The purpose of the test is to verify the device's ability to function properly in the presence of transient overvoltages caused by load switching, capacitor bank switching, resonance due to the switching of devices with SCR, ground faults in the installation, or lightning strikes (excluding direct lightning strikes).
The standardized waveform for the discharge is generated by a specific generator with the shape indicated in the following figure.
With the output in short-circuit, the test generator must produce a current waveform with rise-fall times of 8/20 µs.
The test voltage ranges from 0.5 kV to 4 kV, as required by the product standard, and the test is performed with both positive and negative polarity impulses. The disturbance is coupled to the Equipment Under Test (EUT) using a Coupling Decoupling Network (CDN) with different components depending on whether the disturbance needs to be coupled to the single-phase or three-phase power supply port or to the signals. Additionally, the disturbance is applied both between the various poles (differential mode) and between each pole and ground (common mode).
The EN 61000-4-5
standard, titled "Immunity to Surge," falls under the Electromagnetic Compatibility (EMC) umbrella, specifically within Part 4: Testing and Measurement Techniques, Section 5: Surge Immunity Test. This standard defines the test methodology and the characteristics of the setup and test equipment, including coupling networks or devices. Technical product committees then identify severity levels in terms of voltage levels in kV, coupling networks, and ports to be tested.
During the test, the Equipment Under Test (EUT) must continue to function correctly. However, according to product standards, temporary performance degradation is permissible, with autonomous recovery upon removal of the disturbance.
Elettra has two surge immunity test stations for both single-phase and three-phase devices, capable of testing up to 4 kV voltage levels.