GE D90 Plus Instruction Manual page 162

GROUPED PROTECTION ELEMENTS
Phase distance
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The phase mho distance function uses a dynamic 100% memory-polarized mho
characteristic with additional reactance, directional, and overcurrent supervising
characteristics. The phase quadrilateral distance function is comprised of a reactance
characteristic, right and left blinders, and 100% memory-polarized directional and current
supervising characteristics. When set as 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.
Each phase distance zone is configured individually through its own setting menu. All of
the settings can be independently modified for each of the zones except the common
distance settings specified in the previous section.
The common distance settings must be properly chosen for correct operation of the phase
distance elements. Although all zones can be used as either instantaneous elements
(pickup and dropout FlexLogic™ operands) or time-delayed elements (operate FlexLogic™
operands), only zone 1 is intended for the instantaneous under-reaching tripping mode.
The phase distance element operating curves are shown below.
Ensure that the
Phase VT Secondary Voltage
operation of the associated memory action.
Select the Settings > Protection > Elements > Group 1 > Phase Distance menu item to
open the phase distance configuration window.
Figure 116: Memory voltage logic
setting is set correctly to prevent improper
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: PROTECTION