The load jam protection function uses a total of eight (8) separate setting groups which can be
selected from one common source.
The function can operate on instant or time-delayed mode. In the time-delayed mode the operation can
be set to definite time (DT) delay.
The inputs for the function are the following:
• 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 cumulative counter for the START, TRIP and BLOCKED
events.
The following figure presents a simplified function block diagram of the load jam protection function.
Figure. 5.4.21 - 107. Simplified function block diagram of the Im> function.
Measured input
The function block uses analog current measurement values and uses RMS phase current
measurements. A -20 ms averaged value of the selected magnitude is used for pre-fault data
registering.
Table. 5.4.21 - 177. Measurement inputs of the Im> function.
Signal
Description
Time base
IL1RMS
RMS measurement of phase L1 (A) current
5ms
IL2RMS
RMS measurement of phase L2 (B) current
5ms
IL3RMS
RMS measurement of phase L3 (C) current
5ms
The selection of the used AI channel is made with a setting parameter. In all possible input channel
variations the pre-fault condition is presented with a 20 ms averaged history value from -20 ms from
a START or TRIP event.
A
AQ
Q-M257
-M257
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
IM00021
211
Summary of Contents for AQ-M257
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