IEC Transient pulse immunity

IEC 61000-4-5 Surge

PURPOSE

This test is for electrical and electronic equipment subjected with regard to unidirectional surge caused by overvoltages from switching and lightning transients. A surge is a momentary, very high-energy pulse, which the device must survive unscathed. The standard distinguishes between power lines.

Power system switching transients: Power system switching transients can be separated into transients associated with:

• Major power system switching disturbances, such as capacitor bank switching.

• Minor local switching activity or load changes in the power distribution system.

• Resonating circuits associated with switching devices, such as thyristors.

• Various system faults, such as short circuits and arcing faults to the grounding system of the installation. Lightning transients: The major mechanisms by which lightning produces surge voltages are the following:

• Direct lightning strokes to outdoor circuits injecting high currents and producing over voltages.

• Indirect lightning strikes (i.e. strikes between or within clouds or to nearby objects which produce electromagnetic fields) that induce voltages/currents on the conductors outside and/ or inside a building.

• Lightning ground current flows resulting from nearby direct-to-earth discharges coupling into the common ground paths of the grounding system of the installation. The rapid change of voltages and flows of current which can occur as a result of the operation of a lightning protection device can induce electromagnetic disturbances into adjacent equipment.

Target of the IEC 61000-4-5 is to provide a model to simulate these surges and then to be able to check if the equipment is able to survive them

Test setup for surges applied to EUT Power ports

The 1.2/50 µs surge shall be applied to the EUT power supply terminals via a capacitive coupling network. Decoupling networks are required in order to avoid possible adverse effects on equipment not under test that may be powered by the same lines and to provide sufficient decoupling impedance to the surge wave so that the specified wave may be applied on the lines under test.

Test levels

Level	Open circuit test voltage
Level	Line-to line	Line-to-groundb
1	--	0.5
2	0.5	1
3	1	2
4	2	4
Xa	Special	Special

‘’X’’can be any level, above, below or in between the others. This Level shall be specified by product committees and/or equipment specification for symmetrical interconnection lines, the test can be applied to multiple lines simultaneously with respect to ground, i.e., “lines to ground”