High Voltage Approach Alarm — 40V to 500kV Personal Protection

Why an Active Alarm Beats Passive PPE

Insulating gloves and arc-flash suits stop the worst outcome — but they do not warn you that you are standing 30 cm from a live 22 kV bus. A high voltage approach alarm sounds and vibrates as soon as you enter the dangerous electric-field zone, giving you time to retreat. EK service teams treat it as primary PPE, not an accessory.

1. The Detection Physics

An approach alarm measures the displacement current that flows through the wearer's body when they enter an AC electric field. The threshold scales with voltage and distance — a 22 kV line at 1 m generates a measurable signal; a 500 kV line at 5 m generates the same. The alarm circuit is therefore a calibrated antenna and amplifier, not a contact voltmeter.

2. EK Range Envelope

• A186 wrist type: 40 V to 500 kV detection, 5 selectable sensitivity steps.
• A187 arm type: identical detection, larger antenna for higher-noise environments (transformer yards, switchgear rooms).

3. Sensitivity Steps

Step 1 alarms at 40 V (control circuits); step 5 alarms at 500 kV transmission. Workers select the step matching the assigned task — a substation operator on a 110 kV bus uses step 4; a service entrance crew uses step 2.

4. Battery and Self-Test

1. Single CR2032 lithium cell, 2-year life with daily self-test.
2. Press-and-hold self-test confirms antenna, alarm and battery in 3 s.
3. Low-battery LED at 20 % remaining.

5. Mounting Discipline

The wrist type goes on the dominant hand; the arm type goes on the upper arm of the dominant side. Both must be worn outside any clothing layer that could screen the field — the EK A186/A187 ship with a printed field card showing correct placement.

EK Recommendation

For utility lineman and substation operator PPE the A187 arm-type and A186 wrist-type approach alarms are the EK choice — request samples through EK service teams.