Lightning Protection of Cable TV Network System

Abstract: The lightning damage to the cable system is very strong in the cable television systems, lightning protection design is a very important job. Article for the author based on many years of practice and experience, the impact of lightning on the cable system and cable TV equipment protection work common preventive measures were discussed.

Abstract: Lightning damage to the cable system is very strong. In the cable television systems, lightning protection design is a very important job. This Article discussed lightning's impact on cable television system and the common preventive measures in the protection work of cable television equipment, based on many years of practice and experience.

Keywords: lightning, cable, network systems, lightning protection measures
Keywords:: lightning, cable television, network system, lightning protection measures

0 Introduction
As human society entered the electronic information era, the characteristics of lightning disaster occurred greatly different from the past, can be summarized as follows: �� the affected area is large. �� invasion from the two-dimensional space into a three-dimensional invasion. �� lightning disaster and economic losses greatly increased the degree of harm, it attacks the object itself is sometimes the direct economic loss is not great, but the resulting damage and indirect economic impact is difficult to estimate. For this reason, the importance of mine today, urgency, complexity greatly increased, thunder and lightning from cloud-to-defense protection to system protection, we must stand to the height of the historical era of new understanding and study of modern mine technology, human lightning disaster prevention to improve the comprehensive ability.

1 Generation and devastating consequences of lightning
Ray cloud lightning is close to the eArth, ground sensors out of the opposite charge, when the charge accumulation to a certain extent, resulting in clouds and between clouds and between cloud and ground discharges, burst out of light and sound phenomena. Lightning has enormous destructive disaster, they bring very serious consequences of disasters. the destructive effects of lightning not only bring great harm to human society, causing casualties, great damage, severe damage. lightning are often severely damaged the cable television equipment, in the actual project which, without a good system as a victim of lightning protection measures would have been seriously damaged by lightning, and even paralysis. For a long cable lines large-scale systems, lightning protection design is even more urgent priority.

2, the impact of lightning on the cable system
In the cable TV systems, lightning protection lightning protection design is a very important job, but also cable television workers have long been studying the issue. This is our practice based on many years of work and study, summed up the thunder and lightning on the cable television system impact and prevention initiatives. lightning can be divided into cloud-to, lightning (including electrostatic induction and electromagnetic induction, and spherical mines. on the cable systems of the two main lightning: "cloud-to" and "lightning" (including electrostatic induction and electromagnetic induction. Here, we introduce the two major lightning.

2.1 Thunderstorm for the impact of lightning on the cable system is charged cloud-to-discharge between clouds and the eArth caused. Strong lightning current through the surface structures and ground equipment built into the ground, grabbing a huge high temperature heat and mechanical vibration force to the object being destroyed. lightning current through a resistance or inductance of the objects have a huge voltage drop and induced voltage, insulation damage, so lightning current through, wherever the object heated vaporization, severe swelling, resulting in super big impact mechanical force. destruction of human tissues, building structure, equipment components.

2.2 Induction of lightning sensors on the cable system can be divided into lightning current lightning produced two kinds of electromagnetic induction and electrostatic induction. Cable television system of electronic equipment is mainly caused by induced lightning damage. Electromagnetic induction mine is due to lightning discharges, the great the impact of lightning current rapid changes in the surrounding space generate magnetic field caused by the strong, rapidly changing magnetic fields that can be induced in nearby conductors on a very high force, so that the equipment damage, "Electromagnetic lightning" accounted for nearly 90 lightning rate %, against a wide range. electrostatic lightning clouds charged close to the ground due to the overhead line conductor or other conductive protrusions at the top of a large number of electric charge is induced.

Links to free front end paper download http://www.hi138.com 3 Lightning Protection
3.1 �� determine the receiving antenna to receive antenna lightning location, set up the antenna is necessary to ensure the quality of the received signal but also to avoid the minefields, �� set up lightning rod, lightning conductor, which is a universal and more effective lightning protection measures, the receiving antenna normally mounted on the roof, it is easy to thunder into the front, especially in the satellite antenna, lightning protection measures must be thoughtful, on the one hand make the receiving antenna in the lightning protection zone, on the other hand also lightning rod grounding resistance reduction. �� antenna feed, coaxial cable, optical fiber network and overhead support the shield and other ancillary facilities should have a good grounding to form a good grounding, grounding resistance should be controlled at less than 4��.

�� 3.2 installed lightning protection power supply power mine, when the electricity generated by lightning or other factors that the high pulse voltage, it will damage the devices on the circuit, so the cable room to install the "three-phase power mine" . Its role is in the shortest possible time because of the power line generated a lot of lightning induced pulse energy released into the safe line, so as to protect the front of the engine room equipment. �� room to install on-line UPS, the cable TV transmission frequency bandwidth, there will be interference with electrical equipment of various frequencies through the power into the engine room, resulting in a channel or a certain band interference, affecting air quality. CABLE room while the further introduction of computers, and computer-generated interference with power large, wide band, from time to time the characteristics of the interference of the cable system is extremely serious. Therefore, to the stability and security of electrical equipment, engine room of modern cable must be installed with a certain anti-interference ability of the on-line UPS power supplies. �� do three types of ground work. The first ground - lightning protection grounding, over-voltage protection means or equipment grounding metal structure. If the ground arrester, lightning rod grounding architecture, also known as over-voltage protection grounding, the second grounding - protective grounding, refer to the electrical equipment under normal circumstances, housing and non-conductive pArts and earth and reliable connection, a third ground - ground work, means the power, communications and other systems make use of the earth wire, according to the needs of system operation, realize its inherent reliability and performance of the ground. such as power supply system in the three-phase four-wire system in the ground. However, in cable television systems, using the AC power line is not the majority of neutral grounding of low voltage provided for the power grid, so the ground work has played a protective equipment and protective role of the personal safety of staff.

4, Lightning Protection Cable Network
Cable network's mine: �� electricity being struck by lightning, the cable network equipment due to abnormal high voltage pulsed current and the resulting damage, �� lightning sensor by coaxial cable to the cable network equipment to lightning strikes. The preventive measures are as follows: �� Lightning amplifier and splitter. with joints at both ends of lightning protection devices are amplifiers, each amplifier box should be installed lightning ground (resistance less than 10��, the lightning to the online release of the energy generated to protect the amplifier, If the use of electricity in the amplifier, but also to prevent the introduction of the amplifier because electricity was lightning damage, which may be taken in areas often struck by lightning lightning protection devices installed. �� multi-point grounding the entire network to form the grounding grid, that line reduced by the opportunity to lightning. How: Let coaxial cable shielding system in support of the cable network and the overhead of the strand with a good grounding in every bar stalls at 10, with 1 root (according to soil resistivity can choose multiple 50mm �� 50mm �� 5mm in 1.5m long angle into the ground as grounding, ground fault protection set, lightning and the support strand wire head with iron bar fastened into one. in the system ground, due to the effect of grounding resistance of a large mine backward, we must note that the minimum earth resistance, control the following as the best in the 8��.

5 Conclusion
Present stage of human understanding of lightning and the lightning and the lightning Research, lightning protection cable systems do a good job, lightning is that it can achieve.

References:
[1] Zhang stone, Luo Jiajun, Tsang Cheung standard. Miniature circuit breakers in the mine application [J]. Guangdong Meteorology, 2010, (1. Links http://www.hi138.com Research Papers Download