indicated by function Protection output
FRQ_ADP_FAIL
. When frequency adaptivity
uses backup frequency source, the
FRQ_ADP_BU
output is activated. The tracked
frequency is retained for 3 seconds until the
FRQ_ADP_FAIL
output is activated
and Rated frequency is expected. Outputs
FRQ_ADP_FAIL
,
FRQ_ADP_BU
and
FRQ_ADP_WARN
can be used in the application configuration, if necessary.
See function block Protection for more information.
The operation accuracy of the protection functions in the range of 0.2...1.5 xFn
can be assumed to be according to the technical data given separately for each
function. Slight deviations in operation accuracy are possible outside the frequency
range specified in technical data. Operate time accuracy and reset times given in
technical data are only valid in the frequency range specified for each function.
The specified operate times are expected to increase at lower frequency due to
longer network cycles.
Frequency adaptivity depends on the availability of voltages or currents. The
generator start-up protection can be also extended by using wide peak-to-peak
measurement mode (operational from 2 Hz upward) with designated start-up
overcurrent protection function (PHLPTOC). Before the generator is connected with
the rest of the network by closing the circuit breaker, the designated start-up
overcurrent function should be either blocked or its start value increased, as the
Start value setting is typically lower than the nominal current.
11.6
Measurement modes
In many current or voltage dependent function blocks, there are various alternative
measuring principles.
• RMS
• DFT which is a numerically calculated fundamental component of the signal
• Peak-to-peak
• Peak-to-peak with peak backup
• Wide peak-to-peak
Consequently, the measurement mode can be selected according to the application.
In extreme cases, for example with high overcurrent or harmonic content, the
measurement modes function in a slightly different way. The operation accuracy
is defined with the frequency range of f/fn=0.95...1.05. In peak-to-peak and RMS
measurement modes, the harmonics of the phase currents are not suppressed,
whereas in the fundamental frequency measurement the suppression of harmonics
is at least -50 dB at the frequency range of f= n x fn, where n = 2, 3, 4, 5,...
RMS
The RMS measurement principle is selected with the
Measurement mode setting
using the value "RMS". RMS consists of both AC and DC components. The AC
component is the effective mean value of the positive and negative peak values.
RMS is used in applications where the effect of the DC component must be taken
into account.
RMS is calculated according to the formula:
General function block features
1MRS759142 F
1908
REX640
Technical Manual