Cable aging reasons: external damage. According to the analysis of operation in recent years, especially in Haipu East in the rapid economic development, quite a few cable faults are now caused by mechanical damage. For example: cable laying installation does not regulate the construction, likely to cause mechanical damage; in direct buried in the civil construction is also very easy to run the cable damage and so on. l Sometimes, if the damage is not serious, it will take several months or even years to cause complete breakdown of the damaged site to form a fault, which may cause serious short circuit failure and directly affect the safety of electricity and electricity units.