Current transformer (CT) accuracy is specified by an accuracy class, with lower numbers indicating higher accuracy, such as 0.1%, 0.2%, 0.5%, 1%, or 3%. The accuracy level defines the maximum permissible error in current measurement under specific conditions. Some classes, denoted with an "S" (e.g., 0.5S), are special classes with stricter requirements for performance at lower currents, often down to 1% or 5% of rated current, whereas standard classes (e.g., 0.5) may only guarantee accuracy from 5% or 10% of the rated current upwards.

Current Transformers:Types,Application and FAQ


Types of Current Transformers


There are three main types of current transformers



Solid-Core Current Transformers


These have a single secondary winding forming a solid ring or toroid that passes over the primary conductor before being terminated.



Split Type Current Transformer


These have a single secondary winding designed to be split apart and placed around the already-terminated primary conductor. Clamp-on current meters are a type of split-core current transformers; they are opened and encircled around the conductor to gauge the current flow in amperes.



Bar-Type Current Transformers


The secondary winding is already wound around a bar. The primary conductor is fastened to the bar's ends with bolts, and the current then flows through the bar.