ABB RELION REX640 Technical Manual page 634

Protection functions
For the SOTF module typically longer reset time is needed to prevent unwanted
function reset between the current spikes during intermittent earth fault, setting
SOTF reset time. Recommended setting value is between 300-500 ms.
Applicable settings for the SOTF-module are:
duration, SOTF operate time and SOTF reset time .
Note that setting
applicable in definite time operation, but it must be taken into account in setting
SOTF operate time .
Faulted phase identification
The faulted phase selection module provides information about the faulted phase
(A, B or C) during a single-phase earth fault.
The faulted phase is identified by monitoring the "phase-wise" fault current
estimators as follows:
Maximum value indicates the faulted phase. Actual implementation utilizes
Cumulative Phasor Summing (CPS) together with admittance calculation.
634
Switch-onto-fault (SOTF) logic module enabling requires connection of
breaker close command into input CB_CL_CMD. Switch-onto-fault (SOTF)
logic module can be disabled by not connecting the breaker close
command signal to IFPTOC.
In case SOTF condition is detected, then all other functionality of IFPTOC
function is blocked.
SOTF Cond duration must be set higher than SOTF operate
Setting
time + SOTF reset time . SOTF functionality is reset after SOTF Cond
duration expires or at least when earth-fault detection signal deactivates
(EF_IND).
SOTF logic is not activated in case earth fault is detected (EF_IND =
TRUE) before breaker close command (input CB_CL_CMD is activated).
CB Delay comp (circuit breaker delay compensation) is not
Faulted phase is available in Recorded data as
Monitored data faulted phase is given in FAULT_PHASE.
Enable SOTF mode, SOTF Cond
Faulted phase . In
1MRS759142 F
(Equation 138)
(Equation 139)
(Equation 140)
REX640
Technical Manual