无功补偿原理

1、无功补偿原理当电网电压的波形为正弦波，且电压与电流同相位时，电阻性电气设备如白炽灯、电热器等从电网上获得的功率P等于电压U和电流I的乘积，即：P=U×I。电感性电气设备如电动机和变压器等由于在运行时需要建立磁场，此时所消耗的能量不能转化为有功功率，故被称为无功功率Q。此时电流滞后电压一个角度。在选择变配电设备时所根据的是视在功率S，即有功功率和无功功率的矢量和：S =（P2 + Q2）1/2无功功率为:Q=（S2 - P2）1/2 SPQ有功功率与视在功率的比值为功率因数: cosf=P/S无功功率的传输加重了电网负荷，使电网损耗增加，系统电压下降。故需对其进行就近和就地补

2、偿。并联电容器可补偿或平衡电气设备的感性无功功率。当容性无功功率QC等于感性无功功率QL时，电网只传输有功功率P。根据国家有关规定，高压用户的功率因数应达到0.9以上，低压用户的功率因数应达到0.85以上。如果选择电容器功率为Qc，则功率因数为：cosf= P/ (P2 + (QL- QC)2)1/2在实际工程中首先应根据负荷情况和供电部门的要求确定补偿后所需达到的功率因数值，然后再计算电容器的安装容量：Qc = P(tanf1 - tanf2)=P(1/cos2f1-1)1/2-(1/cos2f2-1)1/2式中:Qc一电容器的安装容量，kvarP一系统的有功功率，kWtanf1-补偿前的功

3、率因数角, cosf1-补偿前的功率因数tanf2-补偿后的功率因数角, cosf2-补偿后的功率因数功率因数与补偿容量查询表补偿前cosf1补偿后功率因数目标值及每KW负荷所需电容器容量(KVar)0.700. 800. 820. 840. 860. 880.900. 920. 940. 960. 981.00.500.710.9821. 0341. 0861. 1391. 1921. 2481. 3061. 3691. 4401. 5291. 3720.510.520.530.540.550.670.620.580.540.500.9370.8930.8500.8090.7690.9890

4、.9450.9020.8610.8211. 0410.9970.9540.9130.8731.0941.0501.0070.9660.9261.1471.1031.0601.0190.9791. 2031.1871.1161.0751.0351.2611.2171.1741.1331.0931.3241.2801.2371.161.1561.3951.3511.3081.2671.2271.4841.4401.3971.3561.3161.6871.6431.6001.5591.5190.560.570.580.590.600.460.420.390.350.310.7300.6920.655

5、0.6190.5830.7820.7440.7070.6710.6350.8360.7690.7590.7230.6870.8870.840.8120.7760.7400.9400.9020.8650.820.7930.9960.9580.9210.8850.8491.0541.0160.9790.9430.9071.1171.0791.0421.0060.9701.1881.15001.1131.0771.0411.2771.2391.2021.1161.1301.4801.4421.4051.361.3330.610.620.630.640.650.280.250.210.180.150.

6、5490.5160.4830.4510.4190.6010.5680.5350.5030.4710.6530.6200.5870.5550.5230.7060.6730.6400.6080.5760.7590.7260.6930.6610.6290.8150.7820.7490.7170.6850.8730.8400.8070.7750.7430.9360.9030.8700.8380.8061.0070.9740.9410.9090.8771.0961.0631.0300.9980.9661.2991.2661.23312011.1690.660.670.680.690.700.120.09

7、0.060.030.000.3880.3580.3280.2990.2700.4400.4100.3800.3510.3220.4920.4620.4320.4030.3740.5450.5150.4850.4560.4270.5980.5680.5360.5090.4800.6540.6240.5940.5650.5360.7120.6820.6520.6230.5940.7750.7450.7150.6860.6570.8460.8160.7860.7570.7280.9350.9050.8750.8460.8171.1381.1081.0731.0491.0200.710.720.730

8、.740.75 0.2420.2140.1860.1590.1320.2940.2660.2380.2110.1840.3460.3180.2900.2630.2360.3990.3710.3430.3160.2890.4520.4240.360.3690.3420.5080.4800.4520.4250.3980.5660.5380.5100.4830.4560.6290.6010.5730.5460.5190.7000.6720.6440.6170.5900.7890.7610.7330.7060.6790.9920.9640.9360.9090.8820.760.770.780

9、.790.80 0.1050.0790.0520.0260.0000.1570.1310.1040.0780.0520.2090.1830.1560.1300.1040.2620.2360.2090.1830.1570.3510.2890.2620.2360.2100.3710.3450.3180.2920.2660.4290.4030.3760.3500.3240.4920.4660.4390.4130.3870.5630.5370.5100.4840.4580.3520.3260.5990.5730.5470.8550.8290.8020.7760.7500.810.820.83

10、0.840.85  0.0260.000 0.0780.0520.0260.0000.1310.1050.0790.0530.0270.1840.1580.1320.1060.0800.2400.2140.1880.1620.1360.2980.2720.2460.2200.1940.3610.3350.3090.2830.2570.4320.4060.3800.3540.3280.5210.4950.4690.4430.4170.7240.6980.6720.6460.6200.860.870.880.890.90    

11、            0.000    0.0530.0270.000  0.1090.0830.0560.0280.0000.1670.1410.1140.0860.0580.2300.2040.1770.1490.1210.3010.2750.2480.2200.1920.3900.3640.3370.3090.2810.5390.5670.5400.5120.4840.910.920.930.940.95       0.0300.000 0.0930.0630.0320.000 0.1640.1340.1030.0710.0370.2350.2230.1