Furse Earthing & lightning protection

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Vydal: ABB s.r.o.

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7430 therefore defines selection parameters for the earthing arrangement, e. 119 TECHNIC REFERENCE ARTHING STANDARDS . These standards provide guidance on (but not limited to): • Maximum permitted step and touch voltages • Methods for calculating earthing system design • High voltage earth electrode selection, including type, material and size • Switching and busbar arrangement • Equipotential bonding • Insulation co-ordination Primary these standards limiting earth potential rise (EPR) under earth fault conditions so that step and touch potential limits are not exceeded, and earth resistance remains low as possible. the size and material for conductors, earth electrodes etc, and makes clear the need for careful consideration of site conditions (soil composition and resistivity).g. The design and specification appropriate earthing arrangement for substations essential to provide low impedance path for earth fault, and lightning currents, and protect personnel on site from potentially fatal step and touch voltages. Taking actual measurements the site is important gauge the expected effectiveness of the earthing arrangement, and guidance is provided for measuring resistance calculations for earth plates, earth rods, ring conductor and foundation earth electrodes. Essentially, use earthing grid consisting horizontal cross-bonded earthing conductors recommended, augmented by earth rods where the site includes low resistivity layers beneath the surface. Where necessary high resistivity areas on rocky ground, treatment the soil through use of earth electrode backfill recommended to improve earth contact resistance. and ENA 41-24 reference the requirements for earthing substations. Substation earthing BS 50522, 7354, IEEE std. These earth rods mitigate seasonal variations earth grid resistance the grid’s burial depth