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1、9.5 工频电压升高 9.5 Frequency voltage rises,工频电压升高在绝缘裕度较小的超高压输电系统中受到很大的注意的原因如下： The reason frequency voltage rise caused by a small margin in insulated EHV transmission system great attention to the following 由于工频电压升高大都在空载或轻载条件下发生，与多种操作过电压的发生条件相同或相似，所以它们有可能同时出现、相互叠加。 Since most of the power frequency vol
2、tage rise under no-load or light load condition occurs, similar to the occurrence of a variety of operating over-voltage conditions, so they are likely to occur simultaneously, superimposed on each other.,工频电压升高是决定某些过电压保护装置工作条件的重要依据，所以它直接影响避雷器的保护特性和电力设备的绝缘水平； Frequency voltage rise is important basi
3、s of working conditions for some over-voltage protection device. so it has a direct impact on the protection of property of the arrester and the insulation level of electrical equipment. 由于工频电压升高是不衰减或弱衰减现象，持续的时间很长，对设备绝缘及其运行条件也有很大的影响。 Due to increased frequency voltage is attenuated or weak attenuati
4、on, continuing a long time, but also has a great impact on equipment insulation and operating conditions.,9.5.1 空载长线电容效应引起的工频电压升高 9.5.1 Frequency voltage rise caused by Long-term effects of load capacitance 9.5.2 不对称短路引起的工频电压升高 9.5.2 Frequency voltage rise caused by asymmetrical short circuit 9.5.3
5、甩负荷引起的工频电压升高 9.5.3 Frequency voltage rise caused by load shedding,本节内容 Contents in this section,9.5.1 空载长线电容效应引起的工频电压升高 9.5.1 Frequency voltage rise caused by long-term load capacitance effects,输电线路在长度不很大时，可用集中参数的电阻、电感和电容来代替，图9-13（a）给出了它的T型等值电路。 Transmission line length is not very large, concentrat
6、ed parameters available resistors, inductors and capacitors instead. Fig 9-15(a) show its T-type equivalent circuit.,图9-13 空载长线的电容效应 （a）T型等值电路（b）简化等值电路（c）向量图 Fig.9-13 Long-term effects of load capacitance (a) T-type equivalent circuit (b) simplified equivalent circuit (c) vector graphics,由于线路空载，可简化成
7、一R、L、C串连电路，如图9-13（b）所示。 Since the load circuit, a can be simplified as R, L, C series circuit, shown in Fig 9-13 (b). 由于电感与电容上的压降反相，且 ，可见电容上的压降大于电源电势，如图9-13（c）所示。 Since the pressure drop on the inductance and capacitance are inverter, and , the voltage drop across the capacitor is greater than the p
8、ower supply potential, as shown in 9-13 (c) below.,随着输电电压的提高、输送距离的增长，在分析空载长线的电容效应时，也需要采用分布参数等值电路，但基本结论与前面所述者相似。为了限制这种工频电压升高现象，大多采用并联电抗器来补偿线路的电容电流以削弱电容效应，效果十分显著。 With the improvement of the transmission voltage, transmission distance of growth, in the analysis of long-term load capacitance effects, a
9、lso requires the use of distributed parameter equivalent circuit, but the basic conclusions similar to those described in the preceding. In order to limit this phenomenon frequency voltage increases, mostly using shunt reactors to compensate for capacitive currents to weaken the line capacitance eff
10、ect, the effect is very significant.,9.5.2 不对成短路引起的工频电压升高 9.5.2 Frequency voltage rise caused by asymmetrical short circuit,不对称短路是电力系统中最常见的故障形式，当发生单相或两相对地短路时，健全相上的电压都会升高，其中单相接地引起的电压升高更大一些。此外，阀式避雷器的灭弧电压通常也就是根据单相接地时的工频电压升高来选定的，所以下面只讨论单相接地的情况。 Asymmetrical short-circuit is the most common form failure
11、of power system .When a single-phase or two relatively short circuit occurs, the voltage will be increased on the sound phase, in which the single-phase voltage to rise due to a larger number. In addition, arcing voltage surge arresters usually based on single-phase ground power frequency voltage in
12、creases to selected, so the following discussion only single-phase ground situation.,单相接地时，故障点各相的电压、电流是不对称的，为了计算健全相上的电压升高，通常采用对称分量法和复合序网进行分析，不仅计算方便，且可计及长线的分布特性。 When single-phase ground fault point of each phase voltage and current is asymmetric, in order to calculate the sound phase voltage rises,
13、usually symmetrical components and composite sequence network for analysis, not only easy to calculate, and may take into account long-term distribution characteristics.,当A相接地时，B、C两健全相上电压的模值为： When the A-phase ground when, B, C two-phase voltage analog values:,系数K为接地系数。它表示单相接地故障时健全相的最高对地工频电压有效值与无故障时
14、对地电压有效值之比。 Coefficient K is the coefficient of grounding. It is said that when the single-phase ground fault, the highest frequency voltage to ground RMS sound when there is no fault with the phase-to-ground voltage rms ratio.,(9-14),(9-15),图9-14 单相接地时健全相的电压升高 Fig. 9-14 Voltage increases of sound ph
15、ase when single-phase ground,按电网中性点接地方式分析健全相电压升高的程度： Analysis by way of neutral point grounding elevated level of sound phase voltage: 对中性点不接地的电网，采用“110避雷器”。 For ungrounded power grid, using “110% surge arresters.“ 对中性点经消弧线圈接地的3560kV电网，采用“100避雷器”。 Neutral point arc suppression coil grounding 35 60kV
16、 grid, using “100% surge arresters.“ 对中性点有效接地的110220kV电网，采用“80避雷器”。 Effectively grounded neutral point of 110 220kV power grid, using “80% of the arrester.“,当输电线路在传输较大容量时，断路器因某种原因而突然跳闸甩掉负荷时，会在原动机与发电机内引起一系列机电暂态过程，它是造成工频电压升高的又一原因。 When a large transmission line capacity in the transmission circuit breaker tripped suddenly for some reason to get rid of the load, causing a series of electromechanical transient processes within the prime mover and generator,
