ABB RELION REX640, Техническое руководство, Страница: 634 / 1960

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.
Setting
SOTF Cond duration must be set higher than SOTF operate
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).
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:
Enable SOTF mode, SOTF Cond
duration, SOTF operate time and SOTF reset time.
Note that setting
CB Delay comp (circuit breaker delay compensation) is not
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:
(Equation 138)
(Equation 139)
(Equation 140)
Maximum value indicates the faulted phase. Actual implementation utilizes
Cumulative Phasor Summing (CPS) together with admittance calculation.
Faulted phase is available in Recorded data as
Faulted phase. In
Monitored data faulted phase is given in
FAULT_PHASE
.
Protection functions 1MRS759142 F
634 REX640
Technical Manual