GE t60 Instruction Manual page 264

5.6 GROUPED ELEMENTS
Three zones of ground distance protection with a minimum 150 ms time delay are provided as backup protection for trans-
formers or adjacent lines.
The ground mho distance function uses a dynamic 100% memory-polarized mho characteristic with additional reactance,
directional, current, and phase selection supervising characteristics. The ground quadrilateral distance function is com-
posed of a reactance characteristic, right and left blinders, and 100% memory-polarized directional, overcurrent, and phase
selection supervising characteristics.
When set to non-directional, the mho function becomes an offset mho with the reverse reach controlled independently from
the forward reach, and all the directional characteristics removed. When set to non-directional, the quadrilateral function
applies a reactance line in the reverse direction instead of the directional comparators.
The reactance supervision for the mho function uses the zero-sequence current for polarization. The reactance line of the
quadrilateral function uses either zero-sequence or negative-sequence current as a polarizing quantity. The selection is
5
controlled by a user setting and depends on the degree of non-homogeneity of the zero-sequence and negative-sequence
equivalent networks.
The directional supervision uses memory voltage as polarizing quantity and both zero- and negative-sequence currents as
operating quantities.
The phase selection supervision restrains the ground elements during double-line-to-ground faults as they – by principles
of distance relaying – may be inaccurate in such conditions. Ground distance zones 1 and higher apply additional zero-
sequence directional supervision. See chapter 8 for additional details.
Each ground distance zone is configured individually through its own setting menu. All of the settings can be independently
modified for each of the zones except:
1. The
SIGNAL SOURCE
GROUPED ELEMENTS
2. The
MEMORY DURATION
TINGS GROUPED ELEMENTS
The common distance settings noted at the start of this section must be properly chosen for correct operation of the ground
distance elements.
Although all ground distance zones can be used as either instantaneous elements (pickup [
Logic™ signals) or time-delayed elements (operate [
under-reaching tripping mode.
Ensure that the
menu) is set correctly to prevent improper operation of associated memory action.
BANK
WARNING
• GND DIST Z1 DIR: All ground distance zones are reversible. The forward direction is defined by the
setting and the reverse direction is shifted by 180° from that angle. The non-directional zone spans between the for-
ward reach impedance defined by the
ance defined by the
• GND DIST Z1 SHAPE: This setting selects the shape of the ground distance characteristic between the mho and
quadrilateral characteristics. The selection is available on a per-zone basis.
5-132
GND DIST Z1 VOLT
MESSAGE
LEVEL: 0.000 pu
GND DIST Z1
MESSAGE
DELAY: 0.150 s
GND DIST Z1 BLK:
MESSAGE
Off
GND DIST Z1
MESSAGE
TARGET: Self-Reset
GND DIST Z1
MESSAGE
EVENTS: Disabled
setting (common for both phase and ground elements for all zones as entered under the
SETTING GROUP 1(6)
setting (common for both phase and ground elements for all zones as entered under the
SETTING GROUP 1(6)
OP
PHASE VT SECONDARY VOLTAGE
GND DIST Z1 REACH
and
GND DIST Z1 REV REACH
T60 Transformer Protection System
Range: 0.000 to 5.000 pu in steps of 0.001
Range: 0.150 to 65.535 s in steps of 0.001
Range: FlexLogic™ operand
Range: Self-Rest, Latched, Disabled
Range: Disabled, Enabled
menu).
DISTANCE
menu).
DISTANCE
] FlexLogic™ signals), only zone 1 is intended for the instantaneous
(see the
SETTINGS SYSTEM SETUP
and
GND DIST Z1 RCA
settings.
GND DIST Z1 REV REACH RCA
5 SETTINGS
] and dropout [
PKP DPO
AC INPUTS
GND DIST Z1 RCA
settings, and the reverse reach imped-
GE Multilin
SETTINGS
SET-
] Flex-
VOLTAGE