Vài giây sau ta mới nghe thấy tiếng nổ, đó là “sấm” (vận tốc ánh sáng nhanh hơn vận tốc của tiếng động nên ta trông thấy tia chớp trước). Nếu có đám mây dông tích điện đi gần mặt đất tới những khu vực trống trải, gặp một vật có độ cao như cây cối, người cầm cuốc xẻng. | BS EN 62305-4 Electrical and electronic systems within structures Inspection and maintenance of an LPMS The object of the inspection is to verify the following The LPMS complies with the design The LPMS is capable of performing its design function Additional protection measures are correctly integrated into the complete LPMS The inspection comprises checking and updating the technical documentation visual inspections and test measurements. Visual inspections are very important and should verify for example if bonding conductors and cables shields are intact and appropriate line routeings are maintained. A visual inspection should also verify that there are no alterations or additions to an installation which may compromise the effectiveness of the LPMS. For example an electrical contractor may add a power supply line to external CCTV cameras or car park lightning. As this line is likely to cross an LPZ suitable protection measures eg SPD should be employed to ensure the integrity of the complete LPMS is not compromised. Care should be taken to ensure that SPDs are re-connected to a supply if routine electrical maintenance such as insulation or flash testing is performed. SPDs need to be disconnected during this type of testing as they will treat the insulation test voltage applied to the system as a transient overvoltage thus defeating the object of the test. As SPDs fitted to the power installation are often connected in parallel shunt with the supply their disconnection could go unnoticed. Such SPDs should have visual status indication to warn of disconnection as well as their condition which aids the inspection. Inspections should be carried out During the installation of the LPMS After the installation of the LPMS Periodically thereafter After any alteration of components relevant to the LPMS After a reported lightning strike to the structure Inspections at the implementation stages of an LPMS are particularly important as LEMP protection measures such as .
