Settings - Siemens SIPROTEC 4 User Manual

On all three-phase connections and single-phase connections of a phase-to-phase voltage, the threshold must
be set as a phase-to-phase value. With a single phase-to-ground connection the threshold must be set as a
phase voltage.
Pickup Values
The setting as overfrequency or underfrequency element does not depend on the parameter threshold values
of the respective element. An element can also function, for example, as an overfrequency element if its
threshold value is set below the nominal frequency and vice versa.
If frequency protection is used for load shedding purposes, the setting values depend on the actual power
system conditions. Normally, a time coordinated load shedding is required that takes into account the impor-
tance of the consumers or consumer groups.
Further application examples exist in the field of power stations. Here too, the frequency values to be set
mainly depend on the specifications of the power system / power station operator. The underfrequency
protection safeguards the power station's own demand by disconnecting it from the power system on time.
The turbo governor 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 the apparent power is reduced by the same degree, turbine-driven generators can,
as a rule, be continuously operated down to 95% of the nominal frequency. However, for inductive
consumers, the frequency reduction not only means an increased current input, but also endangers stable
operation. For this reason, only a short-term frequency reduction down to about 48 Hz (for fN = 50 Hz) or 58
Hz (for fN = 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 an island network). In this way, the frequency increase protection can, for example, be used as over-
speed protection.
Dropout Thresholds
The dropout threshold is defined via the adjustable dropout-difference address 5415 DO differential. It
can thus be adjusted to the network conditions. The dropout difference is the absolute-value difference
between pickup threshold and dropout threshold. The default value of 0.02 Hz can usually remain. Should,
however, frequent minor frequency fluctuations be expected, this value should be increased.
Time Delays
The delay times 81-1 DELAY to 81-4 DELAY (addresses 5405, 5408, 5411 and 5414) allow the frequency
elements to be time coordinated, e.g. for load shedding equipment. The set times are additional delay times
not including the operating times (measuring time, dropout time) of the protection function.

Settings

2.9.3
Addresses which have an appended "A" can only be changed with DIGSI, under "Additional Settings".
Addr. Parameter
5401 FCT 81 O/U
5402 Vmin
5403 81-1 PICKUP
5404 81-1 PICKUP
5405 81-1 DELAY
5406 81-2 PICKUP
5407 81-2 PICKUP
5408 81-2 DELAY
5409 81-3 PICKUP
5410 81-3 PICKUP
SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016
Setting Options
OFF
ON
10 .. 150 V
40.00 .. 60.00 Hz
50.00 .. 70.00 Hz
0.00 .. 100.00 sec; ∞
40.00 .. 60.00 Hz
50.00 .. 70.00 Hz
0.00 .. 100.00 sec; ∞
40.00 .. 60.00 Hz
50.00 .. 70.00 Hz
Default Setting Comments
OFF 81 Over/Under Frequency Protec-
tion
65 V Minimum required voltage for
operation
49.50 Hz 81-1 Pickup
59.50 Hz 81-1 Pickup
60.00 sec 81-1 Time Delay
49.00 Hz 81-2 Pickup
59.00 Hz 81-2 Pickup
30.00 sec 81-2 Time Delay
47.50 Hz 81-3 Pickup
57.50 Hz 81-3 Pickup
Functions
2.9 Frequency Protection 81 O/U
165