J&D sells several different series of current transformers in various window sizes, current ranges, and IEEE C57.13 or IEC 61869-2 accuracy grades. Most power quality and Energy Meters use current, voltage output CTs. J&D CTs are suitable for use in harmonics or Revenue Grade metering or in up to 20 kHz services up to 1000 Vac. To select a CT, we recommend first deciding on a style, either a split-core (opening ),flexible Rogowski coil (opening ) or a solid-core (non-opening) CT, then select the model you need based on the maximum load current you are measuring and the size of the conductor being measured.