国内小水电站单机容量250kW以下的机组,大多采用手动或手动电动调速方式,并普遍采用各种不可控相复励的老式励磁方式。这些小水电站通常都采用投入水阻或电动关车进行飞车保护,并多用过电压继电器来投入飞车保护,以防止过电压和飞车事故的发生。采用可控硅励磁方式的机组,其优点是能实现快速自动调节,当机组突然甩负荷后能自动快速减磁,有效地防止机组产生过电压。因此,使用可控硅励磁方式的机组,无法再用过电压继电器来投入飞车保护。为此,特介绍以下两种实用的飞车保护方案。(一) 水阻保护(见图1)方案 Small hydropower station stand-alone capacity of 250kW below the unit, most of the manual or manual electric speed control method, and the widespread use of uncontrollable phase complex excitation of the old excitation. These small hydropower stations are usually used water resistance or electric off the car for speed protection, and the use of voltage relays to put into the protection of vehicles to prevent over-voltage and speed accidents. The use of SCR excitation unit, its advantage is to achieve rapid automatic adjustment, when the unit suddenly after the load can be quickly and automatically reduce the load, effectively prevent the unit over-voltage. Therefore, the use of SCR excitation unit, can no longer use the over-voltage relay into speed protection. To this end, special introduction of the following two kinds of practical speed protection program. (A) water resistance protection (see Figure 1) program