5-68
745 Transformer Management Relay
GE Multilin
5.6 S4 ELEMENTS
5 SETPOINTS
5
5.6.10 FREQUENCY
a) MAIN MENU
PATH: SETPOINTS
ÖØ
S4 ELEMENTS
ÖØ
FREQUENCY
The 745 can be used as the primary detecting relay in automatic load shedding schemes based on underfrequency. This
need arises if, during a system disturbance, an area becomes electrically isolated from the main system and suffers gener-
ation deficiency due to loss of either transmission or generation facilities. If reserve generation is not available in the area,
conditions of low system frequency occur that may lead to a complete collapse. The 745 provides a means of automatically
disconnecting sufficient load to restore an acceptable balance between load and generation.
The 745 uses both frequency and frequency rate-of-change as the basis for its operating criteria. These measured values
are based on the voltage input or, if voltage is disabled, the Winding 1 Phase A current input. The relay has two (2) under-
frequency and four (4) rate-of-change levels. Thus, four or more separate blocks of load can be shed, according to the
severity of the disturbance.
In addition to these elements, the 745 has an overfrequency element. A significant overfrequency condition, likely caused
by a breaker opening and disconnecting load from a particular generation location, can be detected and used to quickly
ramp the turbine speed back to normal. If this is not done, the overspeed can lead to a turbine trip which would require a
turbine start up before restoring the system. If the turbine speed can be controlled successfully, system restoration can be
much quicker. The overfrequency element of the 745 can be used for this purpose at a generating location.
We strongly recommend the use of either the voltage, current, or both, signals for supervision. If no super-
vising conditions are enabled, the element could produce
undesirable operation
!
b) UNDERFREQUENCY
PATH: SETPOINTS
ÖØ
S4 ELEMENTS
ÖØ
FREQUENCY
Ö
UNDERFREQUENCY 1(2)
FREQUENCY
[ENTER] for more
UNDERFREQUENCY 1
[ENTER] for more
See below.
UNDERFREQUENCY 2
[ENTER] for more
See below.
FREQUENCY DECAY
[ENTER] for more
See page 5–70.
OVERFREQUENCY
[ENTER] for more
See page 5–71.
UNDERFREQUENCY 1
[ENTER] for more
UNDERFREQUENCY 1
FUNCTION: Disabled
Range: Enabled, Disabled
UNDERFREQUENCY 1
TARGET: Self-Reset
Range: Self-Reset, Latched, None
CURRENT SENSING:
Enabled
Range: Enabled, Disabled
MINIMUM OPERATING
CURRENT: 0.20 x CT
Range: 0.20 to 1.00 x CT in steps of 0.01
MINIMUM OPERATING
VOLTAGE: 0.50 x VT
Range: 0.10 to 0.99 x CT in steps of 0.01
UNDERFREQUENCY 1
PICKUP: 59.00 Hz
Range: 45.00 to 59.99 Hz in steps of 0.01
UNDERFREQUENCY 1
DELAY: 1.00 s
Range: 0.00 to 600.00 s in steps of 0.01
UNDERFREQUENCY 1
BLOCK: Disabled
Range: Logc Inpt 1 to 16, Virt Inpt 1 to 16, Output Rly 2 to
8, SelfTest Rly, Vir Outpt 1 to 5, Disabled
ENTER
ESCAPE
ð
ð
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
NOTE
ENTER
ESCAPE
ð
ð
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
Содержание TRANSFORMER MANAGEMENT RELAY 745
Страница 2: ...Courtesy of NationalSwitchgear com ...