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25kV-500kV POC® Bushings (Paper-Oil-Capacitor)
 Jump to 115kV - 500kV POC Series II Bushings
»  PCORE Capacitance Graded Bushings and Services Catalog 1.0 (2.08mb)
PCORE capacitor bushings
for transformer and oil circuit breaker applications are a proven
design based on a capacitor core with aluminum foils and high
dielectric paper impregnated with dried, degassed oil. PCORE
POC bushings meet all ANSI/IEEE standards for outdoor apparatus
bushings, where these standards apply for voltage classes 25
kV through 500 kV. When an application results in
overload above ANSI/IEEE standards, a bushing having a higher
current rating is recommended. PCORE bushings are designed to
carry the short term overloads specifed by ANSI/IEEE
standards. PCORE POC bushings for other applications (e.g.,
oil-to-oil, oil-to-gas, outdoor-to-indoor air, etc.) are available
for various voltage classes and current ratings.
» Instruction Manual for PCORE POC Bushings (384kb)
» Installation Manual for Horizontally Mounted POC Bushings 15kV - 72.5kV (20kb)
Design Features
1.
Gaskets
Nitrile rubber, cork gaskets are designed to provide even
loading and oil-tight seals with extended life.
2. High Compression Coil
Springs
Multiple heavy-duty coil springs provide uniform, active compressive
loading on gaskets to compensate for temperature variations
and to assure oil-tight joints and reliable mechanical strength.
3. Clear-View Oil Reservoir (Medium and
High Voltage Bushings)
The tinted glass oil reservoir filters damaging ultraviolet
rays, preventing oil deterioration. The oil level and condition
is clearly visible from any angle.
4. Magnetic Oil Gauge (Extra High Voltage Bushings)
The oil level is indicated by the pointer on the gauge.
5. Porcelain Housing
The outdoor porcelain housing has sturdy sheds to provide
required leakage and strike distance and has ground surfaces
on top and bottom ends for oil-tight gasket seals.
6. Name Plate Data
The name plate affixed to the mounting flange identifies the
bushing by catalog number, serial number and year of manufacture
with electrical ratings and factory measurement data.
7. Power Factor Test Tap (Medium Voltage Bushings)
25 kV through 69 kV bushings have a power factor test tap.
The test tap is connected to the ground layer of the capacitor
core. An aluminum cap covers the insulated test tap assembly
and grounds the tap to the flange when energized.
8. Voltage Tap or Capacitance Tap (High and Extra
High Voltage Bushings)
Bushings rated at 115 kV and above have a permanent internal
ground. In addition, an insulated tap is connected to a floating
capacitor layer. This tap, designated a capacitance tap or
a voltage tap, is grounded except when used as a voltage source
with a potential device. The voltage tap also serves as a
means of measuring power factor and capacitance of the bushing
core. The tap is ANSI standard type A, normally grounded.
9. Mounting Flange, Ground Sleeve Assembly
The mounting flange and ground sleeve assembly is made of
aluminum and provides nonmagnetic, corrosion-resistant, high-strength
service.
10. Paper-Foil Capacitor Core
Conductive layers of aluminum foil with high dielectric paper
are wound around the conductor and into the bushing core to
produce uniformly valued capacitors in series. This capacitance
grading distributes the voltage and the electrical field uniformly
throughout the core. The core is vacuum-dried and impregnated
with dried, degassed oil.
11. Lower Porcelain Joint
A collar maintains alignment between the ground sleeve and
the porcelain, preventing porcelain-to-metal contact. Nitrile
rubber o-rings and nitrile rubber cork gaskets provide sealing
under cantilever loads.
12. Lower Porcelain Assembly
The lower porcelain has ground gasket surfaces on each end
to facilitate alignment and maintain an oil-tight assembly.
13. Bottom Cap Assembly
A confined nitrile rubber cork gasket provides a leak-proof
seal between the porcelain and the cap. The end cap aligns
the porcelain with the conductor.
14. Dried, Degassed Oil
The internal space in the bushing between its exterior components
and the core is filled with dried, degassed insulating oil.
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