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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 con
2、trol 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 thr
3、ee 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 phas
4、e 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 substat
5、ions 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 IOk
6、v 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 an
7、d 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 mom
8、entary 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 regulationsThe electric power substation is an assembly of equipment man electric power system through which electrical energy is
10、 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 t
11、o 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 other
12、 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 volta
13、ge 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 eq
14、uipment. 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 pipesShunt reactors Shunt reactors are often required for compensation of line capacitance wherelo
15、ng 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 proportionately low-
16、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 commands
17、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 types, a
18、nd 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 grounding is ver
19、y 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 wires and
20、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 outdoor s
21、ubstations ,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，它是电能的主要用户，根据发达
22、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导线与一跟共有的或者中胜线组成，构成了
23、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
24、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
25、，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
26、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建筑物组成的主要的列举在下面: 变压器:包括电磁铁，绕组它改变电压从一端到另外一端，可以有多个不同的电压等级，变电站的变压器的容量范围一般是50KV、到几百MKA，大多书变压器是绝缘的，采用油冷却的方式，足够的警告必须有，为的是防止火灾，包括远离切也设备，仿火墙，火隔离方式。坑和排水沟包含泄漏汕 断路器:它是为拉断开电路有足够的容量，断开最高的电流，几十倍的额定电流，消除高压出现在中断后，开关有额定负载中断容量的称为负载断路开关 隔离开关:没有断开能力，有隔离和连接作用总线:总线连接线和导体在设备问，
27、灵活的导线从一个绝缘器到另外一个绝缘器固体的导线安装在空气的绝缘器上或者圆筒状的管道上， 并联电抗器:用于补偿电容很长的线包含在那里。 并联电容器:为补偿负载电流感应成分 电沛百感器和电压互感器:测量电流和电压，提供低压电流和电压为控制和保护 控制和保护:包括大量的继电器能够快速的检查到变电站任何设备和导线的问题，发出恰当的命令为断路器准确地动作。供电系统高压配电网保护装置采用继电保护装置或者高压熔断器，车间低压配电系统保护装置采用低压断路器和低压熔断器，继电保护装置即各种不同类型的继电器，以一定的方式连结和组合，在系统发生故障时，继电保护装置动作，作用于断路器的脱扣线圈或给出报警信号，以达到
28、对系统进行保护的日的，继电保护装置应该满足选择性，灵敏度，可靠度，速动性的要求 高压断路器的合闸，跳闸回路，继电保护装置中的操作回路，控制回路，信号回路，以及保护回路等所需的电源称操作电源，操作电源有三种:蓄电池供电的直流电源，整流电源和交流电源，蓄电池被整流电源代替，蔡沛择作电源有两种方式即电容补偿和复式整流，整流操作电源要求供给的交流电源更加可靠，一般至少有2个独立电源给整流器供电，共中之一最好与本变电所无直接联系的电源。交流操作电源比整流电源更加简单，不需设置直流回路，可以采用直接动作式继电器，工作可靠。 控制设备:用于电压和电流的恰当的选择为系统配置 故障记录设备 测量设备 辅助电源供应 大多数控制和保护设各是固体电力类型，现在有个趋势是用微型控制器，大多数变电站是自动化，还有手动辅助设备，最少的手动干预，独立的基木信息状态，传送到控制中心通过传送到机器 好的变电姑接的是很重要的为有效的释放和隔离，然而人身的安全在变电站接地时是政府制定的标准，它有赤露的导线连接到地上，所有设各的接地开关柜，支撑物，避雷网和避雷针等等。安全的连接到上面，接地电阻应减少到足够程度，以保证不会因高压与地之间以及设备与地之间的故障在地表面产生太大的电位梯度，而形成对安全的威胁，好的避雷也是必要的为户外变电站，为了消除闪电对设各的影响，避雷提供接地线延伸到变电站
