The research and application on new method of “isolation & floating ground” for lightening Protection of broadband access unit in customer premises

The damage of the broadband access unit in customer premises derived from lightening effect has becoming a very big problem, especially in the layout style of “FTTH+LAN”, which has led to much complaint from customers. The traditional method of lightening protection is to disperse lightening energy to earth using SPD. But for the complex and severe circumstances in customer premises, the implementation of valid earthing is very difficult in China, which decreases the performance of lightening protection system greatly. In addition, the installation and maintenance is expensive and complex for the cheap broadband access unit. As above mentioned reasons, the large scale application of the traditional method for broadband access unit is impractical and uneconomic. According to the unit´s characteristic of small power capacity, small-scale volume and low-probability of direct flash, this article presents a new method of “isolation & floating ground” for the lightening protection of broadband access unit in customer premises. This method uses lightening isolation transformer (LIT) and other insulation enhancement measures to isolate overvoltage out of system. It has some advantages, such as dispensing with earth termination, low-cost construction, simple installation and maintenance. This new method has been application in hundreds of pilots and the result is very satisfaction. According to the research and application, we think this new method is more practical and valid for the broadband access units in customer premises.