View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Aging Wires & Systems Management Standard & Regulation Conference & Report Maintenance & Sustainment Research Protection & Prevention Arcing Miscellaneous
Popular Tags
Visual Inspection MIL-HDBK MIL-HDBK-525 FAR AS50881 FAR 25.1707 Electromagnetic Interference (EMI) Wire System High Voltage Arcing Damage FAR 25.1709 Degradation
All Tags in Alphabetical Order
25.1701 25.1703 Accelerated Aging ADMT Aging Systems Aircraft Power System Aircraft Service Life Extension Program (SLEP) arc damage Arc Fault (AF) Arc Fault Circuit Breaker (AFCB) Arc Track Resistance Arcing Arcing Damage AS22759/87 AS4373 AS4373 Method 704 AS50881 AS5692 AS6019 AS85485 AS85485 Wire Standard ASTM F2799 ATSRAC Attenuation Automated Wire Testing System (AWTS) Bent Pin Analysis Best of Lectromec Best Practice Cable cable testing Carbon Nanotube (CNT) Certification Chafing Chemical Testing Circuit Breaker Circuit Protection Coaxial cable cold bend comparative analysis Compliance Component Selection Condition Based Maintenance Conductor Connector connectors contacts Corona Corrosion Corrosion Preventing Compound (CPC) Cracking D-sub data analysis data cables degradat Degradation Delamination Derating dielectric constant Distributed Power System DO-160 Electrical Aircraft Electrical Component Electrical Testing Electromagnetic Interference (EMI) Electromagnetic Vulnerability (EMV) EMC EMF EN3197 EN3475 EN6059 End of Service Life End of Year Energy Storage engines Environmental Environmental Cycling ethernet EWIS Component EWIS Design EWIS Failure EWIS Thermal Management EZAP FAA AC 25.27 FAA AC 25.981-1C 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 Forced Hydrolysis fuel system fuel tank ignition functional testing Fundamental Articles Future Tech Green Taxiing Grounding Harness Design Hazard Analysis health monitoring heat shrink tubing high current high Frequency high speed data cable High Voltage History Hot Stamping Humidity Variation ICAs Instructions for Continued Airworthiness Insulation insulation resistance IPC-D-620 ISO 17025 Certified Lab Laser Marking life limited parts life projection Maintenance Maintenance costs Mandrel Mechanical Testing MECSIP MIL-C-38999 MIL-C-85485 MIL-DTL-17 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-1560 MIL-STD-1798 MIL-STD-464 MIL-T-7928 MIL-T-81490 MIL-W-22759/87 MIL-W-5088 Military 5088 modeling MS3320 NASA NEMA27500 No Fault Found off gassing Outgassing Overheating of Wire Harness Parallel Arcing part selection Performance Physical Testing Polyimide-PTFE Power over Ethernet Power systems predictive maintenance Probability of Failure Product Quality Radiation Red Plague Corrosion Reduction of Hazardous Substances (RoHS) relays Reliability Research Rewiring Project Risk Assessment SAE Secondary Harness Protection Separation Requirements Series Arcing Service Life Extension Severe Wind and Moisture-Prone (SWAMP) Severity of Failure Shield Shielding signal cable silver plated wire smoke Solid State Circuit Breaker Space Certified Wires stored energy supportability Sustainment Temperature Rating Temperature Variation Test methods Test Pricing Testing Thermal Circuit Breaker Thermal Endurance Thermal Index Thermal Shock Thermal Testing Tin plated conductors Troubleshooting TWA800 UAVs verification Visual Inspection white paper whitelisting Wire Ampacity Wire Certification Wire Comparison wire failure wire properties Wire System wire testing Wire Verification work unit code

270VDC arcing in aircraft wiring

Research

In a recent presentation to the SAE at the biannual meeting, Lectromec presented a summary of the work that was performed by several companies and the Federal Aviation Administration (FAA) last summer. These tests were performed at the FAA’s Technical Center in Atlantic City on 270VDC in aircraft wiring.

There were four test objectives:

  1. Perform testing that would help groups such as the SAE better understand the damage potential from higher voltage arcing events;
  2. Determine the impact from 270VDC due to direct contact electrical arcing to several target types;
  3. Determine the impact from 270VDC due to indirect arc damage; and
  4. Gather 270VDC arc waveform data for Lectromec’s Arc Damage Modeling Tool (ADMT).

The test configurations and methods used were similar to common arc damage techniques previously reported upon, although some modifications were made to handle the 270VDC power source. In the general test configuration, the power source was run through a contactor and to the arc fault location. The adjustable fault current limiting resistors were placed on the return circuit, as was a fuse to limit the arc duration.

During testing performed during the last decade by the FAA and Lectromec, it was found that the swing test was a good representative test procedure for assessing direct contact arc damage. In these swing tests, a cut is made in the wire insulation such that the conductor is exposed. The ends of the wire are then connected to the circuit and attached to a power source. The target, in this example, a section of aircraft structure, is attached to ground. The test begins by pulling the wire from the target, applying the power, then releasing the wire and allowing it to freely swing into the structure, making contact and creating an arcing event.

An example of the configuration and moment of contact is shown in the following figure.

aerospace wiring
Performance of 270VDC arc damage assessment testing at FAA.
Looking to address your challenges with wire system separation? To find out more read Arc Damage Analysis.

Those present during the tests described the testing as, “…the arc sounded more forceful, more energetic, and the flash also seemed brighter as compared to similar testing performed at 115VAC.”

An example waveform from a swing test is shown below. There are three distinct sections to the waveforms generated from these tests.

Part One: Wire Strike for aerospace wiring

This is where the wire makes first contact with the target and causes the damage. In the scenario below, the arc event lasted for approximately 2ms.

Part Two: Shorting

As the wire continues to move closer to the target surface and a larger portion of the surface area is making contact, it creates a shorting event. The current rises, and the voltage drop across the wire-target interface is reduced such that no further damage is done to the target. The shorting event continues until the next event, fuse opening.

Part Three: Fuse Opening

Here, the fuse trips and ends the event. In the testing shown here, the fuse was selected to open after little more than 50ms. During these tests, custom fuses were used to set the duration of the failure event. The durations ranged from 3ms to approximately 200ms and were selected based on the known response time of 270VDC protections schemes in the field.

aircraft wiring

A couple dozen tests were performed with various circuit protection durations. Close examination of the arcing waveforms from each of these configurations show that the 270VDC waveform is similar to a 28VDC arc, albeit with more energy.

Damage at a distance

The testing was also performed to assess the damage at a distance, the potential damage from the arc plume. Although the test and arc duration were limited (less than 200ms), there was sufficient arc energy to cause a measurable impact up to 0.5” away. Further examination and data gathering is necessary for assessing damage at a distance, but the techniques used, proved to be valid for the test parameters chosen.

Arc Modeling and Assessment

In the review of the data gathered from testing, there was a wealth of information that could be used for Lectromec’s Arc Damage Modeling Tool analysis. The waveforms from the physical tests were used as seed data to determine the modeling parameters.

The simulations results indicate that the arc efficiency (the factor of arc energy used to damage the target) was within anticipated boundaries. Lectromec anticipates examining the ‘damage at a distance’ tests in the next couple of months.

So what does it mean for the designer?

Takeaway #1 – Because there are higher voltages, the designs based on 115VAC need to be reevaluated. The same methods used for assessing arc damage at lower voltages such as 115/208VAC are still valid and can be applied to higher voltage events. The SAE is currently working on the proposed test methods and may enter a round-robin method review in the next year.

Takeaway #2 – Review of the data suggests that the electrical arc has a higher power and may be able to cause damage to physically separated systems. Also, it is important consider that for systems operating on 270VDC, unlike AC arcing, there is no voltage potential crossing reaching zero.

Takeaway #3 – The limited damage shown during these tests was only possible because of the rapid circuit protection response. Selection of circuit protection is critical for system safety and limited failure impact.

The test results and analysis will be included in a paper to be presented later this year.

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.