Figure. 5.4.4. - 37. Angle tracking of DOC function (3LN or 3LL+U0 mode).
Notice in picture above that tripping area is linked to the angle of positive sequence voltage U1.
Positive sequence current I1 angle is compared to U1 angle and in case the fault is in correct direction
it is possible to perform trip when amplitude of I
L1
, I
L2
or I
L3
increases above the pick-up limit.
In case 3LL mode is used without U0 measurement in one phase fault situation voltage reference
comes from the healthy phase and current reference from faulty phase. In short-circuit the angle
comes from impedance calculation.
Function blocking
In the blocking element the block signal is checked in the beginning of each program cycle. Blocking
signal is received from the blocking matrix for the function dedicated input. Additionally, directional
overcurrent protection includes internal inrush harmonic blocking option which is applied by user set
parameter. If the blocking signal is not activated when the pick-up element activates, a START signal is
generated and the function proceeds to the time characteristics calculation.
Table. 5.4.4. - 72. Internal inrush harmonic blocking settings
Name
Description
Range
Step
Default
Inrush Harmonic Blocking (Internal
Only Trip)
2
nd
harmonic blocking
enable/disable
0:No
1:Yes
-
No
2
nd
Harmonic Block Limit (Iharm/Ifund)
2
nd
harmonic blocking limit.
0.10…
50.00*%Ifund
0.01*%Ifund 0.01*%Ifund
If blocking signal is active when pick-up element activates a BLOCKED signal will be generated and the
function shall not process the situation further. If START function has been activated before blocking
signal it will reset and the release time characteristics are processed as in case of when pick-up signal
is reset.
From blocking of the function HMI displays event as well as time stamped blocking event with
information of the startup current values and fault type is issued.
Blocking signal can be tested also in the commissioning phase of the stage by software switch signal
when relay common and global testing mode is activated.
User settable variables are binary signals from the system. Blocking signal needs to reach the IED
minimum of 5 ms before the set operating delay has passedfor blocking to be active in time.
AQ-F255
Instruction manual
Version: 2.00
71
© Arcteq Relays Ltd