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.
Figure. 5.4.7. - 87. Cable end differential with natural unbalance in the phase current measurement.
When calculating the residual current from phase currents the natural unbalance may be in total
around 10% and still the used CT:s are in the promised 5P class (probably most common CT accuracy
class). When the current natural unbalance is compensated in this same situation the differential
settings may be set more sensitive and the natural unbalance does not affect into the calculation.
Figure. 5.4.7. - 88. Cable end differential when fault happens.
AQ-T216
Instruction manual
Version: 2.00
107
© Arcteq Relays Ltd
