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ABB | SACE Tmax XT

7 - ROCOF protections
The ROCOF Protection package can be configured in all models as additional SW package.
The protection is described below:

ROCOF Protection Function
ROCOF protection protects against rapid frequency variations: the protection sends a TRIP command if
t the frequency changes faster than control variation f28 set in the unit for longer than t28.
f28 ROCOF

f(Hz) Frequency variation
t28
after failure (1)
Hz/s Frequency fluctuation
(after a failure)
f28
f mis

t28 t(s)

Figure 22
(1) example with positive linear variation of the higher frequency of the set f28 value; the protection
also manages negative variations

The protection excludes itself if the maximum value of the line-to-line voltage is less than 30 V.
To check and simulate the trip times in relation to all the parameters, please consult:
• summary table of the protections with the operating characteristics (page 77)
• the graph with trip curve (page 92)
Parameters
Parameter Description Default
Activates/deactivates the protection and its availability in the
Enable OFF
parameters menu
Activates/deactivates transmission of the open command: if disabled,
Trip Enable the alarm and exceedance of protection time are only managed as OFF
information
establishes the maximum admissible frequency variation rate over
Threshold time; the protection trips if this rate is exceeded. 0,6 Hz/s
f28 The value is given as absolute value (Hz/s) Fn) and can be set within
the range: 0.4 Hz/s to 10 Hz/s in 0.2 Hz/s steps
Trip Establishes whether the protection monitors an increase (Up), a Up or Down
Direction decrease (Down) or both variations (Up and Down)
This is the trip time of the protection; the value is given in seconds
Time f28 0,5 s
and can be set within a range: 0.06 s to 300 s, in 0.01 s steps
Limitations and additional functions
The block functions can also be accessed by means of the service connector (via Ekip Connect) or by
connection to the system bus (page 70).

61 | © 2022 ABB | 1SDH002031A1002 - ECN000212994 Protections | 7 - ROCOF protections