ABB RELION 670 Series Technical Manual page 671

1MRK 502 066-UUS B
Section 10
10.1 Underfrequency protection SAPTUF (81)
10.1.1 Identification
Function description
Underfrequency protection
10.1.2 Functionality
Underfrequency occurs as a result of a lack of generation in the network.
Underfrequency protection SAPTUF (81) measures frequency with high accuracy, and is used for
load shedding systems, remedial action schemes, gas turbine startup and so on. Separate definite
time delays are provided for trip and restore.
SAPTUF (81) is provided with undervoltage blocking.
The operation is based on positive sequence voltage measurement and requires two phase-phase
or three phase-neutral voltages to be connected. For information about how to connect analog
inputs, refer to Application manual/IED application/Analog inputs/Setting guidelines
10.1.3 Function block
V3P*
BLOCK
BLKTRIP
BLKREST
ANSI06000279 V2 EN-US
Figure 361: SAPTUF (81) function block
Technical manual
Frequency protection
SAPTUF (81)
TRIP
PICKUP
RESTORE
BLKDMAGN
FREQ
ANSI06000279-2-en.vsd
IEC 61850 IEC 60617
identification identification
SAPTUF
f <
SYMBOL-P V1 EN-US
Frequency protection
ANSI/IEEE C37.2
device number
81
Section 10
IP15746-1 v3
M14865-1 v5
M13349-3 v12
M13352-3 v6
665