IEC 60255-22-4:2008 specifies the general requirements for electrical fast transient immunity tests for measuring relays and protection equipment for power system protection, including the control, monitoring and process interface equipment used with these systems. Is based on IEC 61000-4-4. The objective of the tests is to confirm that the equipment under test will operate correctly when energized and subjected to repetitive fast transients (bursts) such as those originating from interrupting of inductive loads, relay contact bounce, etc. The main change with respect to the previous edition is the improvement of the test severity level regarding the repetition rate.