Differential Protection of Busbars, Generators, and Motors

Short circuit currents at generators and substations may be very high causing extreme CT saturation, resulting in substantial CT secondary current distortion.  Differential protection systems must be designed to reliably operate under these conditions since the impact on the power system may be serious in both cases.  If the differential protection operates due to CT saturation for an Out-Of-Zone fault (lack of stability) or if it does not operate for an In-Zone fault (lack of dependability), the impact on the system or the equipment damage can be significant.  Special algorithms and solutions must be applied on conventional schemes to satisfy these requirements. Rogowski Coils provide superior differential protection since they are linear (do not saturate), reject external electromagnetic fields, and are accurate, providing simpler and more reliable protection schemes.  In addition, Rogowski Coil physical dimensions and weight are much smaller than conventional current transformers, allowing easier application on existing installations.