Current Transformers (CTs)
Introduction
Current Transformers (CTs) are instrument transformers that are used to supply a reduced value of current that can be handled safely by instruments like meters and protective relays etc.
CT’s provide isolation from the high voltage primary, permit grounding of the secondary for safety, and step-down the magnitude of the measured current to a value that can be safely handled by the instruments.
Burden of a CT
The secondary load of a current transformer is usually called the "burden" to distinguish it from the load of the circuit whose current is being measured.
Burden is the load imposed on the secondary of the CT at rated current and is measured in VA (product of volts and amps).
Types of CTs
According to function the types of CT are:
1) Protection CTs
2) Metering CTs
According to Class the types of CT are:
1) Class C CTs
2) Class T CTs
Class T CTs
CTs that have significant leakage flux within the transformer core - class T; wound CTs, with one or more primary-winding turns mechanically encircling the core.
Class C CTs
CTs with very minimal leakage flux in the core, such as the through, bar, and bushing types.
CT Accuracy Class
The measure of a CT performance is its ability to reproduce accurately the primary current in secondary amperes both is wave shape and in magnitude.
Current Transformers (CTs) are instrument transformers that are used to supply a reduced value of current that can be handled safely by instruments like meters and protective relays etc.
CT’s provide isolation from the high voltage primary, permit grounding of the secondary for safety, and step-down the magnitude of the measured current to a value that can be safely handled by the instruments.
Burden of a CT
The secondary load of a current transformer is usually called the "burden" to distinguish it from the load of the circuit whose current is being measured.
Burden is the load imposed on the secondary of the CT at rated current and is measured in VA (product of volts and amps).
Types of CTs
According to function the types of CT are:
1) Protection CTs
2) Metering CTs
According to Class the types of CT are:
1) Class C CTs
2) Class T CTs
Class T CTs
CTs that have significant leakage flux within the transformer core - class T; wound CTs, with one or more primary-winding turns mechanically encircling the core.
Class C CTs
CTs with very minimal leakage flux in the core, such as the through, bar, and bushing types.
CT Accuracy Class
The measure of a CT performance is its ability to reproduce accurately the primary current in secondary amperes both is wave shape and in magnitude.
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