Table. 5.4.13. - 125. General settings of the function
Name
Description
Range
Step Default
Meas input select De nes which available measured residual voltage is used by the function
1:Select
2:U4 Input
3:U3 Input
4:U0Calc
-
1:Select
Pick-up characteristics
Pick-up of the NOV function is controlled by Uset setting parameter, which de nes the maximum
allowed measured voltage before action from the function. The function constantly calculates the ratio
in between of the Uset and measured magnitude (Um) per all three voltages. Reset ratio of 97 % is
inbuilt in the function and is always related to the Uset value. The setting value is common for all
measured amplitudes and single-, dual- or each voltages Um exceed above the Uset value will cause
pick-up operation of the function.
Table. 5.4.13. - 126. Pick-up characteristics setting
Name
Description
Range
Step
Default
Pick-up setting U0set>
Pick-up setting
1.00 … 99.00%Un
0.01%
20%Un
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 at the beginning of each program cycle. Blocking
signal is received from the blocking matrix for the function dedicated input. 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.
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 voltage 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
The operating timers’ behavior of the function can be set for trip signal and also for the release of the
function in case the pick-up element is reset before the trip time has been reached. There are three
basic operating modes available for the function. Instant operation gives the trip signal with no
additional time delay simultaneously with start signal. De nite time operation (DT) will give trip signal
with user given time delay regardless of the measured or calculated voltage as long as the voltage is
above the Uset value and thus pick-up element is active (independent time characteristics). Inverse
de nite minimum time (IDMT) will give the trip signal in time which is in relation of the set pick-up
voltage Uset and measured voltage Um (dependent time characteristics). IDMT function delay follows
this formula:
AQ-F255
Instruction manual
Version: 2.00
137
© Arcteq Relays Ltd
