2 Functions
110
7UM61 Manual
C53000-G1176-C127-3
Figure 2-33
Logic diagram of the frequency protection
2.17.2 Setting Notes
General
Frequency protection is only effective and available if address
142
FREQUENCY
Prot.
is set to
Enabled
during configuration. If the function is not required
Disabled
is set. Address
4201
O/U FREQUENCY
serves to switch the function
ON
or
OFF
or to block only the trip command (
Block relay
).
Pickup Values
Configuring the rated frequency of the power system and the frequency threshold for
each of the stages
f1 PICKUP
to
f4 PICKUP
in each case the function is established
as either overfrequency or underfrequency protection. If the threshold is configured as
below rated frequency, underfrequency protection is involved. If the threshold is con-
figured as above rated frequency, overfrequency protection is implemented.
Note
If the threshold is set equal to the nominal frequency, the element is inactive.
For the f4 frequency stage, the former applies only if the parameter
4214
THRESHOLD
f4
is set to
automatic
(default setting). If desired, this parameter can also be set to
f>
or
f<
, in which case the evaluation direction (increase or decrease detection) can
be specified independent of the parametrized
f4 PICKUP
threshold.
If frequency protection is used for network decoupling and load shedding purposes,
settings depend on the actual network conditions. Normally a graded load shedding is
strived for that takes into account priorities of consumers or consumer groups.
Further application examples are covered under power stations. The frequency values
to be set mainly depend, also in these cases, on power system/power station operator
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