Overview
IEC 62561-3:2012 - "Lightning protection system components (LPSC) - Part 3: Requirements for isolating spark gaps (ISG)" specifies the requirements and test methods for isolating spark gaps (ISGs) used in lightning protection systems (LPS). ISGs provide an indirect bond between an LPS and nearby metalwork where a direct electrical bond would interfere with the function of the equipment. The standard defines performance, environmental and marking requirements, classification by lightning-current capability, and the electrical and environmental tests an ISG must pass.
Key Topics and Requirements
- Scope and purpose
- Defines ISGs as components that temporarily conduct during a lightning discharge to protect or isolate conductive parts.
- Explicitly excludes applications where follow currents occur.
- Classification
- ISGs are classified by their lightning impulse current capability (classes H, N, 1L, 2L, 3L) to match application duty.
- Electrical characteristics
- Rated impulse sparkover voltage (Uimp,r): manufacturer-declared impulse sparkover used to classify sparkover behaviour.
- Rated withstand voltages: both DC and power-frequency (AC) values (UWD C, U W AC) that characterize isolation under steady-state conditions.
- Isolation resistance: resistance between active parts when in the non-conducting state.
- Lightning current carrying capability: parameters to ensure safe discharge of lightning impulse current.
- Environmental and mechanical requirements
- ISGs intended for outdoor use must be housed in materials resistant to UV, corrosion and erosion (e.g., glass-glazed ceramic or acceptable alternatives).
- Environmental tests (salt mist, sulphur dioxide, ammonia stress-corrosion references) are included.
- Installation and marking
- Manufacturers must provide clear installation instructions, rated parameters, and connection guidance.
- Marking tests and acceptance criteria are specified to ensure traceability and correct selection.
- Testing and documentation
- Detailed test procedures (isolation resistance, impulse sparkover tests, lightning current tests, EMC, and environmental testing).
- Requirements for the structure and content of test reports.
Practical Applications
ISGs are used where direct bonding is undesirable for functional reasons. Typical applications include bonding or indirect connection of:
- Power installation earth terminations
- Telecommunication and measuring earth electrodes
- Rail earth electrodes (AC/DC railways)
- Cathodic protection and stray-current systems
- Service-entry masts and insulated pipeline flanges/couplings
Who should use this standard
- Manufacturers of ISGs and lightning protection components
- LPS designers and consulting engineers (IEC 62305 users)
- Installers and maintenance personnel responsible for bonding and earthing
- Test laboratories and certification bodies verifying compliance
- Owners/operators of power, telecom, rail, pipeline and laboratory installations
Related Standards
Keywords: IEC 62561-3:2012, isolating spark gaps, ISG, lightning protection, LPS, rated impulse sparkover voltage, withstand voltage, lightning current carrying capability, installation instructions.
