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

The arc track resistance test is a basic performance test for most aircraft power carrying wires. As with any component assessment tests, there are many ways to evaluate a wire insulation’s propensity for arc tracking. The European wet short circuit test standard, EN3475 Method 605, is one means to determine the arc track resistance performance of wires and cables. This article discusses some elements of this test, comparison between the test method and other common arc track resistance test, and advantages of this test.

aircraft wire
The physical configuration of the wire harness in the test stand.

Physical Configuration

Prior to performing the wet short circuit test, a seven-wire test harness is prepared such that the conductors at the end of the harness are aligned in the same plane. With the wire ends aligned, the circuits are separated with a short air-gap.

As shown in the figure, the harness is inclined downward at a 10° angle. During test execution, a saline solution is dropped onto the wire harness, bridge the air-gap between the circuits, creating a conductive path between the circuit. The downward incline of the wire harness makes it easy for the saline solution to flow towards the open end of the wire harness.

The saline solution flow rate set such that there is sufficient fluid to initiate electrical arcing but not too high as to over-saturate the sample. Oversaturation with a conducting solution would prevent arcing because the solution creates a conductive path that can result in shorting and cause the circuit protection to trip.

Circuit Configuration

The EN3475 test standard calls for 18 trials to be performed with three trials at six different circuit resistance values. These in-line circuit resistance values are not specified by the standard, but the fault current (the possible current if the circuit is shorted to ground) is specified.

The EN3475 test standard does provide fault currents and recommended circuit protection ratings for several wire gauges that range from 10 – 26AWG. This addresses a gap in the MIL-STD-2223 and AS4373 test method as these methods only specify configurations for 20AWG.

aircraft wire
The electrical power configuration of the seven-wire harness. Each power phase is connected to two wires with the center wire connected to neutral.

Test Performance

During the test performance, the 3-Phase, 115VAC 400Hz power is applied to the test sample, and a saline solution is dripped onto the wire harness. The most common occurrence is an evaporation of the saline solution and brief periods of scintillations or small arcs.

Regardless of the wire type or configuration, there are three possible test outcomes:

  • Nothing happens – Less than 10 mm of the harness may be damaged/destroyed within the 2-hour duration limit.
  • Shorting between wires – Welding and carbon tracking between the wires can cause circuit breakers to trip multiple times. This ends the test.
  • Burn back and damage – The arc could damage/destroy the harness beyond the saline solution drip path. For wire with poor arc track resistance performance, the arcing can propagate for several inches destroying most of the test harness.

Does it Pass?

The pass/fail criteria for the test is determined by the damage length. This is indicated by the length of harness that is destroyed or damaged. The manufacturer’s detail product specification defines the pass/fail criteria for each cable size. Typically, more than 5cm of damage length would indicate a failure criteria.

Those familiar with the AS4373 arc track resistance test methods might anticipate other pass/fail requirements. Since the EN3475 Wet Short Circuit test involves a conductor exposed end on one side of the harness with terminals on the other, there is no method or purpose to test the insulation for breaches. The damage only occurs on the open end of the harness and burns toward the terminal end, therefore, only the damage length is considered.

Comparing to the SAE Methods

The EN3475 wet short circuit test initial harness configuration has a greater propensity for electrical arcing events than the SAE AS4373 wet test method. The test wire harness is prepared to arc more easily in the EN3475 test method since all wires have exposed conductors at the end of the harness (in the AS4373 the insulation of two wires is pre-damaged). Furthermore, the EN3475 test method features six powered wires whereas the AS4373 wire harness is configured with only five active wires and two non-grounded “floating” wires. Since the EN3475 test method better facilitates the initiation of electrical arcing than the AS4373 standard, the EN3475 test calls for a maximum test duration of 2 hours instead 8 hours as specified in the AS4373.

For more information or to discuss your needs, please contact Lectromec

Alexander Petrov

Alexander Petrov

Engineer, Lectromec

Since starting at Lectromec in 2015, Alex has been key in many of test and assessment wire systems assessment projects wire systems assessment. His attention to detail has lead to several key insights in Lectromec’s research initiatives.