Injection Current into the Power Transformer as an Internal Fault Phenomena for Measuring the Differential Relay Performance

In this paper explains the classical aspects in measure the differential relay performance. The classical aspects use the simulation through inrush current into the power transformer under three conditions. The first condition is giving the normal phenomenon as phenomenon of loading, the second condition is giving the fault phenomenon for outside of the protection zone, and the third condition is giving the fault phenomenon for inside of the protection zone. The result of measurement during loading condition, the differential relay not operate, because relay is set with value of 130% of the largest current between the three phases, so that the adjustable current is 4.45 mA. The results of current measurement to the differential relay when the fault condition is provided outside of the protection area, the current value to the differential relay should of zero mA and the differential relay not operate. The result of measurement of the current flow to the differential relay when giving the fault phenomenon inside the protection zone is obtained flow to relay at the phase-R is 127.7 mA, phase-S is 123.9 mA, and phase-T equal to 123.8 mA, while the result of calculation of the current flow to the differential relay of each phase of 152.61 mA, and the differential relay operate. After giving all of three conditions, the differential relay performance is known.