过电压分外过电压和内过电压两大类。
There are two categories of overvoltages, overvoltages and internal overvoltages.
外过电压 又称雷电过电压、大气过电压。由大气中的雷云对地面放电而引起的。分直击雷过电压和感应雷过电压两种。雷电过电压的持续时间约为几十微秒，具有脉冲的特性，故常称为雷电冲击波。直击雷过电压是雷闪直接击中电工设备导电部分时所出现的过电压。雷闪击中带电的导体 ，如架空输电线路导线，称为直接雷击。雷闪击中正常情况下处于接地状态的导体，如输电线路铁塔，使其电位升高以后又对带电的导体放电称为反击。直击雷过电压幅值可达上百万伏，会破坏电工设施绝缘，引起短路接地故障。感应雷过电压是雷闪击中电工设备附近地面，在放电过程中由于空间电磁场的急剧变化而使未直接遭受雷击的电工设备（包括二次设备、通信设备）上感应出的过电压。因此，架空输电线路需架设避雷线和接地装置等进行防护。通常用线路耐雷水平和雷击跳闸率表示输电线路的防雷能力。
The external overvoltage is also known as lightning overvoltage and atmospheric overvoltage. Caused by thunderclouds in the atmosphere to discharge on the ground. There are two types of direct lightning overvoltage and lightning induced overvoltage. The duration of lightning overvoltage is about tens of microseconds, and has the characteristics of impulse, so it is often called lightning shock wave. Direct lightning overvoltage is the overvoltage when lightning strikes directly the electrical part of electrical equipment. Electrified conductor, such as overhead transmission line, is called direct lightning stroke. In the case of lightning blitz, conductor, which is in the normal state of grounding, such as transmission tower, raises its potential and then calls the electrified conductor discharges. The amplitude of lightning overvoltage can reach up to millions of volts, which will damage the insulation of electrical facilities and cause short circuit grounding fault. The overvoltage of the induced lightning is the ground near the electrical equipment of the lightning stroke, and the overvoltage of the electrical equipment (including the two equipment and communication equipment) which is not directly struck by the lightning is caused by the rapid change of the space electromagnetic field during the discharge process. Therefore, overhead transmission lines need to be equipped with lightning protection lines and grounding devices for protection. Lightning protection level and lightning trip out rate are usually used to indicate the lightning protection capability of transmission lines.
内过电压 电力系统内部运行方式发生改变而引起的过电压。有暂态过电压、操作过电压和谐振过电压。暂态过电压是由于断路器操作或发生短路故障，使电力系统经历过渡过程以后重新达到某种暂时稳定的情况下所出现的过电压 ，又称工频电压升高。常见的有：①空载长线电容效应（费兰梯效应）。
Overvoltage caused by Internal Overvoltage changes in internal operation mode of power system. There are transient overvoltages, operating overvoltages and overshoot voltages. Transient overvoltage is due to the operation of a circuit breaker or a short circuit fault, which makes the power system come back to some temporary stability after the transition process, which is also called the increase of the power frequency voltage. Common are: (1) no load long line capacitance effect (Fran effect).