Features:
a special kind of current transformer --rogowski coil.
to be installed in tight spaces easily
no need to dismantling the primary busbar or cables 
flexible and lightweights
no danger from open-circuite secondary
no core saturation or damage if overloaded  
excellent linearity
multi-size are available
Applications
power quality monitoring
power meters
smart logger
energy sub-meters
distributed measurement systems
safety standard : IEC31010-1:2001,600V CAT III