The SIPROTEC 7SS60 system is an inexpensive numerical differential current protection for busbars in a centralized configuration. It is suitable for all voltage levels and can be adapted to a large variety of busbar confi gurations with an unlimited number of feeders. The components are designed for single busbars, 11⁄2-breaker confi gurations and double busbars with or without couplers.

Different primary CT ratios can be matched by using appropriate windings of the input current transformers. The use of matching transformers allows phase-selective measurement. Single-phase measurement can be achieved by using summation current transformers.