Autoreclose (Ansi 79) - GE F35 Instruction Manual

CONTROL ELEMENTS
The steady-state frequency of a power system is a certain indicator of the existing balance between the generated power
and the load. Whenever this balance is disrupted through the loss of an important generating unit or the isolation of part
of the system from the rest of the system, the effect is a reduction in frequency. If the control systems of the system
generators do not respond fast enough, the system can collapse. A reliable method to quickly restore the balance between
load and generation is to automatically disconnect selected loads, based on the actual system frequency. This technique,
called "load-shedding," maintains system integrity and minimize widespread outages. After the frequency returns to
normal, the load can be restored automatically or manually.
UNDERFREQ 1 SOURCE
a live phase voltage available from the selected source. If voltage is not available, the element attempts to use a phase
current. If neither voltage nor current is available, the element does not operate, as it does not measure a parameter
below the minimum voltage/current setting.
UNDERFREQ 1 MIN VOLT/AMP
element to operate. This threshold is used to prevent an incorrect operation because there is no signal to measure.
UNDERFREQ 1 PICKUP
frequency is 60 Hz and the load shedding is required at 59.5 Hz, the setting is 59.50 Hz.
5

5.8.6 Autoreclose (ANSI 79)

SETTINGS  CONTROL ELEMENTS  AUTORECLOSE  AUTORECLOSE 1(6)
 AUTORECLOSE 1

5-208
— This setting is used to select the source for the signal to be measured. The element first checks for
— Selects the minimum per unit voltage or current level required to allow the underfrequency
— Selects the level at which the underfrequency element is to pickup. For example, if the system
Figure 5-108: Underfrequency logic
AR1 FUNCTION:

Disabled
AR1 INITIATE:

Off
AR1 BLOCK:

Off
AR1 MAX NUMBER OF

SHOTS: 1
AR1 REDUCE MAX TO 1:

Off
AR1 REDUCE MAX TO 2:

Off
AR1 REDUCE MAX TO 3:

Off
AR1 MANUAL CLOSE:

Off
AR1 MNL RST FRM LO:

Off
AR1 RESET LOCKOUT IF

BREAKER CLOSED: Off
Range: Disabled, Enabled
Range: FlexLogic operand
Range: FlexLogic operand
Range: 1, 2, 3, 4
Range: FlexLogic operand
Range: FlexLogic operand
Range: FlexLogic operand
Range: FlexLogic operand
Range: FlexLogic operand
Range: Off, On
F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS