PQ测量仪器和技术基础(1).ppt

1、3-Phase Power Systems三相电力系统,Electricity is generated by conductors rotating though a magnetic field电是由在磁场中旋转的导体产生的,Pick a point on a circle, rotating counterclockwise at a fixed speed. When the angle is small the change in height is rapid. As the angle increases towards 90 the change in height slows

2、. The distance from the “the horizon” sweeps out a sine wave. 在圆周上选一个点，该点以固定速率在圆周上向逆时针方向旋转。当旋转的角度比较小时，高度的变化就比较明显；当旋转角度向90方向增长时， 高度的变化也组件减缓。偏离“水平”方向的高度即形成了一个正弦波。,Why Sine Waves ?为什么会是正弦波？,Why 3-Phase?为什么为三相？,At any instant the net current on the neutral is zero. Try it!在任何情况下，零线上的净电流为零。试试看！ Three pha

3、se motors have better starting torque, run more quietly, are more efficient and are smaller than singlephase motors of similar hp rating三相马达具有更好的起动扭矩、运行更平顺、更有效率，并且体积比相同马力的单相马达更小。 If you add more than three phases it adds more cost but doesnt deliver significant performance improvements如果相数多余三个，会增加很多

4、费用，但是性能并没有明显改善。,Three individual voltage phases typically 120 degrees out of phase of each other.三个独立的电压相位彼此之间一般相差120度。 Three individual current phases typically 120 degrees out of phase of each other.三个独立的电流相位彼此之间一般相差120度。 Voltage and current will typically be shifted from each other resulting in “

5、power factor”电压和电流的相位一般不一致，所以就有了“功率因数”,Vector Representation矢量表示,Note that the vectors go in the counterclockwise direction, like the circle in the previous slide注意：矢量呈逆时针运动，类似前面例子中的圆周。,From the Dam to Your Load从发电站到负载,From the Dam to Your Load从发电站到负载,High Voltage (over 100kV) is used for transmissi

6、on. All 3-phase用于电力传输的高压线路（100kV以上）。全为三相系统,Substations use transformers to step down the voltage to medium voltage (4160 to 14kV). PTs are used to measure voltage levels.变电站利用变压器将电压变为中压（4160到12kV）。使用PT来测量电压。,Medium voltage is used for distribution. Mostly 3-phase.使用中压进行配电。大多数为三相系统。,Medium Voltage is

7、 stepped down to 240 or 480 for delivery to customers.中压又被变为240或480伏的电压，然后传输给用户。,Fuses and circuit breakers保险和电路断路器 Protective relays保护继电器 Lightning arrestors避雷器 Switches电闸 “Reclosure” 自动开关,From the Dam to Your Load从发电站到负载,Transformer Connections变压器的连接,Single-phase systems单相系统,Three-phase, Four wire

8、 systems 三相、四线系统,Three-phase, Three wire systems 三相、三线系统,Delta Configuration三角型配置,Comprised of 3 voltages and 3 currents.由三个电压和三个电流组成 No Neutral wire.无零线 Sometimes has a ground wire.有时有地线 Voltage is measure as “phase to phase”.测量的电压为“相相”电压 Typically 480vrms. 一般为480vrms.,Wye ConfigurationY型配置,Almost

9、all commercial and light industrial loads are supplied by Grounded-Y (4-wire Y) transformers. 几乎所有的商业和照明领域的负载都是由接地的Y型（4线Y型）配置的变压器供电的,Comprised of 3 voltages and 3 currents.由三个电压三个电流组成 Neutral wire and ground wire.零线和地线 The Wye delivers two stable voltage levels from one transformer在Y性配置下，变压器可以提供两个电压

10、 Phase to Neutral may be used for smaller loads相零电压，小的负载可以使用这个电压 Phase to phase may be used for larger loads or longer wiring runs相相电压，大负载或配线较长时可以使用该电压,Voltage Levels 电压,Standard voltage levels vary by country各个国家的标准电压会不一样 Most distribution within buildings is 120V to 480V建筑物内的绝大多数配电系统为120V到480V Res

11、idential standards vary considerably 各个国家与住宅有关的标准也不一样 US, Canada, Mexico use a 240V single phase system美国、加拿大、墨西哥使用240V的单相系统 Europe, China, others use 230V single or 3-phase欧洲、中国以及其它国家使用230V单相或三相系统 Typical Wye phase-to-phase and phase-to-neutral voltages are典型的Y型配置下相相和相零电压如下 240/120V (US, Canada, Me

12、xico) 240/120V（美国、加拿大、墨西哥） 400/230V (China, Europe) 400/230V（中国、欧洲） 480/277V (US, Canada, Mexico) 480/277V（美国、加拿大、墨西哥） Voltages from 1kV to 100kV are used to serve large commercial buildings and for utility distribution1kV到100kV的电压一般用于大的商业建筑和公用配电系统 Voltages over 100kV are used for transmission超过100k

13、V的电压一般用于电力传输,Color Codes色标,Varies by country and territory.各个国家和地区不一致 Not always done correctly.不一定都正确使用 Bus bar usually not labeled.通常并不标注母线 Australia Electrical Power Systems Quality Dugan, McGranahan, Beaty；“电力系统的质量”,Power Problems电能问题,Voltage sags and outages电压骤降或断电 Overcurrent (tripping CBs)过流（

14、启动断路器） Utility Bills电费 Energy consumption能量消耗 Peak Demand最高负荷 Power Factor Penalties功率因数的影响 Voltage swells电压骤升 Transients瞬态电压 Voltage imbalance/unbalance电压失衡/紊乱 Excessive harmonics谐波过多 Flicker闪变 Noise噪声 Ground currents or poor grounding接地电流或接地不良,Severity of Voltage Events电压时间的安全性,Most Power Quality

15、events are really voltage events.大多数电能质量时间其实是电压事件 Severity of a voltage event is characterized by magnitude and duration.电压时间的严重程度是由幅度和持续时间表示的。 The larger the change, and the longer it takes place, the more likely it is that equipment will malfunction.事件的变化越大、持续的时间越长，设备就越有可能出现故障 ITIC/CBEMA curves pl

16、ot magnitude and duration of events that are likely to cause problems with computer equipment. ITIC/CBEMA曲线用来绘制可能会导致计算机设备出现故障的事件的幅度和持续时间。,Lets Talk About Standards关于标准,There are two important standards that influenced the design of the Fluke 430有两个重要的标准影响着Fluke 430设计 IEC 61000-4-30 “Testing and Meas

17、urement Techniques for Power Quality Measurement Methods.”IEC 61000-4-30 “电能质量测量的测试和测量技术” EN50160 “Voltage Characteristics of Electricity Supplied by Public Distribution Systems”EN50160 “公共配电系统所供电力的电压特征” EN50160 does not mandate IEC-61000-4-30 measurement techniques, but it is consistentEN50160标准对IE

18、C-61000-4-30测量技术并没有要求，但是一致的。 Both standards are exerting strong influence worldwide!两个标准对全世界有不同凡响的影响！,IEC61000-4-30,IEC61000-4-30 Testing and Measurement Techniques for Power Quality Measurement Methods.IEC61000-4-30 “电能质量测量的测试和测量技术” Refers to other standards like IEC61000-4-7 (Harmonics) and IEC61000-4-15 (Fli