Design Criteria rorIntegral )eband Universal Angle Buses
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weldments weresubstituted onsubsequent jobs.Although welding, whenproperly done,results inanexcellent connection froma conductivity standpoint, itunfortunately hasdecided disadvantages. Thenumberofmenexperienced inaluminumwelding islimited, anditisusually necessary totrain several whocanthen be usedas a nucleus fortraining others. This, ofcourse, results inhigh labor costs asinexperienced welders are slow.Unfortunately itisdifficult to makeasatisfactory weldoutdoors ifthe windisblowing; therefore, itisnecessary todoallweldings withjigs indoors orto provide windbarriers ifoutdoors. Onlarge newsubstations itispractical insomeareastochoose thedayswhen there islittle ifanywind, thereby avoidingtheuseofbarriers. Inorder toprovidereasonable working conditions for thewelder itisusually necessary toprovidea suitable platform ateachweld. This, too,ismoreeconomical withthe larger jobs,as portable or reusable scaffolding canbeutilized. Thewelding equipment itself isexpensive, whichalso tendstomakewelding impracticable on smaller jobs, since itisnoteconomical to equip eachcrewwithwelding equipment andtrained welders. During1953, anumberofhigh-current testson 3'/2-inch aluminumtube, as usedin161-kvsubstations, wereconductedtodetermine thestress imposed ontheinsulator supports during shortcircuit conditions. Theresults ofthese testswerepublished2 in1955,andindicated thatshort-circuit stresses in longspans, suchasthose tested, aresufficient tocausefailure inbusesandin