View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Standard & Regulation Aging Wires & Systems Maintenance & Sustainment Management Conference & Report Protection & Prevention Research Miscellaneous Arcing
Popular Tags
Visual Inspection High Voltage AS50881 MIL-HDBK MIL-HDBK-525 FAR AS4373 Electromagnetic Interference (EMI) Maintenance FAR 25.1707 Wire System Arcing Damage
All Tags in Alphabetical Order
2021 25.1701 25.1703 abrasion AC 33.4-3 AC 43 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 AS29606 AS4373 AS4373 Method 704 AS50881 AS5692 AS6019 AS6324 AS81824 AS83519 AS85049 AS85485 AS85485 Wire Standard ASTM B355 ASTM B470 ASTM D150 ASTM D2671 ASTM D8355 ASTM D876 ASTM F2639 ASTM F2696 ASTM F2799 ASTM F3230 ASTM F3309 ATSRAC Attenuation Automated Wire Testing System (AWTS) Automotive Avionics backshell batteries bend radius Bent Pin Analysis Best of Lectromec Best Practice bonding Cable Cable Bend cable testing Carbon Nanotube (CNT) Certification cfr 25.1717 Chafing Chemical Testing Circuit Breaker circuit design Circuit Protection cleaning clearance Coaxial cable cold bend collision comparative analysis Compliance Component Selection Condition Based Maintenance Conductor Conductor Testing conductors conduit Connector Connector rating connector selection connector testing connectors contacts Corona Corrosion Corrosion Preventing Compound (CPC) corrosion prevention Cracking creepage 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 electric aircraft Electrical Aircraft Electrical Component Electrical Power Electrical Testing Electrified Vehicles Electromagnetic Interference (EMI) Electromagnetic Vulnerability (EMV) Electrostatic Discharge 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 fault tree Fixturing Flammability fleet reliability Flex Testing fluid exposure Fluid Immersion Forced Hydrolysis fuel system fuel tank ignition Functional Hazard Assessment functional testing Fundamental Articles Fuse Future Tech galvanic corrosion Glycol Gold Gold plating Green Taxiing Grounding hand sanitizer handbook Harness Design harness protection hazard Hazard Analysis health monitoring heat shrink heat shrink tubing high current high Frequency high speed data cable High Voltage High Voltage Degradation HIRF History Hot Stamping Humidity Variation HV connector HV system ICAs IEC 60851 IEC60172 IEEE immersion insertion loss 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 lightning protection liquid nitrogen lithium battery lunar Magnet wire 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-7928/5 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 polyamide polyimdie Polyimide-PTFE Power over Ethernet power system Power systems predictive maintenance Presentation Preventative Maintenance Program 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 Separation Requirements Series Arcing Service Life Extension Severe Wind and Moisture-Prone (SWAMP) Severity of Failure shelf life Shield Shielding Shrinkage signal 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 superconductor 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 volume resistivity vw-1 wet arc white paper whitelisting Winding wire 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

Impact of Corona on Electrical Systems

Testing & Assessment

Corona is an area of electrical systems that many have some knowledge, but often only to the point of knowing that there is a voltage that should not be exceeded. It is common knowledge that factors, such as pressure, have an impact on when and how corona will happen, though the source of corona is not. This article describes what is corona and how to assess the susceptibility of materials designed to protect your aircraft electrical system.

Why Corona Matters in Aerospace Systems

Up until recently, corona inception and extinction has been generally ignored in the aerospace industry and for good reason. This is because most aircraft power systems are run on 115 VAC and/or 28 VDC systems (read the article about power systems here). These systems are virtually impervious to corona because the voltages are not high enough to generate an event. New aircraft systems are looking to move to higher voltages with the more-electric aircraft (MEA) movement. The MEA movement is looking to replace pneumatic and hydraulic systems with electric systems when possible to save cost and weight. These systems do a lot of the heavy lifting in aircraft and their electronic equivalents require a vast amount of power. This increase in power requirements of circuitry aboard aircraft essentially forces a move to higher voltages. However, there are practical limitations on the amount power that can be delivered with low voltage power systems.

Analysis has been done that concludes that without going to higher voltages, either weight from too large of a transmission system (large gauge wire) or transmission losses in the circuitry will be prohibitive. Higher voltages very soon get into the realm where corona and partial discharge become a problem.

What is Corona?

EWIS Corona
Use of higher voltages in aircraft electrical systems has significant benefits, but can lead to wire/cable insulation degradation and corona.

Corona is defined as ionization and partial discharge resultant from high voltages. The mechanism of corona hinges on a localized electric field that is strong enough to ionize an insulating medium such as a wire/cable insulation, an air gap, or a non-conductive coating. This phenomenon is distinct from arcing because the ionization from the high potential (voltage) does not extend far enough to reach a grounded voltage source, so generally only small leakage pulses to the surrounding air are witnessed.

Coronal ionization can happen around terminations within an insulated system (such as wires and cables) that are exposed to air or can happen within the insulation itself.

Corona Inception and Extinction

For all things, there is a start and stop; for corona, there are the inception and extinction voltages. Corona inception voltage is defined as the voltage at which corona begins to occur (note: since there can be a difference in the corona inception voltage depending on the rate of voltage increase, most tests are designed to find an inception voltage use a steadily raised voltage). It has been observed that when corona begins, it often continues until the voltage is lowered significantly lower than the corona inception voltage. This prompts the definition of another quantity. If corona is occurring, the corona extinction voltage is the voltage that corona ceases as the voltage is lowered. The corona extinction voltage is lower than the corona inception voltage by definition.

An Accepted Test Method

The ASTM D1868 test standard provides a method for testing an insulation systems corona inception and extinction voltages. This method defines several measurable quantities of interest when it comes to corona such as the effective power loss from corona pulses. It also describes ways of measuring these quantities. These methods use means of noise reduction to reduce noise from common sources such as Electromagnetic Interference (EMI) and the requirement of using a high voltage power supply. They also give measuring speed requirements to capture coronal fluctuations and provide ways of calibrating a test setup to appropriate levels of sensitivity.

The main purpose of this test method, however, is to be able to capture effectively when corona inception and extinction occurs. This requires, in general, highly sensitive equipment and tight controls in the test circuitry. A low corona inception voltage of an insulating material may be indicative of microscopic air bubbles trapped within the insulation.

Quantifying Long Term Insulation Damage

It is well known that corona causes degradation to insulation systems. A new SAE test method is on the horizon to address this: high voltage endurance test method. This effectively puts insulation under a high voltage above their corona inception voltages until a full discharge event occurs. The voltage the insulation is placed under is then varied to generate a time to failure against voltage applied curve.

The failure generally causes lasting damage so that the insulation can no longer withstand the voltages it could at the beginning of the test. A full discharge event is distinct from the partial discharges happening whenever corona is present. This is discussed more fully in this article.

Supporting New and Existing Systems

Long-term exposure to high voltage can have impacts on system components, as well as, the interconnection system. The processes of insulation degradation are understood and methods for its assessment already exist. As products are placed under the strain of higher voltages, it is necessary to assess and quantify component performance before they are place onto aircraft. Contact Lectromec to find out more about how Lectromec can help determine your component’s performance.

Tristan Epp Schmidt

Tristan Epp Schmidt

Engineer, Lectromec

Since starting at Lectromec in early 2015, Tristan 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.