1、- 1 - Lightning protection grounding AbstractThe significance of lightning p.rotection and mitigation on very little money to prevent large losses, and its function is to use scientific means avoid natural disasters. Grounding is to make the system has been included in the lightning protection light
2、ning energy discharge into the earth, and good grounding can effectively reduce the online guide overvoltage, avoid counterattack. Avoid ground is the most important aspect of technology, whether sings rem, induction lightning, or other forms of ray, ultimately the lightning current into the earth.
3、Therefore, no reasonable and good grounding device is cant reliably the lightning strikes. The smaller the grounding resistance, come loose flow is quicker, lightning objects the time to maintain high potential more short, the less risk Key Words:Lightning protection； Grounding； Current； potential 1
4、 introduction In recent years, many domestic and foreign standards do not advocate information equipment using independent grounding device, recommend the use of common earthing system. For example, the 2000 edition of the GB50057-94 design code for protection of structures in point out clearly: eve
5、ry building itself should adopt common earthing system to be the buildings within the various grounding are unified to buildings based on, or outdoor grounding device. When the building was hit by lightning, power system voltage and electrical equipment grounding voltage rises at the same time, keep
6、 the equipment working voltage constant, so that the electronic equipment from lightning strikes can work normally. Common earthing system usually use the building foundation grounding electrode, the grounding resistance less than 1 ohm in general, if the equipment grounding resistance requirement i
7、s lower, should take the minimum value. The ground that has been incorporated into the lightning protection system of lightning energy drain into the earth, good grounding downlead to effectively reduce the voltage on the back, to avoid the occurrence of. In the past some requirements of electronic
8、equipment grounding alone, the purpose is to prevent stray current and transient current in power network disturbance of the normal work of equipment. Before 90 time, forces of the communication navigation equipment electronic tube device, using analog communication mode, analog communication on par
9、ticularly sensitive to interference, interference, so will take power and communications grounding separate way. Now, the lightning protection engineering fields do not advocate a separate ground. In the IEC standards and ITU standards are not advocating a separate ground, American Standard IEEEStd1
10、100-1992more sharply pointed out: not recommended the use of any kind of so-called separate, independent, - 2 - computer, electronic or other such incorrect ground as equipment grounding conductor of a connection point. Grounding is the most fundamental aspect of the lightning protection system. The
11、 ground is not good, all the measures of lightning protection effect can play. Lightning protection grounding is ground communication station Code for construction and acceptance of the basic safety requirements, the grounding of PLC belongs to a low-voltage electrical equipment of single point grou
12、nding mode Low voltage electrical equipment of single point grounding mode can be divided into: tandem type single point grounding, parallel type single point grounding, multiple branching of single point grounding. 2 single point grounding method Tandem type single point grounding: or first groundi
13、ng ways. Method : the number of low voltage electrical equipment grounding terminal equipment with the same root near the ground wire connecting, then through this grounding and grounding device. The grounding system is: save manpower, material resources； while the disadvantage is that: when the pub
14、lic grounding line open circuit, if the grounding system has a device leakage, can cause other equipment which occurred on voltage, a threat to the safety of personnel. Backup ground terminal introducing a grounding line, and then the number of lines at the same time received a grounding device. The
15、 grounding system is: when the grounding system in which a device grounding wire broken circuit, will not cause other equipment enclosure voltage, to ensure personal safety. This grounding mode is: if it is not perfect on the interference of high frequency electronic equipment or other highly sensit
16、ive electrical equipment, high frequency interference from other devices ( such as converter, intermediate frequency stove thyristor converter parts) will be from the common place of string, causing the device is not working properly. Multiple branching of single point grounding: or third grounding
17、ways. Grounding method: each equipment grounding terminal alone received a grounding device. Earthing method and second kinds of grounding is the difference: the device has a separate grounding body ( or a change of: received directly from the grounding body recent grounding device ( or grounded sou
18、rce office ), each device in the electrical ground loop on the distance is far more (for example, more than 50meters ) ). This effectively avoids the mutual electrical equipment Magnetic interference.But this grounding mode time-consuming, laborious and separate grounding the source is not good for.
19、 - 3 - In the usual construction, in fact the grounding of PLC way adopts the second grounding ways, as for electromagnetic interference: if the cabinet is provided with a plurality of high power frequency converter, can be in the PLC power supply is installed in front of a single-phase power filter
20、 can be, generally designed in the inverter PLC near the front end are equipped with power supply filter. The interference effect of DC and AC equipment, can be connected together - even if the DC and AC circuits because of some reason connectivity, because they are not the same as a loop ( groundin
21、g is not part of the loop ), will not cause damage to the equipment. People have AC220V power and DC24V circuit connected to it, but the equipment work remains normal. Digital and analog ground suggested separately ( unless youre a low-voltage electrical equipment power supply voltage only a few ten
22、s of volts ), because the digital circuit belongs to positive and negative 5V,12V,24V level, are vulnerable to interference, and once the external abnormal voltage once the series will very possible equipment damage. I just go to work in the factory has a 1000 tons of SACMI press, because other equi
23、pment and digital ground causes the electronic facilities burned down last several times, Italy sent technicians ( just graduated from secondary school students ) and replacement equipment, conductor of the in situ dug a pit, buried a piece of ground the brass and the earthing filler, engage in a se
24、parate grounding. 3 Lightning proof grounding device for part of a concept (1) Lightning receiving device directly or indirectly accept the lightning rod ( flash ), such as lightning, lightning protection zone ( net ), overhead ground wire and arrester. (2) lead: for the lightning current from the l
25、ightning arrester is conducted to the grounding conductor. (3) grounding: electrical equipment, tower grounding terminal and a grounding body or the zero line connected with the normally not current-carrying metal conductor.(4) grounding body ( polar ): buried in the soil and directly touch the eart
26、h metal conductor, known as the grounding body. Divided into vertical grounding electrode and level of grounding body.(5): grounding device grounding and grounding. (6): grounding grid by vertical and horizontal grounding body composition having discharge and pressure equalizing function network gro
27、unding device. (7): grounding resistance of grounding body or natural grounding resistance to the ground of the sum, a grounding device resistance, its value is equal to the grounding device of voltage to the ground and through the grounding body into ground current ratio. At the same time the grounding resistance of grounding device is a constant level indication. 4 The grounding device is easy to corrosion location mainly
