1、w10kv无功补偿摘自 电力系统分析和设计摘要 改善工业企业用电的功率因数是提高用电效率、节约电能的重要手段。本文通过理论分析和应用实例说明了工业企业无功补偿的意义和作用，并针对目前工业企业供用电系统存在的问题，提出了改进意见和措施。1 引言在工业企业中，绝大多数的用电设备属于感性负荷，这些设备在运行中要吸收大量的无功功率。无功功率的增加使供电系统的功率因数降低，从而出现系统电压下降、电气设备得不到充分利用、增加线路损耗以及降低供电设备的供电能力等情况。因而就地进行无功补偿、提高功率因数对降损节能有着极为重要的意义。2 补偿方式的选择无功补偿分为集中补偿、分散补偿和就地补偿三种。集中补偿，即在
2、高、低压配电所内设置若干组电容器，电容器接在配电母线上，补偿该配电所供电范围内的无功功率，并使总功率因数达到规定值以上。这种补偿方式只能补偿高、低压母线之前线路上的无功功率，它们相当于把无功功率源移到用电企业的配电所，使用户对供电系统要求的无功功率有所减少，达到供电部门所要求的功率因数。而它们对配电母线以下的企业内部的变压器和线路的无功功率不能起到补偿作用，仍有大量的无功功率在企业内部线路上流动并产生损耗。分散补偿是将电容器组分别安装在各个车间的配电盘处，这种安装方式可以使配电变压器以及变电所至车间的线路都可以由于无功负荷的减少而获得补偿效果。就地补偿是把无功补偿器直接接在异步电动机旁或进线端
3、子上。集中补偿方式所用电容器组的容量较分组补偿或就地补偿要小，它的利用率则更高，缺点是对变、配电所各馈线并未得到补偿，仅减轻了电网的无功负荷。分散补偿方式中的电容器组的利用率比就地补偿高，因此总需要量较就地补偿要小，是一种经济合理的补偿方式。无功补偿应遵循“全面规划，合理w布局，分级补偿，就地平衡;集中补偿与分散补偿相结合，以分散补偿为主；高压补偿与低压补偿相结合，以低压补偿为主；调压与降损相结合，以降损为主”的原则。3 补偿容量的确定在电力网中无功功率的消耗是很大的，大约50 %的无功功率消耗在输、变、设备上，50 %消耗在电力用户上。为了减少无功功率消耗，就必须减少无功功率在电网里的流动。
4、最好的办法从用户开始增加无功补偿，提高用户负荷的功率因数，这样可以减少发电机无功出力和减少输、变、配电设备中的无功电力消耗，从而达到降低损耗的目的。补偿的无功功率容量 为cQ2211ososcavP式中 最大负荷日平均有功功率； 未装设补偿装置前的功率因数实avPc测值； 装设补偿装置后所达到的功率因数值。2cos4 无功补偿装置的作用可以根据负荷变化情况决定采用静态还是动态补偿方式。当负荷变化较为平稳时，应采用静态补偿方式，这不仅能较好地降低线路损耗，而且投资少;当负荷变化较大时，应采用动态补偿方式，稳定电压。4.1 降低线损设在某一额定电压下，有功功率恒定不变，由于功率因数变化，其线路损耗
5、变化率 P %为 21cos%()0%PA从表4.1中可以看出提高功率因数对于降低电能损耗，提高经济效益具有十分重要的作用。w表 4.1 功率因数与有功损耗百分率的对应数据若在恒定有功功率条件下，原有的功率因数 为0.60，补偿后的功率因数1cos为 1，0 时，其线损率降低 %为64 %。采用动态补偿装置，将电力电容器分2cos组跟踪补偿，则可由原来不同的功率因数稳定在所规定的功率因数范围内，达到充分补偿的目的。4.2 线路、变压器的增容线路、变压器的增容量 S 为 12cosA加设补偿装置后，可提高功率因数，对企业的直接功率因数经济效益是明显的。因为国家电价制度中，从合理利用能源出发，依据
6、企业的功率因数值来调整电价高低。这种补偿装置对企业和整个电力系统的经济运行都有着重大的经济效。4.3 改善电压质量改善电压质量是指装设动态无功补偿装置前后，作用在补偿地点的线路电压稍有提高。 12210%UtgxQRA式中 未装设补偿装置前 角的正切；1tg1w装设补偿装置后 角的正切；2tg2R 、 x 线路的电阻、电抗。5 工业企业供用电系统存在的问题与解决措施图1为某重型机床厂供电系统示意图。目前，该厂变压器总容量为17660kVA ，共有20台变压器(1 # 20 # 变压器) ，每台变压器的容量范围为501250 kVA ，变比为10kV/ 014kV。变压器低压侧负载主要为电动机，
7、如图中 M1 、 M2 Mn 所示。一般情况变压器负载率基本上维持在28 %29 %之间，最大负载时为7000kW。5.1 采用高、低压相结合的补偿方式取代高压集中补偿从图中可以看到该厂供电网络的功率因数补偿是高压集中补偿，即只在变电所10kV 的高压母线上接电容器组，而低压却没有采取任何补偿措施。这种固定电容器补偿的方法会出现过补偿或欠补偿的情况，并且对二次母线以下的供电线路的功率因数补偿不起作用。由于功率因数低而造成的线路损失和变电设备的损失是很大的，所以补偿时要尽量做到分级，靠近负载处安装电容器。因而提出高压侧集中补偿和低压侧分散补偿相结合的补偿方式。图 5.1 某重型机床厂供电系统示意
8、图5.2 改变供电方式，尽可能避免“大马拉小车”的现象在设备选型时，要考虑留有一定的容量，防止重载时损坏设备，这样大部分时w间都造成设备欠载和严重欠载形成“大马拉小车”运行。由于该厂变压器的负载率基本上在28 %29 % 之间，说明变压器的装机容量过大，变压器容量不能充分利用，既浪费了设备投资又增加了电能损耗。可以通过合理选择变压器的容量以及减少或限制用电设备轻载或空载的时间来防止“大马拉小车”现象。5.3 避免设备的空载运行目前，该厂某些设备的空载运行严重。在提高功率因数时，首先应考虑使设备合理运行，提高耗电设备本身的功率因数。该厂主要负荷是交流电动机，其功率因数随它的负载而改变，电动机在空
9、转时，功率因数约在0.10.3 之间，额定负载时在0.80.85 之间，因而应使电动机接近额定负荷状态下运行。要把电动机功率因数提高，最简单的办法是用电容器和电动机并联，所以避免设备的空载运行是提高设备功率因数的重要途径。5.4 建议完善配电设备或对其进行重新改造在现场测量数据的过程中，我们发现很多配电设备老化现象严重，没有电流表、电压表或者读数不准确，如镗床车间的配电房内完全没有电流表和电压表。6 经济效益分析以该厂供电系统中的2 # 变压器为例，在低压侧加装电容器，使该厂采取高压侧集中补偿和低压侧分散补偿相结合的补偿方式，如图6.1 。图中2 # 变压器容量为800kVA ，型号为S9 -
10、 800/ 10 ，额定铜损耗为 = 715kW ，输电线路型号为cunPAYJV22 。取电价为0.55元/ kW.h 。将功率因数由补偿前的0.59提高到补偿后的0.98 ，表6.1是利用测量仪器在现场测得的变压器运行时二次侧数据，现通过计算分析无功补偿降损节能效益。w图6.1 铸造车间供电图表6.1 变压器运行时二次侧数据表6.1 高压供电线路节电全年节约电能W = h1PA式中 增加的线路电功率， 2211cos3PIRAh 年运行小时数，取5000h 。经计算全年节约电能162217kW.h ，一年内降低的电能损耗费8192万元。6.2 变压器节电变压器的损耗主要有铁损和铜损。提高变
11、压器二次侧的功率因数，可使总的负荷电流减少，从而减少铜损。全年节约变压器铜损耗电能 h 式中12()cuWPAA补偿前变压器实际运行时的铜损耗电功率1PAw 211cunIPA PCu2 补偿后变压器的铜损耗电功率 212coscunPA经计算全年节约电能3150kW.h ，一年内节约变压器铜损耗电费173518元。6.3 功率因数调整电费用户一年内减少因功率因数偏低多支出的罚金:800 0. 5895000 0.55 17.22 %(增收率) =22131 万元补偿后用户一年内得到的功率因数奖金:800 0. 589 5000 0.55 2.7 %(减收率) =315万元两项总计为25181
12、万元由上述计算可知一年内合计增加纯收入34173万元，根据补偿容量需设备投资2715万元，9个月就能收回投资。这说明针对该厂铸造车间的具体情况在变压器二次侧采用分散补偿的方式进行无功补偿是可行的，并且能取得长期且明显的经济效果。wIndustrial enterprises of reactive power compensationFrom:Power System Analysis and DesignAbstractThe improvement of industrial enterprises is to improve the power factor of electric po
13、wer efficiency， an important means of saving energy. In this paper， theoretical analysis and application examples of the industrial enterprises， the significance of reactive power compensation and the role and view of the current power system， industrial enterprises， the problems for the proposed im
14、provements and measures. IntroductionIn industrial enterprises， the vast majority of electrical equipment belongs to perceptual load， these devices in operation to absorb a large number of reactive power. An increase in reactive power supply system power factor to lower system voltage drop to occur，
15、 electrical equipment not fully utilized， increasing line losses and lower-powered equipment， power supply capacity and so on. In situ reactive power compensation and thus improve the power factor of the Energy Conservation has extremely important significance. The choice of method of compensation C
16、ompensation for reactive power compensation is divided into centralized and decentralized compensation for three kinds of compensation and in situ. Focus on compensation， that is， high and low voltage power distribution set up by several groups within the capacitor， capacitor connected to the power
17、distribution bus， the compensation for the distribution of power within the reactive power， and to reach the wrequired value of the total power factor above. This method of compensation can compensate for high and low voltage bus routes prior to the reactive power， which is equivalent to the reactiv
18、e power source to move the electricity distribution companies， allowing users to power the system requirements for reactive power has been reduction in the electricity sector to achieve the required power factor. And their distribution within the enterprise bus following the line of transformer and
19、reactive power compensation can not play a role， there is still a large number of reactive power line flows within the enterprise and generate losses. Dispersion compensation is the capacitors were installed at various workshops at the switchboard， which will enable installation of distribution tran
20、sformer and the substation to the plant lines can be due to a decrease in reactive load compensation effect. Local compensation is the reactive power compensation device directly connected to the induction motor terminals on the side or into the line. Focus on compensation methods used in the capaci
21、ty of capacitor compensation or in-place than the grouping of compensation should be small， its utilization rate is even higher disadvantage is the change in distribution has not been compensated by the feeders， only lightened the load reactive power grid. Dispersion compensation in the way the util
22、ization of capacitor compensation than the in situ high， so the total requirement of compensation is smaller than the spot is an economical and reasonable remedy. Reactive power compensation should follow the “overall planning， rational distribution， classification of compensation， in-place balance;
23、 focus on compensation and dispersion compensation combine to spread-based compensation; high compensation and low voltage compensation combined with low-pressure-based compensation; Regulator combined with lower losses， down are the main loss “principle 1. Compensation capacity to determine In the
24、power grid in the reactive power consumption is a big， about 50% of the reactive power consumed in transmission， transformation and the device， 50% of the consumed electricity users. In order to reduce reactive power consumption， it is necessary to reduce the reactive power in the grid where flow. T
25、he best way to start from the user to increase reactive power compensation， improve user load power factor， so that Generator reactive power can be reduced and the reduction of transmission， wtransformation and distribution equipment in the reactive power consumption， so as to achieve the purpose of
26、 reducing wear and tear 2. Compensation for reactive power capacity of Qc for2211coscoscavQPLoad changes can be decided according to the static or dynamic compensation mode. When the load change is relatively stable， we should use the static method of compensation， which can not only reduce the line
27、 losses， and investment; when the load change is large， dynamic compensation method should be used， stable voltage 3.Reduce line lossesIs located at a rated voltage， active power is constant， due to power factor changes， the line loss rate of change P% for the 21cos%()0%PAAs can be seen from Table 1
28、 to improve the power factor in lowering power consumption， improving economic efficiency plays an important role. Table 1 Power factor and power loss percentage of the corresponding dataIf a constant active power condition， the original power factor cos1 of 0.59， compensated power factor cos2 of 0.
29、98， its line loss rate reduction % to 64%. Dynamic compensation device， Group to track the power capacitor compensation， power factor can be different from the stability provided in the context of the power factor to achieve adequate wcompensation purposes. Lines， transformer capacity increase Lines
30、， transformer capacity increased S for the 12cosSAAdditional compensation device， may improve the power factor， power factor on the business of direct economic benefit is obvious. Because the state electricity system， starting from the rational use of energy， according to the power company to adjust
31、 the price due to high and low values. The compensation device for enterprise and the entire power system economic operation all have significant economic effects . To improve the voltage quality To improve the voltage quality is the dynamic reactive power compensation equipment installed around the
32、 role of place in the line voltage compensation has increased slightly . 12210%UtgxQRAWhere tg1 - compensation device is not installed before the 1 angle tangent; tg2 - compensation equipment installed after the 2 angle tangent; R， x - line resistance， reactance. Industrial enterprises for the power
33、 system problems and solution Fig 1 for a diagram of power supply systems for heavy machine tool plant. At present， the total capacity of the plant transformer 17660kVA， a total of 20 transformers (1 # 20， # transformers)， each transformer capacity range of 50 1250 kVA， changing the ratio of 10kV /
34、014kV. Transformer low voltage side of the load is mainly motor， shown in the M1， M2 Mn shown. In general the rate of transformer load is basically maintained at 28% 29%， and the maximum load of 7000kW. High and low voltage compensation to replace a combination of high concentration of compensation
35、From the figure we can see the plant supply network focused on high-voltage power factor compensation is compensation that is only in the high-voltage busbar 10kV substation capacitor banks on the pick， while the low pressure has not taken any compensation measures. The fixed capacitor compensation
36、method there have been wcompensation or due compensation， and right below the second power supply bus power factor compensation circuit does not work. As the low power factor caused by the line losses and transformer equipment is a big loss， so compensation as far as possible when grading， installat
37、ion of capacitors near the load. Therefore proposed that the high side to focus compensation and dispersion compensation for low-voltage side of a combination of method of compensation .Figure 1 Power Supply System of a Heavy Machine Tool Plant diagramTo change the power supply as much as possible t
38、o avoid the “big horse-drawn cart“ phenomenon In making our selection， we should consider leaving a certain margin， to prevent heavy damage to equipment when， so most of the time caused by equipment， and severe underrun underrun the formation of the “big horse-drawn cart“ Run. As the plant load fact
39、or of the transformer is basically 28% 29%， and shows the transformer capacity is too large， transformer capacity can not be fully utilized， not only a waste of investment in equipment has increased the power loss. Rational choice by the transformer capacity and electrical equipment to reduce or lim
40、it the light-load or no load time to prevent the “big horse-drawn cart“ phenomenon. To avoid the no-load operation of equipment At present， the plant is running a serious load of some equipment. Improving the power factor， the first consideration should be given a reasonable run the equipment to wim
41、prove power factor of power the device itself. The plant main load is AC motor， its power factor load with it change， motor idling， the power factor of about 0.1 0.3 between the rated load at 0.8 0.85 between the motor and thus should be made near the rated load state run. We should improve the moto
42、r power factor， the simplest way is to use capacitors and electric motors in parallel， so to avoid the no-load operation device is to improve the power factor equipment， an important way. Economic Benefit Analysis To the factory power supply system in two # transformers， for example， installation of
43、 capacitors in the low voltage side， so that high-pressure side of the plant to focus on compensation and dispersion compensation combination of low-voltage side of a compensation formula， shown in Figure 2. Graph 2 #transformer capacity of 800kVA， model S9 - 800 / 10， rated copper loss for the 715k
44、W， transmission line model YJV22. Get price of 0.55 yuan / kWh. The power factor by the compensation prior to 0.59 to compensate for post-0.98， Table 2 is the use of measuring instruments measured in the field of transformer secondary side run-time data are analyzed by calculating the loss of reacti
45、ve power compensation reduced energy efficiency.Figure 2 foundry supply diagram Table 2 transformer secondary-side run-time data tablewThe energy-saving high-voltage power lines Throughout the year to save electricity W = h1PAWhere l- the increase in electric power lines，1PA 2211cos3IRThe number of
46、annual operating hours， whichever 5000h. The calculation of annual energy savings 162217kW.h， within one year to reduce electricity consumption costs 81.92 million yuan. Transformer-saving The loss of main transformer iron loss and copper loss. Transformer secondary side to improve the power factor，
47、 can reduce the total load current， thereby reducing the copper loss. Transformer copper loss of the year to save energy W = (PCu1 - PCu2) h where PCu1 - compensation for the actual run-time before the transformer copper loss of electric power， 211CuNIPAPCu2 - compensated transformer copper loss of
48、electric power， w 212cosCuNPAThe calculation of annual energy savings 3150kWh， within a year to save electricity transformer copper loss of 173，518 yuan. Power Factor Adjustment tariff Users within a year to reduce spending more than the low power factor penalty: 800 0. 589 5000 0.55 17.22% (increas
49、e rate) = 221.31 million yuan of compensation within one year after the users get the power factor bonus: 800 0. 589 5000 0.55 2.7% (reduced rate) 3.15 million total of 251.81 million yuan from the two above calculations we can see an overall increase within one year of net income 341.73 million yuan， according to the capacity required to compensate for equipment in
