Current Transformer
An instrument transformer producing secondary current proportional to primary current, for measurement and protection.
A current transformer (CT) produces a precisely proportional secondary current. Enables safe measurement of high currents and provides signals to protective relays.
Standard secondary: 1A or 5A. Classes: metering (normal currents) and protection (high fault currents). Key parameters: ratio, accuracy, burden (VA), knee point voltage. Never open secondary while primary energized.
Essential in HV switchgear, prefabricated substations, substation metering.
QDTB supplies CTs integrated into transformer systems per IEC 61869 and IEEE C57.13.
Related Terms
Knee Point Voltage
The voltage at which a current transformer core begins to saturate, critical for protection CT performance.
Power Transformer
A large transformer (>10 MVA) used in transmission networks for stepping voltage between system levels.
Fault Current
The extremely high current during a short circuit that transformers must withstand mechanically.
More Terms Starting with “C”
CCC Certification
China Compulsory Certification (3C mark) required for electrical equipment sold in the Chinese domestic market.
CE Certification
Conformite Europeenne marking required for electrical equipment in the European Economic Area.
Core Loss
Power dissipated in the transformer magnetic core due to hysteresis and eddy currents, also called iron loss or no-load loss.
Copper Loss
Power lost as heat in transformer windings due to electrical resistance, proportional to the square of load current.
More in “Measurement & Protection”
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