Figure. 5.4.21 - 115. Pick-up levels in the two modes.
Just like the other overcurrent protection functions, this function can be set to definite time (DT) or
inverse definite minimum time (IDMT) delay. However, if IDMT is selected for this function, the time
delay depends on the ratio between the measured current and the current pick-up level at
that moment. This means that the operation time can also shorten as a result of the reduced voltage.
The operational logic consists of the following:
• input magnitude processing
• saturation check
• threshold comparator
• block signal check
• time delay characteristics
• output processing.
The basic design of the protection function is the three-pole operation.
The inputs for the function are the following:
• operating mode selections
• setting parameters
• digital inputs and logic signals
• measured and pre-processed current magnitudes.
The function's outputs are START, TRIP and BLOCKED signals which can be used for direct I/O
controlling and user logic programming. The function generates general time-stamped ON/OFF events
to the common event buffer from each of the three (3) output signals. In the instant operating mode the
function outputs START and TRIP events simultaneously with an equivalent time stamp. The time stamp
resolution is 1 ms. The function also provides a resettable cumulative counter for the START, TRIP and
BLOCKED events.
The following figure presents a simplified function block diagram of the non-directional
overcurrent function.
Genera
Generattor Commander
or Commander
Instruction manual
Version: 2.07
224
© Arcteq Relays Ltd
IM00001
Summary of Contents for Generator Commander
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