%1P ⎡=-⎢⎣中可以看出提高功率因数对于降低电能损耗，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1cos ϕ为0.60，补偿后的功率因数2cos ϕ为1，0时，其线损率降低ΔΡ%为64 %。
采用动态补偿装置，将电力电容器分组跟踪补偿，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ΔS 为12cos 1cos S S ϕϕ⎛⎫=⨯- ⎪⎝⎭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。
12211100%U U tg x U Q R tg xϕϕ-=⨯=+ 式中1tg ϕ—未装设补偿装置前1ϕ角的正切；2tg ϕ—装设补偿装置后2ϕ角的正切；R 、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50～1250 kVA ，变比为10kV/ 014kV。
变压器低压侧负载主要为电动机，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，电动机在空转时，功率因数约在0.1～0.3之间，额定负载时在0.8～0.85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P = 715kW ，输电线路型号为800k VA ，型号为S9 - 800/ 10 ，额定铜损耗为cunYJV22 。
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。
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ΔW =1P h式中1P —增加的线路电功率，22112cos 31cos P I R ϕϕ⎡⎤⎛⎫⎢⎥=- ⎪⎢⎥⎝⎭⎣⎦h —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12()cu cu W P P =-h 式中1P —补偿前变压器实际运行时的铜损耗电功率2112cu cun I P P I ⎛⎫= ⎪⎝⎭21cos cos cu cun P P ϕϕ⎛= ⎝，一年内节约变压器铜损耗电费用户一年内减少因功率因数偏低多支出的罚金万元补偿后用户一年内得到的功率因数奖金22121111cos cos c av Q P ϕϕ⎡⎤=---⎢⎥⎣⎦ Load 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 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 ΔP% for the212cos %1()100%cos P ϕϕ⎡⎤=-⨯⎢⎥⎣⎦ As can be seen from Table 1 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 cosφ1 of 0.59， compensated power factor cosφ2 of 0.98， its line loss rate reduction ΔΡ% 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 compensation purposes.Lines ， transformer capacity increaseLines ， transformer capacity increased ΔS for the1S S ⎛=⨯ ⎝Additional compensation device ， may improve the power factor 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 the price due to high and low values. The compensation device for enterprise and the entire 11U U U Q -=compensation device is not installed before the φ1 angle tangent; equipment installed Industrial enterprises for the power system problems and solutiongrading，installation 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 1Power Supply System of a Heavy Machine Tool Plant diagramTo change the power supply as much as possible to avoid the "big horse-drawn cart" phenomenonIn 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 factor 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 limit the light-load or no load time to prevent the "big horse-drawn cart" phenomenon.To avoid the no-load operation of equipmentAt 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 improve 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 therated load state run. We should improve the motor 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 AnalysisTo the factory power supply system in two # transformers，for example，installation of 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 800kV A，model S9 - 800 / 10，rated copper loss for the 715kW，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 reactive power compensation reduced energy efficiency.Figure 2 foundry supply diagramTable 2 transformer secondary-side run-time data tableThe energy-saving high-voltage power linesThroughout the year to save electricityΔW = 1P hWhere 1P l- the increase in electric power lines ，22112cos 31cos P I R ϕϕ⎡⎤⎛⎫⎢⎥=- ⎪⎢⎥⎝⎭⎣⎦The number of 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-savingThe loss of main transformer iron loss and copper loss. Transformer secondary side to improve the power factor ， can reduce the total load current ， thereby reducing the copper loss. Transformer copper loss of the year to save energy ΔW = (ΔPCu1 - ΔPCu2) h where ΔPCu1 - compensation for the actual run-time before the transformer copper loss of electric power ，211Cu CuN N I P P I ⎛⎫= ⎪⎝⎭ΔP Cu2 - compensated transformer copper loss of electric power ，21cos cos Cu CuN P P ϕϕ⎛= ⎝The calculation of annual energy savings 3150kWh 518 yuan.Power Factor Adjustment tariffUsers within a year to reduce spending more than the low power factor penalty: 800。