Undervoltage Restoration - GE 850 Instruction Manual

CHAPTER 4: SETPOINTS

Undervoltage Restoration

FASTPATH:
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
The 850 relay provides one Undervoltage Restoration (UV Restore) element.
This scheme is initiated by user-defined operands. Once initiated it monitors the bus or line
voltage level, and send a command when the voltage on the programmed number of
phases has risen above the programmed level for a selected time interval. Synchrocheck
supervision may be applied for this command to operate Close Relay #2. The scheme is
equipped with an incomplete sequence timer, so it does not remain initiated for an
indeterminate time, but automatically resets if the voltage does not recover during the
programmed interval. Initiation of the scheme can be cancelled by a Reset command. A
"Block Restoration" logic input is available to prevent both initiation and operation. It is
recommended that if automatic undervoltage restoration is to be used, the Cold Load
Pickup feature is also enabled, in order to prevent the breaker from tripping shortly after it
is automatically closed.
The settings of this function produce Pickup and Close flags. Once the Undervoltage
Restoration is initiated by any of the user-defined elements, the Undervoltage Restoration
Pickup flag is asserted when the measured voltages on the programmed number of
phases are above the MINIMUM value. The Undervoltage Restoration Close flag is asserted
if the element stays picked up for the time defined by the restore time delay.
The incomplete sequence timer automatically resets the element if the voltage does not
recover during the programmed interval after the initiation.
The use of the Undervoltage (UV) Restoration feature must be carefully accessed regarding
the application of the breaker in the power system.
If the "Synchrocheck Supervision" setpoint is not available (per relay's order code) to
program in the UV Restoration menu, or it is available, but is set to "Bypass", the application
of the feature must be limited to the use of breakers associated with de-energized feeders,
lines, and buses.
If the Synchrocheck function is selected in the order code, the UV Restoration can be safely
used for breakers connecting two live lines, or two live buses, providing the setpoint
Synchrocheck Supervision is set to Synchrocheck Breaker Close Permission (Sync1 Close
Perm).
Path:
Setpoints > Control > Undervoltage Restore
FUNCTION
Range: Disabled, Close, Alarm, Latched Alarm, Configurable
Default: Disabled
Output relay #2 "Close" operates only when the Close function is selected, the element
operates, and Synchrocheck supervision is applied. The "ALARM" LED does not turn on if
the element operates when set to function Close.
INITIATION
Range: Off, Ph UV 1 OP, Ph UV 2 OP, Aux UV 1 OP, Aux UV 2 OP
Default: Off
The setpoint selects the FlexLogic operand that initiates the Phase or Auxiliary UV
Restore scheme; typically the operate signals from Phase Undervoltage functions.
CONTROL
4–321