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Current and Voltage Transformers up to 69kV

SUPERBUTE dry-type instrument transformers are engineered and rigorously tested to provide a measureable difference in reliability and durability. Since the very first unit produced in 1955, SUPERBUTE instrument transformers have provided utilities with a number of benefits for enhanced safety and a lower total cost of ownership. SUPERBUTE is designed to meet IEEE C57.13 standards and ANSI standard mounting provisions, terminals, and construction.

GE’s SUPERBUTE family of products supports system voltages up to and including 69kV. The unique design of the SUPERBUTE family addresses the challenges with traditional voltage and current instrument transformers.


GE’s SUPERBUTE product range consists of Inductive Voltage Transformers and Current Transformers:

  • Indoor and outdoor designs
  • Rated voltages up to 69kV
  • Rated basic insulation levels (BIL) up to 350kV
  • Relay class ratings up to T800
  • Standard & Special High Accuracy metering classes

GE’s SUPERBUTE product range includes specifications suitable for a wide range of revenue metering, protection and control applications. Common uses include:

  • Substation metering and relaying
  • Primary metering cabinets
  • Pole-top primary metering assemblies
  • Control power for reclosers, capacitors, and other distribution equipment
  • Current of voltage sensing for switchgear, circuit breakers, and other control equipment

Key Benefits
Longer Product Life

Field studies and accelerated life testing has shown an average  operating life of more than 40 years, with reliability measures 3 times better than published industry benchmarks

Distribution class SUPERBUTE offers compact designs for more efficient application to solid-state metering and other modern installations.

Station class SUPERBUTE offers higher burden, higher thermal rating, and extra creep distance for substations or installations where higher ratings are required.

Enhanced Safety

Internal insulation is made from epoxy resin which is encapsulated in tough, elastic butyl rubber, dampening and minimizing the impact of high energy events

Environmentally Friendly & Minimum Maintenance

Unique dry-type construction ends oil leakage problems, eliminates breakage and vandalism issues, and does not support combustion

Lower Total Cost of Ownership

The dry-type design eliminates the need for oil testing or filtering and allows for a compact design which facilitates mounting flexibility for more economical installations such as on existing steel structures, inside a cabinet, or on a pole

Fast Delivery

Extensive vertical integration within the factory allows for standard lead times of 4-6 weeks, nearly half the industry average

Tough & Resilient Insulation
HY-BUTE 60™ butyl rubber as the external insulation

The outer shell of SUPERBUTE transformers are made with GE’s proprietary formula of butyl rubber, which is called HY-BUTE 60. This material adds the following timeless advantages over epoxy resins or porcelains designs:

  • Encapsulating the unit with a tough, elastic rubber provides an inherent safety advantage as it dampens the severity of any potential failure
  • Unique chemistry provides for non-arc tracking surface, significantly reducing risk of failure from flashover
  • Legendary durability as this material does not easily chip, crack, or shear
  • Will not stress crack due to the external environment, even in extreme conditions such as -50°C
  • Maintains hydrophobicity over the life of the transformer
  • Does not support combustion
  • Does not oxidize or corrode

GE’s proprietary formula of non-arc tracking butyl rubber showed no carbonization after 4,000 hours in salt-fog testing, compared to standard butyl rubber which failed after 107 hours or standard porcelain which failed after 400 hours under the same conditions

Cross section of a JVS350 station-class voltage transformer showing cycloaliphatic epoxy encapsulated with HY-BUTE 60 butyl rubber shell

Cycloaliphatic epoxy as the internal insulation

Cycloaliphatic epoxy takes the place of oil as the internal insulation and winding impregnation. The advantage of this design includes:

  • Reduced footprint with a compact design with up to 30% less height than the leading oil-filled designs
  • High tensile strength which allows for mounting in any position including vertical, horizontal, upside down, or at any angle
  • Environmentally friendly design eliminates hidden costs associated with traditional liquid-filled designs such as:
  • oil-leakage problems
  • oil filtering or testing
  • construction requirements for a large installation space or dedicated
       support structure
Superior Design Features
SUPERBUTE Advantage: Superior primary winding design and extra creep distance ensure accurate, reliable performance in harsh conditions

SUPERBUTE instrument transformers are designed for quality and reliability with features engineered to withstand high voltage stresses and extreme environmental conditions, while delivering the highest accuracies possible, all within a compact design. The result is a reliable, long-lasting, easy to handle design that ultimately lowers total cost of ownership.

Lattice-type windings for voltage transformer

Originally patented by GE, lattice-type windings have precise controlled positioning and distribution of each turn to reduce maximum voltage stress within the winding. This unique design also minimizes the possibility of partial discharges within the winding. The coil configuration, and the outer electrostatic shields distribute steep voltage fronts across the coil to reduce concentration of stress.

Lattice-type winding in a JVS350 station-class VT

Multi-gap type primary in a JKW350 station-class CT

Built-in surge protection for current transformers

A unique multi-gap type primary by-pass on current transformers 600 amps and below protects windings during line disturbances or steep current wave fronts. The gaps are factory adjusted to fire at 5000-7500 crest volts, thereby by-passing surge currents up to 100 times rated, which could otherwise result in excessive voltages across the primary winding.

High accuracy, extended range ratings for current transformers

The use of high accuracy instrument transformers with solid-state metering allows for improved billing accuracy and/or the potential to reduce inventory requirements. GE offers high accuracy and extended range ratings which meet the accuracy needed for these applications. Since introducing the first dry-type high-accuracy transformer solution in 1991, GE’s high accuracy product line has grown to a portfolio that includes a wide variety of voltage classes up to and including 69kV.

Compact size & mounting flexibility

SUPERBUTE transformers require up to 30% less height and up to 40% less floor space compared to the leading oil-filled designs, and can be mounted in any position. This allows substation design flexibility including mounting on a substation steel structure or a pole.

Extra creep & strike

Even with 30% less height, standard units can be used in environmentally severe conditions and in high altitude (10,000ft) applications. Station class units have creep distances that exceed the requirements for even the next-level voltage class.

SUPERBUTE station-class creepage distances versus IEEE C57.13-2008
required levels, by system voltage

SUPERBUTE transformers are more compact and lower profile compared to the lead liquid filled transformers

Advanced Testing
SUPERBUTE Advantage: Tested above and beyond IEEE C57.13 requirements to ensure manufacturing consistency and maximize life expectancy

All SUPERBUTE instrument transformers are designed and tested per IEEE C57.13 standards and the manufacturing facility is ISO® 9001 certified. In addition to IEEE routine testing requirements, GE instrument transformers undergo additional testing designed to ensure manufacturing consistency and maximize life expectancy.

IEEE C57.13 routine factory tests
  • Applied Potential Test: Checks insulation between windings and windings to ground
  • Induced Potential Test: Checks insulation within windings (2x normal turn to turn)
  • Accuracy and Polarity Test: Checks ratio and phase angle at highest rated burden
  • Certified test reports and electronic test date can be saved and e-mailed in various formats, upon request

Impulse and partial discharge testing a 72.5kV, 350kV BIL substation-class PT. Both chop wave and full wave impulse testing is performed as a routine test on all SUPERBUTE units 8.7kV and above

GE specific routine tests
  • Select units are 100% impulse tested as short-term reliability screen
  • Partial Discharge & Ionization Tests: Partial Discharge performed to IEEE C57.13 standards as well as testing with GE specific connections
Additional GE performance controls
  • Accelerated Life Test as a weekly process control audit, in place since 1988
  • Unit tested at 180% rated voltage, 180HZ
  • Minimum expectation is 40 year life
Field performance tracking
  • Establishes benchmark for reliability
  • Helps GE demonstrate produce performance
  • Helps customer pinpoint system problems
  • Correlated to GE accelerated life test results
Voltage Transformers

SUPERBUTE Product Overview: Inductive Voltage Transformers

Outdoor Voltage Transformers: Outdoor voltage transformers are available at 5-69kV and 60-350kV BIL. These units are offered in two distinct sizes for efficient sizing:

Station class: Higher burden, higher thermal rating, and extra creep distance for metering and/or relaying applications in substations or installations where higher ratings are required such as high altitude or high contamination locations.

Distribution class: Compact designs, with lighter burden and thermal rating for more efficient application to solid-state metering and other modern relay and control power installations.


Indoor Voltage Transformers: Indoor Voltage Transformers are available at 5-25kV system voltage and 60-200kV BIL. Type JVM95 is a metering voltage transformer to be used in conjunction with the Type JKM-95 current transformer for primary metering of underground distribution systems.

Current Transformers

SUPERBUTE Product Overview: Current Transformers

Outdoor Current Transformers: Outdoor wound-type current transformers (CTs) are available 5-69kV, 60-350kV BIL, up to 1200A. Wound-type units are available in two distinct sizes:

Station class: Station class CT’s have a versatile design that is suitable for metering and/or relaying applications. Units are larger in size, have additional creep distance, and are rated for heavier metering burdens.

Distribution class: Distribution class CT’s are more compact and are designed specifically for maximum efficiency in solid-state revenue metering applications. These CT’s generally do not have a relay rating.

Outdoor current transformers are also available in Bar-Type and Window-Type styles, 5-15kV, 60kV-110kV BIL, up to 4000A.


Indoor Current Transformers: Indoor Current Transformers are available 5-15kV system voltage and 60-150kV BIL. Product types include wound type up to 1200A, and window-type or bar-type up to 4000A, plus a specialty CT for underground distribution systems.