A multichannel openable-core stage-connection comparator for on-site test of the output current transformers of AC generators

A multichannel openable-core stage-connection comparator for on-site test of the output current transformers of ac generators is developed. It can be used for on-site test and calibration of the output CT of ac generators when the ac generators are in a state of short-circuit testing. The rated capacities of the comparator are 2500-15000 A and above. Testing of the comparator indicates that ifs accuracy is better than 4/spl times/10/sup -4/ over a current range from 1% to 120% at a full-scale rated capacities, including the error of ratio and phase angle. The error in repeatability of openable-core is 2/spl times/10/sup -5/, and the error in the 50 mm lack of alignment between the measuring head of the comparator and the bus of the current to be tested is less than 4/spl times/10/sup -5/ . The ability of resistance to external magnetic field is greater than 1/spl times/10/sup -2/ T. The principle of the operation and the characteristics of the comparator segmented shield structure and the test results are discussed.