P rotection relays are used to protect the network from various electricaldisturbances, both external and internal. The relay will work if the currentinformation is sent by the current transformer so that the determination of thespecifications of a current transformer will determine how the protection relay canwork correctly. For main protections such as differential relay, distance relay andrestricted earth fault relay, it is necessary to design specifications of currenttransformers or sizing current transformers and saturation calculations as the mainparameters of a current transformer to ensure that the current transformer will beable to work in providing information in fault conditions. Sizing and saturationcalculations of a current transformer are determined from the design stage. Thiswas done in this study by calculating the value of the primary current, the ratio ofthe current transformer, the value of the current fault on the network, the value ofthe lead resistance, find out the dimensioning factor and calculate the knee pointvoltage to be compared with the results of the Factory Acceptance Test.Parameters for calculating the saturation point are lead resistance (RL), remittancefactor (K), relay resistance (RR) and resistance in current transformer (RCT).33qwBased on the calculation of the current transformer knee point voltage andcompare the results with the Factory Acceptance Test, the knee point voltage ofcurrent transformer value obtained from the calculation is no more higher thanknee point voltage point value of the Factory Acceptance Test results, the currenttransformer is considered sufficient.