Pick-up
The
I
set
setting parameter controls the pick-up of the I> function. This defines the maximum allowed
measured current before action from the function. The function constantly calculates the ratio
between the
I
set
and the measured magnitude (
I
m
) for each of the three phases. The reset ratio of 97 %
is built into the function and is always relative to the
I
set
value. The setting value is common for all
measured phases, and when the
I
m
exceeds the
I
set
value (in single, dual or all phases) it triggers the
pick-up operation of the function.
The trip characteristic can be set to directional or non-directional. In the non-directional mode only the
pick-up value of the positive sequence current magnitude must be fulfilled in order for the function to
trip. In the directional mode the fault must also be in the monitored direction to fulfill the
terms to trip. By default, the tripping area is ±88° (176°). The reference angle is based on the
calculated positive sequence voltage
U
1
angle. If the
U
1
voltage is not available and only line-to-line
voltages are measured, the reference angle is based on a healthy line-to-line voltage. During a short-
circuit the reference angle is based on impedance calculation.
If the voltage drops below 1 V in the secondary side, the angle memory is used for 0.5 seconds. The
angle memory forces the reference angle to be equal to the value measured or calculated before the
fault. The angle memory captures the measured voltage angle 100 ms before the fault starts. After 0.5
seconds the angle memory is no longer used, and the reference angle is forced to 0°. The inbuilt reset
ratio for the tripping area angle is 2°.
Table. 5.3.4 - 64. Pick-up settings.
Name
Description
Range
Step
Default
Characteristic direction Switches between directional and non-directional
overcurrent mode.
Directional
Non-directional
-
Directional
Operating sector size
(+ / -)
Pick-up area size in degrees.
±1.0…170.0°
0.1°
±88°
Operating sector
center
Turns the operating sector
-180.0…180.0° 0.1°
0°
Pick-up setting I
set
Pick-up setting
0.10…40.00×I
n
0.01×I
n
1.20×I
n
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.
Figure. 5.3.4 - 89. Angle tracking of the Idir> function (3LN/3LL + U
0
mode).
A
AQ
Q-T215
-T215
Instruction manual
Version: 2.04
111
