Frequency Rate Of Change (Ansi 81R) - GE L30 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 Frequency rate of change (ANSI 81R)

SETTINGS  CONTROL ELEMENTS  FREQUENCY RATE OF CHANGE  FREQUENCY RATE OF CHANGE 1(2)
 FREQUENCY RATE
 OF CHANGE 1
5-270
— 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 5-142: Underfrequency logic
FREQ RATE 1

FUNCTION: Disabled
FREQ RATE 1 SOURCE:

SRC 1
FREQ RATE 1 TREND:

Increasing
FREQ RATE 1 PICKUP:

0.50 Hz/sec
FREQ RATE 1 OV SUPV

PICKUP: 0.700 pu
FREQ RATE 1 OC SUPV

PICKUP: 0.200 pu
FREQ RATE 1 MIN

FREQUENCY: 45.00 Hz
FREQ RATE 1 MAX

FREQUENCY: 65.00 Hz
FREQ RATE 1 PICKUP

DELAY: 0.000 s
FREQ RATE 1 RESET

DELAY: 0.000 s
Range: Disabled, Enabled
Range: SRC 1, SRC 2
Range: Increasing, Decreasing, Bi-directional
Range: 0.10 to 15.00 Hz/sec in steps of 0.01
Range: 0.100 to 3.000 pu in steps of 0.001
Range: 0.020 to 30.000 pu in steps of 0.001
Range: 20.00 to 80.00 Hz in steps of 0.01
Range: 20.00 to 80.00 Hz in steps of 0.01
Range: 0 to 65.535 s in steps of 0.001
Range: 0 to 65.535 s in steps of 0.001
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS