Distance - GE G60 Instruction Manual

5.6 GROUPED ELEMENTS
a) MAIN MENU

PATH: SETTINGS GROUPED ELEMENTS
 DISTANCE

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-
5
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
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
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 operand
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 magnitude at this
time. When the selected operand is de-asserted (logic 0), the distance functions follow other conditions of the memory volt-
age logic.
The
FORCE SELF-POLAR
will give higher priority to forcing self-polarization as indicated in the logic below. This is consistent with the overall philoso-
phy of distance memory polarization.
The memory polarization cannot be applied permanently but for a limited time only; the self-polarization may be
applied permanently and therefore should take higher priority.
NOTE
5-160

SETTING GROUP 1(6)

DISTANCE

SOURCE: SRC 1
MEMORY
MESSAGE
DURATION: 10 cycles
FORCE SELF-POLAR:
MESSAGE
Off
FORCE MEM-POLAR:
MESSAGE
Off
 PHASE DISTANCE Z1
MESSAGE

 PHASE DISTANCE Z2
MESSAGE

 PHASE DISTANCE Z3
MESSAGE

setting specifies the length of time a memorized positive-sequence voltage should be used in the
 
AC INPUTS VOLTAGE BANK
long enough to ensure stability on close-in reverse three-phase faults. For this purpose, the maxi-
and settings should never be asserted simultaneously. If this happens, the logic
FORCE MEM-POLAR
G60 Generator Protection 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 5–161.
See page 5–161.
See page 5–161.
identifies the signal source for all dis-
DISTANCE SOURCE
menu.
setting. Any user-selected con-
FORCE SELF-POLAR
FORCE MEM-POLAR
5 SETTINGS
5.6.3 DISTANCE
MEMORY DURA-
setting. Any user-selected
GE Multilin