Table of Contents

Siemens / Underfrequency protection (ANSI 81U) _ Setting & highlights _ SI5054

Table of Contents

Overview

The “Underfrequency protection” function is used to detect underfrequencies in electrical power systems or machines, monitor the frequency band and output failure indications, decouple power systems, load shedding to ensure power system stability and protect motors, and disconnect generating units when the power system frequency is critical (for example, f < 0.95 frated).

For more detailed information on “Underfrequency protection” function, refer to SIPROTEC 5 devices, V8.30 & higher manuals.

To see other supported functions, click here.


Structure/Embedding of the Function

Structure/Embedding of the Underfrequency protection Function

Setting Parameters


Setting parameters for Underfrequency protection

Addr. Parameter C Setting Options Default Setting
General
_:2311:101 General:Minimum voltage   3.000 V to 175.000 V 37.500 V
_:2311:109 General:Dropout differ- ential   20 mHz to 2000 mHz 20 mHz
Stage 1
_:61:1 Stage 1:Mode   off
on
test
off
_:61:2 Stage 1:Operate & flt.rec. blocked   no
yes
no
_:61:3 Stage 1:Threshold   30.00 Hz to 70.00 Hz 49.80 Hz
_:61:6 Stage 1:Operate delay   0.00 s to 600.00 s 10.00 s
Stage 2
_:62:1 Stage 2:Mode   off
on
test
off
_:62:2 Stage 2:Operate & flt.rec. blocked   no
yes
no
_:62:3 Stage 2:Threshold   30.00 Hz to 70.00 Hz 47.50 Hz
_:62:6 Stage 2:Operate delay   0.00 s to 600.00 s 10.00 s
Stage 3
_:63:1 Stage 3:Mode   off
on
test
off
_:63:2 Stage 3:Operate & flt.rec. blocked   no
yes
no
_:63:3 Stage 3:Threshold   30.00 Hz to 70.00 Hz 47.00 Hz
_:63:6 Stage 3:Operate delay   0.00 s to 600.00 s 10.00 s

Logic Diagrams & highlights


Logic Diagram of the Underfrequency-Protection Stage

Logic Diagram of the Underfrequency-Protection Stage

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