Conventional Vs Structural Earthing Analysis of Lightning Protection in Structures
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Analysis on injury to living being by electric shock due to a direct lightning strike in the structure
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Electrical Safety and Power Frequency Fault Voltage
Industrial / IT and commercial establishments generally use TN-S network for L.V electrical distribution with in the facility. For establishments with number of electronic systems, TN-S is the recommended network by every latest standards . The method is explained and recommended in IS 3043 as PME (Protected Multiple Earthing).
Properly implemented structural earthing ensures easy implementation of PME and there by reduce the power frequency fault voltage between electricity using equipment and extraneous conductive parts in a building during a fault. Equipotential bonding thus created avoids GDQJHURXV VSDUN RYHU DQG ÀUH GXULQJ D IDXOW
Protection of Electronics
Modern day electronic installations are highly sensitive to Transients. Transients in a building are created due to radiated Electro Magnetic Pulse (EMP) due to various reasons. Future electronic installations will be smaller & faster which means more sensitive to EMP. Electro Magnetic Shielding plays a major role in protecting modern day electronics.
A properly installed Structural Earthing system mean a large volume shield created by natural components of the structure such as the metal reinforcement in ceilings, ZDOOV DQG ÁRRUV, WKH PHWDO IUDPHZRUN, WKH PHWDO URRIV
and metal facades. These components together create a grid-like spatial shield (faraday cage). The current LQMHFWHG LQWR WKH UHLQIRUFLQJ URGV LV DVVXPHG WR ÁRZ
through a large number of parallel paths. The impedance of the resulting mesh is thus low and, as a consequence, the voltage drop due to the lightning current is less. The PDJQHWLF ÀHOG JHQHUDWHG E\ WKH FXUUHQW LQ WKH UHLQIRUFLQJ
steel mesh is weak due to the low current density and the parallel current paths generating opposing HOHFWURPDJQHWLF ÀHOGV. ,QWHUIHUHQFH ZLWK QHLJKERULQJ
electrical conductors is correspondingly reduced.
With out any doubt, structural earthing Provides the best equipotentialisation and protection of electronic systems.
Corrosion and Associated problems
Steel inside concrete have the advantage that, if the concrete is of adequate construction and covers the steel by at least 50 mm, they are reasonably protected against corrosion, throughout the life of the building. Where as a conventional LPS is subjected to corrosion,
heft, vandalism etc hence need periodic inspection and maintenance
A properly installed Structural earthing system is permanent in the building well shielded provided welded iron reinforcing bars are used for concrete outer walls. Note that a good electrical bond is necessary. In several situations the steel reinforcing bars may not represent an adequate shield. An well-designed and implemented lightning conductor with conductive connections to structural steel is an alternate method. Some tips about this conductor are
- Galvanised steel inside concrete may create problem to concrete and hence avoid GI inside
- All penetrations of steel in reinforcement to an outer area need careful design and installation. Use only Copper, Copper coated steel or SS material for this application.
- Use only copper, copper coated steel or SS in soil if connected to steel in reinforcement as recommended in IS/IEC standard.
Cheap and Best in long run
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system, the design should be carried out during the building conception stage and before construction. This allows one to optimize the use of the natural components of the structure and to choose the best compromise for WKH FDEOLQJ OD\RXW DQG HTXLSPHQW ORFDWLRQ. )RU D UHWURÀW
of Shielding measures in conventional LPS the cost is generally higher than the cost for new structures.
Structural earthing and Bonding system
h More safety for human beings during lightning
h More safety for electrical installations during fault & lightning
h Protect Electronic systems against EMP
h No Corrosion and Less Maintenance
h Cheap and Best in long run
Structural Earthing is a standard construction practice in developed countries