Section 3: How Does the Testing Work? A Step-by-Step Overview
The standard defines the precise methods, severity levels, and success criteria for conducting electrostatic discharge (ESD) tests.
3.1. The Two Key Test Methods
The standard specifies two primary methods for applying a static discharge to the equipment.
| Test Method | Description |
| Contact Discharge Method | The electrode of the test generator is held in direct contact with the equipment, and the discharge is triggered by a switch inside the generator. |
| Air Discharge Method | The charged electrode of the test generator is brought close to the equipment until a spark jumps across the air gap to the device. |
The contact discharge method is the preferred and most common method. However, the air discharge method is used as an alternative when the surfaces of the equipment being tested are made of non-conducting materials (like plastic casings).
3.2. Understanding Test Severity Classes
Tests are performed at different voltage levels to simulate various environmental conditions. These levels are organized into “Test severity classes.”
Table 1 – Test severity classes
| Class | Contact discharge (kV) | Air discharge (kV) |
| 0 | – | – |
| 1 | 2 | 2 |
| 2 | 4 | 4 |
| 3 | 6 | 8 |
| 4 | 8 | 15 |
As you can see from the table, a higher class number corresponds to a higher test voltage, making it a more severe and challenging test for the equipment.
For practical purposes, the single most important detail is that Class 3 is considered the normal test severity class for protection equipment used in environments like power plants, substations, and industrial plants.
3.3. What Counts as a “Pass”?
The criteria for accepting that a device has passed the test are straightforward:
- During the test: No incorrect operation is allowed. However, transient false information, such as a flickering indicator light (LED), is tolerated as it does not represent a functional failure.
- After the test: The equipment must still perform according to its technical specifications, with no degradation in function.
By following these standardized methods, severity levels, and acceptance criteria, the standard ensures that critical protection equipment is robust and reliable.