过电压是指工频下交流电压均方根值升高，超过额定值的10%，并且持续时间大于1分钟的长时间电压变动现象；过电压的出现通常是负荷投切的结果，例如：切断某一大容量负荷或向电容器组增能（无功补偿过剩导致的过电压）。

Overvoltage refers to the increase of the mean square root of the ac voltage in the operating frequency, more than 10 percent of the rating, and a prolonged period of voltage change over one minute. The emergence of overvoltage often are the result of load cutting, such as: cut a large capacity load or capacitor Banks can increase reactive power compensation overvoltage caused by excess ().

电力系统在特定条件下所出现的超过工作电压的异常电压升高，属于电力系统中的一种电磁扰动现象。电工设备的绝缘长期耐受着工作电压，同时还必须能够承受一定幅度的过电压，这样才能保证电力系统安全可靠地运行。研究各种过电压的起因，预测其幅值，并采取措施加以限制，是确定电力系统绝缘配合的前提，对于电工设备制造和电力系统运行都具有重要意义。

It is an electromagnetic disturbance phenomenon in the electric power system. The electrical equipment insulation resistance with a working voltage for a long time, at the same time must also be able to withstand the amplitude of overvoltage, which ensures that the power system safe and reliable line operation. All kinds of the causes of overvoltage, the ability to predict its amplitude, and take steps to limit, is to determine the power system, the premise of insulation coordination for electrical equipment manufacturing and electric power system has important significance.