中压电缆电网运行方式及故障模型仿真分析

【作者】 白挺玮；

【导师】 束洪春；

【作者基本信息】 昆明理工大学 ， 电力系统及其自动化， 2012， 硕士

【摘要】 随着城市电网不断发展,电力电缆越来越多地应用于中压配电网络,由于空间和美观的需要,不少城市的配电网已经出现全部由电缆出线组成的电缆网。配电网中电缆数量的不断增加,网络的容性电流不断增大,有的网络容性电流甚至超过几百安培。近年来国内各省逐步推行“大经济圈”战略——各大城市强强联合,打造区域更富竞争力的城市群,这便使得原本就不断增长的城市配网电流“手拉手”后面临成倍增长,这将使得原有的运行方式受到很大挑战。目前大多数针对中压配电网线路故障的研究还只是停留在以架空线为主,电缆线路为辅的思维模式,一些针对架空线提出的理论模型并不适用于电缆,这就使得对于电缆线路可能产生的过电压和故障分析产生难以避免的偏差。因此,以电缆网这一极具代表性中压配电网络为对象,研究适用于它的故障模型是很有意义的。电力系统中的电缆线路属于具有分布参数的电路元件。分布参数电路的电磁暂态过程属于电磁波传播过程,简称波过程。暂态过程中形成的过电压以波的形式从线路传播到变压器、发电机或者输电线路的末端,也可以从一条线路传播到相连的另一个线路。电缆线路中的每种过电压也可以用波过程解释。对中压电缆网中几种典型过电压进行理论分析,可以为选择适当的运行方式和仿真实验提供理论基础。对现有架空线间歇性接地电弧理论基础上做出了改进,构建了适用于中压电缆网的间歇性电弧模型；使用受控制开关导通与关断单相接地电弧及可变电阻模拟电弧电阻,使其能更好地体现电弧的动态特性。研究了电缆绝缘破坏到电缆发生燃烧的过程。在理论研究的基础上,并根据电缆间歇性电弧模型建立了考虑热量积累效应的电弧烧毁模型；使用热量比较结果控制电弧接地开关的关断以实现故障类型的转化。这一模型更好地契合了中压电缆网实际运行中电弧故障的情况。结合对中压电缆网过电压的理论分析,使用PSCAD软件进行了仿真,并结合不同运行方式下过电压仿真结果进行了对比,指出中性点经小电阻接地方式对于瞬时性单相接地故障引起的过电压限制效果最好,且最有利于保护系统。中性点经消弧线圈接地方式对于各种过电压都能起到较好的限制作用,但不利于保护系统动作。更多还原

【Abstract】 With the city power grid development, more and more power cables used in medium voltage distribution network. Due to space and aesthetic needs, many of the city’s distribution networks have all cables outlet. The increasing number of cable in distribution network, the capacitive current of the network is increasing. Some capacitive current of the network even more than a few hundred amperes. In recent years, many provinces progressively implement the strategy of economic circle. Major cities are in combination to create the region more competitive urban agglomerations. This makes the already growing distribution network current doubling after "hand in hand and the original operation mode will face a serious challenge.Most for medium voltage distribution network failures which remain in the mode of thinking mainly of overhead lines, cable lines, supplemented by. The proposed theoretical model for overhead lines do not apply to cable. This makes the cable’s over-voltage and failure analysis difficult to avoid deviation. Therefore, it is great significance for the study a fault model applied to cable networks which is a highly representative object in medium voltage distribution network.Cable lines in the power system are distributed parameters of the circuit elements. The electromagnetic transient process of distributed parameter circuit belongs to the electromagnetic wave propagation process, referred to as the wave process. The formation of over-voltage in the transient process from propagates form the line to the end of the transformer, generator or transmission line and also spread from one line to another line connected in the form of waves. Each of the over-voltage cable lines can also be explained with wave process. Several typical voltage theoretical analysis for medium voltage cable network can provide a theoretical basis for the selection of the appropriate operating mode and simulation.Make improvements to intermittent arc ground theory which on the basis of the existing overhead lines and build the intermittent arc model suitable for medium voltage cable network; using a controlled switch turn-on and turn-off single-phase ground arc, and using variable resistor simulated arc resistance, to enable them to better reflect the dynamic characteristics of the arc. Make a study to cable insulation damage to combustion process. On the basis of theoretical studies, based on the intermittent arc model of cable to establish the arc burned model to consider the effect of heat accumulation. Using heat compared results to controlled the turn-on and turn-off of the arc grounding switch in order to achieve the transformation of the type of fault. This model fit the medium-pressure arc fault in the actual operation of the cable network more better.Combination of front theoretical analysis of medium voltage cable network over-voltage, applicant of PSCAD software simulation and combine with a different operating mode voltage simulation results compared. Pointed out that the neutral point grounding with via low resistance caused by the transient single-phase ground fault over-voltage limit best. And the most conducive to the protection system. Neutral via arc suppression coil grounding method for a variety of over-voltage can play a better role in limit, but not conducive to the protection system action.更多还原