Victor Polymer Insulators
Technical Details
A) Background
Victor began development of distribution class polymer insulators in 1997, after an extensive analysis of the needs of the marketplace, the performance history of other manufacturers products, and improvements in designs and materials that have taken place in the past decade.
It was immediately apparent that the single greatest deficiency of the products offered in the marketplace was a lack of uniformity (interchangeability) between insulators manufactured by different suppliers.
This situation had arisen due to the lack of existing standards for the products in the era when they were being developed.
The result is a confusing mix of section lengths, electrical values, test protocols, etc. It is left to the user to sort out the necessary characteristics for the system application and to then try and determine what available product comes closest to meeting the application needs.
Since Victor has always been active in the ANSI and NEMA standards making process, we have been deeply involved in the development of standards and proposed standards for polymer insulators.
At present, there is a draft standard (C29.13) covering distribution polymer dead ends, and Victor chose to design the new product line based on the characteristics specified in this proposed standard. We believe that this will become an ANSI Standard by the end of 1999.
We are supplying insulators that may be referenced simply by an ANSI Class Number, assuring the user of interchangeability and of course of guaranteed characteristics.
In supporting the ANSI process in this way, Victor is making sure that the user has a sound basis for selection of product and that interchangeability with products from other manufacturers who design and market product to the standard. This not only makes product selection easier, but provides for the most competitive and available supply.
In addition to the design electrical and mechanical characteristics, the choice of qualification test protocols was analyzed to determine what existing and proposed test standards would offer both Victor and our customers the assurance that the new products were capable of providing years of trouble free service in all operating environments.
The specifications that were selected as the basis for the design and development program were:
ANSI C29.11
ANSI C29.13
IEC 1109
CEA LWIWG-01
In summary, the underlying philosophy of the development process was to design and manufacture distribution class deadend insulators that complied with all relevant test specifications for these types of products and provided standardized performance characteristics.
Additionally, it was determined early in the development process that the following criteria were fundamental to a successful product and would be followed explicitly:
a) use of proven polymeric materials from nationally recognized suppliers for the housings
b) use of proven fiberglass rod manufactured by nationally recognized suppliers for the load bearing core
c) use of malleable/ductile iron end fittings
d) use of injection molding to form the housings as a continuous sheath
e) use of crimping as the method of attachment of end fittings
f) use of an independent outside laboratory for prototype and design testing
B) Design Details
To meet these criteria the following steps were taken:
The market has a need for both EPDM and Silicone materials depending on application environment. Victor decided to develop insulators with both materials so that the needs of customers could be met in the most economical way.
An extensive review process of available materials was conducted and the suppliers chosen based on years of successful supply to the industry were:
EPDM: Colonial Rubber
Silicone: Wacker Silicones
Formulations were chosen to provide the optimum in performance in the field combined with ease of injection molding and complete bonding to the fiberglass core.
Victor specified 11/16 inch diameter polyester fiberglass for the core rod (larger diameter than most suppliers) in order to provide the best mechanical (tensile and torsion) resistance. Glasforms was selected as the suppler of the core based on that company's experience in this type of product.
The use of a solid rod type core instead of the "matrix" type offered by some suppliers provides much greater resistance to permanent deformation under torsion loading and also enables the insulator to meet the SML rating after the application of rated torsion load.
Ontario Hydro Technologies was selected as the independent laboratory to perform the necessary prototype and design testing. This laboratory has all necessary equipment to complete the testing and is very experienced in the qualification testing for polymeric insulators.
Prototype and design tests were performed to ANSI, IEC and LWIWG standards on both silicone and EPDM insulators.
C) Production Details
Housings (both materials) are injection molded using the latest technology. The housings are continuous (one piece) and completely and securely bonded to the core throughout the entire length of the housing/core interface.
Silicone and EPDM insulators (for each voltage class) are molded using the same mold so that the housings are identical except for the rubber material.
Cold runner injection molding is used to ensure that the housings are free from defects and that waste is kept to a minimum.
Specialized crimping equipment was purchased to provide uniform and reproducible crimping pressure for the assembly of the end fitting onto the core rod.
Crimping to pressure was chosen as the preferred method to ensure that all end fittings would have the same strength of attachment to the core. Crimping is verified through an extensive series of QA tests described below.
Insulators are manufactured in a tightly controlled process. Molds are of the highest quality and durability to ensure that the injection molded parts are uniform and free from objectionable parting lines, blisters, etc.
Each assembled insulator is routine proof tested to 7,500 lbs. prior to packaging.
Each days production is verified by performing tensile tests to destruction on samples from the production run.
Statistical recording and analysis of destruction tests ensures that the insulators meet the requirements of the relevant standards and Victor's drawings.
Production and test equipment are calibrated and checked on a regular schedule to ensure a consistent process.
Production is made to sales forecasts and a minimum inventory level specified for each Catalog number to ensure that insulators are in stock at all times and available for immediate shipment to meet customers' needs.
D) Approvals and Shipment History
Victor has received acceptance from the United States Department of Agriculture, RUS Division for the polymer dead ends. This assures RUS members that they may use the products and meet the necessary criteria for approval of construction.
This one agency (RUS) specifies acceptable materials for all member cooperatives. Thus, with this acceptance in place, the primary customer base for our new products has to date been the RUS market served through distributors.
On a parallel basis, we have been seeking product approval from Investor Owned Utilities Public Power and Municipalities. To date we are making significant progress in this area. Samples and test data have been submitted to all major customers.
Units have been installed for test at a number of locations including TXU and Florida Power Corp. We have been approved by JEA, TXU, SCE, Florida Power Corp and many other utilities.
Insulators are also under test at AEP and the Southern Company.
A partial list of users is available for review.