報告書番号

T03

タイトル（和文）

電線路の雪害とその防止

タイトル（英文）

POWER LINE FAILURES DUE TO SNOW ACCRETION ONWIRES AND PREVENTIVE COUNTER-MEASURES AGAINST THEM.

概要 （図表や脚注は「報告書全文」に掲載しております）

架空送電線路の雪害防止対策の確立を目的として，自然着雪観測，人工着雪実験及び架空線の機械的挙動の検討を行い，次の結果を報告している。１．電線の着雪には雪片の焼結等による負の気温と弱風下で発生するものと，毛管力による正の気温で発生するものがある。２．電線への着雪量は電線の捩れ剛性を大きくすると減少する。３．着雪の熱収支の理論解析によると，電線の冬季連続許容電流の３０～５０％の電流により防止できるが，一旦着雪が筒雪に発達するとこれを融解除去するのは困難である。このことは実験によっても裏づけされた。４．任意の地点の或る再現期間を有する着雪量推定法を提案した。５．電線への着雪重量は電線への風の傾き角の正弦に比例する。６．以上の知見を総合し，電線路の各部耐雪性能を評価し、信頼性を協調させると共に、連鎖倒壊の防止を計る方法を提案した。

概要 （英文）

FOR SEEKING RATIONAL COUNTER MEASURES AGAINST POWER LINE FAILURE DUE TO SNOW ACCRETION ON WIRES,NUMEROUS OBSERVED DATA OF NATURAL SNOW ACCRETION ON ACTUAL LINES AND SHORT LENGTH WIRES HAVE BEEN COLLECTED THROUGHOUT COUNTRY,SIMULATED WIND TUNNEL TESTS WERE CONDUCTED AND ANALYTICAL WORKS ON MECHANICAL BEHAVIOR OF LINES HAVE BEENCARRIED OUT. MAIN RESULTS ABTAINED ARE AS FOLLOWS: 1.TWO TYPES SNOW ACCRETION MECHANISM ARE IDENTIFIED AS FOLLOWS: A.DRY TYPE DUE TO SINTERING OF SNOWFLAKES UNDER THE TEMPERATURE BELOW FREEZING POINT AND LOW WINDSPEED. B.WET TYBE DUE TO CAPILLARITY UNDER THE TEMPERATURE ABOVE FREEZING POINT AND REGARDLESS ON WIND SPEED. 2.DENSITY AND ABHATVE FORCE OF SNOW SLEEVE ON WIRES ARE STRONGLY DEPENT ON WIND SPEED AND ALSO DEPEND ON AIR TEMPERATURE. 3.MATHEMATICAL MODEL OF SNOW ACCRETION ON WIRES ARECONSTRUCTED,AND METHOD ESTIMATIONG SNOW LOAD HAVING A CENTRAIN RETURN PERIOD FOR PARTICULAR LOCATION IS PROPOSED. 4.SNOW LOAD ON WIRE DECREASE WHEN TORTIONAL RIGIDITY OF WIRE INCREASE. SO DECREASING SUB-SPAN LENGTH OF BUNDLED CONDUCTOR OR BITTING COUNTER WEIGHTS IN SPAN ARE APPEAREDA GOOD COUNTER MEASURE FOR PREVENTING POWER LINE FAILURE DUE TO SNOW ACCRETION. 5.SNOW LOAD ON WIRES ARE DIRECTLY PROPORTIONAL TO THE WIND SPEED COMPONENT PERPENDICULAR TO WIRE AXIS. 6.A METHOD EVALUATING RELATIVE RELIABILITY OF LINE COMPONENTS IS PROPOSED,AND DEFECT OF CURRENT DESIGN PRACTICES ARE SUGGESTED. 7.DIFFICULTY FOR PREVENTING CASCADING FAILURE UNDER SNOW LOAD ARE POINTED OUT AND APPLICATION OF MECHANIFCAL FUSE CONCEPT IS SUGGESTED. 8.AMOUNT OF LOAD CURRENT NEEDED FOR PREVENTING GROWTH OF SNOW ACCRETION ON WIRES ARE CALCULATED BASED ON HEAT BALANCE,AND VERIFIED BY EXPERIMENTAL WORKS

報告者

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