Cable with overall shield for protection from lightning and faults

Lightning can cause damage to electrical systems from direct and induced effects. A study was conducted to devise means to prevent or control the effects of lightning on instrument and control systems. The results indicate that the best approach is to use instrument cables with an overall shield grounded at both ends. The overall shield functions as a magnetic shield, not because of the mere presence of metal, but because it generates a counter, or opposition, current which nearly cancels out the interfering current on the signal conductors. The overall shield is used in conjunction with protective devices and a single point ground system