Pick-up
The
I
set
and
I0
set
setting parameters control the current-dependent pick-up and activation of the
current transformer supervision function. They define the minimum and maximum allowed measured
current before action from the function. The function constantly calculates the ratio between the setting
values and the measured magnitude (
I
m
) for each of the three phases and for the selected residual
current input. The reset ratio of 97 % and 103% are built into the function and is always relative to the
I
set
value. The setting value is common for all measured amplitudes, and when the
I
m
exceeds the
I
set
value (in single, dual or all currents) it triggers the pick-up operation of the function.
Table. 5.5.1 - 129. Pick-up settings.
Name
Range
Step
Default
Description
I
set
high
limit
0.01…40.00×I
n
0.01×I
n
1.20×I
n
Determines the pick-up threshold for phase current measurement. This
setting limit defines the upper limit for the phase current's pick-up
element.
If this condition is met, it is considered as fault and the function is not
activated.
I
set
low
limit
0.01…40.00×I
n
0.01×I
n
0.10×I
n
Determines the pick-up threshold for phase current measurement. This
setting limit defines the lower limit for the phase current's pick-up
element.
This condition has to be met for the function to activate.
I
set
ratio
0.01…100.00%
0.01%
10.00%
Determines the pick-up ratio threshold between the minimum and
maximum values of the phase current.
This condition has to be met for the function to activate.
I2/I1 ratio
0.01…100.00%
0.01%
49.00%
Determines the pick-up ratio threshold for the negative and positive
sequence currents calculated from the phase currents.
This condition has to be met for the function to activate.
The ratio is 50 % for a full single-phasing fault (i.e. when one of the
phases is lost entirely). Setting this at 49 % allows a current of 0.01 ×
I
n
to flow in one phase, wile the other two are at nominal current.
I
sum
difference
0.01…40.00×I
n
0.01×I
n
0.10×I
n
Determines the pick-up ratio threshold for the calculated residual phase
current and the measured residual current. If the measurement circuit is
healthy, the sum of these two currents should be 0.
Time
delay for
alarm
0.000…1800.000s 0.005s
0.5s
Determines the delay between the activation of the function and the
alarm.
The pick-up activation of the function is not directly equal to the START signal generation of the
function. The START signal is allowed if the blocking condition is not active. When the activation of the
pick-up is based on binary signals, the activation happens immediately after the monitored signal is
activated.
Read-only parameters
The relay's
Info page displays useful, real-time information on the state of the protection function. It is
accessed either through the relay's HMI display, or through the setting tool software when it is
connected to the relay and its Live Edit mode is active.
A
AQ
Q-T256
-T256
Instruction manual
Version: 2.06
© Arcteq Relays Ltd
IM00028
207
Summary of Contents for AQ-T256
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Page 2: ......
