Relay Class Current Transformers

Relay Class Current Transformers(CTs) available in the 600 v class series of current transformers. Available with either Leads or Terminals, and have CSA/UL approval.

Relay Class Current Transformers are typically used for supplying current to protective relays and when a higher rating factor is required. This will allow a meter to detect larger fluctuations in the primary current.

These current transformers will guarantee the transformer will not saturate at 20 times the rated current and be within +/- 10% accuracy. The wider range of current allows the protective relay to operate at different fault levels.

How is a Relay Class Calculated?

• 20 (x times) (Rated Secondary Current) (x times) (Burden) = Relay Class Rating
• Example: 20 x (5 amps) x (1.0 ohm burden) = C100

A Current Transformer (CT) is a type of transformer that is used to reduce or multiply an alternating current (AC). It produces a current in its secondary which is proportional to the current in its primary.

Current Transformers, along with voltage or potential transformers, are instrument transformers. Instrument transformers scale the large values of current to small, standardized values that are easy to handle for measuring instruments and protective relays. The Instrument transformers isolate measurement or protection circuits from the high voltage of the primary system. These units provide a secondary current that is accurately proportional to the current flowing in its primary, presenting a negligible load to the primary circuit.

These units are the current sensing units of the power system and are used at generating stations, electrical substations, and in industrial and commercial electric power distribution.

Advantages of Current Transformers are that the units can measure high current easily, high electrical isolation, simple construction, and easy maintenance and installation.

Features:

• High accuracy
• Leads or Terminals
• Window Style

Applications:

• Ammeters
• Energy Systems
• Low Voltage panel boards
• Low Voltage switchboards
• Motor Control Centers (MCC)
• Voltmeters
• Wattmeters

Standards:

• IEEE C57.13.

Approvals:

• CSA 

 191   (1.25″window)(100:400 A)(relay class C10-C20) 

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192  (1.75″window)(100-500 A)(relay class C10-C20)  

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193  (2.13″window)(100-600 A)(relay class C10)   

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112 (2.25”window)(50-1200 A)(relay class C10-C200) 

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194  (2.50″window)(100-1600 A)(relay class C10)  

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113 (2.75″window)(50-1500 A)(relay class C10-C200) 

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114  (3.25″window)(50-1600 A)(relay class C10-C200) 

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115 (4.00″window)(50-3200 A)(relay class C10-C200) 

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100 (4.00”window)(200-3000 A)(relay class C10-C50) 

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117 (4.62″window )(50-4000 A)(relay class C10-C100) 

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120 (5.75″window)(200-4000 A)(relay class C10-C50)