4.8.1.3 Functionality
The underpower protection function 32U is used for protecting generators and prime
movers against the effects of very low power outputs or reverse power condition.
The function operates when the measured active power falls below the set value. The
operating characteristics are according to definite time DT.
This function contains a blocking functionality. It is possible to block the function outputs,
timer or the function itself, if desired.
4.8.1.4 Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are “Enable” and “Disable”.
The operation of 32U can be described using a module diagram. All the modules in the
diagram are explained in the next sections.
TRIP
PICKUP
Directional
calculation
Power
calculation
Level
detector
t
Timer
DISABLE
I_B
I_A
I
1
I_C
U_B_BC
U_A_AB
U
1
U_C_CA
Blocking
logic
BLOCK
GUID-C92BE6B7-2B96-404B-8C42-0FD29135B44C V1 EN
Figure 358: Functional module diagram
Power calculation
This module calculates the apparent power based on the selected voltage and current
measurements as described in Table 621. The Measurement mode setting determines
which voltage and current measurements are to be used.
It is also possible to use positive-sequence components for calculating apparent power,
which makes the determination of power insensitive to the possible asymmetry in currents
or voltages and corresponds to the real load of the prime mover of the generator.
Section 4 1MAC059074-MB A
Protection functions
718 615 series ANSI
Technical Manual
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