Rocof Protections - ABB SACE Tmax XT7 Operation And Maintenance Manual

12 - ROCOF protections

ROCOF Protection
t
f28
69 | © 2020 ABB | 1SDH001821A1002 - ECN000135670
The ROCOF Protection package is available by default for Ekip G Hi-Touch and configurable in the remaining
models as additional SW package
The protection is described below:
Function
ROCOF protection protects against rapid frequency variations: the protection sends a TRIP command if the
frequency changes faster than control variation f28 set in the unit for longer than t28.
ROCOF
f(Hz)
t28
Hz/s
f
mis
Figure 30
(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 89)
• the graph with trip curve (page 106)
Parameters
Parameter Description
Activates/deactivates the protection and its availability in the parameters
Enable
menu
Activates/deactivates transmission of the open command: if disabled, the
Trip Enable
alarm and exceedance of protection time are only managed as information
establishes the maximum admissible frequency variation rate over time; the
protection trips if this rate is exceeded.
Threshold 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
Establishes whether the protection monitors an increase (Up), a decrease
Trip Direction
(Down) or both variations (Up and Down)
This is the trip time of the protection; the value is given in seconds and can
Time f28
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 78).
Frequency fluctuation
(after a failure)
Frequency variation
after failure
(1)
f
28
t t
28 (s)
Protections | 12 - ROCOF protections
ABB | SACE Tmax XT
Default
OFF
OFF
0,6 Hz/s
Up or Down
0,5 s