Sensors detect overloaded cables preventing fires
7 December 2015 | 0
Flickering lights, tripping breakers, and discoloured outlets are among the ways one can guess that wiring is overloaded. Add visual access, and you can tell if the sheathing may appear discoloured.
But some of us who’ve been around electricity for a while have also developed an acute sense of smell for wiring trouble. There’s a distinctive acrid odour that can be caused by melting components on a PCB, the plastic around a part, or the polyvinyl chloride (PVC) covering on the wire emitting vapour.
That odour on its own, even without visible smoke, is a heads-up to troubleshoot the wiring.
There are, however, flaws in the sniffing method of overloading detection. What happens if the overloading occurs in an overhead crawl space, for example? Or at a remote, non-staffed installation?
Scientists think they have the answer, with a new gas sensor that detects the emissions, “thereby detecting the fires originated in electrical cabinets at early stages,” Sensors and Transducers Journal says.
Multi-metal oxide gas sensor
The German scientists involved in the project have developed a gas sensor called a Multi metal oxide gas sensor (MOG) that works in concert with signal analysis. It should detect overloading before a fire starts.
They say their sensor can detect emissions at “relatively low sample heating temperatures even before a visible colour-change of the PVC isolation material,” the publication says.
It works by analysing “conductance profiles” by measuring electrical resistance in the sensor.
That measurement throws out “four specific conductance signatures, the evaluation of which provides information on the composition and concentration of the gas,” the Karlsruhe Institute of Technology (KIT) says in its press release.
In other words, the MOG is doing the plastic vapour smelling for you, and knows what the odours represent.
It is not the first time that the gas sensor idea has been used for fire detection. It’s actually proven to be a reliable way to detect fires, the scientists explain in their paper.
However, the hybrid sensor and unique algorithm that the team have developed can “identify and analyse a variety of target gases or gas mixtures,” the Institute of Applied Informatics and KIT scientists say in the paper.
Other gasses unrelated to the cabling can cause false alarms.
This targeting allows the results to show “good identification capabilities and concentration estimation accuracy,” according to the paper. That leads to “better incident identification and a very sensitive, more robust detection with a low false alarm rate.”
One benefit is that the more accurate the estimation of the potential hazard, the more appropriate a response can be. Are you sending in an engineer with a replacement wiring harness, or launching a full, possibly unnecessary and costly, lights and sirens response?
That becomes an even more important question to be answered the more remote the location—like on an oil and gas line station, for example.
Presumably, as the algorithms develop, one would know what kind of replacement wiring loom needed replacing in that case. Is it the cable covered in PVC, or the one with the Kevlar in it, for example?
The researchers think that their identifying technique could apply to other kinds of gasses, including dangerous ones.
“The highly sensitive and very reliable hybrid sensors might increase safety in cable ducts,” KIT says.
“In addition, their capability of finding gas mixtures and determining individual gas concentrations might be useful for detecting toxic mould gases during food control, explosive gases in fertiliser silos, or leaks of natural gas pipelines,” it says.
Patrick Nelson, IDG News Service