Application Guide - NP900 Series
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A996A
The function can be operating on instant or time delayed mode. In time delayed mode the
operation can be selected for definite time or IDMT. For IDMT operation IEC and ANSI
standard time delays are supported as well as custom parameters.
The operational logic consists of input magnitude processing, input magnitude selection,
threshold comparator, block signal check, time delay characteristics and output
processing.
Inputs for the function are the operating mode selections, setting parameters and
measured and pre-processed current magnitudes and binary input signals. Function
outputs START, TRIP and BLOCKED signals which can be used for direct IO controlling
and also for user logic programming. The function registers its operation into 12 last time-
stamped registers and also generates general time stamped ON/OFF events to the
common event buffer from each of the three output signal. In instant operating mode the
function outputs START and TRIP events simultaneously with equivalent time stamp.
Time stamp resolution is 1ms. Function provides also cumulative counters for START,
TRIP and BLOCKED events.
In the following figure is presented the simplified function block diagram of the CUB
function.
Figure 3.2.7-46 Simplified function block diagram of the CUB function.
3.2.7.1
M
EASURED INPUT VALUES
Function block uses analog current measurement values. Function block utilizes
calculated positive and negative sequence currents. In broken conductor mode (I2/I1) also
the phase currents RMS value is used for the minimum current check. Zero sequence and
the component sequence angles are used for the fault registering and for fault analysis