Siemens Siprotec 7UM611 User Manual

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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Siemens Siprotec 7UM611 Specifications

General

Brand	Siemens
Model	Siprotec 7UM611
Category	Relays
Language	English