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Iec 600995 Pdf May 2026

The IEC 60099-5 standard, titled "Surge arresters – Part 5: Selection and application recommendations," is a critical international guideline for power engineers and utility managers. It provides comprehensive instructions on how to select, apply, and coordinate surge arresters in three-phase systems with nominal voltages above 1 kV.

For an electrical engineer, mastering IEC 60099-5 is essential for ensuring that a 50 kA lightning strike does not destroy a multi-million dollar transformer. It ensures the delicate balance between reliability (the arrester surviving the grid) and protection (the grid surviving the surge). iec 600995 pdf

The latest version is the third edition (2018), which replaces the 2013 version to align with updated arrester classifications introduced in IEC 60099-4:2014. Key Scope and Applicability The IEC 60099-5 standard, titled "Surge arresters –

The updated standard expands on the move from old line discharge classes to a new energy/charge handling classification (Annexes H and I). Expanded Guidance: Selection of surge arresters: The standard provides guidance

  1. Selection of surge arresters: The standard provides guidance on selecting the right surge arrester for a specific application, taking into account factors such as system voltage, fault levels, and environmental conditions.
  2. Application of surge arresters: IEC 60099-5 covers the installation, commissioning, and testing of surge arresters, including their connection to the electrical power system.
  3. Maintenance and diagnostic testing: The standard recommends procedures for inspecting, testing, and maintaining surge arresters to ensure their continued safe and reliable operation.

Specifically for systems with rated voltages 52 kV and below, as defined in IEC 60099-6. Externally Gapped Line Arresters (EGLA):

Step 4: Determine the Protective Level ($U_p$)

The user must calculate the Lightning Impulse Protective Level (LIPL) and Switching Impulse Protective Level (SIPL). These values represent the "clamping voltage"—the maximum voltage the arrester lets through during a surge.