Energy Monitor Can Find
Electrical
Failures Before They Happen
Sensor can monitor wiring in a building or ship, and signal when repairs are needed.
By David L. Chandler, M.I.T. News
Failures Before They Happen
Sensor can monitor wiring in a building or ship, and signal when repairs are needed.
By David L. Chandler, M.I.T. News
March 21, 2019 -- A new system
devised by researchers at MIT can monitor the behavior of all electric devices
within a building, ship, or factory, determining which ones are in use at any
given time and whether any are showing signs of an imminent failure. When
tested on a Coast Guard cutter, the system pinpointed a motor with burnt-out
wiring that could have led to a serious onboard fire.
The new sensor, whose readings can
be monitored on an easy-to-use graphic display called a NILM (non-intrusive
load monitoring) dashboard, is described in the March issue of IEEE
Transactions on Industrial Informatics, in a paper by MIT professor of
electrical engineering Steven Leeb, recent graduate Andre Aboulian MS ’18, and
seven others at MIT, the U.S. Coast Guard, and the U.S. Naval Academy. A second
paper will appear in the April issue of Marine Technology, the
publication of the Society of Naval Architects and Marine Engineers.
The system uses a sensor that
simply is attached to the outside of an electrical wire at a single point,
without requiring any cutting or splicing 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
analyzing 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 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
About 20 different motors and
devices were being tracked by a single dashboard, connected to two different
sensors, on the cutter USCGC Spencer. The sensors, which in this case had a
hard-wired connection, showed that an anomalous amount of power was being drawn
by a component of the ship’s main diesel engines called a jacket water heater.
At that point, Leeb says, crewmembers were skeptical about the reading but went
to check it anyway. The heaters are hidden under protective metal covers, but
as soon as the cover was removed from the suspect device, smoke came pouring
out, and severe corrosion and broken insulation were clearly revealed.
“The ship is complicated,” Leeb
says. “It’s magnificently run and maintained, but nobody is going to be able to
spot everything.”
Lt. Col. Nicholas Galanti, engineer
officer on the cutter, says “the advance warning from NILM enabled Spencer to
procure and replace these heaters during our in-port maintenance period, and
deploy with a fully mission-capable jacket water system. Furthermore, NILM
detected a serious shock hazard and may have prevented a class Charlie
[electrical] fire in our engine room.”
The system is designed to be easy
to use with little training. 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.
Detecting anomalies before they
become serious hazards is the dashboard’s primary task, but Leeb points out
that 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.
“It’s a three-legged stool,” Leeb says.
The system allows for “energy scorekeeping, activity tracking, and
condition-based monitoring.” But it’s that last capability that could be
crucial, “especially for people with mission-critical systems,” he says. In
addition to the Coast Guard and the Navy, he says, that includes companies such
as oil producers or chemical manufacturers, who need to monitor factories and
field sites that include flammable and hazardous materials and thus require
wide safety margins in their operation.
One important characteristic of the
system that is attractive for both military and industrial applications, Leeb
says, is that 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, Leeb says, “if
the noncontact version was installed” in that part of the ship, “we would see
almost the same thing.”
The research team also included
graduate students Daisy Green, Jennifer Switzer, Thomas Kane, and Peer Lindahl
at MIT; Gregory Bredariol of the U.S. Coast Guard; and John Donnal of the U.S.
Naval Academy in Annapolis, Maryland. The research was funded by the U.S.
Navy’s Office of Naval Research NEPTUNE project, through the MIT Energy
Initiative.
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