GE L60, Instruction Manual, Page: 180 / 498

5-88 L60 Line Phase Comparison Relay GE Multilin
5.5 GROUPED ELEMENTS 5 SETTINGS
5
5.5.5 DISTANCE
a) MAIN MENU
PATH: SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) DISTANCE
Three common settings (
DISTANCE SOURCE
,
MEMORY DURATION
, and
FORCE SELF-POLAR
) and six menus for three zones of
phase and ground distance protection are available. The
DISTANCE SOURCE
identifies the Signal Source for all distance
functions. The Mho distance functions use a dynamic characteristic: the positive-sequence voltage – either memorized 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
setting specifies the length of time a memorized positive-sequence voltage should be used in the
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 AC INPUTS VOLTAGE BANK
menu.
Set
MEMORY DURATION
long enough to ensure stability on close-in reverse three-phase faults. For this purpose, the maxi-
mum fault clearing time (breaker fail time) in the substation should be considered. On the other hand, the
MEMORY DURA-
TION
cannot be too long as the power system may experience power swing conditions rotating the voltage and current
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
FORCE SELF-POLAR
setting. Any user-selected con-
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
FORCE MEM-POLAR
setting. Any user-selected
condition (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. When
the selected operand is de-asserted (logic 0), the distance functions follow other conditions of the memory voltage logic.
DISTANCE DISTANCE
SOURCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4
MESSAGE
MEMORY
DURATION: 10 cycles
Range: 5 to 25 cycles in steps of 1
MESSAGE
FORCE SELF-POLAR:
Off
Range: FlexLogic™ operand
MESSAGE
FORCE MEM-POLAR:
Off
Range: FlexLogic™ operand
MESSAGE
PHASE DISTANCE Z1
See page 5–89.
MESSAGE
PHASE DISTANCE Z2
See page 5–89.
MESSAGE
PHASE DISTANCE Z3
See page 5–89.
MESSAGE
GROUND DISTANCE Z1
See page 5–98.
MESSAGE
GROUND DISTANCE Z2
See page 5–98.
MESSAGE
GROUND DISTANCE Z3
See page 5–98.