Overfrequency - GE Multilin 350 Series Instruction Manual

S3 PROTECTION

Overfrequency

6–108
Courtesy of NationalSwitchgear.com
The relay is equipped with two Overfrequency elements per setpoint group, ANSI device
number 81O-1, and 81O-2. Voltage channel phase A is used for frequency measurement.
The steady-state frequency of a power system is an indicator of the existing balance
between generated power and the load. Whenever this power is disrupted through
disconnection of significant load or the isolation of a part of the system that has surplus of
generation, it would result in increase of frequency. If the control system of the generators
do not respond fast enough to quickly ramp the turbine frequency back to normal, the
overspeed can lead to turbine trip. The overfrequency elements can be used to control the
turbine frequency at a generating location. This element can also be used for feeder
reclosing as part of the "after load shedding restoration"
The following path is available using the keypad. For instructions on how to use the
keypad, please refer to Chapter 3 - Working with the Keypad.
PATH:
SETPOINTS > S3 PROTECTION > SETPOINT GROUP 1(2) > OVER-FREQUENCY1(2)
OVERFREQ 1(2) FUNCTION
Range: Disabled, Alarm, Latched Alarm, Trip
Default: Disabled
The selection of the Latched Alarm, Alarm, or Trip setting enables the Overfrequency
function. The output relay #1 "Trip" will operate, if the function is selected as a Trip, and
the measured frequency is above the OVERFREQ PKP setting for a time longer than the
selected OVERFREQ DELAY time. The "ALARM" LED will not turn on if the Overfrequency
function is set to Trip. The "ALARM" LED will flash upon Overfrequency operating
condition, with the overfrequency function selected as Alarm, and will self-reset, when
the operating condition clears. If Latched Alarm is selected, the "ALARM" LED will flash
during the overfrequency condition, and will stay "ON" after the condition clears until
reset command is initiated. The output relay #1 "Trip" will not operate if the Latched
Alarm or Alarm setting is selected. Any or all of output relays 3 to 6 can be selected to
operate when the Overfrequency function is selected as Latched Alarm, Alarm, or Trip.
OVERFREQ 1(2) PKP
Range: 40.00 to 70.00 Hz in steps of 0.01
Default: 60.50 Hz
This setting defines the Overfrequency pickup level, and it is usually set to a frequency
level considered dangerous for the stability of the system.
OVERFREQ 1(2) DELAY
Range: 0.1 to 600.0 s in steps of 0.1
Default: 2.0 s
This setting specifies the time delay before overfrequency operation.
OUTPUT RELAY 3 to 6
Range: Do Not Operate, Operate
Default: Do Not Operate
Any or all of output relays 3 to 6 can be selected to operate upon an Overfrequency
condition. The selection of relay outputs operation is available no matter whether the
Latched Alarm, Alarm, or Trip function is selected.
BLOCK 1/2/3
Range: Off, Contact Input 1 to 10[8], Virtual Input 1 to 32, Remote Input 1 to 32, Logic
Element 1 to 16
Default: Off
Three blocking inputs are provided in the menu for each of the two Overfrequency
elements. One blocking input "high" is enough to block the function. The available
selections for each block include Contact input, Virtual Input, Remote Input, or Logic
Element.
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS