CHAPTER 7: PROTECTION CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 297
Figure 256: POTT scheme configuration settings
The following settings are available.
Function
Range: Enabled, Disabled
Default: Disabled
This setting enables and disables the permissive over-reaching transfer trip (POTT)
scheme.
Permissive Echo
Range: Enabled, Custom, Disabled
Default: Disabled
If this setting is “Enabled,” the scheme sends a permissive echo signal to the remote
ends using pre-programmed logic (refer to the following logic diagram). If set to
“Custom,” the echo signal is sent if a condition selected via the
Echo Condition setting is
satisfied. The echo is sent only once and then the logic locks out for the time specified by
the
Echo Lockout setting. The duration of the echo pulse is specified by the Echo
Duration setting. Operation of the overreaching protection elements (distance zone 2 or
the
Ground Directional OC Forward setting) inhibits the echo.
Echo Condition
Range: any FlexLogic operand
Default: OFF
This setting selects and applies an echo condition and only if the
Permissive Echo setting
is “Custom.”
RX Pickup Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.000 seconds
This setting enables the relay to cope with spurious receive signals. Set this delay value
to be longer than the longest spurious TX signal that can be received simultaneously
with the zone 2 pickup. The selected delay increases the response time of the scheme.
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