ESD Control and High Voltage – Is it safe to ground our personnel working with or around high voltage?

Grounding operators that handle ESD susceptible devices is one of the requirements for an ESD Control Plan. In fact, it is the basis of the ESD Association’s ANSI/ESD S20.20-2014 Standard. Grounding the body and maintaining maximum resistance to ground (Rtg) of less than 35 megohms prevents the operator from generating more than 100 volts. 

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The preferred and recommended grounding point for all conductors in the ESD Protected Area is to the electrical equipment ground (AC ground or 3rd wire ground). However, bonding to the electrical ground may increase the risk of electrical shock, should the body come into contact with line or high voltage. If working with less than 250 VAC, the ESD Association requires that an ESD wrist strap ground cord have at least 1 a megohm of resistance. This amount is sufficient to limit current to 0.5 milliamps and protect the human body up to 250 VAC. The ESD Association also recommends the use of ground fault circuit interrupters (GFCI) to sense potentially hazardous levels of voltage, and to consider alternate paths to ground that could by-pass built-in resistors in a wrist strap, such as when an operator is using both a wrist strap and conductive foot wear.

In applications where the voltage is greater than 250 VAC, the ESD Association does NOT recommend grounding the human body with a wrist strap and notes that a conducive floor may also pose a hazard (ANSI/ESD STM97.1-2006). ESD control should only be implemented after safety requirements are met. It is up to the facility to determine the level of voltage that is acceptable, provide training to the operators with regards to high voltage applications, and maintain compliance in those areas.

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