The Department of Energy's Oak Ridge National Laboratory has developed a direct-current detector technology to help emergency responders safely detect high voltages, which they have licensed to North Carolina-based Hotstick USA.

The DC hotstick voltage probe can accurately detect the presence of DC voltages in a hybrid electric vehicle. (Image courtesy of Carlos Jones/Oak Ridge National Laboratory, U.S. Dept. of Energy)

In emergency situations, first response teams often rely on voltage detectors such as the AC Hotstick, to sense the presence of dangerously high alternating current electric voltages from a safe distance. The increase in electric vehicles on the road and solar panels on homes, however, means high voltages could also originate from direct current sources, which are not accurately detected by existing technologies. Battery packs are typically situated in the rear of EVs, with electrical cables running to the controller up front and to other devices. In an accident, the car's battery could still be connected and energized at 400 to 600 volts. The vehicle may be splayed open, and first responders need to know whether the car is carrying a charge before they can even touch it, much less cut through cables to extract a victim. That much voltage is potentially lethal and can cause arc flash hazards or trigger explosions.

In certain cases, you can measure electrical fields from DC, but the fields are easily interfered with by plastics and other kinds of materials. The probe is therefore designed with a piercing tool to cut through plastic cable insulation that may obstruct contact with the vehicle's battery and to indicate that a valid electrical connection is made. This ensures good contact for an accurate voltage reading in a situation where decisions must be made in seconds.

While the system was designed for electric vehicles and solar panels, it could also be used to make measurements in a variety of settings. The circuit can detect the presence of both AC and DC energy — or can ensure that there is no stored energy present — a feature not available in existing electrical instruments.

A team of ORNL specialists in experimental physics and sensing technologies worked with Hotstick to develop the DC-detection prototype. It is a handheld device equipped with easy-to-read indicator lights that show whether the probe has established a connection and whether the electricity source is hot. Early results from field testing have yielded a positive response according to the Hotstick team. They plan to expand its functionality, including collecting, sharing, and storing voltage data. They also envision the development of more probes, including versions to check for DC voltage on the smaller gauge wires found in other electrical systems. Future work could also see the addition of a microcontroller to the probe to give a digital readout, and to capture and process data.

For more information, contact Sara Shoemaker at 865-576-9219, This email address is being protected from spambots. You need JavaScript enabled to view it..

Sensor Technology Magazine

This article first appeared in the September, 2018 issue of Sensor Technology Magazine.

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