The SIPROTEC 7SJ80 relays can be used for feeder protection of high and medium-voltage networks with grounded, low-resistance grounded, isolated or a compensated neutral point. The relays have all the required functions to be applied as a backup relay to a transformer differential relay. The SIPROTEC 7SJ80 features “flexible protection functions”. Up to 20 additional protection functions can be created by the user. Therefore, protection of change for frequency or reverse power protection can be realized, for example. The relay provides circuit-breaker control, further switching devices and automation functions. The integrated programmable logic (CFC) allows the user to add own functions, e.g. for the automation of switchgear (interlocking). The user is also allowed to generate user-defined messages.