电气主要功能
Main electrical functions
为了保证一次设备运行的可靠与安全，需要有许多辅助电气设备为之服务，能够实现某项控制功能的若干个电器组件的组合，称为控制回路或二次回路。这些设备要有以下功能：
In order to ensure the reliability and safety of the operation of a equipment, many auxiliary electrical equipment are required to serve it, which can realize the combination of some electrical components of a certain control function, called the control loop or the two circuit. These devices have the following functions:
1、自动控制功能：高压和大电流开关设备的体积是很大的，一般都采用操作系统来控制分、合闸，特别是当设备出了故障时，需要开关自动切断电路，要有一套自动控制的电气操作设备，对供电设备进行自动控制；
1, automatic control function: the volume of high voltage and high current switching equipment is very large, usually uses the operating system to control and switch, especially when the equipment fails, it needs switch to cut off the circuit automatically, have a set of automatic control electric operation equipment, and control the power supply automatically.
2、保护功能：电气设备与线路在运行过程中会发生故障，电流（或电压）会超过设备与线路允许工作的范围与限度，这就需要一套检测这些故障信号并对设备和线路进行自动调整（断开、切换等）的保护设备；
2, protection function: electrical equipment and line will fail during operation, current (or voltage) will exceed the scope and limit of equipment and line, which requires a set of protective equipment to detect these fault signals and adjust the equipment and line automatically (disconnection, switching and so on).
3、监视功能：电是眼睛看不见的，一台设备是否带电或断电，从外表看无法分辨，这就需要设置各种视听信号，如灯光和音响等，对一次设备进行电气监视；
3, monitoring function: electricity is invisible to the eye, a device is charged or power off, from the appearance can not be resolved, this needs to set all kinds of audio-visual signals, such as lighting and sound, and so on, the electrical monitoring of a device;
4、测量功能：灯光和音响信号只能定性地表明设备的工作状态（有电或断电），如果想定量地知道电气设备的工作情况，还需要有各种仪表测量设备，测量线路的各种参数，如电压、电流、频率和功率的大小等。
4, measurement function: light and sound signal can only qualitatively show the working state of the equipment (electricity or power break). If you want to know the working condition of the electrical equipment, there are various instrument measuring equipment to measure the parameters of the line, such as voltage, current, frequency and power.
在设备操作与监视当中，传统的操作组件、控制电器、仪表和信号等设备大多可被电脑控制系统及电子组件所取代，但在小型设备和就地局部控制的电路中仍有一定的应用范围。这也都是电路实现微机自动化控制的基础。
In the operation and monitoring of equipment, traditional operating components, control appliances, instruments and signals can be replaced by computer control systems and electronic components, but there are still some applications in small equipment and local local control circuits. This is also the basis for the realization of microcomputer automation in circuits.