Research On Influence Of Current Transducer Saturation On Transformer Differential Protection

The mal-operation accidents of differential relays of main transformers occasionally occurred due to the saturation of the current transformers of the differential relay. Many research and development works have been done on this subject and great progress has been achieved. However, few research work is focused on the influence of the saturation of the current transducers of transformer numeric differential relays, and which is the main subject of this thesis.The saturation of the current transducers of transformer differential protective relay is examined by numerical real time dynamic simulation system ( RTDS) . The test results proved that the saturation of current transducers does affect the operation correctness of differential relays. The factors which affect the performances of the current transducers are analyzed. The improving methods are then proposed and new AC boards are made under the guidance of the method. The new differential relays passed the RTDS test and have run steadily and safely for about 2 years up to now in the substations of the power supply company which the author is working with, which proved the validity of the methods proposed herein has been proved.Besides the guide line of type selection of current transducers are proposed in this paper.