General guidelines for high voltage area?

What is general guide lines for EPA area, where live AC and DC equipment is used?


If personnel are handling ESD sensitive devices, the general guidelines are the same as for any other ESD Protected Area. See my ESD Guide.

However where high voltages are present there may be a safety concern about earthing the body either through a wrist strap or through conductive footwear and flooring. In this case the risks must be evaluated and if necessary, the ESD precautions modified to reduce safety risks to an acceptable level.

Usually, wrist straps and footwear for ESD use have a minimum of 750k ohm resistance, which is designed to give some protction for up to 250Vac systems. For higher voltages higher resistance (pro rata) can be used if desired. If the risk of shock is unnacceptabe it may be necessary to avoid grounding personnel and use other ESD protection methods. There is no general advice on this as far as I am aware.

Can electrostatic discharges harm people?

Can static electricity cause any physical damage to people?

Static electricity discharges do have significant current flow, which can be several amps or tens of amps for a few hundred nanoseconds. The stored energy which is released in a discharge is also important.

Small static discharges do not do damage to a person and may not even be felt. At the other extreme lightning is a static electricity discharge and can certainly kill. So between the two extremes we can expect there to be a range over which a person could be injured in some ways. Where that range lies, and what the effects are, is not well documented as far as I know.

There are standards which may be helpful, PD 6519-2:1988 probably being the most relevant in this case:

PD 6519-3:1999 (IEC 60479-3:1998).Guide to effects of current on human beings and livestock. Effects of currents passing through the body of livestock.

PD IEC/TR 60479-4:2004. Effects of current on human beings and livestock. Effects of lightning strokes on human beings and livestock.

DD IEC/TS 60479-1:2005. Effects of current on human beings and livestock. General aspects.

PD 6519-2:1988, (IEC 60479-2:1987). Guide to effects of current on human beings and livestock. Special aspects relating to human beings. (Under review)

Can rubbing the contacts damage a DIMM module?

A friend told me to clean the finger contacs of a DIMM memory module with an eraser :))).. I told him don't do it that way because you will get esd damage.... am I wrong????

To be honest, I don't know the answer to this. I think the main thing is that you should wear a wrist strap to ground your body while handling the module. If you are not doing this the risk is far greater that ESD from your body will damage the module.

If you are wearing a grounded wrist strap while handling the board, and working on a grounded work surface (if you are using a work surface), then I think the ESD risk from static generation as you rub the contacts is probably small.

There must be a better way to clean the contacts, but I don't know it.