GE 850 User Manual

8–48 850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
UNDERVOLTAGE RESTORATION CHAPTER 8: CONTROL
Undervoltage Restoration
The 8 Series relay provides up to two Undervoltage Restoration (UV Restore) elements.
NOTE
NOTE:
When the 850 relay is ordered to support two UV Restoration elements, the UV Restore 1
element is always associated with Breaker 1, and UV Restore 2 element is always
associated with Breaker 2. Other combinations are not possible. The UV Restore element
will send close command only to this output relay that is selected under Close Relay Select
setpoint of the corresponding breaker
This scheme is initiated by user-defined operands. Once initiated it monitors the bus or line
voltage level, and sends 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 the output relay programmed for
BKR 1 Close Relay Select setpoint. 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.
FAST PATH:
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 > UV Restoration 1(X)
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.

GE 850 Specifications

General

Brand	GE
Model	850
Category	Protection Device
Language	English