Page 260 - Electrical Safety of Low Voltage Systems

CHAPTER15

Applications of

Electrical Safety in

Special Locations

and Installations

I studied with the masters long ago,
And long ago did master all they know;
Here now the end and issue of it all,
From earth I came, and like the wind I go!
omar khayyam

15.1 Introduction
In this final chapter we will analyze the safety requirements against
indirect contact employed in special installations or locations, where
environmental conditions may increase the risk of indirect contact
defined in Eq. (3.5) as r(t) = [1 − S(t)]k(t)v(t).
Following are examples of special locations and installations:
Locations where the presence of water or moisture decreases
the resistance-to-ground of the person’s body by lowering
his/her skin resistance. This does increase the probability
v(t) that the superficial touch voltage appearing over a faulty
equipment is harmful to the person.
Wet locations where the humidity can increase the failure rate
of equipment by compromising the integrity of its basic in-
sulation, thereby raising the probability 1−S(t) that the metal
enclosure is energized.

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