Download the full PDF article here.

Download full PDF article here.

LiveWire Test Labs will dispatch its trained technicians directly to your site, to help you diagnose the most aggravating of your electrical problems – intermittent faults.

How our Fault Detection Service Works:

Step 1 is to contact our staff and discuss the details of your electrical environment and the problems you face, to make sure the LiveWire technology is applicable, and to customize our tools for your environment. The following items will need to be discussed prior to an on-site visit:

• wire and connector types;
• reproducibility of the fault;
• network topography (e.g. branching)
• wire lengths involved.

Guaranteed Fault Detection Location:

If we make a site visit and can’t determine the distance to fault, you don’t pay. It’s that simple. The only provisos are that we accurately confirm the nature of the electrical environment at your site, and that the fault is reproduced while we’re there.

Get Started:

To discuss the details of your electrical wiring issues, please contact us.

What an Integrated Circuit Time Domain Reflectometer is:

The LiveWire SSTDR-ASIC is a cutting edge integrated circuit that detects and locates intermittent fault conditions in high noise environments (e.g. live electrical power circuits, communication lines, sensors and safety systems, various types of concrete/steel structures) in real time.

How an Integrated Circuit Time Domain Reflectometer Works:

The LiveWire ASIC can be integrated with your technology to reduce maintenance / troubleshooting / monitoring costs, increase system reliability, and can extend the useful life of assets by providing accurate real time monitoring.  LiveWire’s unique core technology is Spread Spectrum Time Domain Reflectometry, or SSTDR.  The technological foundation of cell phone communications, spread spectrum is used to transmit a small but nevertheless recognizable signal in a high noise environment.  By combining spread spectrum with TDR technology, LiveWire has achieved a significant breakthrough in being able to monitor changes in wiring systems, in real time. Changes that occur for as brief a time period as one millisecond can be detected, characterized, and located (distance to fault) within an accuracy of +/- 2% over distances from a few inches to hundreds of meters.

Who Uses It:

The LiveWire SSTDR-ASIC is used in a variety of situations, including aging aircraft, electrical power utility grids, construction and mining equipment and vehicles and many more. To see a more comprehensive list of applications, click here.

Key Features:

• Small form factor easily integrates into existing products.
• Reduces maintenance costs for existing assets by pinpointing the location of intermittent fault conditions live during operation.
• Increases the LTV of assets by keeping them in service longer and with fewer problems.
• Increases safety and reduces downtime.
• Works on systems of all types and sizes (power, communications, sensors, etc..)

Technical Specifications:

• Spread Spectrum Time Domain Reflectometry (SSTDR)
• Continuous Monitoring 1 Channel:
• Scans Wire ~3000 scans/sec
• Multiplexed Monitoring 4 Channels
• Each wire between ~2000 scans/sec and ~500 scans/sec
• 1 Differential Receiver Channel
• SPI mode 0 or 3 Interface – 24 MHz Nominal up to 48MHz max
• Digital Control Interface
• Arc Fault Capture Mode
• Test Frequencies: 1.5 MHz to 96MHz
• Covers wide range of cable lengths
• LWA-1001N = 8mm X 8mm Leadless Package (QFN)

Operating Characteristics:

• 3.3 VDC +/- 5% @ ~175 mA Typical
• Ambient Operating Temperature of -40 °C to +105°C
• 4kV Human Body Model (HBM) ESD protection levels
• Transmit voltage level 2mV to 500mV peak to peak
• 24 MHz Crystal/Oscillator
• 2 KB SRAM Cache Holds 10 scans
• Internal Power On Reset

Public scrutiny has prompted strongly worded recommendations from the likes of NASA, the U.S. Federal Aviation Administration, and the National Transportation Safety Board (NTSB). “The safety of the nation’s wire systems is an issue of major importance to us all,” noted a White House report issued in 2001. Several months earlier, the NTSB concluded its lengthy investigation of TWA 800 with the verdict that a short circuit sparked an explosion in the center wing fuel tank. The condition of the wiring, it noted, was “not atypical for an airplane of its age.” Among the NTSB’s recommendations was to incorporate into aircraft “new technology, such as arc-fault circuit breakers and automated wire test equipment.”

Failing the test of time

Typically, a copper conductor (from 1 to 10 mm in diameter) is covered by a thin outer insulation (from 0.5 to 2 mm thick). Damaged insulation can expose the copper, giving rise to arcs, shorts, and electromagnetic emission and interference. As the wire ages, the insulation may become brittle and crack. Chafes appear as wires vibrate against each other, a tie-down, or any other hard surface. Maintenance can also be hard on wires, as they may be nicked by workers’ pliers, or bent beyond their tolerable radius, or sprinkled with metal drill shavings, chemicals or water, or even used as stepladders in hard-to-reach places. Even simple moisture condensation can spell trouble, particularly in conjunction with polyimide insulation, which breaks down when exposed to moisture and heat, not a good scenario for a vehicle that must contain drip loops in the wiring, because it is normally wringing wet after each flight! Moisture creating a short circuit between compromised wires can cause a tiny arc, gradually carbonize the insulation, and finally result in flashover and fire. And it isn’t just old planes that have problems. In areas such as the wheel well, nearly 1/3 of all planes will have wiring faults within the first year.

The hazard of these pervasive “wet arcs” has prompted the development of arc fault circuit breakers. Ordinary circuit breakers are heat-sensitive bimetal elements that trip only when a large current passes through the circuit long enough to heat the element. This power may be on the order of 1000 percent of the rated current for 0.35 to 0.8 seconds. By comparison, a single arc fault may last only 1.25 ms, and a series of events may last 20–30 ms. Too fleeting to trip the circuit breaker, these arc faults can nonetheless cause catastrophic local damage to the wire. Fires have been known to break out with the breaker still intact.

Arc-fault circuit breakers contain sophisticated electronics to sample the current on the wire at submillisecond intervals. Both time and frequency domain filtering are used to extract the arc-fault signature from the current waveform. This signature may be integrated over time to discriminate, by means of pattern-matching algorithms, between a normal current and a sputtering arc-fault current. And so ordinary transients, due to, say, a motor being turned on and off, can be distinguished from the random current surges that occur with arcing.

Arc-fault breakers are already required in new home wiring in the United States and are now being miniaturized for use on aircraft. One of the most significant problems that is limiting the adoption and implementation of arc-fault breakers is lack of a method for locating the tiny damage left on the wire after the breaker has tripped. The figure below shows the damage left after a traditional thermal circuit breaker has tripped, damage that is clearly visible or that could be found with today’s test methods, and damage that could have started a fire if flammables had been near the fault when it occurred. The figure on the right shows the damage left after the arc fault circuit breaker has tripped, damage that is so small that the wire is still fully functional, has an impedance discontinuity of less than an ohm, and damage that would be extremely difficult or impossible to locate.
LiveWire Test Labs can locate these faults – a critical enabling technology for the deployment of arc fault circuit breakers.

Not to panic

If you happen to be flying this week, do not panic. Few wiring problems end in disaster. There is cause for concern, though, as the air fleet continues to age, and our reliance on air transport grows. While an aircraft’s other major systems undergo preflight testing and regular inspection and maintenance, its central nervous system–wiring–has been long neglected. Sorely needed are new maintenance methods that account for the aging of wires, as is done for aging structural and computer systems.

Diagnosis is good. Prognosis is better. And prevention is better still. This last may require a new way of thinking for electrical engineers, who tend to be more at home with obsolescence than geriatrics. For aging aircraft wiring, the dream of smart systems that can detect and locate the intermittent faults before they cause disasters like TWA 800 and Swissair 111 is on the horizon. LiveWire Test Labs is proud to be making a difference in how the most basic neuron in our electrical nervous system, the wire, is understood and maintained. Soon, this tiny neuron will have a mind all its own, whether it is in an aging airplane, train, ship, skyscraper, nuclear power plant, communication network, or even in your family car.

For more information on how Livewire’s technology has direct application to your product, please contact us.

Download full PDF article here.

Download full PDF article here.

What It Is:

LiveWire’s Mobile Service Pack, dubbed WILMA (Wiring In-Line Maintenance Aid), is a portable Spread Spectrum Time Domain Reflectometer.

How It Works:

The LiveWire Mobile Service Pack (MSP) detects and locates intermittent faults on live and dead wires/cables. It records the type of fault, distance to fault, and time of occurrence and reports the information to an instrumentation computer via USB.

Applied Uses:

The Mobile Service Pack WILMA can be applied in a variety of contexts, including: aerospace, industrial, communications, computer networks, structural cables and anything with complex wiring systems.

Key Features:

• Detection and location of intermittent faults on live or dead wires
• Multiple frequency testing allows the monitoring of wires up to 900 feet
• Monitors 1 to 4 Wires (see detail below)
• Detection of 5 millisecond or longer duration arc faults.
• Location of open circuits, short circuits, and arc faults
• Unique technology allows fault location in noisy environments  (e.g. live communication and power distribution wires)

Technical Specifications:

• Distance to Fault Accuracy:
  • +/- 2 feet for Wire Length <= 150 ft.
• Maximum Input Ratings for Powered Lines
  • Voltage below are Out of the box and can be customized for different applications
  • Powered AC Voltages: Up to 285 VAC @ 60 or 400 Hz (800 V peak-to-peak)
  • Powered DC Voltages: Up to 600 VDC
• Monitors 1 to 4 Wires (Wires are Multiplexed)
  • Single wire monitoring for Live arc faults
  • Up to 4 wires for non-powered or communication wires
• External Power:
  • USB 2.0 Power Lines from Laptop
  • USB Cable Included
• Cable Connectors: Custom Per Purchase Order (6 Pin Amphenol standard)
• Output Signal Amplitude: 0.016– 0.124 V peak-to-peak selectable
  • EMI certified as per MIL-STD-461
• PC Software:
  • Wire Test Studio version 6.0
  • Operating system: Windows XP

The on-site tests revealed that LiveWire’s SSTDR technology can be used to detect and locate changes in baseline anchor cable performance under the following conditions:

• Up to 160 feet from the test point
  • In electrically isolated concrete anchors
• Both grouted and ungrouted
• Partial breaks or corrosion down to 50% of baseline performance

Prior to making a site visit, LiveWire technical staff and the structure’s owners / operators exchange technical information to provide permanent access points for the initial and all subsequent tests. This may include some minor drilling to provide a point of connection between the anchor(s) and the LiveWire test equipment. Anchors must be electrically isolated, which can be easily determined.

During the initial visit, LiveWire personnel and the owners / operators work together to install and calibrate the system and establish baseline readings for each anchor cable to be monitored. This data is stored for future comparisons.

At virtually any interval specified by the owner/operator of the structure, a LiveWire specialist returns, records fresh data from the same test access points, compares the results from the previous visit, and detects and locates any faults that may have developed in the interim.

This detection and location of faults in a high noise environment (such as steel embedded in concrete) is made possible by LiveWire’s unique technology known as Spread Spectrum Time Domain Reflectometry, or SSTDR, whereby the signals from the noise are extracted from the reflected signals, permitting isolation of any real changes in the health of the system. For more technical information, please see Technology or contact us.

Download full PDF article here.