• operating mode selections
• setting parameters
• digital inputs and logic signals
• measured and pre-processed frequency 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 df/dt>/< function.
Figure. 5.4.15 - 89. Simplified function block diagram of the df/dt>/< function.
Measured input
The rate-of-change of frequency protection function compares the measured df/dt>/< ratio to the pick-
up setting (given in Hz/s). The source of the measured frequency depends on the user-defined tracking
reference which can be changed from the
Frequency tab of the Measurement menu. There are three
(3) frequency references available:
• Frecuency reference 1: CT1IL1, CT2IL1, VT1U1, VT2U1
• Frecuency reference 2: CT1IL2, CT2IL2, VT1U2, VT2U2
• Frecuency reference 3: CT1IL3, CT2IL3, VT1U3, VT2U3.
Table. 5.4.15 - 144. Measurement inputs of the df/dt>/< function.
Signals
Description
Time base
VT1 U1, U2, U3
L-N voltages of the first voltage transformer
5 ms
VT2 U1, U2, U3
L-N voltages of the second voltage transformer
5 ms
General settings
The following general settings define the general behavior of the function. These settings are static i.e.
it is not possible to change them by editing the setting group.
A
AQ
Q-M257
-M257
Instruction manual
Version: 2.07
170
© Arcteq Relays Ltd
IM00021
Summary of Contents for AQ-M257
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