However , a large amount of harmonic is generated in the power network when the electrified railroads loads consume fundamental frequency electric power . these harmonics make bad effect on the operation of protection relays and the precision of electricity measures , worsen the power quality and threaten the security of traction substations as well as other equipments in power system 但是电气化铁道从电网取得工频能量的同时，向电网注入了大量的高次谐波电流，降低了供电质量，影响了继电保护的正确动作和电气量测量的精度，威胁牵引变电所的安全运行及电网中其他用电设备正常工作。
The main work of this thesis includes : 1 . using energy theory , the cable sag and bending stiffness effects are investigated on the determination of cable tension forces through cable ' s fundamental frequency . based on the curve fitting , the practical formulas are proposed where the cable tension can be easily estimated using measured fundamental frequency 本文的主要工作包括： 1 .考虑拉索的垂度和抗弯刚度对基频的影响，用能量的方法，并辅以曲线拟合，提出了由基频计算索力的实用公式，公式与理论解的误差在以内，并对公式的适用范围进行了讨论。
