannot be directly observed according to the curve of temperature vs. tensile force but needs be calculated
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