Functions
2.23 Frequency Protection (ANSI 81)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
183
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 specifications. In this context, frequency decrease
protection ensures the power station's own demand by disconnecting it from the power system on time. The
turbo regulator regulates the machine set to the nominal speed. Consequently, the station's own demands can
be continuously supplied at nominal frequency.
Under the assumption that apparent power is reduced to the same degree, turbine-driven generators can, as
a rule, be continuously operated down to 95 % of nominal frequency. However, for inductive consumers, the
frequency reduction not only means greater current consumption but also endangers stable operation. For this
reason, only a short-time frequency reduction down to about 48 Hz (for f
N
= 50 Hz) or 58 Hz (for f
N
= 60 Hz) is
permissible.
A frequency increase can, for example, occur due to a load shedding or malfunction of the speed regulation
(e.g. in a stand-alone system). In this way, the frequency increase protection can, for example, be used as over-
speed protection.
Setting example:
Time Delays
The delay times T f1 to T f4 entered at addresses 4204, 4207, 4210 and 4213) allow the frequency stages
to be graded. The set times are additional delay times not including the operating times (measuring time,
dropout time) of the protective function.
Minimum Voltage
Address 4215 Umin is used to set the minimum voltage which, if undershot, blocks frequency protection. A
value of approx. 65 % U
N
is recommended. The parameter value is based on phase-to-phase voltages. The
minimum voltage threshold can be deactivated by setting this address to 0.
2.23.3 Settings
Stage Cause Settings
for f
N
= 50 Hz for f
N
= 60 Hz Delay
f1 Disconnection from the
network
48.00 Hz 58.00 Hz 1.00 sec
f2 Shutdown 47.00 Hz 57.00 Hz 6.00 sec
f3 Warning 49.50 Hz 59.50 Hz 20.00 sec
f4 Alarm or tripping 52.00 Hz 62.00 Hz 10.00 sec
Addr. Parameter Setting Options Default Setting Comments
4201 O/U FREQUENCY OFF
ON
Block relay
OFF Over / Under Frequency Protec-
tion
4202 f1 PICKUP 40.00 .. 66.00 Hz 48.00 Hz f1 Pickup
4203 f1 PICKUP 40.00 .. 66.00 Hz 58.00 Hz f1 Pickup
4204 T f1 0.00 .. 600.00 sec 1.00 sec T f1 Time Delay
4205 f2 PICKUP 40.00 .. 66.00 Hz 47.00 Hz f2 Pickup
4206 f2 PICKUP 40.00 .. 66.00 Hz 57.00 Hz f2 Pickup
4207 T f2 0.00 .. 100.00 sec 6.00 sec T f2 Time Delay
4208 f3 PICKUP 40.00 .. 66.00 Hz 49.50 Hz f3 Pickup
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