View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Aging Wires & Systems Standard & Regulation Management Maintenance & Sustainment Conference & Report Research Protection & Prevention Arcing Miscellaneous
Popular Tags
Visual Inspection AS50881 MIL-HDBK MIL-HDBK-525 High Voltage FAR Electromagnetic Interference (EMI) FAR 25.1707 AS4373 Maintenance Wire System Arcing Damage
All Tags in Alphabetical Order
2021 25.1701 25.1703 abrasion AC 33.4-3 Accelerated Aging ADMT Aging Systems AIR6808 AIR7502 Aircraft Power System aircraft safety Aircraft Service Life Extension Program (SLEP) altitude arc damage Arc Damage Modeling Tool Arc Fault (AF) Arc Fault Circuit Breaker (AFCB) Arc Track Resistance Arcing Arcing Damage AS22759 AS22759/87 AS23053 AS4373 AS4373 Method 704 AS50881 AS5692 AS6019 AS83519 AS85049 AS85485 AS85485 Wire Standard ASTM D150 ASTM D2671 ASTM D8355 ASTM F2696 ASTM F2799 ASTM F3230 ASTM F3309 ATSRAC Attenuation Automated Wire Testing System (AWTS) Automotive backshell batteries Bent Pin Analysis Best of Lectromec Best Practice bonding Cable Cable Bend cable testing Carbon Nanotube (CNT) Certification Chafing Chemical Testing Circuit Breaker circuit design Circuit Protection Coaxial cable cold bend collision comparative analysis Compliance Component Selection Condition Based Maintenance Conductor conductors conduit Connector connector selection connectors contacts Corona Corrosion Corrosion Preventing Compound (CPC) Cracking D-sub data analysis data cables degradat Degradation Delamination Derating design safety development diagnostic Dielectric breakdown dielectric constant Dimensional Life disinfectant Distributed Power System DO-160 dry arc dynamic cut through E-CFR Electrical Aircraft Electrical Component Electrical Power Electrical Testing Electromagnetic Interference (EMI) Electromagnetic Vulnerability (EMV) EMC EMF EN2235 EN3197 EN3475 EN6059 End of Service Life End of Year Energy Storage engines Environmental Environmental Cycling environmental stress ethernet eVTOL EWIS certification EWIS Component EWIS Design EWIS Failure EWIS sustainment EWIS Thermal Management EZAP FAA FAA AC 25.27 FAA AC 25.981-1C FAA Meeting failure conditions Failure Database Failure Modes and Effects Analysis (FMEA) FAQs FAR FAR 25.1703 FAR 25.1707 FAR 25.1709 fault tree Fixturing Flammability fleet reliability Flex Testing fluid exposure Forced Hydrolysis fuel system fuel tank ignition Functional Hazard Assessment functional testing Fundamental Articles Future Tech galvanic corrosion Glycol Gold Gold plating Green Taxiing Grounding hand sanitizer handbook Harness Design Hazard Analysis health monitoring heat shrink heat shrink tubing high current high Frequency high speed data cable High Voltage HIRF History Hot Stamping Humidity Variation HV system ICAs IEC60172 IEEE Inspection installation installation safety Instructions for Continued Airworthiness insulating material insulating tape Insulation insulation breakdown insulation resistance insulation testing interchangeability IPC-D-620 ISO 17025 Certified Lab ISO 9000 J1673 Kapton Laser Marking life limit life limited parts Life prediction life projection Lightning liquid nitrogen lunar maintainability Maintenance Maintenance costs Mandrel mean free path measurement mechanical stress Mechanical Testing MECSIP MIL-C-38999 MIL-C-85485 MIL-DTL-17 MIL-DTL-23053E MIL-DTL-3885G MIL-DTL-38999 MIL-E-25499 MIL-HDBK MIL-HDBK-1646 MIL-HDBK-217 MIL-HDBK-454 MIL-HDBK-516 MIL-HDBK-522 MIL-HDBK-525 MIL-HDBK-683 MIL-STD-1353 MIL-STD-1560 MIL-STD-1798 MIL-STD-464 MIL-T-7928 MIL-T-81490 MIL-W-22759/87 MIL-W-5088 MIL–STD–5088 Military 5088 modeling moon MS3320 NASA NEMA27500 Nickel nickel plating No Fault Found OEM off gassing Outgassing Over current Overheating of Wire Harness Parallel Arcing part selection Partial Discharge partial discharge at altitude Performance physical hazard assessment Physical Testing polyimdie Polyimide-PTFE Power over Ethernet power system Power systems predictive maintenance Presentation Probability of Failure Product Quality PTFE pull through Radiation Red Plague Corrosion Reduction of Hazardous Substances (RoHS) regulations relays Reliability Research Resistance Revision C Rewiring Project Risk Assessment S&T Meeting SAE SAE Committee Sanitizing Fluids Secondary Harness Protection Separation Requirements Series Arcing Service Life Extension Severe Wind and Moisture-Prone (SWAMP) Severity of Failure shelf life Shield Shielding Shrinkage signal cable Silver silver plated wire silver-plating skin depth skin effect Small aircraft smoke Solid State Circuit Breaker Space Certified Wires Splice standards Storage stored energy supportability Sustainment System Voltage Temperature Rating Temperature Variation Test methods Test Pricing Testing testing standard Thermal Circuit Breaker Thermal Endurance Thermal Index Thermal Runaway Thermal Shock Thermal Testing tin Tin plated conductors tin plating tin solder tin whiskering tin whiskers top 5 Transient Troubleshooting TWA800 UAVs UL94 USAF validation verification video Visual Inspection voltage voltage differential Voltage Tolerance vw-1 wet arc white paper whitelisting Wire Ampacity Wire Bend Wire Certification Wire Comparison wire damage wire failure wire performance wire properties Wire System wire testing Wire Verification wiring components work unit code

Evaluating Secondary Wire Harness Protection Performance

Protection & Prevention Testing & Assessment

There are several reasons to deploy secondary harness protection (SHP): chafe protection, maintenance protection, fire protection, harness cable management and, in some cases, arc protection. The EN6059-502 test examines secondary harness protections and the potential damage from arcing. This article runs through the test method and problems that could occur if the results are misinterpreted.

Test Performance

The EN6059-502 test starts with placing the sample secondary harness protection around a target wire harness. The protection is then closed by appropriate means (lacing tape or equivalent). A second wire harness that has a common configuration with the EN3475 wet arc short circuit test method is referred to as the aggressive wire bundle. The aggressive wire bundle is attached to the outside of the SHP; this is the group that initiates the acting event. The samples are placed into the test jig and, after the test power is applied, saline drops hit the active arcing harness until an arcing event occurs.

The EN6059-502 test method provides the parameters on how to perform on a variety of aggressive bundle conditions. If the SHP is thin, then it may only be rated to be tested with 20AWG wires and 7.5A thermal circuit breakers. Thicker or more stout protection types can be evaluated with heavier gauge wire. It is important to understand this distinction and arc damage resistance rating when selecting SHPs.

EN6059 arc protection testing
The EN6059-502 test examines the effectiveness of electrical arcing outside of the protection. The same level of protection should not be assumed for arcing inside of the protection.

Pass Fail Criteria

The pass/fail criteria for SHP are specification/product dependent and include limitations on the SHP protected wire harness damage. For the interior SHP wires, superficial damage is permitted but breaches to the wire conductor are not. The presence of wire insulation breaches are determined by a posttest dielectric voltage withstand test.

How Results Can be Misinterpreted

The EN6059-502 SHP resistance to electrical arcs test examines what can happen when an arc occurs outside the harness protection, not inside. It is important to understand the differences that can occur when the arc is inside of secondary protection. When the arcing wire harness is placed on the outside of the secondary harness protection, the energy from the arcing event can escape and may not impact the secondary protection. Assuming an equal energy distribution from the electrical arc, it is likely that the secondary harness protection is exposed to less than 20% of the total arc plume energy. Of the total arc plume energy, most is deflected and not readily absorbed by the SHP. Under these conditions, it is possible for low quality materials to pass this test under low energy conditions.

If an arcing event were to occur inside of a wire harness protected by SHP (possible by crush damage or by insulation degradation), the energy is contained within the SHP without a means for escape. This trapped energy can cause damage to more wires in the harness or create a hole in the SHP creating a jet of arc energy. This means that a SHP that successfully passed a test with an arcing wire on the outside may not pass when the same arcing event occurs inside the SHP.

Beyond the Test

Just because a protection does not pass a particular configuration, it does not mean that it is a bad construction. This test evaluates intra-bundle protection; the SHP may still be viable as inter-bundle protection. Consider the following: an aggressive wire harness constructed with 16AWG wire is strapped to a SHP material fails when tested. If the separation distance between the wire harness is increased to 0.5 inches, the percentage of an arc energy incident to the SHP is reduced by more than 50%. Further separation provided greater reductions of incident arc energy.

In that sense, the secondary protection does offer a segregation material the might be necessary for system safety such as those areas where physical separation cannot be achieved. In the consideration of FAA Regulation 25.1709, the aircraft level impact of each wire harness loss must be considered. But the protection is only viable if the contained wires are signal wires. Inclusion of power wires inside will violate the separation offered by the protection.

Conclusion

The use of secondary harness protection material is a necessary part of EWIS design and protection. There are certain applications where it is a great solution and can benefit the overall EWIS reliability. But the secondary harness protection is not a blanket solution for all wire problems. Thoughtful consideration must be given to where this is used and how the other parts of the EWIS are impacted. Lectromec can help you identify the correct secondary harness protection solutions from the component to system level.

Michael Traskos

Michael Traskos

President, Lectromec

Michael has been involved in wire degradation and failure assessments for more than a decade. He has worked on dozens of projects assessing the reliability and qualification of EWIS components. Michael is an FAA DER with a delegated authority covering EWIS certification and the chairman of the SAE AE-8A EWIS installation committee.