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Lapp 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.
Lapp POC bushings meet all ANSI/IEEE standards for outdoor
apparatus bushings, where these standards apply for
voltage classes 25 kV through 800 kV. When a transformer
application results in overload above ANSI/IEEE standards,
a bushing having a higher current rating is recommended.
Lapp bushings are designed to carry the short term overloads
specifed by ANSI/IEEE transformer standards. Lapp 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.
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.
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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.
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