The standard provides a framework for classifying test severity based on environmental conditions and details the precise characteristics of the required test equipment.

3.1. Test Severity Classes

Five severity classes are defined to cover different environmental conditions. The test voltage is chosen from the table below, with Class 3 being designated as the normal test severity class for protection equipment.

Table 1: Test Severity Classes

Note: For severe electrostatic environments, higher voltage levels may be required. For specific situations, such as when relay covers are removed for settings changes, manufacturers may claim a lower severity class (e.g., Class 2).

3.2. Discharge Generator Characteristics

The discharge generator must conform to the detailed specifications in IEC 1000-4-2. Key parameters are:

• Energy storage capacitance (Cs + Cd): 150 pF ± 10%
• Discharge resistance (Rd): 330 Ω ± 10%
• Charging resistance (Rc): 50 MΩ to 100 MΩ
• Output voltage tolerance: ±5%
• Polarity of output voltage: Positive and negative
• Holding time: At least 5 seconds
• Mode of operation: Single discharges (at least 1 s between discharges) or repetitive discharges (up to 20 discharges per second for exploratory purposes).

3.3. Waveshape of the Discharge Current

The output current of the generator must meet the specific waveshape parameters outlined in the table below. The rise time (tr) for the first peak is between 0.7 ns and 1 ns.

Table 2: Waveshape of the Discharge Current