2 Functions
90
7UM61 Manual
C53000-G1176-C127-3
2.13.2 Setting Notes
General The forward active power protection is only effective and available if this function was
set on protective functions configuration (section 2.2, address 132, FORWARD POWER
= to Enabled. If the function is not required Disabled is set. The address 3201
FORWARD POWER serves to switch the function ON or OFF or to block only the trip
command (Block relay).
Pickup Values,
Time Delays
The setting of the forward power protection depends very much on the intended pur-
pose. General setting guidelines are not possible. The pickup values are set in percent
of the secondary apparent power rating S
Nsec
= √3 · U
Nsec
· I
Nsec
. Consequently, the
machine power must be converted to secondary quantities:
with
Psec Secondary power corresponding to setting value
S
Nsec
Secondary rated power = √3 · U
Nsec
· I
Nsec
P
Mach
Machine power corresponding to setting value
S
N, Mach
Nominal apparent power of the machine
U
N, Mach
Nominal voltage of the machine
I
N Mach
Nominal current of the machine
U
N prim
Primary Nominal Voltage of the voltage transformers
I
N prim
Nominal primary CT current
Address 3202 serves to set the threshold of the forward power to an undershoot (Pf<)
and address 3204 (Pf>) serves to set it to overshoot. Addresses 3203 T-Pf< and
3205 T-Pf> serve to set the associated time delays.
In address 3206 MEAS. METHOD the user can select whether a fast or a precise mea-
suring procedure is to be used for the forward power calculation. In most cases, the
precise measuring procedure is preferred in the power station sector (as a rule),
whereas the fast procedure is applied for use as mains decoupling.
The set times are additional time delays not including the operating times (measuring
time, drop-out time) of the protective function.
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