Portable time domain reflectometers (TDRs) are one of the primary diagnostic tools used by public utility companies, telecommunications providers, and even aircraft support services to detect faults in cables and wires. When an outage or a failure occurs, technicians need to know its precise location before they can implement a fix, and ripping up untold lengths of infrastructure or installation work to locate the problem isn’t an option. TDRs, however, are the perfect fault locators.
They’re more than just diagnostic tools, though. As critical testing and inspection equipment, they’re equally effective when incorporated into the standard maintenance schedule that every cable-owning network operator needs to have. That’s why if you’re in a business where fault-free cabling and wiring are crucial, a TDR needs to be on your equipment roster.
Time Domain Reflectometers Help Simplify Locating Faulty Cabling
Let’s be honest: even under ideal conditions, troubleshooting cable faults is problematic. That’s because their location is rarely ever as obvious as a glaring rupture. Faults in buried, enclosed, and even concrete-encased cable systems can sometimes take days to locate, which is why a portable time domain reflectometer is such an irreplaceable tool for entities who operate or maintain any type of metallic cabling network.
Whether it’s the result of intermittent resistance brought on by aging and corroded cables, or a sudden outage caused by an overly zealous excavator operator who neglected to dial before digging, cable faults and breaks are inevitable. Accurate fault detection is critical to minimizing the cost and inconvenience caused by these interruptions, and a TDR fault locator is the ideal instrument for:
· Identifying the precise location of interruptions and resistive faults;
· Determining actual cable and wire lengths; and,
· Finding the location of any joints or connections along the length of a cable or wire.
Make no mistake: TDRs are indispensable assets for restoring lost network connectivity. With high-quality TDR test equipment at their disposal, the time and resources that utilities and other network-controlling entities would otherwise need to allocate to searching for faults can go toward preventing them. They’re simple to operate, and can be used on any type of metallic wire or cable, regardless of its power rating or mode of transmission.
Core Detection Features That Good Reflectometers Rely On
Just as their name suggests, a TDR reflectometer is designed to send a low voltage pulse through a cable, and to display any changes in impedance that could be indicative of a fault or short as it’s reflected back to the instrument. Unlike fixed-site time-domain analyzers, however, modern, IP-rated graphical TDR reflectometers are designed especially for portable cable run testing.
Whether they’re used for indoor site circuit testing, or isolating the location of underground circuit failures, these lightweight, handheld fault detectors are the optimal diagnostic tool for sparkies, technicians, and network engineers, and boast a typical range of features that include:
· Pulse ranges of up to 6km (19,000 feet);
· Selectable output impedances;
· Adjustable propagation velocities;
· Adjustable scan rates per second; and,
· Output pulse widths from 3 nanoseconds to 3 milliseconds.
The amplitude readings from a modern TDR cable tester can even help operators instantly identify whether a fault is due to higher or lower network resistance. It’s a vital piece of information to have when reacting to faults, especially for power transmission operators, allowing them to make an instant assessment as to whether the fault could potentially cause system-wide damage, or even trigger a secondary hazard.
What Constitutes a Fault, and Where Do TDRs Come In
Accurate locating is everything when it comes to TDR equipment. And with top-quality units claiming detection measurements to within half a meter of the “faulty end” of a cable, network owners can avoid costly hit-or-miss excavation works when searching for the kinds of situations that could lead to impedance changes, such as:
· Cable shorts, or open cables;
· Poor cable splices, or loose connectors or joints; or,
· An intrusive interruption.
The last position any network operator ever wants to find themselves in, however, is persistently chasing line faults. That’s why even though TDRs are excellent line fault locator instruments, they’re even more effective when used as an integral part of a preventive maintenance program. Establishing baseline transmission readings for all of an organization’s network cabling is an essential part of these programs, and it’s no surprise that TDRs fill that role perfectly.
Using TDRs for Scheduled Maintenance as Well as Diagnostics
A solid preventive maintenance program starts by establishing a baseline for all of a network’s performance attributes before failures have a chance to occur. That includes measurements on critical parameters such as:
· Propagation velocity (the relative speed an electrical signal is capable of travelling through the cable);
· Overall cable length (the distance between the cable’s various termination points, joints, and connections); and,
· Cable capacitance (the cable’s ability to store charges between those termination points).
Typically though, these parameters simply aren’t known values for a lot of older, and poorly documented cable installations. And where conditions like corrosion, degradation, or water ingress have had an opportunity to creep in over time, propagation and capacitance in particular aren’t likely to be anywhere near what their values were when the network was originally installed.
Regardless of what the network’s design parameters were, what’s important is knowing what those normal operating parameters are right now. And not only can a TDR cable tester be instrumental in determining what those essential parameters are, but as part of a regular maintenance schedule, it can be effectively used to recognize possible fault patterns before they develop into a costly system failure.
The Final Word
At the end of the day, no matter which type of transmission network you’re responsible for, keeping it in operation is a priority. Faults and outages can occur anywhere along a transmission line though, and having detection equipment that can pinpoint the source of the problem can literally prevent kilometres of cabling and wiring from being taken out of service in an effort to locate the cause.
Whether it’s used as a routine diagnostic tool, or as an emergency fault locator, a portable time domain reflectometer is the tool that every network operator needs to maintain their system’s integrity. And with a TDR on their maintenance equipment roster, they can put an end to costly and frustrating outages.
