JOIXT DE VELOPMENT A ND LOW-FREQ UENC V IND UCTIOX 2 1 7 



structure that the Hue will in effect be fault- resistive. Increasing 

 demands for better service by the public combine with considerations 

 of inductive coordination to justify greater attention to fault-resistive 

 line construction. 



F"aults may result from improper guying of poles, i.e., guys so located 

 that the spacing between guys and conductors is inadequate, or the 

 path from insulator to crossarm brace and thence to the guy is insuffi- 

 cient to withstand the voltages imposed. The conductor spacing may 

 be inadequate or the configuration of the circuits may be such that the 

 sudden unloading of conductors coated with sleet will result in their 

 whipping together, or, if a ground wire is used, it may be so located that 

 the unloading of sleet will cause the conductors to whip into the ground 

 wire, or the design of the line, either steel tower or wood pole, may be 

 such that inadequate strength is provided for the mechanical loads 

 incurred. 



Attention is being given to the location of lines as a material factor 

 in limiting the number of outages resulting from external sources, such 

 as lightning, broken trees, blasting, and automobiles. For example, 

 lines built in valleys are less subject to failures due to lightning and 

 wind storms than lines built over hills. 



There is little need to call attention to the grade of insulation em- 

 ployed on power lines as recent lightning studies and papers have 

 emphasized the importance of rationalization of insulation throughout 

 the plant. By this method it is hoped that preferential points of 

 failure would be established, thus permitting prompt restoration of 

 service without damage to expensive equipment since most of the faults 

 would be confined to the line. 



The amount of insulation to be employed on lines is aftected by 

 topographical and climatic conditions. Lines in areas relatively free 

 from lightning or shielded from lightning disturbances may, of course, 

 employ less insulation without increasing the number of faults. On 

 the other hand, lines built in areas where lightning is prevalent may 

 justify not only higher insulation but also, on steel tower lines, the use 

 of ground wires as an additional protection. Areas where salt fog, 

 smoke, or chemical fumes are prevalent require special treatment as to 

 the form of insulation used. 



Laboratory tests and limited field experience indicate that a proper 

 utilization of the inherent insulating properties of wood in structures 

 may result in considerable improvement in line operation. The sub- 

 committee is investigating the service performance of wood pole lines 

 of differing designs with a view to determining how much may be ac- 

 complished in reducing the number and severity of faults by suitable 



