Pick-up characteristics
Pick-up of the NEF function is controlled by I0set setting parameter, which de nes the maximum
allowed measured current before action from the function. The function constantly calculates the ratio
in between of the Iset and measured magnitude (Im) per all three phases. Reset ratio of 97 % is inbuilt
in the function and is always related to the Iset value. The setting value is common for all measured
phases and single-, dual- or all phases Im exceed of the Iset value will cause pick-up operation of the
function.
Table. 5.4.3. - 64. Pick-up characteristics setting
Name
Description
Range
Step
Default
I0set
Pick-up setting
0.0001 … 40.00xIn
0.0001xIn
1.20xIn
The pick-up activation of the function is not directly equal to start-signal generation of the function.
Start signal is allowed if blocking condition is not active.
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, non-directional
earth-fault 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. 5.4.3. - 65. 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 a HMI display 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.
Operating time characteristics for trip and reset
This function supports de nite time delay (DT) and inverse de nite minimum time (IDMT) delay types.
For detailed information on these delay types refer to chapter General properties of a protection
function.
AQ-F255
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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