Siemens Siprotec 7UM611, Руководство пользователя

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2.19 Rate-of-Frequency-Change Protection df/dt (ANSI 81R)
119
7UM61 Manual
C53000-G1176-C127-3
Figure 2-37 Logic Diagram of the Rate-of-Frequency-Change Protection
2.19.2 Setting Notes
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
.
Address
4501 df/dt Protect.
serves 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
4502 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 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
active power. The frequency drops and leads to a negative frequency change.
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