Hi. In PX class CT , burden is not mentioned in nameplate? and Ie at Vk/2 is mentioned.what significance on Vk/2
Does this help?
The magnetizing characteristics of both LV & HV sides Ps class CTs used for differential protection must have the same knee point voltage Vk and the same excitation current Ie at Vk/2. If there is variation in knee point voltage of CTs, the CT having less knee point voltage(KPV) will get saturated in case of the external fault and the differential protection relay will get tripped with nuisance tripping. Therefore, both the set of CTs used at the primary and secondary side of the equipment must have the same knee point voltage and the excitation current(Ie) at Vk/2.
Source - Electricalvolt