Using a Revenue Grade Current Transformer for Utility Tariff Metering

Precise measurements of load currents require accurate power usage readings for the purpose of tariff metering and it is critical that properly dimensioned current transformers are used for these specific applications.

For this article, we’ll outline three current transformers designed specifically for applications that require highly accurate metering, including the JAK-0C, JAK-0S and JAB-0C window-type current transformers for utility revenue metering applications. These models have high rating factors (2.0, 3.0 and 4.0) at low ratios and a very high metering accuracy class of 0.3% or greater. A test card showing the accuracy reading is included with each unit.

JAK-0C Solid Core Current TransformerIntended Use

Used primarily for industrial and commercial service metering applications that require high accuracy class current transformers.

Applications

Designed for indoor service but can be mounted in a weather-resistant outdoor metering enclosure. Suitable for operating meters and instruments on both single-phase two-wire circuits and three-phase circuits. An outdoor model with secondary conduit box is offered as an option. Contact FLEX-CORE for details.

Construction

The core and coil assembly is encapsulated in resin within a molded case. The material has excellent electrical and mechanical properties over a wide temperature range, has low water absorption and is resistant to oil and a variety of chemicals. The core is made from high quality grain oriented silicon steel while the secondary winding is made from heavy enameled copper wire evenly distributed around the core for maximum accuracy and resistance to stray magnetic fields.

Mounting

Low Base – Flex-Core commonly stocks the low base JAK-0C. Other mounting options (call for availability) include: no base, wide base and high base.

Primary Bus Bar Assembly Kits – These are also commonly stocked in sufficient quantities and are sold separately from the current transformers. If purchased together with the JAK-0C current transformers, Flex-core will ship these as fully assembled units.

Specifications

  • Insulation level – 0.6kV, 10kV BIL
  • Frequency – 60Hz
  • Thermal rating factors:
    • 4.0 @30° C for ratios from 100:5A to 400:5A
    • 3.0 @30° C for ratio 500:5A
    • 2.0 @30° C for ratios 600:5A up to 1000:5A
    • 1.5 @30° C for ratios 1200:5A and 1500:5A
    • 1.0 @30° C ambient for 2000:5A ratio.
  • Accuracy – 0.3%.
  • Window I.D. – 100:5A ratio has window opening size of 1.5”ID while the 200:5A ratio has a 2.60”ID and the higher ratios from 300:5A up to 2000:5A have 3.062”ID window opening sizes.

Availability

Most ratios are in stock and available for immediate shipment. Ratios not in stock require a lead time of 5 weeks.

Additional Options

Custom JAK-0C units rated at 25Hz – Flex-Core recently supplied a water treatment and sewage plant with models that work with their existing legacy equipment. They successfully tested at 25Hz rating.

Custom JAK-0C units rated at 50Hz with IEC metering class are also available. Contact Flex-Core for assistance.

JAK-0S High Accuracy Solid-Core Metering Class Current TransformerFeatures

Maximize revenue metering assembly with very high accuracy class of 0.15% extended beyond IEEE requirements; simplify CT selection and billing multipliers, improving productivity and minimizing risk of error; reduce inventory and part number requirements, reducing asset and operational costs.

The JAK-0S is a revenue metering high accuracy current transformer which maintains IEEE 0.15% accuracy class from 1% of rated current up through its rating factor. This is accomplished using specialized amorphous core material which minimizes electrical core losses. The result is an extremely accurate current transformer that can maintain high accuracy over an extended range of current. This model designed for indoor service but can be mounted inside the outdoor metering enclosures. Optional primary bar kits are available.

Construction

The core and coil assembly is encapsulated in resin within a molded case. The material has excellent electrical and mechanical properties over a wide temperature range, has low water absorption and is resistant to oil and a variety of chemicals. The core is made from high quality grain-oriented silicon steel while the secondary winding is made from heavy enameled copper wire evenly distributed around the core for maximum accuracy and resistance to stray magnetic fields.

Mounting

Low Base – Flex-Core commonly stocks the low base JAK-0S, 750X333012, 600:5A.

Primary Bus Bar Assembly Kits – These are optional and are sold separately from the current transformers. If purchased together with the JAK-0S current transformers, Flex-core will ship these as fully assembled units.

Specifications

  • Insulation level of 0.6kV, 10kV BIL
  • Frequency 50-60Hz
  • Thermal rating factors:
    • 2.0 @30° C ambient
    • 1.5 @55° C ambient
  • Window I.D. – 3.062″

Availability

Flex-Core have adequate quantities in stock of the 750X333012, 600:5A. This high accuracy current transformer has an accuracy of 0.15% from 1% of rated current (6.0A) up to its rated factor of 1200A, which exceeds the IEEE requirements.

JAB-0C Solid Core Current TransformerIntended Use

Customers buying these current transformers are distributors and contractors who use these for their industrial and commercial clients that require high accuracy class current transformers for their service metering.

Applications

Designed for indoor service and especially designed for installation over the secondary bushings of pad mounted transformers. For revenue metering applications and window opening ID of 4.5” x 3.5”. An 85° C version is available.

Contact Flex-Core for catalog number of the high temperature version.

Construction

The core and coil assembly are encapsulated in resin within a molded case. The material has excellent electrical and mechanical properties over a wide temperature range, has low water absorption and is resistant to oil and a variety of chemicals. Cast units are molded in polyurethane resin and have slightly larger dimensions. The core is made from high quality grain-oriented silicon steel while the secondary winding is made from heavy enameled copper wire evenly distributed around the core for maximum accuracy and resistance to stray magnetic fields.

Mounting

The JAB-0C can be mounted in any position but is usually installed on the pad mount transformer terminal blade using the Valox “grabbers”. The grabbers are removable, and the transformer also has two mounting holes allowing it to be attached to a mounting bracket.

Window opening size – All the JAB-0C units have the same window opening size of 4.5” x 3.5”.

Specifications

  • Insulation level of 0.6kV, 10kV BIL
  • Frequency 50-60Hz
  • Thermal rating factors:
    • 4.0 @30° C for ratios from 100:5A, 200:5A, 400:5A (cast resin units) and non-cast resin units 200:5A, 300:5A and 400:5A
    • 3.0 @30° C for ratio 300:5A, 500:5A, 600:5A, and 800:5A. ratio.
  • Rating factors of other ratios are as shown in the data sheet.
  • Accuracy – 0.3%.

Availability

Most ratios are in stock and available for immediate shipment. Ratios not in stock require a lead time of 7 weeks.