10.2.7.3 Blocking
M14958-13 v6
It is possible to block overfrequency protection SAPTOF (81) partially or completely, by binary
input signals or by parameter settings, where:
BLOCK: blocks all outputs
BLKTRIP: blocks the TRIP output
If the measured voltage level decreases below the setting of
MinValFreqMeas
in the preprocessing
function both the PICKUP and the TRIP outputs are blocked.
10.2.7.4 Design
M14958-24 v8
The frequency measuring element continuously measures the frequency of the positive sequence
voltage and compares it to the setting
PUFrequency
. The frequency signal is filtered to avoid
transients due to switchings and faults in the power system. The time integrator operates due to
a definite delay time. The design of overfrequency protection SAPTOF (81) is schematically
described in figure
365.
Voltage
PICKUP
PICKUP
TRIP
Pickup
&
Trip
Output
Logic
Time integrator
Definite Time Delay
TimeDlyOperate
TimeDlyReset
Comparator
V < IntBlockLevel
BLOCK
en05000735_ansi.vsd
Frequency Comparator
f > PuFrequency
TRIP
BLKDMAGN
BLOCK
OR
BLKTRIP
ANSI05000735 V1 EN-US
Figure 365: Simplified logic diagram for SAPTOF (81)
Section 10 1MRK 502 066-UUS B
Frequency protection
674
Technical manual
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