Split-Core Current Transformer

Split-core CTs are very common in residential current monitoring because they can be installed without disconnecting the circuits. Though convenient, they are generally more expensive and less accurate than solid-core CTs. Split-core CTs either have a section of the CT that is removed for installation (left in figure below) or have a section that opens on a hinge (right in figure).

Two configurations of split-core CTs.
Lieko Earle