ABB RELION REX640, Техническое руководство, Страница: 584 / 1960

fact that the phase angle difference between U
o
and I
o
increases as the
capacitive earth-fault current contribution increases. Phase angle difference
may become so high that correct operation of traditional protection functions
is endangered. This is not the case for IFPTOC, as fault current estimate is not
affected by the capacitive earth-fault current contribution of the protected
feeder itself.
- In case earth fault occurs during abnormal network topologies, or when
fault current compensation is temporarily not effective or when network is
operated heavily over- or under-compensated.
• Magnitude of true fault current is estimated without need on any pre-defined
information on the network topology.
• Also, the effect of fault resistance can be considered and compensated in the
estimated earth-fault current magnitude applying dedicated fault resistance
compensation method. This functionality allows acceleration of protection
operation speed during high(er) ohmic earth fault when actual fault current
magnitude is low.
IFPTOC includes also dedicated protection functionality for important practical
earth-fault scenarios such as switch onto fault (SOTF) condition, for intermittent
earth faults and for high current cross-country earth-faults. Each of such fault
condition can be tripped with individually defined operation criteria enabling high
application flexibility and reliability.
4.2.10.4 Analog channel configuration
IFPTOC has four analog group inputs which must be properly configured.
Table 625: Analog inputs
Input Description
I3P Three phase currents
IRES Residual current (measured or calculated)
U3P Three phase voltages
URES Measured or calculated residual voltage
See the preprocessing function blocks in this document for the possible
signal sources.
There are a few special conditions which must be noted with the configuration.
Table 626: Special conditions
Condition Description
U3P connected real meas-
urements
Recommendation to connect all three phase-to-earth voltage
channels. Alternative is at least two phase-to-earth / phaseto-
phase voltages and measured residual voltage (URES).
URES calculated Three phase-to-earth voltages must be connected for calcu-
lating the residual voltage. Setting
VT connection
must be
"Wye" in that particular UTVTR.
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
check the contents of this chapter and also the preprocessing blocks in this
Protection functions 1MRS759142 F
584 REX640
Technical Manual