To carry out the error commissioning test after installation of a UHV current transformer（CT）

standard CT

high-current generator and other equipment are required to connect from the outside through two outlet-bushings of the CIS to form a closed high capacity current test circuit.However

this method is difficult to be implemented

and needs to design the circuit breaker

disconnecting switch and other equipment in accordance with the composition of high capacity current circuit because of the adoption of the grounding switch

which means higher requirements for equipment manufacturing.To solve this problem

a double-winding design of CT secondary side is proposed based on the Ampere circuital theorem to form 1:1 self-calibration mode of the coil current

then in test only one of the CT secondary windings is applied with the rated secondary current.To verify the feasibility of this technology

the design principle and operation mode of the CT are introduced

a mathematical model and a simulation model of the CT are established to carry out vector analysis of the self-calibration CT error

and the error characteristics of the same CT in two operation states are analyzed through comparison between the differences of the self-calibration CT and the schematic circuit.Moreover

based on the typical parameters of the CT in the Anhui-to-East UHV Transmission Line Project

a CT prototype is developed to carried out insulation test and error test.Test data show that the insulation of the developed CT meets the requirement of the UHV project

both operation error and self-calibration error are within the limit of 0.2 S level

and the variation of the errors with the rated current is consistent

the deviation is within the error limit of 0.1 level.Theoretical analysis and measurement show that the self-calibration data can reflect the error situation in the case of operation.This design method may provide a technical support for simplifying the onsite error commissioning test for UHV CT.