Addressing SSTDR Technology

Security and alarm business makes sense of complexities

Security and alarm systems become more complex every day as new services, features, technologies and capabilities are added. This complexity is powered by good old electricity, and without a reliable and consistent source of power, the systems are useless. All of the wiring configurations within each system that carry data, video, signal and voice, Cat-5, coax cable and Romex are the backbones that transmit the information about the overall health of each system.

Power over Ethernet, low-voltage sensor lines and AC and DC voltages all flow over these different types of conductors. If something goes wrong, you want to know about it as soon as possible and figure out what to do about it for the customer. But what happens when an intermittent condition pops up and trips alarms or sets off sensors? And then what happens when a technician responds and shuts off the power to check the circuits but finds nothing? How does a system get checked for electrical faults while it is running, without disturbing the service to the customer?

What if you could look into the electrical workings of any cables such as security and alarm, CCTV coax, data, electrical power, high-voltage utility cable and/ or aircraft cables while they are carrying voltage, video or even high-speed data, and see active faults such as intermittent shorts or arc faults? Well, now you can. A new technology is making its way to market, and the impact on all these things will be tremendous.

The new technology is an advanced form of spread-spectrum time-domain reflectometry (SSTDR), and it is being developed and commercialized by two American companies for worldwide applications of all types.

SST has been around for a long time. It was first thought of during World War II for use in secure communications from submarines. Qualcomm developed a version of this concept to help cellphones connect with each other over a noisy and uncertain wireless environment. The reason someone in Hong Kong can dial your cellphone and reach only you, not the other 7 billion people on earth, is mostly due to spreadspectrum implementation. What has happened over the wireless world is now coming to the wired world.

The advanced form of this technology promises to revolutionize the TDR cable-testing market and make it safer and easier to see exactly what is happening on live, energized circuits on all types of equipment and over all types of conditions.

A time-domain reflectometry (TDR) cable tester uses a generated pulse that is shot down a cable to seek out opens and shorts that exist in the cable. The reflected pulse shows a delay in time that can be translated into distance or location of the fault. Traditional TDRs can work only when the cable they are testing is off or unpowered. This is because the voltage noise on the line interferes with the pulse, and the reflection is lost in this noise. Advanced SSTDR fixes this by skipping or “floating” around the noise by generating multiple frequency pulses that cut through all the interference and capture the reflected pulse to show exactly where the fault occurs, when it occurred and what its characteristics are. In addition, unlike older TDR technology, SSTDR also can do dynamic testing, which can monitor an energized cable system while it is under load or stress and in use and wait for a fault to occur.

This is handy for those faults that are intermittent due to some outside influence, such as voltage surges or outside signal interference, that changes the character of the circuit. An example of this is a short in a power cord attached to a piece of machinery that shorts out only when a parts cart rolls over it, or an aircraft that has some abraded insulation in its wiring harnesses that is shorting for only nanoseconds during takeoff or landing.

SSTDR technology was developed out of a need to see what is happening on live circuits on a 24/7 basis.

Developed at Utah State University and University of Utah physics labs, the technology got its major impetus after the July 1996 crash of TWA Flight 800, which blew up over the south shore of Long Island, N.Y., killing all 230 people aboard. The cause of that crash was later attributed to an abraded control cable that went through the belly tank of the 747 aircraft. The wiring was arcing against a strut intermittently, for what could have been months, and the fuel in the center tank exploded with a terrible result. This event triggered development grants from DOT, FAA and the military for ways to avoid or locate these types of faults in aircraft wiring.

Fifteen years and 16 patents later, the advanced form of SSTDR is now being commercialized into handheld and portable test equipment as well as applications where it can be embedded to act as a watchdog for “events” on cabling systems inside data system switches, monitoring equipment for security/ alarm systems or fire alert systems. By being able to report live and immediately, SSTDR technology gives a clear, real-time view of any electrical event that happens, no matter how briefly and at what intervals.

In addition, the sensitivity of the technology offers another interesting possibility. By using new capacitive coupling techniques, a security/alarm technician can clamp on the insulation of a pair of conductors without touching bare wire or disconnecting anything and monitor the lines continuously to detect, locate and characterize an intermittent problem that could be reported wirelessly to his or her cellphone. This remote monitoring of electrical conditions within a security system could pinpoint bad connections or failing cable without having to take the entire system offline.

Where Will it be Used?

Advanced SSTDR technology will be used on the new electromagnetic braking systems being designed by major truck manufacturers. It is now being tested by the Navy for inclusion in flight-line equipment on carriers and shipboard systems fleet-wide. The smart grid can now be smarter with SSTDR modules inside of power switches, distribution points and even circuit breakers at homes and businesses. Street lighting systems can report light outages or cable theft attempts instantly, mining equipment can be monitored underground to mitigate explosions caused by electrical arcing in equipment and cables, and security and alarm systems will have a new tool that can keep customer systems running and without interruptions.

Key monitoring switches, servers and sensors might have this technology embedded inside their control units so it could self-test 24 hours a day. The applications for such a revolutionary and disruptive technology are many and varied.

What it Means

The detection, location and characterization of intermittent electrical faults on live energized conductors can now be done easily, which will create safer electrical, data and video systems in all industries and let service organizations keep networks running smoothly. For security and alarm system installers and servicing organizations, it means finding intermittent faults faster and determining the reason for the faults more accurately, while making systems more reliable for the customer.

A new emerging technology such as SSTDR will make a lasting and important contribution to the security and alarm business both in the form of handheld or portable testing equipment and with OEM equipment that will have it built in as an important safety feature for each and every cable run.

Advances such as this will help the complexity of newer security enhancements being added to networks work better and more reliably.

This article originally appeared in the June 2012 issue of Security Today.


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