it means accuracy class of CT. 5 p means 5 % of composite error will happen till 20 times of current is applied . So CT will follow its rated characterstics upto 20 times currentRead more: What_does_mean_by_5p20_CT
The expression (5P10) denotes a permutation, specifically the number of ways to arrange 10 objects taken 5 at a time. However, since 10 exceeds 5, (5P10) is mathematically undefined and equals 0, as you cannot choose more items than are available. In general, the formula for permutations is (nPr = \frac{n!}{(n-r)!}), where (n) is the total number of items and (r) is the number of items to arrange.
Two types of CTs. one is for metering another one is for ProtectionThe metering CT has very less error,the protection CT has more error but thathas more saturation level.5 - 5% error. P for protection and 10 indicates 10 times the rated current.