Functions
168
7UM62 Manual
C53000-G1176-C149-3
Figure 2-78 Logic Diagram of the Rate-of-Frequency-Change Protection
2.24.2 Setting Hints
General
The rate-of-frequency-change protection is only effective and accessible if during the
configuration address
has been set accordingly. 2 or 4 stages
can be selected. The default setting is
Address
allows to switch the function ON or OFF, or to block
only the trip command (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
N
or a frequency drop at f< f
N
.
For stage 1, for instance, this setting is made at address
. The pick-
up value is set as an absolute value at address
. The setting of
address
informs the protection function of the applicable sign.
The pickup value depends on the application and is determined by power system con-
ditions. 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 ac-
tive power. The frequency drops and leads to a negative frequency change.
4503 STAGE df1/dt
>df1/dt block
5504
>df/dt block
5503
4518 U MIN
4504 T df1/dt
5512
df/dt BLOCKED
5514
df/dt U< block
5232
f1 picked up
ON
OFF
4505 df1/dt & f1
"1"
&
OR
+df/dt>
-df/dt<
4502 df1/dt >/<
"1"
&
&
OR
df/dt
df/dt
≤
f
≤
fn
df/dt
df/dt
≥
f
≥
fn
&
OR
U1
≤
U1
f1
f3
f2
f4
5520
df1/dt TRIP
5521
df2/dt TRIP
5522
df3/dt TRIP
5523
df4/dt TRIP
Tripping
matrix
Tmin TRIP
CMD
5516
df1/dt pickup
5517
df2/dt pickup
5518
df3/dt pickup
5519
df4/dt pickup
