Human society into the information age, all kinds of advanced electronic equipment due to extensive and widely used, its chances of being struck by lightning damage greatly increased. In particular substation electronic devices, attached to the subject in a range of lightning protection equipment, the effects of lightning probability greater. And the use of traditional lightning protection measures, the more protection there is improper and should pay attention to.
Lightning hazards in several ways
Ray's Watch and shielding
Thundercloud IBM Thinkpad T41 battery single floating over the earth, dragging its electric charge opposite the charge of surface wind move like a shadow. If the surface via the substation lightning rod or other protrusion, the protrusion to the top of the charge will lead to distortion of the electric field concentration. Lightning started the bottom of the thundercloud before the first pilot of origin by way of intermittent grading leap to the surface development, when 50 ~ 100m from the ground, by the lightning rod and other surface protrusions where the electric field distortion resulting vertical concentration of head-up pilot. Two-phase, into the Watch or shielding of the main discharge stage.
Usually the local surface protrusion height h, below the thundercloud electric field strength greater than and equal to the average 580h-0.7kV / m, then the protrusion will be vulnerable to direct lightning stroke. The reason is the lightning rod of height h can affect the Thundercloud single downward direction of the radius of the originating guide, using the formula expressed as: R = 16.3h0.61m. The formula also shows that the independent rod surface after installation, will be in the vicinity of a large number of scattered hit, and even HP Compaq NC6400 Battery lightning rod for Watch, by the lightning rod for the objects within the scope of protection shielding.
A lightning discharge is generally the main amps to tens of thousands of hundreds of thousands of amps. Instant heat and electric power, will result in concrete pole burst, small cross-section metal melting, causing fire and explosion, the metal conductor connection part of the fracture damage, collapsed buildings, electrical equipment damage.
Lightning counter-attack
Direct lightning stroke current through the resistance of the surface protrusion into the earth diffuser. If the ground resistance of 10Ω, a 30kA lightning current will make the ground potential rise to net 300kV. If the transmission line by lightning from a different substation grounding grid substation, then rising on the ground and power lines will form a great contrast to the potential, leading to transmission lines connected to the electrical equipment damage. Not only transmission lines, HP Pavilion dv1000 Battery power cables, metal pipes any introduction substation will cause lightning counter-attack.
Another lightning counter-attack, damage to the substation's electronic equipment can not be ignored. Lightning current along the substation grounding grid diffuser, on the branch points of the lightning current and potential vary widely. Connected to different potentials to the Internet and other electronic devices. If there have been electrical contact, then beyond its permitted capacity of the ground potential difference will result in equipment damage.
Lightning
Direct lightning stroke discharge of energy through electromagnetic induction and electrostatic induction means to the surrounding radiation, leading to over-discharge device, for the lightning. Clearly, the lightning hazard is a large area, is the bane of electronic equipment.
Data calculations show that, when the HP EliteBook 6930P Battery lightning current is 30kA angle wave, Thundercloud height of 3 km, wire height of 10m, 500m hit from the end of the match midpoint 100m long overhead lines at the ground, the line width on the induced voltage of 150kV value of the oscillation. This wave is electromagnetic induction, and the result of electrostatic induction.
There calculations show that a part of the I-beam structure and the metal Faraday cage connected to 10 layers (60m × 30m × 100m, each high-10m) of the building, was -2.6/40us, 100kA lightning in the roof , the layers of floor 1m vertical height of the induced electric field amounted to several kV / m, with the lower floors tend to be uniform induced electric field strength, but no major strength of the overall attenuation.
In fact, in the production practice, several times the destructive power of lightning in the electrostatic induction electromagnetic induction. Electrostatic induction of the secondary effects of lightning can also be used to explain the theory. Charged thundercloud floating above the surface, surface to bring equal and opposite thundercloud charge. When lightning after lightning charge into the surface point relative hole, surrounded by high-charge region and the ground potential relative to the charge on the COMPAQ Presario CQ70 Battery insulated conductors, like the sudden firing of the waves by the same lightning toward the point of ignition lead equipment, insulation damaged and electronic equipment failure. Of particular note is the high-impedance input of electronic equipment circuits, signal circuits such as lead longer, and directly connected to the metal at a larger size, although for electromagnetic shielding (with shielded cable and the shield grounded at both ends) will continue to suffer bad luck.
Lightning invasion wave
Distant lightning, Watch, or by electrostatic induction and electromagnetic induction method from high-voltage transmission lines, distribution lines, low-voltage power lines, communication lines, cable lines, metal pipes and other means of intrusion substation, due to the relatively long pipeline, and there is a distribution inductance and capacitance, the lightning spread has slowed, the transmission of such a phenomenon with the wave theory to explain the concept known as lightning. Lightning wave transmission line with different parameters of the connection or line endpoint, change in impedance will produce reflection, refraction, wave resistance mutations can result in HP EliteBook 8530P Battery voltage rise at many, and increased equipment damage.
Substation lightning protection measures and the lack of protection for electronic equipment
Lightning rod
Against direct lightning stroke to damage the substation and the general architecture with separate lightning rod lightning rod, some valley line substation lightning protection is used. The structures were divided into air-termination system, deflectors and grounding, lightning protection on the same principle.
In order to prevent the counter, requiring lightning protection device between the air and being a distance not less than 5m, to the distance of not less than 3m. General framework of a lightning rod for 110kV and above, and after the installation of grounding the main focus to network connections.
Independent of the scope of Canon EOS 5D Mark II Battery Grip protection lightning rod on the ground of 1.5h (pin high), high of more than half of the space needle scope of its protection can only be checked within 45 ° angle. Current international law on the popular theory of a ball lightning protection independent checking more realistic. Watch and law theory that the ball around the strike and the thunder cloud with power on, the smaller the energy the more easy to produce lightning shielding. Can be interpreted as the image with a radius with Thundercloud Thundercloud charge proportional to the pilot as the center of the ball, rolled on the ground to hit the lightning rod tip up. Point of contact with the ground ball to the tip of this arc, if you can not touch the protected object was to protect property in the protected area. Such as moderate-intensity Thundercloud (U0 = 50MV), leading the blitz by lightning distance formula rs = 1.63U01.75, can get the ball radius of 133m. Obtained in this case than the radius of the design procedures to protect the larger. Lightning protection by checking specifications, general use of 110kV substation medium-sized 3 5, 35kV Canon Battery Grip substation 1 to 4 of about 30m lightning rod, to cover all the protected areas.
Microwave tower is an independent lightning rod. For the inside of a microwave tower, microwave tower rules of order must be connected to network and communications room. Communications room and the main control room to network integration, network lightning current to discharge through the main control room. By the previous analysis, if the high voltage power distribution room, control room, communications room to protect, monitor, meter, RTU and other places connected to the network far away, and we have the power contacts, the electronic equipment inside the probability of being counter- more.
The annual number of lightning strikes the lightning rod, according to the empirical formula N = 0.015 · n · k (l 5h) (b 5h) 10-6 calculated. Where n is the number of annual thunderstorm days, K is the correction factor to take the metal structure 2. l, b, h, respectively, for the building length, width and height. According to the type in thunderstorm days for the 40-year area, 35kV outdoor substation terminal, bus architecture 5.5m high, the probability of Nikon D60 Battery Grip lightning strikes per year by 0.000454 times, plus a 30m high lightning rod, the 0.027 times each year will be subject to lightning. If a substation with 4 needles on each side separated by 50m, compared to 0.048 times the probability of lightning strikes / year.
Greatly increase the probability of lightning strikes the lightning rod, making the devices currently attached to a large number of update protection, monitoring, and communications integrated microelectronic devices from the experience greatly increased the chances of lightning damage, damage in many ways, so that the power production to bring it Nikon Battery Grip large losses.
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