Siemens SIPROTEC 7RW80 Manual page 86

Functions
2.6 Flexible Protection Functions
Settings
The pickup thresholds, delay times and dropout ratios of the flexible protection function are set in the „Settings"
dialog box in DIGSI.
The pickup threshold of the function is configured via parameter . The OFF-command delay time is set via pa-
rameter T TRIP DELAY. Both setting values must be selected according to the required application.
The pickup can be delayed via parameter T PICKUP DELAY. This parameter is usually set to zero (default
setting) in protection applications, because a protection function should pick up as quickly as possible. A setting
deviating from zero may be appropriate if a trip log is not desired to be started upon each short-term exceeding
of the pickup threshold, for example, when a function is not used as a protection, but as a monitoring function.
The dropout of pickup can be delayed via parameter T DROPOUT DELAY. This setting is also set to zero by
default (standard setting) A setting deviating from zero may be required if the device is utilized together with
electro-magnetic devices with considerably longer dropout ratios than the digital protection device (see Chapter
2.2 for more information). When utilizing the dropout time delay, it is recommended to set it to a shorter time
than the OFF-command delay time in order to avoid both times to "race".
Parameter BLK.by Vol.Loss determines whether a function, with measured variable based on a voltage
measurement (measured variables voltage), should be blocked in case of a measured voltage failure/loss of
potential (set to YES) or not (set to NO).
The dropout ratio for the function can be set via the parameter DROPOUT RATIO. The standard dropout ratio
of protection functions is 0.95 (default setting). If the dropout ratio is decreased, it would be sensible to test the
pickup of the function regarding possible "chatter".
The dropout difference of the frequency elements is set under parameter DO differential. Usually, the
default setting of 0.02 Hz can be retained. A higher dropout difference should be set in weak systems with
larger, short-term frequency fluctuations to avoid chattering of the message.
The frequency change measured value (df/dt) works with a fixed dropout difference of 0.1 Hz/s.
Renaming Messages, Checking Configurations
After parameterization of a flexible function, the following steps should be noted:
• Open matrix in DIGSI
• Rename the neutral message texts in accordance with the application.
• Check configurations on contacts and in operation and fault buffer, or set them according to the require-
ments.
86
SIPROTEC, 7RW80, Manual
C53000-G1140-C233-1, Release date 10.2010