EN IEC 60099 Recommendations for Lightning Arresters

The “EN IEC 60099 Recommendations for lightning arresters” standard, developed by the International Electrotechnical Commission (IEC) and later published as a European standard as part of harmonization efforts, consists of the following sub-sections published under the same title:

• The standard “EN IEC 60099-1 Part 1: Nonlinear resistive type interval surge protectors for alternating current systems” describes the requirements and test methods for a specific type of surge protector (lightning protector) used in alternating current (AC) systems. Essentially, this standard applies to surge protectors consisting of one or more nonlinear resistors (typically silicon carbide-based in older designs) in series with single or multiple spark gaps (interval design). These devices protect electrical equipment from overvoltages caused by lightning or switching surges.

This standard has been discontinued. It has been largely replaced by modern standards for gapless metal oxide surge protectors (primarily addressed in EN IEC 60099-4, which uses zinc oxide varistors without a spark gap and is now the active and dominant standard for most high-voltage surge protectors).

Modern surge protectors (especially medium and high voltage) are almost entirely of the gapless metal oxide type and have been tested according to the EN IEC 60099-4 standard. The EN IEC 60099-1 standard remains valid only for older gap protectors or for reference purposes.

• The standard “EN IEC 60099-2 Part 2: Spray-type lightning arresters” applies to spray-type lightning arresters (spray arresters). These are a specific class of surge protection devices consisting of single or multiple spark gaps in series with an arc chamber (typically containing fiber or gas-producing materials). When a surge occurs, the spark gaps jump, and the resulting arc expels hot gases to extinguish the current and interrupt the follow-up current in distribution systems. They were primarily used to protect medium-voltage overhead lines and equipment from lightning strikes.

Resistor type: Ventilated (vented, gas vented) design. It differs from intermittent nonlinear resistor types (EN IEC 60099-1 standard) or modern continuous metal oxide types (EN IEC 60099-4 standard).

This standard has been withdrawn and is no longer actively used for new designs. Drainage-type arresters are largely obsolete and have been replaced by more reliable, maintenance-free, continuous metal oxide surge arresters.

• The standard “EN IEC 60099-4 Part 4: Gapless metal-oxide surge protectors for alternating current systems” applies to nonlinear metal-oxide resistive surge protectors without spark gap, designed to limit voltage fluctuations in alternating current (AC) power circuits with a maximum system voltage of at least 1 kV. This standard covers the requirements, classification, values, tests (type/design, routine, acceptance), and performance criteria for these modern surge protectors used to protect equipment from lightning and switching overvoltages in distribution, transmission, and substation applications.

In the latest update of this standard, the old line discharge classification system has been replaced with a new energy/charge processing classification based on:

• Repeated charge transfer rate
• Thermal energy level
• Thermal charge transfer degree

This better reflects real-world stresses on metal oxide varistors.

This standard has been harmonized within the scope of the relevant EU directives (e.g., the low voltage directive for its applicable aspects) and is the primary reference in Europe for gapless metal oxide surge protectors.

Almost all new surge protectors manufactured and installed worldwide (especially those with a voltage of at least 1 kV) comply with the EN IEC 60099-4 standard.

• The standard “EN IEC 60099-5 Part 5: Selection and application recommendations” provides informative guidance, recommendations and background information (not mandatory requirements) for the selection, application, installation and coordination of surge protectors in three-phase alternating current systems with nominal voltages above 1 kV. This standard covers:
• Gap-free metal oxide surge protectors according to EN IEC 60099-4 standard.
• Surge protectors with series and parallel clearance configurations, with a maximum nominal voltage of 52 kV, according to the EN IEC 60099-6 standard.
• External series gap metal oxide surge protectors for overhead lines according to EN IEC 60099-8 standard.

The main content areas are as follows:

• System overvoltage stresses (lightning, switching, transient overvoltage)
• Protective rating voltage selection: continuous operating voltage, rating voltage, MCOV, protection levels
• Energy management and thermal considerations (including formulas for energy/charge transfer requirements compliant with EN IEC 60099-4 standard classification)
• Transient overvoltage capacity
• Coordination with equipment isolation
• Installation aspects (assembly, contamination, height, mechanical loads)
• Application examples for distribution, transmission, and substations, and line surge arresters.
• Risk assessment for retaining failure modes and protection zones.

This standard is purely advisory, but it is widely referenced in specifications, tenders, and engineering practices across Europe and the world.

• The standard “EN IEC 60099-6 Part 6: Surge protectors with series and parallel spacing configurations - System voltage up to 52 kV” describes the requirements and test procedures for nonlinear metal oxide resistor type surge protectors with spark spacing (both series and parallel spacing configurations) designed to limit voltage fluctuations in alternating current (AC) power circuits with a maximum system voltage of at least 1 kV and up to 52 kV.

This standard covers primarily cavity-type distribution metal oxide surge protectors, housed in porcelain or polymer enclosures. These designs are used to protect equipment from lightning and switching overvoltages in medium-voltage distribution networks and offer advantages in certain applications, such as improved transient surge withstand capability or energy processing, compared to pure cavity-free types.

The classification is based on the following:

• Repeated charge transfer rate
• Thermal energy level
• Thermal charge transfer degree
• The standard “EN IEC 60099-8 Part 8: External series interval metal oxide surge protectors (EGLA) for overhead lines” describes the requirements and test procedures for external interval line arresters (EGLA). These are metal oxide surge protectors consisting of the following components:
• A series varistor unit made of nonlinear metal oxide resistors housed in a polymer or porcelain enclosure.
• Under normal conditions, an external series air gap (spark gap) isolates the series varistor unit from the line.

External spacing line arresters are mounted in parallel to insulator arrays on overhead transmission and distribution lines (AC systems greater than 1 kV) to protect the insulator assembly from lightning-induced surges only. The external spacing is designed to withstand switching overvoltages and transient overvoltages, and ensures the protector primarily engages for lightning surges (high steepness, short duration). It is not designed for switching surge protection or substation class duties.

Key features and differences from other protective products are as follows:

• Unlike gapless station/distribution protectors (EN IEC 60099-4), external gap extends service life and reduces leakage current by preventing continuous voltage stress on MO resistors.
• The design focuses on lightning discharge capability through repetitive load transfer rate, energy processing, and cavity spark coordination tests.
• The standard “EN IEC 60099-9 Part 9: HVDC converter station surge arresters” applies to nonlinear metal oxide resistor type surge protectors without spark gap, specifically designed to limit overvoltages in high-voltage DC converter stations. This standard covers:
• Two-terminal, multi-terminal and series-connected high-voltage DC systems with operating voltages up to plus/minus 1100 kV.
• Porcelain-bodied, polymer-bodied, and gas-insulated metal-enclosed holders used in DC busbars, DC line/cable holders, or AC filter circuits.
• Holders exposed to direct current (DC) voltages, including pole reversals (even infrequent ones).

Holders for voltage-sourced converters are excluded from this scope. Holders on the AC side of the converter station are tested according to the EN IEC 60099-4 standard. Holders in AC filters comply with this standard due to harmonic voltages.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its customers, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the "EN IEC 60099 Recommendations for Lightning Arresters" standard.