Functions
2.23 Frequency Protection (ANSI 81)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
182
Figure 2-75 Logic diagram of the frequency protection
2.23.2 Setting Notes
General
Frequency protection is only in effect and accessible if address 142 FREQUENCY Prot. is set to Enabled
during configuration of protective functions. 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
By 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 overvoltage or undervoltage protec-
tion. Set the pickup threshold lower than nominal frequency if the element is to be used for underfrequency
protection. Set the pickup threshold higher than nominal frequency if the element is to be used for overfrequen-
cy protection.
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.
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