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Dry Type (Non-Oil) Paperless Bushings (RIS and RIF®) For T&D Power Systems
Introduction
The main purpose of a transformer bushing is to safely transfer power through the earthed transformer tank. OIP and RIP type bushings have been the industry standard
for many years and in general have performed satisfactorily. However, as our transformer assets age, paper deterioration in the original supplied bushings can cause
these bushings to fail; some even catastrophically.
The main purpose of a transformer bushing is to safely transfer power through the earthed transformer tank. OIP and RIP type bushings have been the industry standard
for many years and in general have performed satisfactorily. However, as our transformer assets age, paper deterioration in the original supplied bushings can cause
these bushings to fail; some even catastrophically.
Today we are seeing more movement towards silicone insulated, dry type (non-oil), paperless condenser bushings as they offer better safety, no oil leakage concerns,
optional maintenance and a lighter installation weight. There are now several suppliers that can offer this bushing technology.
What is the Difference Between RIS and RIF®
optional maintenance and a lighter installation weight. There are now several suppliers that can offer this bushing technology.
What is the Difference Between RIS and RIF®
RIS which stands for Resin Impregnated Synthetic is the industry’s generic terminology for the dry type (non-oil), paperless bushing. RIF® which stands for Resin Impregnated Fiberglass is a registered trademark name for the dry type (non-oil), paperless insulation technology developed by RHM International. Even though the RIF® bushing falls within the RIS category of bushings it is a distinctive technology that offers many unique advantages over the other RIS bushings currently on the market. The RIF® bushing technology is the more mature bushing technology, introduced to the market in 2003 and having over 22,000 units installed worldwide. The RIS bushing is a relative newcomer which was introduced to the market in 2014.
A major difference between RIS and RIF® is how the condenser core is manufactured. The RIS bushing condenser cores are wound with synthetic fabric [6] (Figure 1) after which the wound condenser core is encapsulated under vacuum where it is impregnated with epoxy resin and cured [6] (Figure 2).
Figure 1: Synthetic Fabric Wrapping Process [6]