GE T60, Instruction Manual

Page: 339 / 796

GE Multilin T60 Transformer Protection System 5-193
5 SETTINGS 5.6 GROUPED ELEMENTS
5
Five 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
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
setting (common for both phase and ground elements for all zones as entered under the
SETTINGS

GROUPED ELEMENTS

SETTING GROUP 1(6)

DISTANCE
menu).
2. The
MEMORY DURATION
setting (common for both phase and ground elements for all zones as entered under the
SET-
TINGS

GROUPED ELEMENTS

SETTING GROUP 1(6)

DISTANCE
menu).
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 [
PKP
] and dropout [
DPO
] Flex-
Logic signals) or time-delayed elements (operate [
OP
] FlexLogic signals), only zone 1 is intended for the instantaneous
under-reaching tripping mode.
Ensure that the
PHASE VT SECONDARY VOLTAGE
(see the
SETTINGS

SYSTEM SETUP

AC INPUTS

VOLTAGE
BANK
menu) is set correctly to prevent improper operation of associated memory action.
• GND DIST Z1 DIR: All ground distance zones are reversible. The forward direction is defined by the
GND DIST Z1 RCA
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
GND DIST Z1 REACH
and
GND DIST Z1 RCA
settings, and the reverse reach imped-
ance defined by the
GND DIST Z1 REV REACH
and
GND DIST Z1 REV REACH RCA
settings.
• 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.
MESSAGE
GND DIST Z1 VOLT
LEVEL: 0.000 pu
Range: 0.000 to 5.000 pu in steps of 0.001
MESSAGE
GND DIST Z1
DELAY: 0.150 s
Range: 0.150 to 65.535 s in steps of 0.001
MESSAGE
GND DIST Z1 BLK:
Off
Range: FlexLogic operand
MESSAGE
GND DIST Z1
TARGET: Self-Reset
Range: Self-Rest, Latched, Disabled
MESSAGE
GND DIST Z1
EVENTS: Disabled
Range: Disabled, Enabled
NOTE