Setting Notes - Siemens SIPROTEC 4 7VE61 Manual

[logik-frequenzaenderungsschutzes, 1, en_GB]
Figure 2-43

Setting Notes

2.7.2
General
The rate-of-frequency-change protection is only effective and accessible if during the configuration address
145 df/dt Protect. has been set accordingly. 2 or 4 stages can be selected. The default setting is 2
df/dt stages.
At address 4501 df/dt Protect., the function ON or OFF can be set, or only the trip command can be
blocked (Block relay).
Pickup Values
The setting procedure is the same for all stages. In a first step, it must be determined whether the stage is to
monitor a frequency rise at f>f
address4502 df1/dt >/<. The pickup value is set as an absolute value at address 4503 STAGE df1/dt. The
setting of address 4502 informs the protection function of the applicable sign.
The pickup value depends on the application and is determined by power system conditions. In most cases, a
network analysis will be necessary. A sudden disconnection of loads leads to a surplus of active power. The
frequency rises and causes a positive frequency change. A failure of generators, on the other hand, leads to a
deficit of active power. The frequency drops and leads to a negative frequency change.
The following relations can be used as an example for estimation. They apply for the change rate at the begin-
ning of a frequency change (approx. 1 second).
SIPROTEC 4, 7VE61 and 7VE63, Manual
C53000-G1176-C163-3, Edition 10.2017
Logic diagram of the rate-of-frequency-change protection
or a frequency drop at f<f
N
2.7 Rate-of-frequency-change protection
. For stage 1, for instance, this setting is made at
N
Functions
93