Lightning Protection of Cable TV System

Abstract: In the cable TV systems, lightning protection design is a very important job, but also a number of cable TV workers to long-term study. This article analyzes the impact of lightning on the cable TV system, for lightning damage, lightning protection cable system made a number of measures.

Keywords: lightning; cable television system; mine

Introduction

a cable television system is a cable TV signal through cable access, or by building through the satellite antenna and a group of high-quality shared open-circuit TV system antenna signal, the front-end treatment, the way cable television system television signals distributed to all end users. In the cable television system, the lightning protection design is a very important job, but also a number of cable TV workers to long-term study. The severity of lightning performance of its enormous destructive, and its characteristics of high voltage, lightning current amplitude big changes fast, the discharge time is short, a large lightning current wave steepness. The destructive effects of lightning current is strong, hot temperature, severe shock waves, dramatic changes in the electromagnetic field and a strong physical effects of electromagnetic radiation, to bring great harm to human society, causing casualties, great damage, caught fire and exploded, seriously loss. Lightning often severely damaged the cable television equipment, which in practical engineering, there is no good system as a victim of lightning protection measures would have been seriously damaged by lightning, and even paralysis. For large systems with longer lines, lightning protection design is imperative for the event. In the cable television system, the lightning protection design is a very important task, here we work according to their own practice and learn to talk about the impact of lightning on the cable TV system as well as preventive measures against lightning.


Two effects of lightning on the cable system

effects of lightning on the cable system there are mainly two: "cloud-to" and "lightning." Thunderstorm for a discharge between charged clouds and the earth caused. When the thunder cloud is very low, around the opposite sex and no Thundercloud charge, they will on the ground or induces opposite charges on the building, the formation of clouds to the ground or buildings electric discharge; discharge current can reach tens or even hundreds of thousands of security , the discharge time is 50 ~ 100us, which is cloud-to-discharge. Thunderstorm for the building and person, animal safety jeopardized. For cable television systems, cloud-to-rate of only about 10% of lightning, though damage is great, but the damage range is generally small, can use the lightning rod, lightning arrester line and nets to prevent avoidance. Installation of a lightning rod, the cable television system of electronic equipment even in the scope of its protection, may still be damaged by lightning, most of them are burning fuses, power transformer, rectifier components, three-terminal voltage regulator, may also be serious damage to integrated circuits and other components. This shows that lightning is not introduced from the antenna, but from the introduction of the power cord can be seen, although the lightning rod to protect the building, but could not put protection of electronic equipment inside the cable, which is caused by lightning. Induction into the lightning and the lightning current electrostatic induction electromagnetic induction generated by the two causes. Electrostatic induction is when the charged clouds (thunder cloud) near the transmission line, the sensor in the opposite charges on them, these opposite charges are charges tied Thundercloud, Thundercloud nearby when the target or air terminals (lightning rod is the earliest The most commonly used air terminals) discharge, and in its charge quickly, and transmission lines will be free of charge bound charge, the formation of local induction of high potential. This induction occurred in the low voltage overhead high voltage lines that can reach 100KV, the cable lines up to 40 ~ 60KV, and it can be along the line transmission of electronic equipment, causing damage. Electromagnetic induction is a great thunder after lightning current in the alternating magnetic field generated around the room, near the equipment due to electromagnetic induction sensors to high voltage, so that the equipment damage. "Lightning" rate of nearly 90% of the total lightning, damage covers a wide range of electronic equipment, cable systems damaged by lightning, mainly caused by lightning.

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