1、 Power Suppying Technology and Intelligent Building The electric distribution system is a part of an electric power system that supplies electric energy to the individual user or consumer .The distribution substations that supply them, the distribution transformers ,and appropriate protective and co
2、ntrol devices The three general classes of individual user are industrial ,residential, and rural The three-phase alternating-current (ac) system is practically universal ,although a small amount of direct-current systems are in operation .Three-phase transformer and subtransmission lines require th
3、ree wires ,learned phase conductors. Most of the low-voltage three phase distribution systems consist of three phase conductions and a common or neutral conductor ,making a total of four wires .single-phase branches (consisting of two wires)supplied from the three-phase mains are used for single pha
4、se utilization in residences, small stores ,and farms,loads are connected in parallel to common supply circuits. The distribution substation is an assemblage of equipment for purpose of switching, changing and regulating the voltage from subtransmission to primary distribution .More important substa
5、tions are designed so that the failure of a piece of equipment in the substation or one of the subtransmission lines to the substation will not cause an interruption of power to the load The primary system leaving the substation is most frequently in the 6-35kv range. A particular voltage used is IO
6、kv line-to-line and 5.8kv fine to neutral(conventionally written 10/5.8kv).some utilities use a lower voltage ,such as 3/1.7kvThe use of voltage in the 35kv class is increasing for its lower electric loss Secondary voltages are derived from distribution transformers connected to the primary system a
7、nd they usually correspond to utilization voltages .Most loads are supplied by 380/220volt single-phase four-wire systems, some high power -rate motorsrequire 3kv or 6kv. Good voltage means that the average voltage level is correct ,that variations do not exceed prescribed lim it ,and that sudden mo
8、mentary changes in level do not cause objectionable light flicker .Utilization voltage varies with changing load on the system ,but a voltage variation of less than 5% at the consumers meter is common .to achieve this result, distribution systems are designed for a plus and minus voltage spread from
9、 the nominal voltages .This is accomplished by proper wire size for the circuits,application of capacitors ,both permanently connected and switched, and the use of voltage regulations The electric power substation is an assembly of equipment man electric power system through which electrical energy
10、is passed for transmission, distribution, interconnection ,transformation ,conversion ,or switching. A substation includes a variety of equipment .the principal items are listed and briefly described below. Transformers. Transformers involve magnetic core and windings to transfer power from one side
11、 to the other side at different voltages .Substation transformers range from small size of 50kva to large size of several hundred MVA most of transformers are insulated and cooled by oil ,and adequate precautions have to be taken for fire hazard, These precautions include adequate distances from oth
12、er equipment, firewalls fire extinguishing means, and pits and drains for containing leaked oil Circuit breakers， Circuit breakers are required for circuit interruption with the capability of interrupting the highest fault current, usually 20-50times over the normal current, and withstanding high vo
13、ltage surges that appear after interruption. Switches with normal load-interruption capability are called load break switches. Disconnect witches. Disconnect witches have isolation and connection capability without interruption capability. Bus-bars Bus -bars arc connecting bars or conductors between
14、 equipment. Flexible conductor are stretched from insulator to insulator, where more common solid buses(commonly made of aluminum alloy)are installed on insulators in the air or in gasenclosed cylindrical pipes Shunt reactors Shunt reactors are often required for compensation of line capacitance whe
15、re long lines are involved Shunt capacitors Shunt capacitors are often required for compensation of inductive components of load current Current transformers and potential transformers， Current transformers and potential transformers are for measuring currents and voltages and provide proportionatel
16、y low-level currents and voltages for control and protection Control and protection， Control and protection include a) a variety of protective relays which can rapidly detect faults anywhere in the substation equipment and lines, determine which part of the systems is faulty ,and give appropriate co
17、mmands for opening of circuit breakers ；(b) Control equipment for voltage and Current control and proper selection of the system conf gmation；(c) fault-recording equipment ；(e)metering equipment； and (f) auxiliary power supplies. Many of the control and protection devices are solid-state electronic
18、types, and there is a trend toward digital techniques using microprocessors. most of the substations are fullv automated locallv with a provision for manual override .the minimum manual interface required ,alone communications channels to the dispatcher in the central office. Good substation groundi
19、ng is very important for effective relaying and insulation of equipment； the design of the personnel is of substation grounding .It usually consists the governing criterion in of a bare wire grid, laid in the ground； and all equipment groundings points ,tanks, support structures, fences ,shielding w
20、ires and poles ,and so forth ,are securely connected to it， the is reduced to be low enough that a fault from high voltage to ground does not create such high potential gradients on the ground, and from the structures to ground ,to present a safe hazard. good overhead shielding is also essential for
21、 outdoor substations ,soas to eliminate the possibility of lighting directly striking the equipment. Shielding is provided by overhead ground wires stretched across the substation or tall grounded poles 供 电技术 供电系统是电力系统的一部分，它提供电能给消费者。供电系统包括一次电路和变电站，配电变压器，合适的保护和控制设备 三大用电户是工厂，住宅，农村，工厂供电系统是电力系统的主要组成部分，它
22、是电能的主要用户，根据发达国家的统计，工厂用电量占全国发电量的 50%甚至 70%以上，绝大多数的工厂由国家电力系统供电。所谓电力系统，就是由包括不同类型的发电机，配电装置，输配电线路，升压及降压变电所和用户，它们组成一个整体，对电能进行不间断地生产和分配，我国 1985 年建成第一条 500K，的高压送电线路根据国民经济的发展 ，更高的高压送电线路的研究正在研究中，提高送电电压将增大送电容量，节约有色金属，降低线路造价，减少电压损耗，提高电压质量，降低送电线路功率和能量损耗。三相交流系统实践上应用非常广泛，尽管还有一小部分直流电还在使用，三相电传输和分支要用到三根导线大多数低压配电系统由三相
23、导线与一跟共有的或者中胜线组成，构成了四根线，单相分支有 2 根线组成，从三相主电路中获得，用于单相用电设备，广泛存在于居民生活区，个大商场，农村负荷与公共供电线路相关 变电站是一种综合设施，它可以从分支输电网到初级配电网对电压进行切换 和调节更加重要的变电站被设计以达到一个设各的失效或者一条分支传输线失去作用后，不会引起到负载的电源中断变电站的初级系统一般是 6-35 千伏的范围，一个实用的电压 l0 KV 线电压 5.8KV 的相电压，习惯上这样写 10/5.8KV，一些设备使用更低的电压，例如 3/1.7KV, 35KV 电压的使用电压。 表示电气设备的元件与其相互关系的连接顺序的图称为
24、接线图，分 2 类，二次接线图和主接线图，一般来说，主接线图只表示电气装置的一相连接，因为三相交流电力装置中的所有三相连 接方法相同，所接的电气设各也一样，称为单线图，图中的主要元件包括发电机，变压器，交流器，断路器，隔离开关等，以及相互的连接。 二次电压是通过一次侧系统相连接的配电变压器取得，其电压与应用电压相一致，大多数负载采用三相四线制的单相电压供电， 380/220V。一些高电压动力需要 3KV 到 6KV 工厂变电站是终端降压变电站，一般是 110KV 及以下的地方电网，电源绝大多数由国家电网供电，决定工厂供电质量的指标为电压，频率，可靠性， 频率的要求对电压的要求严格得多，一般不得
25、超过或低于 0.5%. 好的电压意味着平均电压水平是准确的，波动范围没有超过允许的范围，突然出现的闪变电压不会导致事故，设备电压的改变是随着电力系统的电压改变而改变的，小于 5%的电压变化是可以接受的，为了达到这个目的，配电系统设计了在额定电压上下的最小电压和冲击电压，通过合适导线尺寸就可完成，电容器的应用，开关，电压调整器，用很多办法多可以达到电力装置的工作可靠，例如，可将电力装置分成为几个部分，正常时并联工作，当电力装置的一部分发生故障时，它就自动的被切断，而电力装置的其它部分仍保持工作，为了使装置可靠，接线图应该力求简单清晰 ，电器装 置 是电力装置的最 薄 弱部分，所以不应该不适当的增加电器的数目，以免引起事故 变电站是一个集中设各的地方，通过它电能传输，分配，转换，连接，转化，切换，变电站包括各种各样的设各，它由变压器，配电装置，保护及控制设各，测量仪表以及附属设施及有关
