Figure. 5.4.5. - 26. Simpli ed function block diagram of the CUB function.
Measured input values
Function block uses analog current measurement values. Function block utilizes calculated positive
and negative sequence currents. In broken conductor mode (I2/I1) also the phase currents RMS
values are used for the minimum current check. Zero sequence and the component sequence angles
are used for the fault registering and for fault analysis processing. -20ms averaged value of the
selected magnitude is used for pre-fault data registering.
Table. 5.4.5. - 75. Analogic magnitudes used by the CUB function.
Signal
Description
Time base
I1
Positive sequence current magnitude
5 ms
I2
Negative sequence current magnitude
5 ms
IZ
Zero sequence current magnitude
5 ms
I1 ANG
Positive sequence current angle
5 ms
I2 ANG
Negative sequence current angle
5 ms
IZ ANG
Zero sequence current angle
5 ms
IL1RMS
Phase L1 (A) measured RMS current
5 ms
IL2RMS
Phase L2 (B) measured RMS current
5 ms
IL3RMS
Phase L3 (C) measured RMS current
5 ms
Selection of the used AI channel is made with a setting parameter. In all possible input channel
variations pre-fault condition is presented with 20 ms averaged history value from -20 ms of Start or
Trip event.
General settings
The following general settings de ne the general behavior of the function. These settings are static i.e.
it is not possible change them with setting group switching.
Name
Description
Range Step Default
Meas side
De nes which current measurement module is used by the function. Visible if unit
has more than one current measurement module.
1:Side1
2:Side2
-
1:Side1
Measured
magnitude
De nes if the ratio between positive and negative sequence currents are
supervised or if only negative sequence is used in unbalance detection.
1:I2pu
2:I2/I1
-
1:I2pu
AQ-T257
Instruction manual
Version: 2.00
67
© Arcteq Relays Ltd
