<p style="text-align:justify"><span style="font-size:14px">When the power transformer is energized, the worst magnetizing inrush current can be as large as 10 times the CMR of transformer primary. This current exponentially reduces to a normal value after 15-30 cycles depending upon L/R ratio. Hence, the setting of instantaneous overcurrent unit has to be set beyond this inrush value. If there is an internal fault within the transformer which can be 6-8 times the CMR of the transformer, it will be taken care of by time delayed unit only. The internal faults are dangerous and can shatter the transformer. A numerical relay offers a facility in which it discriminates between inrush function and fault function. Inrush current rises from zero to 10 times the rated current of transformer. It also contains many harmonic components. Thus, it is distorted. Also, it is exponentially decaying. This behaviour of current is analyzed and tagged as inrush function. Whereas, fault current rises from about rated current (1 time the CMR) to 5-8 times CMR. The waveshape is also different. This is tagged as fault function. If it is an inrush function, the high-set (I &gt;&gt; and/or I &gt;&gt;&gt;) setting is temporarily multiplied automatically by n (adjustable) times the set value till the inrush continues. Once inrush dies down, the instantaneous setting resumes to original set value automatically. In case of fault function, this multiplication does not take place. This facility allows the instantaneous setting to be decided at a value less than the possible inrush value. The similar is the case of motor starting current which is of the order of 6 times CMR of motor. Starting time varies from 6 seconds to as large as 30 seconds in case of large inertia motors like PA fan motor in thermal power plant. In this case also, it is possible to set instantaneous unit setting at a value less than starting current if we use numerical relay.</span></p>