Annex A: Examples of Relay Settings

This informative annex provides examples of relay settings and input quantities to establish the operate/non-operate conditions during testing. The goal is to set the relay close to its operating threshold to maximize sensitivity to disturbances. Examples include:

• Independent time overcurrent relay: Energize with a current equal to the actual operate value minus a quantity corresponding to the claimed variation (e.g., -10% of set current).
• Instantaneous undervoltage relay: Energize with a voltage equal to the actual operating value plus a quantity corresponding to the claimed variation (e.g., +10% of set voltage).
• Under impedance relay: Energize with a current and voltage that results in an impedance equal to the actual operate value plus a quantity corresponding to the claimed variation (e.g., +15% of set impedance).

Annex B: Explanatory Notes on ESD

This annex provides context on the physics and practical aspects of electrostatic discharge.

• Source of ESD: The primary concern is discharge from the human body, especially in environments with dry atmosphere and synthetic fabrics. Charges are generated when an operator walks on a carpet or through friction with clothing.
• Discharge Behavior: The nature of the discharge depends on the path to earth. A good earth connection results in a very short duration, high amplitude current pulse (a few nanoseconds). A poor earth connection (high impedance) results in a damped oscillatory wave.
• Selection of Test Severity Classes: This annex provides environmental context for the severity classes.