Lightning protection and grounding is divided into two concepts, one is lightning protection, to prevent damage caused by lightning strikes; the second is electrostatic grounding, to prevent electrostatic hazards. First, the factory lightning protection is divided into the overall structure of lightning protection, that is, the main plant lightning protection, the main foundation to play the grounding pole, grounding strap, forming a grounding network, grounding resistance is less than 10 ohms. And then connected to the main body of the steel or steel structure of the main plant. Cement concrete roof connected to the lightning belt or lightning rod, the ground outside the wall must also be left with a grounding test point, the steel structure should be galvanized flat iron as a direct lead to the roof.
Two, the power supply system grounding is divided into protective grounding and work point grounding, protective grounding is the shell of the charged equipment grounding. Work point grounding refers to the zero line grounding, grounding network practices and lightning grounding the same way, grounding resistance is less than 4 ohms. If the requirements are not met, the grounding pole should be added, the conditions are not good, electrolytes should be added and (or) replacement of soil. Work grounding and protective grounding in the distribution room independent lead, the system can be merged into one. Work, such as ground and zero separate, can also be combined into one lead to the electricity system (or equipment). Grounding system shall be repeated grounding.
Lightning protection and grounding construction of common problems:
One, lightning belt, lead wire, grounding body, even pressure ring lap length is not enough, welding at the slag, weld tumor and air holes.
Second, the ground steel mesh connection point of the wrong welding, leakage of welding, omission of the external lead grounding joint or detection point of pre-embedded parts.
Three, in the use of structural steel instead of lightning rod (net) and its lead wire, the destruction of the galvanized layer of antirust paint, bolted connecting piece of untreated, slit between the piece and the piece, etc..
Four, the lead down point spacing is large, the lead across the deformation joints are not added to the compensator, grounding body installation buried depth is not enough or the lead line is not anticorrosion treatment.
Fifth, the roof metal objects (such as pipes, ladders, flag poles and equipment shells, etc.) are not connected to the roof lightning protection system, equipotential bonding across the ground wire diameter is insufficient.
VI, electrical equipment grounding (zero) branch line is not connected to the grounding trunk.
Lightning protection and grounding construction requirements:
1, the material in line with the specifications and design requirements, reliable connection, corrosion protection measures in place, grounding system smooth, complete.
2, the use of building foundation reinforcement for grounding body and lead wire connection specifications, complete information; lightning belt, grounding wire installation straight, beautiful, firmly fixed; roof and exposed metal components grounding integrity; equipment metal casing and equipment foundation grounding without missing.
3, the grounding point is clearly labeled, lightning protection and grounding test point is complete.
4, grounding wire lap in line with the requirements.