Oil-Type Bushing CT

Product Image - OBCT



Oil-Type Bushing Current Transformers (OBCTs) can be used for a variety of measuring, revenue metering and protection applications. Peak Demand OBCTs are designed and manufactured in accordance with customer specifications and to IEEE, IEC or GOST standards. Each OBCT is 100% routine tested in accordance to the specified standard and test reports are sent with each order.


Generally used in power transformers, Oil-Type BCTs are immersed in oil to measure primary currents up to 8000A. As there are no standard ratings for OBCTs, each unit is custom designed for its application. In addition to the current ratio, accuracy class and power frequency, some information regarding the equipment must be provided. To determine the physical size the limiting dimensions must be given. These are the minimum ID, the maximum OD and the maximum stack height.



The core is constructed from wound layers of electrical grade steel or low loss, high accuracy materials, depending on the customer’s specifications. The core is protected with insulation rings to protect the coil winding from damage. Cores are wrapped with coated copper wire to ensure against damage and potential short circuits. The secondary winding, or core and coil assembly, is insulated with a cotton tape specifically manufactured for immersion in oil.

Technical Specifications

  • Primary currents: up to 8,000 Amps
  • Secondary current: 1 & 5 Amps
  • Frequency: 50 and 60 Hz
  • Inner diameter: Up to 36” [915mm]
  • Outer diameter: Up to 40” [1016mm]
  • Rating Factors: Up to RF 4.0 @ 55°C
  • Safety Factors: 5, 10
  • Relaying class: Up to C800 (IEEE) / 5P20-200VA (IEC)
  • Metering class: Exceeds 0.15S (IEEE) / 0.1 thru 5.0 (IEC)
  • Burdens: B0.1 thru B1.8 / 5 – 200 VA
  • Single Ratio (SR) or Multi Ratio (MR) available.
  • NOTE: Sizes and accuracy class depend on current ratio.

Design and Test

Winding wire is terminated with either leads or terminal connections per the customer specification. Various types and sizes of lead wires are crimped and soldered with the winding wire to ensure high quality, solid connections. Lead wires are one color or color coded and marked for simple connections as per customer requirements. Standard tests include accuracy, polarity, double induced, di-electric, turns-ratio, and excitation for every unit. Each OBCT has a unique serial number which allows the customer to track each test record. Certified test reports are provided with every OBCT shipment.


Packaging and Shipping

Packaging and shipping options such as collapsible and returnable crates and direct shipment are available upon customer request.