Skipper has pioneered the design and manufacture of Instrument Transformers over the past three decades. Skipper Instrument Transformers are globally known for consistent accuracy, reliability and maintenance-free operation over life time. Skipper manufactures the entire range of Instrument Transformers viz. :

arrowOil Filled, Outdoor
arrow Resin Cast, Indoor/Outdoor
arrowMetering Units, Indoor/Outdoor
power transformer
Oil Filled Current Transformers

Skipper manufactures Oil Filled Current Transformers upto 220 kV class. Skipper make transformers are currently in operation in challenging locations and have been delivering outstanding performance consistently for over 25 years. These transformers comply with international quality, safety and environment specifications standards.

Outdoor Potential Transformers

Skipper complements its range of Current Transformers with Potential Transformers.

  • The PTs are usually built up of multi cores designed for Metering and Protection in dead tank construction.
  • The PTs built in stacked core construction employ high permeability cold rolled grain oriented magnetic steel.
  • The PTs are designed and manufactured in accordance with specific user’s specification and are suitable for Indoor / Outdoor application.
  • Skipper is equipped to Design and Manufacture PTs upto 220 kV Class system voltage, with in-house Testing facilities for conducting all routine Tests. However, Skipper also conducts Type and Special Tests to validate the design at third party NABL accredited Test Laboratories like CPRI and ERDA.


Oil filled current transformers use current transformation principle to convert highline current (in HV system) to a low current reduced by a fixed ratio. The current transformers are designed generally in live tank construction for optimum performance.

The primary winding is manufactured from copper conductor and is placed in the top housing.

The windings are rigid, concentric with uniformly distributed secondary winding to deliver high mechanical strength against short circuit forces.

The secondary windings and the cores are contained in closely fitting rigid shell. The shell is fully insulated from the top housing. The secondary leads are taken to the base passing through a hollow insulator.

Insulation is provided by electrical grade high grade Kraft paper. The fully assembled CTs are dried and oil filled under vacuum in evacuated heating chambers. Optimum insulation and long life is achieved by drying the paper insulation by heat in vacuum. Oil, impregnated under vacuum, complements the insulation.



Skipper uses brown glazed porcelain insulator with shed profile as per IEC 60815 for the CTs. Optionally grey shade porcelain and other profiles can be offered as per specific requirements. The porcelain insulator is cemented to flanges on both ends for maximum mechanical strength. The top housing contains core coil assembly and is made of corrosion resistant aluminium alloy.

The top of the tank has an oil filling plug. The CT is protected from the vagaries of weather and can withstand extreme temperature variations. Core of wound ring type are manufactured from high quality silicon steel. However, Mu-metal cores are used for select applications. Design, material and process selection ensure that all requirements relating to metering and protection are met. The secondary winding is uniformly distributed over the circumference of the core to minimize the reactance of the winding. This also ensures accurate transformation ratio. The CT base chamber is fabricated from structural steel. This chamber is provided with secondary terminal box, oil sampling valve and earthling pads.


Skipper’s test laboratories are fully equipped with latest testing equipment and are capable of conducting all routine tests including Partial Discharge test.

Skipper oil filled instrument transformers are tested under stringent conditions for their performance, reliability and durability at NABL accredited labs such as ERDA and CRPI.

Type tests and special tests are also conducted on all new designs to verify that the product design meets all operational requirements.

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Quality Management System

Skipper’s experienced and quality conscious workforce carries out quality control at each stage of production. A series of quality checks are performed at each unit before handing over the same for the next stage. The Quality Assurance department maintains and updates all quality control documents and carries out its own additional inspection at critical hold points. Skipper’s quality system is in accordance with ISO 9001 : 2008 and products are CE certified.

Technical specification

OIL Filled Instrument Transformers



success Installations
132kV CTs & PTs Mizoram State Electricity Board, India
success Installations
132kV, CTs & PTs PHED, Rajasthan, India
success Installations
132kV CTs & PTs TCN, Kaduna, Nigeria
success Installations
132kV CTs & PTs Dangote Cement, Congo
success Installations
132kV CTs & PTs Lafarge Cement, Ogun State, Nigeria
success Installations
132kV, 66kV & 33kV CTs & PTs, United Brothers, Nepal
success Installations
132kV CTs & PTs TI Steels, Himachal Pradesh, India
success Installations
3000 x 33kV CTs & PTs to NIPP since 2010. Additional 3000 CTs & PTs to Various DISCOMs & TCN Nigeria