T h e system earth-resistance should be such that, when any fault occurs against which earthing is designed to give protection, the protective gear will operate to make the faulty main or plant harmless. In most cases, such operation involves isolation of the faulty main or plant, for example, by circuit-breakers or fuses. In the case of underground systems, there is no difficulty whatever but, for example, in the case of overhead-line systems protected by fuses or circuit-breakers fitted with over-current protection only, there may be difficulty in arranging that the value of the system earth-resistance is such that a conductor falling and making good contact with the ground results in operation of the protection. A low system-earth resistance is required even in the cases where an arc- suppression coil is installed, as its operation may be frustrated by too high an earth-electrode resistance. We, at Atul Casting and Metal Works manufactures all earthing related products such as G.I Strips, G.I plates, G.I Rods, G.I Pipes, C.I covers, Cable Trays, G.I Wire, Manhole Covers and Route Markers for past 50 + Years in heart of New Delhi. Call us at +91 9873361672 for best deals.