NEMA HV 3
Suggested Purchase Specification Guidelines for High Voltage Insulators
|Publication Date:||1 January 2019|
Scope and Purpose
High voltage insulators of the best possible quality are essential to obtain long-term reliable service demanded of today's electric utility infrastructure. This document describes best practices on the part of purchasers and suppliers of high voltage insulators toward assuring a consistent and reliable supply of best quality high voltage insulators. It is the intent of these guidelines to provide assistance to those responsible for specifying and purchasing high voltage insulators to identify those best quality insulators most suitable for their specific application and service conditions, which can be consistently and reliably supplied.
Assurance in obtaining the best quality high voltage insulators is greatly aided if the purchaser has a comprehensive Purchase Specification covering all aspects of the procurement process.
Members of the NEMA High Voltage Insulator Section (NEMA 8HV Section) have committed to industry best practices as described in these Guidelines to consistently and reliably supply quality high voltage insulators that are certified with respect to all aspects of their design, manufacture, and testingThis includes a requirement, when so specified, for third-party certification if needed in the opinion of the purchaser, and particularly when a manufacturer lacks the necessary in-house qualified test facilities.
There are two main types of high voltage insulators defined in the various American National Standards Institute (ANSI) C29 and the Canadian Standards Association (CSA) CAN C411 and C156 series of insulators Standards; ceramic and non-ceramic insulators.
Ceramic insulators include both wet-process porcelain and toughened glass insulators. Non-ceramic insulators, also called polymers, have a reinforced fiberglass core rod with an elastomeric outer housing. Both types are defined in the various ANSI and CSA Standards. While vastly different in design, materials, and production methods, the recommendations given here for items and requirements that should be included in purchase specifications for high voltage insulators are applicable for both types of high voltage insulators.
In today's business environment, high voltage insulators may be obtained directly from on-shore or offshore manufacturers, or from re-sale suppliers. Regardless of the source, purchasers will obtain the best quality insulators if the procedures and requirements described here are strictly applied and followed.