GE L90 Instruction Manual page 265

5 SETTINGS
a) MAIN MENU
PATH: SETTINGS GROUPED ELEMENTS
DISTANCE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
Four common settings are available for distance protection. The
tance functions. The mho distance functions use a dynamic characteristic: the positive-sequence voltage – either memo-
rized or actual – is used as a polarizing signal. The memory voltage is also used by the built-in directional supervising
functions applied for both the mho and quad characteristics.
The setting specifies the length of time a memorized positive-sequence voltage should be used in the
MEMORY DURATION
distance calculations. After this interval expires, the relay checks the magnitude of the actual positive-sequence voltage. If
it is higher than 10% of the nominal, the actual voltage is used, if lower – the memory voltage continues to be used.
The memory is established when the positive-sequence voltage stays above 80% of its nominal value for five power system
cycles. For this reason it is important to ensure that the nominal secondary voltage of the VT is entered correctly under the
SETTINGS SYSTEM SETUP
Set long enough to ensure stability on close-in reverse three-phase faults. For this purpose, the maxi-
MEMORY DURATION
mum fault clearing time (breaker fail time) in the substation should be considered. On the other hand, the
cannot be too long as the power system may experience power swing conditions rotating the voltage and current
TION
phasors slowly while the memory voltage is static, as frozen at the beginning of the fault. Keeping the memory in effect for
too long may eventually lead to incorrect operation of the distance functions.
The distance zones can be forced to become self-polarized through the
dition (FlexLogic™ operand) can be configured to force self-polarization. When the selected operand is asserted (logic 1),
the distance functions become self-polarized regardless of other memory voltage logic conditions. When the selected oper-
and is de-asserted (logic 0), the distance functions follow other conditions of the memory voltage logic as shown below.
The distance zones can be forced to become memory-polarized through the
condition (any FlexLogic™ operand) can be configured to force memory polarization. When the selected operand is
asserted (logic 1), the distance functions become memory-polarized regardless of the positive-sequence voltage magni-
tude at this time. When the selected operand is de-asserted (logic 0), the distance functions follow other conditions of the
memory voltage logic.
GE Multilin
SETTING GROUP 1(6)
DISTANCE
SOURCE: SRC 1
MEMORY
DURATION: 10 cycles
FORCE SELF-POLAR:
Off
FORCE MEM-POLAR:
Off
PHASE DISTANCE Z1
PHASE DISTANCE Z2
PHASE DISTANCE Z3
GROUND DISTANCE Z1
GROUND DISTANCE Z2
GROUND DISTANCE Z3
AC INPUTS VOLTAGE BANK
L90 Line Current Differential System
DISTANCE
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 5 to 25 cycles in steps of 1
Range: FlexLogic™ operand
Range: FlexLogic™ operand
See page 5–130.
See page 5–130.
See page 5–130.
See page 5–139.
See page 5–139.
See page 5–139.
identifies the signal source for all dis-
DISTANCE SOURCE
menu.
setting. Any user-selected con-
FORCE SELF-POLAR
FORCE MEM-POLAR
5.6 GROUPED ELEMENTS
5.6.5 DISTANCE
MEMORY DURA-
setting. Any user-selected
5-129
5