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4.5.6.2
Function block
24
I_C
TRIP
I_B
I_A
V_A_AB
I
1
PICKUP
BLK_RESTART
COOL_ACTIVE
V
1
V_C_CA
V_B_BC
F
BLOCK
GUID-0ED14E17-5F46-4005-8254-65E0038E2F2B V1 EN
Figure 319:
Function block
4.5.6.3
Functionality
The overexcitation protection function 24 is used to protect generators and power
transformers against an excessive flux density and saturation of the magnetic core.
The function calculates the V/f ratio (volts/hertz) proportional to the excitation level of the
generator or transformer and compares this value to the setting limit. The function picks
up when the excitation level exceeds the set limit and trips when the set tripping time has
elapsed. The tripping time characteristic can be selected to be either definite time (DT) or
overexcitation inverse definite minimum time (overexcitation type IDMT).
This function contains a blocking functionality. It is possible to block the function outputs,
reset timer or the function itself, if desired.
4.5.6.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of 24 can be described using a module diagram. All the modules in the
diagram are explained in the next sections.
Section 4
1MAC059074-MB A
Protection functions
642
615 series ANSI
Technical Manual
Содержание Relion 615 series
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