The 7SD610 relay is a differential protection relay suitable for all types of applications and incorporating all those functions required for differential protection of lines, cables, and transformers. Transformers and compensation coils within the differential protection zone are protected by means of integrated functions, which were previously to be found only in transformer differential protection. It is also well-suited for complex applications such as series and parallel compensation of lines and cables.It is designed to provide differential and directional backup protection for all voltage levels and types of networks. The relay features high speed and phase-selective short circuit measurement. The unit is thus suitable for single-phase and three-phase fault clearance.Digital data communication for differential current measurement is effected via fiber-optic cables, networks or pilot wires connections so that the line ends can be quite far apart. The serial protection interface (R2R interface) of the relay can flexibly be adapted to the requirements of all existing communication media. If the communication method is changed, flexible retrofitting of communication modules to the existing configuration is possible.Apart from the main protection function, i.e. the differential protection, the 7SD610 has a full range of configurable emergency and/or backup protection functions such as phase and earth over current protection with directional elements if voltage transformers are connected. Overload, under and over-voltage/frequency and breaker failure protection round off the functional scope of the 7SD610.