Test and Investigations on Extra High-Tension Insulators From a Purchasing Engineer´s Point of View, with Special Reference to Methods of Test for Acceptance, Tests for Porosity and Deterioration

Owing to repeated failures (the number of which increased as time went on) of 66,000-volt transmission line insulators (pin type) of the first Hydroelectric undertaking, carried out by the New Zealand Government, in 1914, and having in mind that Hydroelectrical Power was to be developed to the utmost of the Dominion´s power resources??of which there are many??the investigations contained herein were commenced at the suggestion of Mr. E. Parry, B. Sc. M. I. E. E. late Chief Electrical Engineer to New Zealand Government, and has been continued for the past five years with the sanction and support of Mr. L. Birks, B. Sc. M. I. E. E. Chief Electrical Engineer to New Zealand Government, with a view to ascertaining the cause of such failures. It is the purpose of the paper to show 1. To what extent deterioration has set in on the 66,000-volt line referrwill line referred to. 2. That the cause is due to the fact that the insulators wiere initially porous. initially porous. 3. That tests at present in vogue with regard to ascertaining the porosity of insulator porcelain are. totally inadequate, as the authors consider, immersion of the complete unbroken insulator under a pressure ranging from 1500 to 2000 lb. and the total amounting to 250,000 to 300,000 lb-hours the least that will give reliable results. 4. That non-porous insulators can be made that will remain good in service for an indefinite period and withstand perfectly the tests fot porosity as recommended. 5.