Introduction Several towers of some 110 kV or 220 kV transmission lines built in 1980s and 1990s were destroyed under typhoon strike. The reasons of towers collapse shall be analyzed for reinforce and rebuild transmission lines.
Method Wind load calculation formula of transmission line for 1979, 1990, 2002 and 2012 China code were introduced. The differences of wind speed, height variation factor of wind pressure, shape factor, adjustment coefficient of wind load and icing load factor were compared, wind load of a tower section and conductor for four edition China codes were calculated.
Result The results show that the 12 code's design wind speed is 5%~10% greater than that of 79, 90 and 02 code, the 79 code's tower wind load for tower height under 60 m is underestimated without considering adjustment coefficient of wind load and 1979, 1990, 2002 and 2012 code's wire wind load of 110 kV or 220 kV transmission lines are seriously underestimated without considering adjustment coefficient of wind load.
Conclusion The difference of 79, 90, 02 and 12 code's wind load for tower and wire is mainly affected by wind speed return period and adjustment coefficient of wind load, which are main reasons for tower collapse.
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