UNIT 24 ELECTRICAL DISTRIBUTION SYSTEM
配电系统
1. The design of electrical distribution systems varies between commercial nuclear power plants, but they all contain the following:
a. High voltage, offsite distribution
b. high voltage and medium voltage, onsite power
c. Low voltage, control and instrumentation distribution.
每个商业运行和电站的配电系统设计不尽相同，但它们都包含以下部分： a.高压厂外配电系统
b.高压和中压厂内配电系统 c.低压控制和仪表配电系统 2. The offsite power system includes two or more power sources capable of operating independently of the onsite power sources and encompasses the grid, transmission lines, transmission line control system, switchyard battery system, etc. 高压厂外配电系统由2条或以上、相互独立的电源线组成，包括：电网、输电线、线路控制系统和开关站等。 3. The onsite electric power system consists of the main generator, the unit station transformers, the common station service transformer, the diesel generators and the electric distribution system. 厂内配电系统由主发电机，主变压器，厂用变压器，柴油发电机和相关的配电设备组成。
4. Class 1E is the safety classification of the electric equipment and systems that are essential to emergency reactor shutdown, containment isolation, reactor core cooling and containment and reactor heat removal etc. 1E级电源是定义为与以下系统安全相关电源：紧急停堆、安全壳隔离、反应堆冷却、以及安全壳和反应堆的热量导出。 5.The offsite (preferred) power system is, as the name implies, the preferred source of power for class 1E loads. 厂外电源系统作为1E级电源的首选馈电。
6.The onsite electric power system is divided into vital and non-vital distribution. 厂内配电系统分为重要和非重要配电系统。
7. Vital distribution system includes shutdown boards, the diesel generators and interconnecting bus work and the loads supplies by this portion are safety-related and are required to place the plant in a safe shutdown condition. 厂内重要配电系统由安全母线，应急柴油机和联结的母线组成。这部分的负荷是安全相关的，保证电站处于安全停堆的状态。
8. The main generator converts the mechanical energy of the turbine into electric energy. 主发电机将汽机的机械能转化为电能。
9.Under normal operating conditions, the main generators supply electrical power through distribution buses to the main step-up transformers and the unit station service transformer; during startup and shutdown, power is supplied from the offsite power through the common station service transformer.
正常运行时，发电机发出电能至配电母线，然后通过主变压器和厂用变；在启动和停堆阶段，自厂外电经厂用变馈电。
10. The standby onsite power is supplied by diesel generators. Each of which is sized to provide all the electric power required to operate the engineered safety features equipment assigned to the corresponding electrical power train. 柴油发电机（EDG）作为电站备用电源。每一台都具备向一个系列的专设安全设施设备供电的能力。 11. Diesel generators start automatically on receipt of an engineered safety features actuation signal, loss of voltage to the shutdown board or emergency start initiated by the operator.
EDG自启来自专设安全设施信号和安全母线失电信号，也可由RO应急手动启动。 12.The vital DC control power system is a class 1E system whose safety function is to provide control power for engineered safety equipment, emergency lighting, vital inventors and other safety related DC power equipment for the entire plant. 重要直流系统是1E级系统，其功能就是向专设，应急照明，重要通风系统和整个电站内其他安全相关的设备提供控制电源。
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