1、 利用系數法確定計算負荷用利用系數法確定計算負荷時，不論計算范圍大小，都必須求出該計算范圍內用電設備有效臺數及最大系數，而后算出結果。（1）用電設備組在最大負荷班內的平均負荷：有功功率 kW（5-2-12）無功功率 kvar（5-2-13）式中 用電設備組的設備功率，kW；用電設備組在最大負荷班內的利用系數，見表5-2-6；用電設備組的功率因數角的正切值，見表5-2-6。表5-2-6 利用系數、及用電設備組名稱一般工作制小批生產用金屬切削機床（小型車、刨、插、銑、鉆床、砂輪機等）0.10.120.501.73一般工作制大批生產用金屬切削機床0.120.140.501.73重工作制金屬切削機床（

2、沖床、自動車床、六角車床、粗磨、銑齒、大型車床、刨、銑、立車、鏜床）0.160.551.51小批生產金屬熱加工機床（鍛錘傳動裝置、鍛造機、拉絲機、清理轉磨筒、碾磨機等）0.170.601.33大批生產金屬熱加工機床0.200.651.17生產用通風機0.550.800.75衛生用通風機0.500.800.75泵、空氣壓縮機、電動發電機組0.550.800.75移動式電動工具0.050.501.73不聯鎖的連續運輸機械（提升機、皮帶運輸機、螺旋運輸機等）0.350.750.88聯鎖的連續運輸機械0.500.750.88起重機及電動葫蘆（=100%）0.150.200.501.73電阻爐、干燥箱、

3、加熱設備0.550.650.950.33試驗室用小型電熱設備0.351.000.0010t以下電弧煉鋼爐0.650.800.75單頭直流弧焊機0.250.601.33多頭直流弧焊機0.500.701.02單頭弧焊變壓器0.250.352.67多頭弧焊變壓器0.300.352.67自動弧焊機0.300.501.73點焊機及縫焊機0.250.601.33對焊機及鉚釘加熱器0.250.701.02工頻感應電爐0.750.352.67高頻感應電爐（用電動發電機組）0.700.800.75高頻感應電爐（用真空管振蕩器）0.650.651.17（2）平均利用系數為（5-2-14）式中 各用電設備組平均負荷

4、的有功功率之和，kW；各用電設備組的設備功率之和，kW。（3）用電設備的有效臺數是將不同設備功率和工作制的用電設備臺數換算為相同設備功率和工作制的有效值。故（5-2-15）式中 單個用電設備的設備功率，kW。1）當有效臺數為4臺及以上，且最大一臺設備功率與最小一臺設備功率的比值m3時，取（5-2-16）在確定值時，可將組內總功率不超過全組總設備功率5%的一些最小用電設備略去。2）當3和0.2時，取（5-2-17）如按上式求得的比實際臺數還多，則取。3）當3和0.2時，取（5-2-18）（5-2-19）（5-2-20）以上式中用電設備臺數；用電設備中，單臺設備功率不小于最大一臺設備功率一半的臺數

5、；臺數的相對值；各用電設備組的設備功率之和，kW；臺設備的總設備功率，kW；功率的相對值；有效臺數相對值，可根據相對值和，從表5-2-7查得。表5-2-7 用電設備有效臺數相對值3 設備所用的需用系數應用范圍照明回路普通插座廚衛插座空調0.90.90.950.51.00.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.010.010.010.010.010.020.020.020.020.030.030.040.050.060.080.100.140.200.320.520.020.020.020.020.030.0

6、30.030.040.040.050.060.070.090.110.140.190.260.360.510.710.030.030.030.030.040.040.050.060.070.080.080.110.130.160.210.270.360.490.640.810.040.040.040.040.050.060.070.080.090.100.120.150.180.220.270.340.440.570.720.860.050.050.050.060.070.070.080.100.110.130.150.180.220.260.330.410.510.640.790.900.0

7、60.060.060.070.080.090.100.120.130.150.180.210.260.310.380.470.580.700.830.920.080.080.080.090.110.120.130.150.170.200.240.280.330.400.480.570.680.790.890.940.100.090.100.120.130.150.170.190.220.250.290.340.400.470.560.660.760.850.920.950.150.140.160.170.200.230.250.280.320.370.420.480.560.670.720.8

8、00.880.930.950.200.190.210.230.260.290.330.370.420.470.540.640.690.760.830.890.930.950.250.240.260.290.320.360.410.450.510.570.640.710.780.850.900.930.950.300.290.320.350.390.430.480.530.600.660.730.800.860.900.940.950.350.330.370.410.450.500.560.620.680.740.810.860.910.940.950.400.380.420.470.520.5

9、70.630.690.750.810.860.910.930.950.450.430.470.520.580.640.700.760.810.870.910.930.950.500.480.530.580.640.700.760.820.870.910.940.550.550.520.570.630.690.750.820.870.910.940.950.600.570.630.690.750.810.870.910.940.950.650.620.680.740.810.860.910.940.950.700.660.730.800.860.900.940.950.750.710.780.8

10、50.900.930.950.800.760.830.890.940.950.850.800.880.930.950.900.850.920.951.000.95（4）計算負荷及計算電流：有功功率 kW（5-2-21）無功功率 kvar（5-2-22）視在功率, kVA（5-2-23）計算電流, A（5-2-24）式中 額定電壓，kV；最大系數 表5-2-8的Km數據是按0.5h最大負荷計算的。計算以中小截面導線為基準，其發熱時間常數為10min，負荷的熱效應達到穩態的持續時間t，按指數曲線約為3，即0.5h。對于變電所低壓母線或低壓干線來說，20min，t1h。當t0.5h，最大系數按下式換

11、算，根據有效臺數和平均利用系數，從表5-2-8查得。表5-2-8 最大系數0.10.150.20.30.40.50.60.70.80.943.433.112.642.141.871.651.461.291.141.0553.232.872.422.001.761.571.411.261.121.0463.042.642.241.881.661.511.371.231.101.0472.882.482.101.081.581.451.331.211.091.0482.722.311.991.721.521.401.301.201.081.0492.562.201.901.651.471.371.

12、281.181.081.03102.422.101.841.601.431.341.261.161.071.03122.241.961.751.521.361.281.231.151.071.03142.101.851.671.451.321.251.201.131.071.03161.991.771.611.411.281.231.181.121.071.03181.911.701.551.371.261.211.161.111.061.03201.841.651.501.341.241.201.151.111.061.03251.711.551.401.281.211.171.141.10

13、1.061.03301.621.461.341.241.191.161.131.101.051.03351.561.411.301.211.171.151.121.091.051.02401.501.371.271.191.151.131.121.091.051.02451.451.331.251.171.141.121.111.081.041.02501.401.301.231.161.141.111.101.081.041.02601.321.251.191.141.121.111.091.071.031.02701.271.221.171.121.101.101.091.061.031.02801.251.201.151.111.101.101.081.061.031.02901.231.181.131.101.091.091.081.051.021.021001.211.171.121.101.081.081.071.051.021.021201.191.161.121.091.071.071.071.051.051.021601.161.131.101.081.051.051.051.041.021.022001.151.121.091.071.051.051.051.041.011.012401.141.