ABB RELION 650 Series Applications Manual page 132

Section 7
Impedance protection
be used from an overreaching zone. The selection of the
security.
Mode is set to UlLvl&Imp , the condition for tripping is an ORed between UlLevel and
When
Impedance .
tDuration : The setting of the timer for the release of UlLevel is, by default, 0.02 seconds, which
has proven to be suitable in most cases from field experience. If a shorter time delay is to be
set, it is necessary to consider the voltage recovery time during line energization.
tOperate : The time delay for the START_DLYD input to activate TRIP when Mode is set to
Impedance or UlLvl&Imp is, by default, set to 0.03 seconds.
126
Impedance mode gives increased
Application manual
1MRK 505 363-UEN A