Arm Proximity Alarms

An arm proximity alarm is a personal safety device fastened to the upper arm with a strap during overhead line work; it detects the electric field of a live conductor without contact and gives an audible warning. Because the device is worn on the arm rather than held in the hand, protection continues while the hands are busy with tools and materials. Distribution and transmission line crews working on poles and from aerial work platforms (bucket trucks) are the main users.

The three models share the same housing: approximately 45 g, 78 × 82 × 25 mm, a single CR2032 battery and a sound level of at least 65 dB. They differ in the voltage band they work in and, accordingly, in the distance at which the alarm starts.

Which model?

Model	Operating voltage	Alarm start distance	Typical use
HXA-6	AC 6.6 kV – 33 kV	80 cm (standard conditions)	Medium-voltage distribution lines
HXA-30	AC 11 kV – 66 kV	70 cm at 11 kV	33 kV-class distribution and lines up to 66 kV
HXA-70	AC 66 kV – 110 kV	150 cm at 66 kV	Overhead lines of 66 kV and above

Base the choice on the line voltage your crew works on most often. For a crew working on both 20 kV and 35 kV lines, the HXA-30, which covers both levels, can be considered; if work is only on lines up to 33 kV, the HXA-6 is sufficient. As the HXA-6 is built for either 50 Hz or 60 Hz, the network frequency (50 Hz in Europe) must be specified when ordering.

Points to note in use

An arm alarm is a warning device; it does not prove the absence of voltage. Before work begins, the line must be checked with a suitable voltage detector and earthed. The alarm distance varies with voltage, conductor arrangement and nearby earthed structures; it does not replace the minimum approach distances required by the applicable rules. At the start of each shift, check the battery and that the strap sits firmly on the arm.

All alarm types are listed on the hot-line proximity alarms page; for the operating principle, read our article What Is a Proximity Alarm?.

Frequently Asked Questions

Can an arm alarm be used inside cubicles and panels?

The manufacturer specifies the HXA-6 for overhead line work only. For work inside cubicles and panels, wrist proximity alarms are more suitable.

Is there a version that mounts on the helmet instead of the arm?

Yes, the same voltage bands are also available as helmet proximity alarms (HXA-6S, HXA-30S, HXA-70S).