Equations for the differential characteristics are as below:
Differential current (calculation is based on user selected inputs and direction):
Bias current (calculation is based on user selected mode):
Characteristics settings are calculated as follows:
Function blocking
In the blocking element the blocking signal is checked in 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 Trip 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 Trip 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 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.
typical applications for this function are presented in the following gures.
AQ-F255
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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