5-68 750/760 Feeder Management Relay GE Multilin
5.6 S5 PROTECTION 5 SETPOINTS
5
5.6.8 FREQUENCY
a) MAIN MENU
PATH: SETPOINTS ÖØ S5 PROTECTION ÖØ FREQ
The 750/760 can be used as the primary detecting relay in automatic load shedding schemes based on underfrequency.
The need for such a relay arises if during a system disturbance, an area becomes electrically isolated from the main sys-
tem and suffers a generation deficiency due to the loss of either transmission or generation facilities. If reserve generation
is not available in the area, conditions of low system frequency will occur which may lead to a complete collapse. The 750/
760 provides two underfrequency and one rate-of-change of frequency protection elements which can automatically dis-
connect sufficient load to restore an acceptable balance between load and generation.
b) UNDERFREQUENCY
PATH: SETPOINTS ÖØ S5 PROTECTION ÖØ FREQ ÖØ UNDERFREQ 1(2)
There are two identical underfrequency protection elements, ANSI devices 81U-1 and 81U-2. The setpoints for the Under-
frequency 1 element are shown above; the Underfrequency 2 setpoints are identical.
• MIN OPERATING CURRENT: Enter the minimum voltage required to allow the underfrequency element to operate.
This setpoint is used to prevent incorrect operation before energization of the source to the relay location, and during
voltage dips.
• MIN OPERATING CURRENT: Enter the minimum value of current required on any phase to allow the underfrequency
element to operate. This setpoint is used to prevent underfrequency tripping during periods of light load, when this
action would have an insignificant effect on the system.
îš„ FREQ
îš„ [ENTER] for more
îš„ UNDEFREQ 1
îš„ [ENTER] for more
See below.
îš„ UNDEFREQ 2
îš„ [ENTER] for more
îš„ FREQ DECAY
îš„ [ENTER] for more
See page 5–70.
îš„ UNDEFREQ 1
îš„ [ENTER] for more
UNDEFREQ 1
FUNCTION: Disabled
Range: Disabled, Trip, Alarm, Latched Alarm, Control
UNDEFREQ 1
RELAYS (3-7): -----
Range: Any combination of 3 to 7 Auxiliary relays
See 5.6.1: Overview on page 5–32 for details.
UNDEFREQ 1
PICKUP: 59.00 Hz
Range: 20.00 to 65.00 Hz in steps of 0.01
See 5.6.1: Overview on page 5–32 for details.
UNDEFREQ 1
DELAY: 2.00 s
Range: 0.00 to 600.00 s in steps of 0.1
See 5.6.1: Overview on page 5–32 for details.
MIN OPERATING
VOLTAGE: 0.70 x VT
Range: 0.00 to 1.25 x VT in steps of 0.01
MIN OPERATING
CURRENT: 0.20 x CT
Range: 0.00 to 1.25 x CT in steps of 0.01
ENTER
ESCAPE
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ENTER
ESCAPE
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MESSAGE
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Courtesy of NationalSwitchgear.com
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