CHAPTER 7: PROTECTION CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 311
Figure 262: Directional comparison unblocking scheme configuration settings
The following settings are available.
Function
Range: Enabled, Disabled
Default: Disabled
This setting enables and disables the directional comparison unblocking scheme.
Block
Range: any FlexLogic operand
Default: OFF
This setting allows the user to assign any FlexLogic operand to block the directional
comparison unblocking scheme. Contact inputs from a pilot cut-out switch are typically
used for this purpose.
Permissive Echo
Range: Disabled, Enabled, Custom
Default: Disabled
Enabling this setting sends a permissive echo signal to the remote ends under certain
conditions (see the logic diagram). If set to “Custom,” the echo signal is sent if a condition
selected with the
Echo Condition setting is satisfied. The echo is sent only once and then
the echo logic locks out for the time specified by the
Echo Lockout setting. The duration
of the echo pulse is programmable by the
Echo Duration setting. The echo is returned
only if no overreaching and reverse protection elements operate.
Echo Condition
Range: any FlexLogic operand
Default: OFF
This setting specifies and applies an echo condition when the
Permissive Echo setting is
“Custom.”
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