SIST EN 3841-308:2005

Overview

EN 3841-308:2004 is a CEN/AECMA-STAN aerospace series standard that specifies a test method to verify the ability of circuit breakers to withstand the indirect effects of a stroke of lightning. The standard is intended to be used together with EN 3841-100 (General) and references ISO 7137 for mounting and test procedures. It was approved by CEN in December 2004 and adopted by national bodies in the member states.

This part (308: Lightning) focuses on replicable, long-wave impulse conditions to ensure circuit breaker performance under realistic indirect lightning stress and to confirm that devices do not unintentionally trip when exposed to specified impulses.

Key Topics

• Scope: Verifies resistance of circuit breakers to indirect lightning effects; to be used alongside EN 3841-100.
• Normative references: ISO 7137 (Aircraft - Environmental conditions and test procedures for airborne equipment) is essential for procedure and mounting details.
• Test mounting: Circuit breakers shall be mounted in accordance with Figure 22.2 in ISO 7137 (test procedure 3.8).
• Test levels: Tests use the long-wave test category M with the following quoted parameters: 1 600 V and 320 A, duration 6,4 µs, 70 µs as specified in the referenced ISO document.
• Impulse sequence: Five positive and five negative impulses shall be superposed every minute on each of the nominal voltages indicated in the technical specification.
• Loading condition: Circuit breakers shall be loaded at 0.9 In during testing.
• Acceptance criterion: The circuit breakers shall not trip during the test sequence.

Applications

• Certification testing for aerospace circuit breaker products where immunity to indirect lightning is required.
• Design validation during development of circuit protection devices for aircraft electrical systems and avionics installations.
• Supplier and quality assurance testing to demonstrate conformity with aerospace electrical environmental requirements.

Practical benefits include consistent test procedures for repeatable results, clear acceptance criteria (no unintended trip), and alignment with established environmental test methods (ISO 7137). Use of EN 3841-308 helps manufacturers and certification bodies demonstrate product reliability under lightning-induced transient conditions.

Related Standards

• EN 3841-100 - Aerospace series - Circuit breakers - Test methods - Part 100: General (to be used together with Part 308).
• ISO 7137 - Aircraft - Environmental conditions and test procedures for airborne equipment (test procedure 3.8 and Figure 22.2 referenced).

For procurement, certification, or design assurance, reference EN 3841-308:2004 alongside EN 3841-100 and ISO 7137 to ensure compliant test setup, parameters, and pass/fail criteria for lightning-induced long-wave impulses.