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1MRK 505 288-UEN A
Technical manual
input connected. The signal received by SMAI is processed internally and in total 244
different electrical parameters are obtained for example RMS value, peak-to-peak,
frequency and so on. The activation of BLOCK input resets all outputs to 0.
SMAI_20 does all the calculation based on nominal 20 samples per line frequency
period, this gives a sample frequency of 1 kHz at 50 Hz nominal line frequency and 1.2
kHz at 60 Hz nominal line frequency.
The output signals AI1...AI4 in SMAI_20_x function block are direct outputs of the
connected input signals GRPxL1, GRPxL2, GRPxL3 and GRPxN. GRPxN is always
the neutral current. If GRPxN is not connected, the output AI4 is zero. The AIN output
is the calculated residual quantity, obtained as a sum of inputs GRPxL1, GRPxL2 and
GRPxL3 but is equal to output AI4 if GRPxN is connected. The outputs signal AI1,
AI2, AI3 and AIN are normally connected to the analog disturbance recorder.
The SMAI function block always calculates the residual quantities in
case only the three phases (Ph-N) are connected (GRPxN input not
used).
The output signal AI3P in the SMAI function block is a group output signal
containing all processed electrical information from inputs GRPxL1, GRPxL2,
GRPxL3 and GRPxN. Applications with a few exceptions shall always be connected
to AI3P.
The input signal REVROT is used to reverse the phase order.
A few points need to be ensured for SMAI to process the analog signal correctly.
•
It is not mandatory to connect all the inputs of SMAI function. However, it is very
important that same set of three phase analog signals should be connected to one
SMAI function.
•
The sequence of input connected to SMAI function inputs GRPxL1, GRPxL2,
GRPxL3 and GRPxN should normally represent phase L1, phase L2, phase L3
and neutral currents respectively.
•
It is possible to connect analog signals available as Ph-N or Ph-Ph to SMAI.
ConnectionType should be set according to the input connected.
•
If the GRPxN input is not connected and all three phase-to-earth inputs are
connected, SMAI calculates the neutral input on its own and it is available at the
AI3P and AIN outputs. It is necessary that the ConnectionType should be set to
Ph-N.
•
If any two phase-to-earth inputs and neutral currents are connected, SMAI
calculates the remaining third phase-to-neutral input on its own and it is available
at the AI3P output. It is necessary that the ConnectionType should be set to Ph-
N.
•
If any two phase-to-phase inputs are connected, SMAI calculates the remaining
third phase-to-phase input on its own. It is necessary that the ConnectionType
should be set to Ph-Ph.
Section 15
Basic IED functions
483
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