IEC 60099-8:2017

Overview

IEC 60099-8:2017 is the International Electrotechnical Commission standard for metal-oxide surge arresters with external series gap (externally gapped line arresters, EGLA) used on overhead transmission and distribution lines of a.c. systems above 1 kV. The standard is limited to EGLAs applied solely to protect insulator assemblies from lightning-caused over-voltages (lightning-caused flashovers). Edition 2.0 (2017) is a technical revision that aligns rating and test methods with IEC 60099-4 Ed.3 (2014) and introduces updated tests and normative requirements.

Key topics and requirements

• Scope and exclusions: Covers EGLAs where metal-oxide resistors are not permanently connected to the line. It explicitly excludes several items from consideration, such as switching-impulse spark‑over voltage, residual voltage at steep-front and switching impulses, thermal stability, long-duration current impulse duty, power-frequency voltage vs. time characteristics, disconnector testing, and aging duties by power‑frequency voltage.
• Identification & classification: Standard ratings (voltages, frequencies, nominal discharge currents) and service-condition definitions for overhead line applications.
• Type, routine and acceptance tests: Detailed procedures for insulation withstand, residual-voltage, high-current duty, lightning discharge capability and new repetitive charge transfer rating (Qrs) tests, short‑circuit performance, mechanical load and vibration tests, weather‑ageing, and radio‑interference voltage (RIV) testing.
• Series-gap specific tests: New procedures for evaluating the performance and repetitive charge/energy handling of the EGLA series gap in addition to MO resistor testing.
• Protection coordination & follow current interrupting: Tests to verify coordination between insulator withstand and EGLA protective level and to confirm follow‑current interrupting capability under realistic conditions.
• Mechanical and environmental requirements: Bending, vibration, wind‑load and mounting considerations plus guidance for special service conditions and end‑of‑life criteria.

Practical applications

• Selection, specification and type‑approval of EGLAs for overhead transmission and distribution lines to reduce lightning‑caused flashovers.
• Test programs and acceptance criteria used by manufacturers and test laboratories to validate EGLA designs.
• Utility procurement and installation specifications to ensure EGLAs meet coordination, mechanical and environmental performance for power systems above 1 kV.

Who should use this standard

• Transmission and distribution utilities specifying line protection against lightning-caused over-voltages
• Surge‑arrester manufacturers and design engineers developing EGLA products
• Independent test laboratories conducting type, routine and acceptance tests
• Standards and compliance engineers preparing product documentation and procurement specs

Related standards

• IEC 60099‑4 (metal-oxide surge arresters - energy/charge rating methods) - referenced for Qrs methods
• Other parts of the IEC 60099 series for general surge arrester design and testing

Keywords: externally gapped line arresters (EGLA), lightning‑caused over‑voltages, surge arresters, metal‑oxide arresters, repetitive charge transfer rating (Qrs).