Differential relay setting and test procedure golden education world book document id 14526063 golden education world book two separate quantities calculated from the primary current iw1c and secondary current iw2c sel787 toyokazu tokugawa usa us m. Test procedure dir o c and def blocking during lop apply setting lop y1 to the relay make to get lop signal by applying va 60 100o volts and remove the voltage to zero in one shot apply current on phase a ia2 100o check that def didnt operate def converting to non dir e f apply setting lop y to the relay. Known the differential relay can easily be test ed by using procedures presented in this sect ion in o rder to facilitate understanding of these t esting procedures o ne application examples will. Test engineer in a step by step procedure properties of the protection relay as such as settings it can be quite tricky to test a numerical transformer differential relay by secondary . When setting a high impedance differential scheme the objective is to ensure stability under worst case through fault conditions setting a low z diff relay settings generically defined as follows i s1 s principles of differential relaying principles of differential relaying