The IEC 61000-4-4 is an EMC standard by the International Electrotechnical Commission for the immunity requirements of electrical and electronic equipment to repetitive electrical fast transients. This standard specifies the limits, requirements, and procedures to evaluate the performance of the Equipment Under Test (EUT) when exposed to repetitive fast transients (bursts) on supply, signal, and control ports. These transient bursts are the disturbances created by switching power currents, the opening of circuit contacts leading to sparks, and the switching of loads in a circuit. 

IEC 61000-4-4 defines the EUT’s test voltage waveform, range of test levels, test equipment, test set-up, and test procedures. The test equipment to be used according to the standard is:

• Test Generator
• Ground reference plane
• Capacitive coupling clamp
• Decoupling network

According to the IEC 61000-4-4 standard, EFT test pulses are single 5 kHz unidirectional pulses lasting for 15 milliseconds each, repeated at three bursts per second for about one minute. These pulses are injected into the AC and DC power ports of the device under test using coupling-decoupling networks, whereas capacitive clamps are used for injection into the signal and control ports.

The standard also classifies the test levels for EFT/B testing according to the requirements of the electromagnetic environment. These levels are: 

1. Level 1: Well-protected Environment e.g., a computer room.
2. Level 2: Protected Environment e.g., a control room of an industrial plant.
3. Level 3: Typical industrial Environment e.g., a relay room of open-air, high voltage power plant or substation of manufacturing plant.
4. Level 4: Severe Industrial Environment e.g., substation switchyards.

The range of test levels for the electrical fast transient test, applicable to power supply, protective earth (PE), signal and control ports of the equipment as per IEC 61000-4-4 are given as follows. The test levels are measured on the open-circuit output test voltage (ą10 %) and the repetition rate of the impulses (ą20 %).

Table: Test levels for EFT Test

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