Based on the application of ct either measuring or protection. It is classified as measuring class or protection class ct
Where the measuring class requires much precision and accuracy in measurement. Ex class 1,o.5 etc which indicates the percentile inaccuracy in measurement is 1% and 0.5%.
Coming to the protection class where the current can go upto 20 times based on the seviority of fault. Where the accuracy is less important the ct class will be 5p10 5p20 5p30.
Where the first numerical indicates the percentile inaccuracy the letter p indicated protection, class where it can withstand 10,20,30 times current than the rated current of the ct.
The ASCT brand HPT series protection current transformer produced by HEYI Electric can be used in the power system of 100/5A-8000/5A, the protection level can be 5P5, 5P10, 5P15, 5P20, 5P30, and the rated capacity is 2.5VA to 20VA