Thanks Denis, Drake, Stuart, Stevem and Doug for your fast response.

        To make things clearer, we refer electrical ground as the AC ground
and for ESD ground we need to plunge a electrode 6 -7 feet into the ground.
As a safety precautions for the operators, all the wrist straps has got a 1
Meg Ohm resistor installed, whether you are grounded to the ESD or
Electrical ground. We are using a 240 V power supply, so with 1 Meg Ohm
resistor, even if there is a short, the current that flows through the
operator will be less than 0.5 mili-amps. This is alright at the safety
stand point.

        My concern is that will there be a potential difference between the
ESD and electrical ground? Say for example, my board(machine) is connected
to the AC ground and the operator is connected (by wrist straps) to the ESD
ground, if a potential difference of 5 volts exsist, there will be a flow of
charge whenever the operator touches the board.

        The reason my management is thinking of switching to the ESD ground
is that sometimes there is a short of the live to the AC ground in our
machine. That way we can isolate the operators grounding from the machines'.

        As for the lightning scenario, I am not sure but can the ELCB helps
in this case?

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