3.7.2无功功率补偿容量的计算?字体?javascript:void(0);[大]?javascript:void(0);[中]?jav
ascript:void(0);[小]电容器组额定容量的确定：单相接线的电容器，其容量按下式计算：(3-1)三相三角形接线的电容
器组，其容量按下式计算：(3-2)三相星形接线的电容器组，其容量按下式计算：(3-3)以上各式中CX——单相等效电容(μF);
UX——相电压(kV);UX-X——线电压(kV);ω——角频率(Hz)。若已知最大负荷月的平均负荷P(kW)以及补偿前后
的功率因数cos?1、cos?2，则需补偿的无功功率可按下式计算：(3-4)补偿后的功率因数cos?2的确定应适当。当cos?2
大于0.95到cos?2=1时电容量的增长很快。将功率因数由0.95提高到1和由0.7提高到0.9所需补偿的容量应近似相等。从经济
上看，将功率因数提高到1是不合适的。为计算方便，可直接从表3-18查得每千瓦有功功率，由补偿前的功率因数cos?1达到补偿后的功率
因数cos?2所需补偿的无功功率，然后乘以有功功率的千瓦数，即可得到所需补偿的无功功率。表3-18每1千瓦有功功率所需无功功率
补偿量/(kvar/kW)补偿前cos1补偿后cos20.800.820.840.860.880.900.920.940.96
0.981.00.400.410.420.430.440.450.460.470.480.490.501.5421.4731.41
21.3521.2881.2341.1801.1251.0761.0360.9811.5961.5271.4661.4061.34
21.2881.2341.1791.1301.0901.0351.6471.5781.5171.4571.3931.3391.28
51.2301.1811.1411.0861.6991.6301.5691.5091.4451.3911.3771.2821.23
31.1931.1381.7531.6841.6231.5631.4991.4451.3911.3361.2871.2471.19
21.8071.7381.6771.6171.5531.4991.4451.3901.3411.3011.2461.8661.79
71.7361.6761.6121.5581.5041.4591.4001.3601.3051.9291.8601.7991.73
91.6751.6211.5671.5221.4631.4231.3682.0031.9341.8731.8131.7491.69
51.6411.5961.5371.4971.4422.0902.0211.9601.9001.8361.7821.7281.68
31.6241.5841.5292.2932.2242.1632.1032.0391.9851.9311.8761.8271.78
71.732续表补偿前cos1补偿后cos20.800.820.840.860.880.900.920.940.960.981
.00.510.520.530.540.550.560.570.580.590.600.610.620.630.640.650.6
60.670.680.690.700.710.720.730.740.750.760.770.780.790.9390.8900.
8490.8080.7660.7280.6910.6550.6180.5830.5490.5150.4810.4500.4370.
3880.3570.3270.2970.2700.2410.2120.1850.1570.1310.1030.0780.0520.
0240.9930.9440.9030.8620.8000.7820.7450.7090.6720.6370.6030.5690.
5350.5040.4770.4420.4110.3810.3510.3240.2950.2660.2390.2110.1850.
1570.1320.1060.0781.0440.9950.9510.9130.8710.8330.7960.7600.7230.
6880.6540.6200.5860.5550.5220.4930.4620.4320.4020.3750.3460.3170.
2900.2620.2360.2080.1830.1570.1291.1061.0471.0060.9650.9230.8850.
8480.8120.7750.7400.7060.6720.6380.6070.5740.5450.5140.4840.4540.
4270.3980.3690.3420.3140.2880.2600.2350.2090.1811.1601.1011.0601.
0190.9770.9390.9020.8660.8290.7940.7600.7260.6920.6610.6280.5990.
5680.5380.5080.4810.4520.4230.3960.3680.3420.3140.2890.2630.2351.
2141.1551.1141.0731.0310.9930.9560.9200.8830.8480.8140.7800.7400.
7150.6820.6530.6220.5920.5620.5350.5060.4770.4500.4220.3960.3680.
3430.3170.2891.2731.2141.1731.1321.0901.0521.0150.9790.9420.9070.
8730.8390.8050.7740.7410.7120.6810.6510.6210.5940.5650.5360.5090.
4810.4550.4270.4020.3760.3481.3361.2771.2361.1951.1531.1151.0781.
0421.0050.9700.9360.9020.8680.8370.8040.7750.7440.7140.6840.6570.
6280.5990.5720.5440.5180.4900.4650.4390.4111.4101.3511.3101.2691.
2271.1891.1521.1161.0791.0441.0100.9760.9420.9110.8780.8490.8180.
7880.7580.7310.7020.6730.6160.6180.5920.5640.5390.5130.4851.4971.
4381.3971.3561.3141.2761.2391.2031.1661.1311.0971.0631.0290.9980.
9650.9360.9050.8750.8450.8180.7890.7600.7350.7050.6790.6510.6260.
6000.5721.6901.6111.6001.5591.5171.4791.4421.4061.3691.3441.3001.
2661.2321.2011.1681.1391.1081.0781.0481.0210.9920.9630.9360.9080.
8820.8540.8290.8030.775对于电动机的无功功率补偿，一般应按电动机空载时功率因数补偿到1为好。而不能按前述几种
方法选择，即不能按负荷情况计算。否则在电动机空载(或轻载)时将造成过补偿。过补偿的电动机在切断电源后，由于电容器的放电，供给电
动机以励磁电流，使仍在旋转中的电动机变成了感应发电机，这时电压将超出电动机额定电压好多倍，对电动机的绝缘和电容器均不利。同时旋转中
的电动机立即合闸时，在电容器冲击电流的作用下，电动机会产生很大的瞬时转矩，可能损坏电动机轴和靠背轮等。对于电动机补偿容量可按式(
3-5)计算：(3-5)式中：U——电动机的电压(kV);I0——电动机的空载电流(A)。补偿容量可由表3-19查出。表3-19
与电动机常接电容器最高容量参考表电动机功率/kW电机转速/(r/min)300015001000750600500电容器最
高容量/kvar7.5111518.5223037455575901101502.53.55.06.07.08.511.013.0
17.021.525.032.540.03.03.04.05.07.08.511.013.017.022.026.032.5403
.54.56.06.58.510.012.515.018.025.029.033.042.54.56.57.58.510.012.
515.018.022.029.033.036.045.05.07.58.510.012.515.018.022.027.533.
040.045.055.07.09.011.514.515.518.523.026.033.038.045.052.565.0对2
20kV及以下电网的容性无功补偿设备总容量，可按下式计算：(3-6)式中Qc——容性无功补偿设备总容量;k——最大自然无功负荷系
数，由表3-20查得;QD——最大自然无功负荷;QG——本网发电机的无功功率;QR——主网和邻网输入的无功功率;QL——线路和电缆
的充电功率。表3-20220kV及以下电网的最大自然无功负荷系数电网电压/kV变压级数220110633510最大自然无功负荷
系数/(kvar/kW)220/110/35/101.25～1.41.1～1.251.0～1.150.9～1.05220/110
/101.15～1.301.0～1.150.9～1.05220/63/101.15～1.301.0～1.150.9～1.0
5注：本网中发电机有功功率比重较大时，宜取较高值;主网和邻网输入有功功率比重较大时，宜取较低值。电网的无功补偿水平用无功补偿度表
示，可按下式计算：(3-7)式中WB——无功补偿度(kvar/kW);QC——容性无功补偿设备容量(kvar);PD——最大
有功负荷(或装机容量)(kW)。对220kV及以下电压等级的变电所中，应根据需要配置无功补偿设备，其容量可按主要变压器容量的0
.10～0.30确定。在主变压器最大负荷时，其二次侧的功率因数不小于表3-21中所列数值，或者由电网供给的无功功率与有功功率比值不
大于表3-21中所列数值。表3-21220kV及以下变电所二次侧功率因数规定值电压等级/kV22035～110功率因数0.95～10.9～1无功功率/有功功率0.33～00.48～0注：①由发电厂直接供电的变电所，其供电线路较短时，功率因数可取表3-21中较低值，其他变电所的功率因数应取较高值。②经技术经济比较合理时，功率因数可高于表中上限值。在10(6)kV配电线路上宜配置高压并联电容器，或者在配电变压器低压侧配置低压并联电容器。电容器的安装容量不宜过大，一般约为线路配电变压器总容量的0.05～0.10，并且在线路最小负荷时，不应向变电所倒送无功。如配置容量过大，则必须装设自动投切装置。 |
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