Accuracy Class of CT(Current Transformer)-Electronicsinfos

What is the Accuracy Class of C.T. (Current Transformer)?

The accuracy class of a CT tells us how accurately it can measure the electric current flowing through it. The most commonly used accuracy classes for current transformers are defined by international standards, such as IEC (International Electrotechnical Commission) and ANSI (American National Standards Institute).

Accuracy Class of CT

Accuracy Class of C.T. (Current Transformer)

For example, According to the IEC 61869-2:2012 accuracy classes for current transformers are as follows

1. Class 0.1
2. Class 0.2
3. Class 0.5
4. Class 1
5. Class 3

Class 0.1 Current Transformer(C.T)

Class 0.1 is used for highly accurate measurements, for laboratory or research applications. The maximum permissible error is ±0.1% of the rated primary current. Class 0.1 CTs require periodic calibration and testing to maintain their accuracy. 

Accuracy Class of CT

Key characteristics of Class 0.1 accuracy include

• Highly Precision
• Low Error Rate
• Balanced and Reliable Performance

Class 0.2 Current Transformer(C.T)

Class 0.2 is used for precision measurement applications, such as energy metering. The maximum permissible error is ±0.2% of the rated primary current. Class 0.2 accuracy is another high-precision accuracy class specified for current transformers (CTs). 

Accuracy Class of CT

Key characteristics of Class 0.2 CT

• Rated accuracy limit factor (ALF) of 0.2
• Low burdens to minimize voltage drops.
• Highly resistant to saturation effects for extremely accurate readings.
• Suitable for a wide frequency range.
• Minimal phase shift

Class 0.5 Current Transformer(C.T)

Class 0.5 is used in industrial and commercial applications where a high level of accuracy is required. The maximum permissible error is ±0.5% of the rated primary current.

Accuracy Class of CT

Key characteristics of Class 0.5 

• High Precision
• Low Error Rate
• Balanced Performance
• used for general protection 

Class 1 Current Transformer(C.T)

Class 1 is widely used for general-purpose measurements. The maximum permissible error is ±1% of the rated primary current.

Accuracy Class of CT

Key characteristics of Class 1 C.T

• Rated accuracy limit factor (ALF) of 1.
• Low burdens to minimize voltage drops
• Reliable measurement even at peak current values.
• Accurate measurement of fundamental frequency and harmonics.
• High-quality materials for stability and reliability.
• Adherence to international standards (e.g., IEC or ANSI/IEEE)

Class 3 Current Transformer(C.T)

class 3 is used for protection and control purposes, where a higher error tolerance is acceptable. The maximum permissible error is ±3% of the rated primary current.

Accuracy Class of CT

Class 3 accuracy is a lower accuracy class specified for current transformers (CTs) that are typically used for protection and control purposes. 

Key characteristics of Class 3 CT

• rated accuracy limit factor (ALF) typically around 3
• Can have higher burdens compared to Class 1 or Class 0.2 CTs.
• Suitable for a moderate frequency range.
• Moderate phase shift
• Operates within a specified temperature range
• Suitable for certain monitoring and control applications rather than precision metering or protection.

CT Accuracy Class Table

Accuracy Class of CT

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