Answer Key

1. The primary objective of the tests is to confirm that the equipment under test will not maloperate when it is energized and subjected to an electrostatic discharge. These tests are type tests and are applicable only to relays and protection equipment in new condition.
2. The two main test methods are the contact discharge method and the air discharge method. In the contact discharge method, the electrode of the test generator is held in contact with the equipment, and the discharge is actuated by a switch within the generator. In the air discharge method, the charged electrode is approached to the equipment, and the discharge is actuated by a spark to the equipment.
3. The contact discharge method is the preferred method of testing. The air discharge method should only be used in cases where the accessible surfaces of the equipment under test are non-conducting.
4. Class 3 is the normal test severity class for protection equipment. The corresponding test voltage for the contact discharge method is 6 kV, and the test voltage for the air discharge method is 8 kV.
5. Key characteristics of the discharge generator include an energy storage capacitance (Cs) of 150 pF ± 10%, a discharge resistance (Rd) of 330 Ω ± 10%, and a minimum holding time of 5 seconds. The generator must also be able to produce both positive and negative polarity discharges.
6. A ground reference plane is a metallic sheet (copper or aluminum) of at least 0.25 mm thickness that is provided on the floor or workbench of the laboratory. Its minimum size is 1 m², and it must project beyond the equipment under test by at least 0.1 m on all sides. The plane must be connected to the protective ground system.
7. The test must be repeated on each selected test point at least 10 times with a positive polarity test voltage and 10 times with a negative polarity test voltage. The recommended time interval between successive single discharges is 1 second.
8. During the test, no incorrect operation shall occur. Transient false information given by indicating devices like LEDs is tolerated. After the test, the equipment under test must still comply with its relevant performance specification.
9. The primary source of concern is the human body. Electrostatic charges are easily generated in an environment with dry atmosphere and synthetic fabrics, such as when an operator walks over a carpet. At each step, the operator loses or gains electrons relative to the fabric, resulting in a charge.
10. Direct application is the application of the test discharge directly to the equipment under test. Indirect application involves applying the test to a coupling plane in the vicinity of the equipment to simulate a personal discharge to objects which are adjacent to the equipment.