EMR-4000
IM02602009E
LOP - Loss of Potential
Available elements:
LOP
Ensure that the LOP has enough time to block faulty tripping of modules that use LOP.
That means, the delay time of the LOP should to be shorter than the tripping delay of
modules that use LOP.
In case of transformer protection relays the LOP element uses current and
voltage measured at the winding side determined by paramter:
[System Para / VT / VT Winding Side ].
LOP function detects the loss of voltage in any of the voltage input measuring circuits and uses the following measured
values and information to detect an LOP condition:
•
Three-phase voltages;
•
Ratio of negative-to-positive sequence voltages;
•
Zero sequence voltage;
•
Three-phase currents;
•
Residual current (I0);
Once an LOP condition is detected and it lasts longer than an adjustable minimum pickup time, the LOP Pickup will be
set. The LOP Block will only be set if the LOP-Block control setting is set to enabled (activated). The LOP Pickup and
LOP Block signals can both be used as logical signal to block the protective functions which use the voltage information
such as voltage restraint. The minimum pickup timer is used to prevent short time incorrect operation of the LOP
function during breaker switching-on operation.
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