ABB RELION REX640 Technical Manual page 635

1MRS759142 F
Fault resistance estimation
Protection function IFPTOC includes fault resistance (R
based on information on the faulted phase, the faulted phase voltage and estimated
earth fault current magnitude (fundamental frequency). Fault resistance magnitude
can be estimated with equation:
Where
Actual implementation utilizes Cumulative Phasor Summing (CPS).
Trip logic
Protection function IFPTOC supports both tripping and alarming earth-fault
handling defined with setting
With
OP_SOTF/OP_INTR outputs are not activated.
applicable in networks, where due to low touch voltages tripping of earth-fault
is not required (requires existence of Global Earthing System, GES). Monitoring
of prevailing earth-fault current and/or touch voltage magnitude can be done via
Monitored data.
When start conditions of touch voltage protection, earth-fault current protection,
cross-country fault protection, intermittent earth-fault protection or switch
onto fault protection are fulfilled, this is indicated by activation of START
and corresponding ST_EF/ST_XC/ST_SOTF/ST_INTR outputs. When operate
conditions are fulfilled and setting
by activation of OPERATE and corresponding OP_EF/OP_XC/OP_SOTF/OP_INTR
outputs.
REX640
Technical Manual
Faulted phase information is not given in case of cross-country fault
(XC_FLT = TRUE).
= Faulted phase voltage magnitude, fundamental frequency [V]
= Estimated earth-fault current magnitude, fundamental frequency [A]
Magnitude of estimated fault resistance in primary ohms is available in
Recorded data:
given: RF.
Fault resistance estimation is not done in case of cross-country fault
(XC_FLT = TRUE).
In case of intermittent earth fault, fault resistance estimation is not
accurate.
Operation mode = "Alarming EF", OPERATE and corresponding OP_EF/OP_XC/
Fault resistance . In monitored data this information is
Operation mode = "Alarming EF" or "Tripping EF".
Operation mode = "Alarming EF" is
Operation mode = "Tripping EF", this is indicated
Protection functions
) magnitude estimation
F
(Equation 141)
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