Lead Sheath Power Cables

Friend--

Zone1 and Zone2, according to my code book, are equivalent to Class1 Division1 or Division2 locations (in terms of the types of materials to be used therein). The underground areas beneath these locations are classed the same as the locations above ground. Lead sheathed cable is a type of MC cable, and is approved for use in these areas, if protected from physical damage. I suspect that the use of lead sheathed cables is based on lead's high resistance to corrosion and chemical attack in the soils. I would expect lead sheathing to survive better than most other metal conduit or sheathing systems (other than its softness permitting puncture or cutting under some preventable conditions). I would also expect the lead sheath to be quite impermeable to most flammable liquids or gases in those environments.

I have no first-hand experience on which to base definitive answers. I hope what I have said helps. --JMM

Lead sheath is used for protection of control cables against common mode induction.

The use of the well known copper sheath doesa not protect cables agaisnt this kaind of induction, limiting the protection to longitudinal induction, very frequent in low voltage systems, where short circuit currents may rise to extremely high values.

The situation for common mode occurs when a cotrol cable is layed adjacent to extra high voltage cables and an isolator switching may lead to high commonmode voltage values.

This kind of problem occurre in the past and now may be overcome with the use of optic fiber for the asme application.

I interviewed with a company one time that made lead sheathed cables for powering down hole pumps in sour oil wells. So I might guess that use in non oil well applications would be in extremely acid and/or hot conditions.