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115kv-500kv POC® Series II Bushings (Paper-Oil-Capacitor)

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.

The Next Generation of Interchangeable Bushings

Take a look at these advantages:

  • INCREASED maximum altitude to 10,000 feet for standard bushings
  • 33% LESS weight
  • 30% LESS oil
  • 17% SMALLER diameter below the mounting flange
  • MORE cantilever strength than required by existing ANSI/IEEE standards
  • QUALIFIED for use in oil circuit breakers by actual oil circuit breaker tests at KEMA's high voltage test facility
  • HIGHER critical flashover to allow use of uncorrected electrical values during transformer production tests
  • LARGER oil expansion margin
  • IMPROVED performance during emergency overloads specified by ANSI/IEEE transformer standards
  • INCREASED design testing, including "front-of-wave" test specified in ANSI/IEEE transformer standards
  • "SMART" numbering system that identifies the bushing type, electrical rating, porcelain glaze and special bushing requirements
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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