The system uses a sensor that’s attached to the outside of an electrical wire at a single point, without any cutting or spilcing of wires. From that single point, it can sense the flow of current in the adjacent wire and detect the distinctive “signatures” of each motor, pump, or piece of equipment in the circuit by analysing tiny, unique fluctuations in the voltage and current whenever a device switches on or off. The system can also be used to monitor energy usage, to identify possible efficiency improvements and determine when and where devices are in use or sitting idle.
The readings are monitored on a graphic display called a NILM (non-intrusive load monitoring) dashboard. The computer dashboard features dials for each device being monitored, with needles that will stay in the green zone when things are normal but swing into the yellow or red zone when a problem is spotted.
The technology is especially well-suited for relatively small, contained electrical systems such as those serving a small ship, building, or factory with a limited number of devices to monitor. In a series of tests on a Coast Guard cutter based in Boston, the system provided a dramatic demonstration last year, revealing a motor with burnt-out wiring that could have led to a serious onboard fire.
Detecting anomalies before they become serious hazards is the dashboard’s primary task, but it can also perform other useful functions. By constantly monitoring which devices are being used at what times, it could enable energy audits to find devices that were turned on unnecessarily when nobody was using them, or spot less-efficient motors that are drawing more current than their similar counterparts. It could also help ensure that proper maintenance and inspection procedures are being followed, by showing whether or not a device has been activated as scheduled for a given test.
All of its computation and analysis can be done locally, within the system itself, and does not require an internet connection at all, so the system can be physically and electronically isolated and thus highly resistant to any outside tampering or data theft.
Although for testing purposes the team has installed both hard-wired and noncontact versions of the monitoring system — both types were installed in different parts of the Coast Guard cutter — the tests have shown that the noncontact version could likely produce sufficient information, making the installation process much simpler.
While the anomaly they found on that cutter came from the wired version, the researchers said, “if the noncontact version was installed” in that part of the ship, “we would see almost the same thing.”