The Utility Source February 2019 - Page 14

Unique Insulators and Insulator Mounting Systems of tracking, each additional insulator also statistically increases the potential points of creepage paths to ground (due to dirt or a crack) and failure.  In other words, the fewer the number of insulators, the higher the reliability.  By maximizing insulator strength to control both static and fault forces, the required number of points for mounting and points of possible tracking are minimized. Among the design features that are critical to IPB’s are the support insulators that hold the heavy-gauge, high amperage conductors in place. These electrical stand-offs must withstand high tempera- tures, worse case mechanical fault forces and electrical stresses regardless of the IPB’s operating conditions and environment. Salt, moisture, coal dust and ambient particulate can all be present and potentially accumulate within the housing. In this regard, Crown Electric’s Insul-Mount™ support design re- sults in the fewest required insulators per linear span.  Each stand- off insulator is mounted within a welded aluminum casting (known as a “window”). This “window” design provides superior ease of in- sulator access, facilitates cleaning of the insulators in place without the need for removal, as well as visual inspection of the mounting hardware and the local internal IPB conductor. In the IPB design from Crown Electric, high strength, high creep porcelain insulators are used to provide better resistance against tracking to ground.  The insulators also have  carefully chosen dew point ratings so as to eliminate potential failures associated with environmental moisture and condensation.  This totally passive “belt and suspenders” approach ensures this modern version of the Westinghouse design never loses its nameplate rating. Most other IPB designs require the opening of an insulator’s mount- ing / cover plate and the complete removal of that insulator before it can be inspected and cleaned.  This is a tedious and time-con- suming process which also increases the possibility of the insulator being dropped or in other ways damaged when removed.  Addition- ally, re-installing of the stand-off insulator covers and their mating gaskets can lead to re-sealing issues with an associated continuous leakage of air. ments to IPB insulators, insulator mountings and to the continuous housing assembly – among others.  These iterative improvements continue to strengthen the well-known and respected reputation for rugged reliability of the Westinghouse-based IPB design. Unlike designs requiring the introduction of auxiliary forced pressurization to control condensation, this approach negates the needs for costly space heaters and pressurization systems that are mandatory for others. If IPB conductors could magically be suspended in the center of the housings, voltage withstand would never be an issue.  But until that time comes, stand-off insulators are required to center and support the IPB conductors. Because each IPB support insulator is ultimately a potential point Continuous Housings Continuous housings are fabricated from lightweight aluminum sheets rolled and then seam welded to the appropriate diameter for each rating.  Cylindrical sections are butt joined by various perimeter welding techniques to maximum strength and conduc- tivity, creating an effective weather tight enclosure that protects conductors and support insulators from the surrounding environ- mental conditions.  These lightweight IPB sections are specifically engineered to be shipped in the greatest practical lengths with fewer joints to field weld.  Unlike older non-continuous designs, continuous IPB has more inherent rigidity and structural strength, creating a self-support- ing framework.  Simple hangers or mounting feet (aka – “saddles”) can easily carry the weight of long IPB spans. With a continuous IPB design, the enclosure acts as its own ground plane, eliminating the need for a separate ground bus.  The enclosure is at ground potential over its entire length so a single connection to the station ground can usually provide complete grounding. A continuous housing design eliminates the electrically isolated sections associated with older non-continuous designs.  As there is no voltage potential between enclosure sections, failures due to inter-sectional arcing is eliminated. TRACTION IN FORWARD AND REVERSE FOR 1/2 TON TO CLASS 8 VEHICLES • UTILITY TRUCKS • FIRE TRUCKS • AMBULANCES • SCHOOL BUSES • PLOW TRUCKS • TRACTOR TRAILERS *Approved for use in states with chain control areas 12 TUS Magazine • February ‘19 800-766-7768 The continuous house design also inherently neutralizes its own conductor flux; thereby shielding nearby support steel and control wiring from the severe magnetic effects of stray loss heating and unintended control signal impingement. With power generation facilities so dependent on reliable IPB systems, plant engineers and maintenance managers have a responsibility to ensure serious faults will not occur that can harm personnel or connected capital equipment.  By taking advantage of significant Crown Electric design improvements that build on the already reliable, well established Westinghouse foundations, Iso Phase Bus duct has never been more rugged or reliable. •