Analysis of the Meaning of 5P20 in Current Transformers

Explanation of Accuracy Grade

In current transformers (CTs), 5P20 is an identifier that represents its performance characteristics. This identifier consists of three parts: Accuracy Class, Protection Class, and Accuracy Limit Factor.

• Accuracy Class (5): The number 5 represents the accuracy class of this current transformer. The accuracy class reflects the measurement error of the current transformer under specific conditions. A smaller number indicates higher accuracy. Accuracy class 5 is typically used for applications that do not require high precision, such as monitoring or protection, where small errors in measurement are acceptable.

• Protection Grade (P): The letter P denotes that this is a current transformer for protection purposes. Protection grade current transformers are designed to carry fault currents and maintain their accuracy under fault conditions.

• Accuracy Limit Factor (20): The number 20 represents the Accuracy Limit Factor (ALF) of the current transformer. This factor indicates the magnitude of the fault current that can safely flow through the primary winding of the CT without causing it to saturate. In this case, it means that when the primary current reaches 20 times the rated current due to a short circuit, the composite error of the transformer is less than 5%.

Practical Application

Current transformers of the 5P20 type are typically used in applications that can accept lower levels of accuracy, such as some general-purpose monitoring or control systems. While they may not be suitable for applications requiring high precision current measurements, in many cases, they offer sufficient performance and remain a popular choice due to their cost-effectiveness and reliability.

Summary

In summary, 5P20 denotes a protective class current transformer with an accuracy class of 5, capable of maintaining a total error within 5% when the primary current is up to 20 times its rated current. This characteristic makes it widely applicable in various protection and monitoring applications.