Design of a non-invasive current sensor for application on high voltage lines

This paper describes the design and construction of an openable core current transformer (CT) to be used on high-voltage lines or busbars. The current sensor consists of a high current stage with a ratio of 400:1 and a low current stage with a ratio of 100:1. Both have a toroid core and are of the enhanced core type. The high current stage is cut in two halves to be able to connect without breaking the high voltage line. The overall accuracy is limited by the cut core of the high current stage. The accuracy is <; 10 μA/A and <; 5 μrad.