配网开关式消弧引发PT保险熔断的机理研究
发布时间：2019-02-20 18:50
【摘要】：随着配网不接地系统中电缆线路的广泛使用,系统电容电流越来越大,传统的消弧线圈面临容量不够、消弧效果差等问题,为此一种开关式消弧装置在10 kV系统中逐渐开始推广使用。然而现场发现传统配置下的电压互感器在该装置动作过程中频繁发生过流烧保险现象,严重威胁电力系统的稳定运行。因此本文通过电磁暂态计算和高电压模拟试验,明确了开关式消弧下PT熔断的机理和最优的抑制措施,对于该装置接入配网后的安全、可靠运行具有重要的理论和工程指导价值。本文结合实际开关式消弧装置的结构,分析了开关式消弧的动作机制,阐述了开关式消弧过程中通过主动的单相接地与切除动作,从而激发铁磁谐振、低频非线性振荡的机理;从理论上分析了两种暂态过程的特点,并总结了常见的抑制措施与相应优缺点。基于实际变电站的设备参数,针对国内文献在PT仿真中普遍忽略磁滞和涡流损耗的问题,采用考虑磁滞涡损与深度饱和励磁特性的单相PT改进模型,并基于分段线性化与逐点递推法求解了模型的励磁曲线;针对一体式的抗谐振4PT结构,基于其磁路特征建立了适用于仿真的简化电路模型,通过正序和零序试验确定了模型的正序、零序参数。考虑到线路对地电容值越来越大,仿真分析了分频谐振和低频非线性振荡下PT 一次电流的特性,确定了引发PT保险熔断的主要原因是低频非线性振荡,并且其影响因素主要有系统电容值与零序阻尼。本文还搭建了 10kV中性点不接地系统模拟试验平台,在不同的系统电容电流下对三类典型单相PT进行了单相接地与切除的试验,并将试验结果与仿真结果比较,验证了仿真模型的准确性。试验中发现即使远离Peterson谐振区域,单相接地消失仍会激发分频谐振,产生的半波脉冲电流幅值很高,容易导致PT熔断器熔断;而在系统参数合适时,还会激发出准周期谐振,产生的电流幅值同样很高。对于常用的改变系统参数和增大阻尼这两类消谐措施,结合仿真、高电压试验以及现场验证性试验进行了消谐、抑制PT过电流效果的比较,分析其优缺点,最后比较了几大措施对零序电压测量精度的影响,研究结果表明采用4PT结构是开关式消弧接入系统后最优的消谐与防PT保险熔断措施。
[Abstract]:With the wide use of cable lines in ungrounded distribution systems, the capacitance current of the system becomes larger and larger, and the traditional arc-suppression coil is faced with problems such as insufficient capacity, poor arc suppression effect and so on. For this reason, a switch type arc suppression device is gradually popularized in 10 kV system. However, it is found in the field that the overcurrent burning occurs frequently during the operation of the device, which seriously threatens the stable operation of the power system. Therefore, through electromagnetic transient calculation and high voltage simulation test, the mechanism and optimal suppression measures of PT fuse breakage under switching arc suppression are defined, and the safety of the device after it is connected to the distribution network is discussed. Reliable operation has important theoretical and engineering guiding value. Combined with the structure of the actual switch type arc suppression device, this paper analyzes the action mechanism of the switch type arc suppression, and expounds the mechanism of excitation of ferromagnetic resonance and low frequency nonlinear oscillation through active single-phase grounding and excising action in the process of switching type arc suppression. The characteristics of the two transient processes are analyzed theoretically, and the common suppression measures and their advantages and disadvantages are summarized. Based on the equipment parameters of actual substation, aiming at the problem that hysteresis and eddy current loss are generally ignored in domestic literatures in PT simulation, a single-phase PT improved model considering hysteresis vortex loss and depth saturation excitation characteristics is adopted. The excitation curve of the model is solved based on piecewise linearization and point-by-point recursive method. Based on the magnetic circuit characteristics of the integrated anti-resonant 4PT structure, a simplified circuit model suitable for simulation is established. The positive sequence and zero sequence parameters of the model are determined by positive sequence and zero sequence experiments. Considering the increasing value of the line capacitance to the ground, the characteristics of the primary current of PT under the frequency division resonance and the low frequency nonlinear oscillation are simulated and analyzed, and the main cause of the fuse breaking of the PT is determined to be the low frequency nonlinear oscillation. The main influencing factors are system capacitance and zero sequence damping. In this paper, the simulation test platform of 10kV neutral ungrounded system is also built, and the single-phase grounding and removal of three typical single-phase PT are carried out under different capacitance currents, and the experimental results are compared with the simulation results. The accuracy of the simulation model is verified. It is found that even if far away from the Peterson resonance region, the single-phase grounding will still excite the split-frequency resonance, resulting in a high amplitude of half-wave pulse current, which can easily lead to the fuse of the PT fuse. When the system parameters are suitable, quasi periodic resonance will be excited, and the current amplitude will also be very high. For the two kinds of harmonic elimination measures, such as changing system parameters and increasing damping, harmonic elimination measures are combined with simulation, high voltage test and field verification test. The effects of suppressing PT overcurrent are compared, and their advantages and disadvantages are analyzed. Finally, the effects of several measures on the accuracy of zero-sequence voltage measurement are compared. The results show that the 4PT structure is the best harmonic elimination and anti-PT fusing measures after switching arc-suppression access system.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM732;TM475
本文编号：2427149
[Abstract]:With the wide use of cable lines in ungrounded distribution systems, the capacitance current of the system becomes larger and larger, and the traditional arc-suppression coil is faced with problems such as insufficient capacity, poor arc suppression effect and so on. For this reason, a switch type arc suppression device is gradually popularized in 10 kV system. However, it is found in the field that the overcurrent burning occurs frequently during the operation of the device, which seriously threatens the stable operation of the power system. Therefore, through electromagnetic transient calculation and high voltage simulation test, the mechanism and optimal suppression measures of PT fuse breakage under switching arc suppression are defined, and the safety of the device after it is connected to the distribution network is discussed. Reliable operation has important theoretical and engineering guiding value. Combined with the structure of the actual switch type arc suppression device, this paper analyzes the action mechanism of the switch type arc suppression, and expounds the mechanism of excitation of ferromagnetic resonance and low frequency nonlinear oscillation through active single-phase grounding and excising action in the process of switching type arc suppression. The characteristics of the two transient processes are analyzed theoretically, and the common suppression measures and their advantages and disadvantages are summarized. Based on the equipment parameters of actual substation, aiming at the problem that hysteresis and eddy current loss are generally ignored in domestic literatures in PT simulation, a single-phase PT improved model considering hysteresis vortex loss and depth saturation excitation characteristics is adopted. The excitation curve of the model is solved based on piecewise linearization and point-by-point recursive method. Based on the magnetic circuit characteristics of the integrated anti-resonant 4PT structure, a simplified circuit model suitable for simulation is established. The positive sequence and zero sequence parameters of the model are determined by positive sequence and zero sequence experiments. Considering the increasing value of the line capacitance to the ground, the characteristics of the primary current of PT under the frequency division resonance and the low frequency nonlinear oscillation are simulated and analyzed, and the main cause of the fuse breaking of the PT is determined to be the low frequency nonlinear oscillation. The main influencing factors are system capacitance and zero sequence damping. In this paper, the simulation test platform of 10kV neutral ungrounded system is also built, and the single-phase grounding and removal of three typical single-phase PT are carried out under different capacitance currents, and the experimental results are compared with the simulation results. The accuracy of the simulation model is verified. It is found that even if far away from the Peterson resonance region, the single-phase grounding will still excite the split-frequency resonance, resulting in a high amplitude of half-wave pulse current, which can easily lead to the fuse of the PT fuse. When the system parameters are suitable, quasi periodic resonance will be excited, and the current amplitude will also be very high. For the two kinds of harmonic elimination measures, such as changing system parameters and increasing damping, harmonic elimination measures are combined with simulation, high voltage test and field verification test. The effects of suppressing PT overcurrent are compared, and their advantages and disadvantages are analyzed. Finally, the effects of several measures on the accuracy of zero-sequence voltage measurement are compared. The results show that the 4PT structure is the best harmonic elimination and anti-PT fusing measures after switching arc-suppression access system.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM732;TM475
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