Siemens SIPROTEC 4 7UT6 Series Manual page 293

rent power, this option is preferred and the phase-angle errors of the current and voltage transformers must
be compensated by means of the respective setting of the error angle in address 803 CORRECT. U Ang
(Section 2.1.4 Power System Data
Irrespective of which measuring value or calculated value was supposed to be determined by a flexible func-
tion, determine under Pickup whether the function is supposed to pick up on exceeding or undershooting the
limit value, which shall be set at a later stage.
Function Setting
Under Function a flexible function can be activated or deactivated. If message only is set, this function only
triggers a message and not a trip command. The command can be blocked if the function is activated (block.
relay).
Enter the pickup value pickup threshold in a suitable dimension for the function. The dimension automati-
cally appears in accordance with the above configured specifications of the evaluated value. The setting with
regard to whether the limit value is to be monitored on exceeding or undershooting, has already been deter-
mined by the configuration settings.
The pickup and the drop-off of the fault detection can be delayed. Delay of the pickup means that after
noncompliance with the limit value condition, this period must first expire before a pickup can be indicated
and result in further actions. Delay of the drop-off means that, after activated pickup, same can be main-
tained and delayed by such time period after non-compliance of the limit value has stopped.
The trip command (if desired) is thus delayed by means of the trip command delay. The time starts on activa-
tion of the pickup (if necessary, also after time delay). Please note that the command delay must be set in
such manner that it is significantly longer than a possibly set reset delay. Otherwise, every pickup will result in
a trip because the pickup for the reset delay is maintained, although the criterion to be monitored is no longer
complied with.
Please also note that the set times are pure additional delays that do not include the inherent operating time
of the function (functional internal pickup and drop-off times). This has an effect especially on accurate power
functions as these carry out measurements over 16 network period.
The dropout ratio can be set to wide ranges. If functions react on exceeding a limit value, such value is smaller
than 1; if the functions that react on undershooting the limit value, such value is greater than 1. The possible
setting range is automatically determined in accordance with the function, which has either been configured
to exceeding or undershooting.
The drop-out ratio to be set depends on the application. In general, it can be stated that: the limit value must
be closer to 1 the lesser the pickup value differs from the operating valid values. Latching of the pickup due to
short-term fluctuations of the measured values during operation must be avoided.
Conversely, the drop-out ratio should not be set more sensitive (closer to 1) than necessary, thus avoiding an
intermitting pickup to be caused in conditions close to the pickup value.
Apart from internal blockings that, for example, are activated outside the working range of the functions,
internal monitoring of the measured values can lead to the blocking of a flexible function.
If a flexible function has been configured in such manner that it reacts on the processing of voltages (voltage
or power), a blocking on failure of measured voltages can be effected. This applies to undervoltage func-
tions and exceeding of power components, but also to the detection of negative sequence and zero systems.
However, there may be cases where overfunctioning is preferred to underfunctioning. In such case set to no.
A blocking on voltage failure is usually not required for overvoltage functions.
If a flexible function is configured in such manner that it reacts on the processing of currents (current or
power), a blocking on wire break in the current path can be effected. This applies to undercurrent functions
and exceeding of power components, but also to the detection of negative sequence and zero systems.
However, there may be cases where overfunctioning is preferred to underfunctioning. In such case set to no.
A blocking on wire break in the current path in overcurrent functions is usually not required.
Additional Steps
If an additional flexible function has been created, configured and set, the corresponding indications are
entered in the DIGSI configuration matrix. These indications are kept general and assign the ld. number to the
flexible functions, e.g. "Flx01 Pickup L1". You can now change their names to texts in accordance with your
application.
Thereafter, configure these indications to binary inputs/outputs, if required.
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
1).
Functions
2.22 Auxiliary Functions
293