Over-current protection relay SIPROTEC 7SJ8 series

frequencytransmission linefor feeder

The overcurrent and feeder protection relays can be used for line/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. Features Hardware •4 current transformers •0/3 voltage transformers •3/7/11 binary inputs (thresholds configurable using software) •5/8 binary outputs (2 changeover / form C contacts) •1 life contact •Pluggable current and voltage terminals. Functions •Definite and inverse time-overcurrent protection (phase/ground) (50, 50N, 51, 51N) •Directional time-overcurrent protection (phase/ground) (67, 67N) •Directional sensitive ground fault protection (67Ns, 50Ns) •Overvoltage protection, zero-sequence system (59N) •High-impedance restricted ground-fault protection (87N) •Inrush restraint •Trip-circuit supervision (74TC) •Undercurrent monitoring (37) •Overload protection (49) •Undervoltage/overvoltage protection (27/59) •Forward-power, reverse-power protection (32) •Power factor (55) •Overfrequency/underfrequency protection(81O/U) •Circuit-breaker failure protection (50B/F) •Intermittent ground fault protection •Directional intermittent ground fault protection (67Ns) •Unbalanced-load protection (46) •Phase-sequence-voltage supervision (47) •Voltage dependent inverse-time overcurrent protection (51V) •Synchrocheck (25) •Automatic reclosing (79) •Fault locator (FL) •Lockout (86) •Rate-of-frequency-change protection (81R) •Rate-of-voltage-change protection (27R/59R)