利用系数法确定计算负荷

;.;.5.2.5利用系数法确定计算负荷用利用系数法确定计算负荷时，不论计算范围大小，都必须求出该计算范围内用电设备有效台数及最大系数，而后算出结果。（1）用电设备组在最大负荷班内的平均负荷：有功功率Pp=K1PN，kW（5-2-⑵无功功率Qp=Pptg①，kvar（5-2-13）式中PN——用电设备组的设备功率，kW；K1——用电设备组在最大负荷班内的利用系数，见表5-2-6；tg3一一用电设备组的功率因数角的正切值，见表5-2-6。表5-2-6利用系数K1、cosP及tg3用电设备组名称K1cos3tg3一般工作制小批生产用金属切削机床（小型车、包U、插、铣、钻床、砂轮机等）0.1~0.120.501.73一般工作制大批生产用金属切削机床0.12~0.140.501.73重工作制金属切削机床（冲床、自动车床、六角车床、粗磨、铣齿、大型车床、刨、铣、立车、镗床）0.160.551.51小批生产金属热加工机床（锻锤传动装置、锻造机、拉丝机、清理转磨筒、碾磨机等）0.170.601.33大批生产金属热加工机床0.200.651.17生产用通风机0.550.800.75卫生用通风机0.500.800.75泵、空气压缩机、电动发电机组0.550.800.75移动式电动工具0.050.501.73不联锁的连续运输机械（提升机、皮带运输机、螺旋运输机等）0.350.750.88联锁的连续运输机械0.500.750.88起重机及电动葫芦（8=100%）0.15~0.200.501.73电阻炉、干燥箱、加热设备0.55~0.650.950.33试验室用小型电热设备0.351.000.0010t以下电弧炼钢炉0.650.800.75单头直流弧焊机0.250.601.33多头直流弧焊机0.500.701.02单头弧焊变压器0.250.352.67多头弧焊变压器0.300.352.67自动弧焊机0.300.501.73点焊机及缝焊机0.250.601.33对焊机及铆钉加热器0.250.701.02工频感应电炉0.750.352.67高频感应电炉（用电动发电机组）0.700.800.75高频感应电炉（用真空管振荡器）0.650.651.17（2）平均利用系数为ZPK=——p1pZPN(5-2-14)式中ZPp——各用电设备组平均负荷的有功功率之和，kW；ZPN——各用电设备组的设备功率之和，kW。（3）用电设备的有效台数几yr是将不同设备功率和工作制的用电设备台数换算为相同设备功率和工作制的有效值。故yxnyx(ZPN)二N—ZP21N(5-2-15)式中P1N——单个用电设备的设备功率，kW。1）当有效台数为4台及以上，且最大一台设备功率PNmax与最小一台设备功率Pvmin的比值m^3时，取1N,max1N,minn=n(5-2-16)yx在确定nW值时，可将组内总功率不超过全组总设备功率5%的一些最小用电设备略去。yx2）当m〉3和K1p三0.2时，取ZPnyx0.5P1N,max(5-2-17)如按上式求得的“yr比实际台数还多，则取%丫=n。yxyx3）当m〉3和K1p<0.2时，取，0.95（EPn）n=nn六N^^^^（P）2（ZP—P）2n1+Nn1nn一n11（5-2-18）n0.95n=yx^Xyxn（p'）2（1一p'）2n，1一n，（5-2-19）nPn——，,p=-n^~nZpN以上式中n——用电设备台数；（5-2-20）n1——用电设备中，单台设备功率不小于最大一台设备功率一半的台数;n'——n1台数的相对值；ZPn—-各用电设备组的设备功率之和，kW；Pn1——n1台设备的总设备功率，kW；PPn1功率的相对值；n二一一有效台数相对值，可根据相对值n'和P’,从表5-2-7查得。yx.f表5-2-7用电设备有效台数相对值nvryx3设备所用的需用系数应用范围照明回路普通插座厨卫插座空调0.90.90.950.5;.P'n，1.00.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.010.010.010.010.010.020.020.020.020.030.030.040.050.060.080.100.140.200.320.520.020.020.020.020.030.030.030.040.040.050.060.070.090.110.140.190.260.360.510.710.030.030.030.030.040.040.050.060.070.080.080.110.130.160.210.270.360.490.640.810.040.040.040.040.050.060.070.080.090.100.120.150.180.220.270.340.440.570.720.860.050.050.050.060.070.070.080.100.110.130.150.180.220.260.330.410.510.640.790.900.060.060.060.070.080.090.100.120.130.150.180.210.260.310.380.470.580.700.830.920.080.080.080.090.110.120.130.150.170.200.240.280.330.400.480.570.680.790.890.940.100.090.100.120.130.150.170.190.220.250.290.340.400.470.560.660.760.850.920.950.150.140.160.170.200.230.250.280.320.370.420.480.560.670.720.800.880.930.950.200.190.210.230.260.290.330.370.420.470.540.640.690.760.830.890.930.950.250.240.260.290.320.360.410.450.510.570.640.710.780.850.900.930.950.300.290.320.350.390.430.480.530.600.660.730.800.860.900.940.950.350.330.370.410.450.500.560.620.680.740.810.860.910.940.950.400.380.420.470.520.570.630.690.750.810.860.910.930.950.450.430.470.520.580.640.700.760.810.870.910.930.950.500.480.530.580.640.700.760.820.870.910.940.550.550.520.570.630.690.750.820.870.910.940.950.600.570.630.690.750.810.870.910.940.950.650.620.680.740.810.860.910.940.950.700.660.730.800.860.900.940.950.750.710.780.850.900.930.950.800.760.830.890.940.950.850.800.880.930.950.900.850.920.951.000.95;.;.;.(4)计算负荷及计算电流：有功功率尸=KSp,kw(5-2-21)jsmp无功功率。=KSQ,kvar(5-2-22)jsmp视在功率S.,=P2+Q2,kVA(5-2-23)jsjsjsS计算电流I.,=4：，A(5-2-24)js3UN式中UN——额定电压，kV;Km——最大系数1,根据有效台数几和平均利用系数K,,从表5-2-8查得。myx1p表5-2-8最大系数KmK1pnyx0.10.150.20.30.40.50.60.70.80.943.433.112.642.141.871.651.461.291.141.0553.232.872.422.001.761.571.411.261.121.0463.042.642.241.881.661.511.371.231.101.0472.882.482.101.081.581.451.331.211.091.0482.722.311.991.721.521.401.301.201.081.0492.562.201.901.651.471.371.281.181.081.03102.422.101.841.601.431.341.261.161.071.03122.241.961.751.521.361.281.231.151.071.03142.101.851.671.451.321.251.201.131.071.03161.991.771.611.411.281.231.181.121.071.03181.911.701.551.371.261.211.161.111.061.03201.841.651.501.341.241.201.151.111.061.03251.711.551.401.281.211.171.141.101.061.03301.621.461.341.241.191.161.131.101.051.03351.561.411.301.211.171.151.121.091.051.02401.501.371.271.191.151.131.121.091.051.02451.451.331.251.171.141.121.111.081.041.02501.401.301.231.161.141.111.101.081.041.02601.321.251.191.141.121.111.091.071.031.02701.271.221.171.121.101.101.091.061.031.02801.251.201.151.111.101.101.081.061.031.02901.231.181.131.101.091.091.081.051.021.021表5-2-8的Km数据是按0.5h最大负荷计算的。计算以中小截面导线为基准，其发热时间常数t为10min,负荷的热效应达到稳态的持续时间t,按指数曲线约为3t,即0.5h。对于变电所低压母线或低压干线来说，TN20min,tN1h。当t>0.5h,最大系数按下式换算

1001.211.171.121.101.081.081.071.051.021.021201.191.161.121.091.071.071.071.051.051.021601.161.131.101.081.051.051.051.041.021.022001.151.121.091.071.051.051.051.041.011.012401