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
www.onspot.com
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.
www.crown-electric.com •