706 



BELL SYSTEM TECHNICAL JOURNAL 



found to contribute somewhat to the total insulation, depending on the 

 dryness of the wood and on the efficiency of the insulator itself. 



The effect of the pin may be measured by comparing insulators 



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O 



^ 



a. 



a. 



O 



X 



O 



u 



u 

 o 

 < 



< 



UJ 



5-00 



5:20 



5.40 



6-00 



TIME 



Fig. 8 — Illustrates effect of pin length and baffle on d.-c. surface leakage. 



mounted on wood pins in the standard manner with similar ones 

 mounted on wood pins which have been covered with a thin metal foil, 



.04 



03 



z 



o 



a. 

 lij 

 a. 



(/) 

 O 02 



I 



O 

 a. 

 o 



.01 



Q 



10 12 



6 

 AM 



10 



12 2 



-.— PM— ^ 



Fig. 9 — Illustrates effect of coating and bonding of wood pins on d.-c. surface leakage. 



the coatings of a pair of pins being electrically joined. Thus, both the 

 pins and the crossarm between them are short circuited. 



Fig. 9 shows the results of such a test on the type of insulator shown 



