Selection Considerations: Hardened Glass vs. Polymer Insulators

What type of insulator is best for your transmission line? Why are hardened glass insulators more attractive to vandals? How well do each type of insulator shed water and what are the best maintenance practices to prevent current leakage? Polymers are superior with water, but susceptible to wetting corona damage and flash-under. The paper examines the advantages, disadvantages, and challenges associated with each insulator type. Included will be a section that also discusses the present value and life-cycle costs, and a comparison of costs between the insulator types. In this stated purpose, there are then two main functional considerations that need to be addressed by any selected insulator: (1) Mechanical considerations in terms of strength and integrity to provide mechanical support of conductors (2) Electrical considerations in ensuring that the air gap and electrical strength (clearance) is maintained and is not degraded to the point where leakage current exists Each of these functional consideration areas will be addressed and compared for each of the insulator types.

I. Introduction

As part of transmission project design, a review of the characteristics and considerations of different types of insulators is prudent in order to perform selection and provide for decision making related to the subject of insulation type for use on the transmission line.