【作者】 金雄飞；

【导师】 乐秀璠；

【作者基本信息】 河海大学 ， 电力系统及其自动化， 2004， 硕士

【摘要】 在电力系统中35kV及以下电压等级的母线由于没有稳定问题，一般未装设专门母线保护，母线故障要由较长延时的后备保护来切除，使不少本可以得到控制的故障被发展和扩大，造成了巨大的经济损失。因此有必要研制一种造价低、原理简单、适用于中低压母线的专用母线保护。 高电压等级母线微机保护已经进入到成熟发展阶段，本文在对国内外现有母线保护进行研究分析的基础上，根据中低压母线的特点，提出了一种基于分组原理的母线保护，可以很好地解决中低压母线保护的实际工程问题，使得系统简单、可靠、经济、灵活、易于扩展，而且容易附加其它的保护功能。 目前微机保护最常用的方法是电流瞬时值差动保护，这种方法受电流互感器(TA)饱和的影响而容易误动。小波理论是近年来发展起来的用于数字信号处理的有力工具。本文利用小波变换能对奇异点进行准确分析定位的原理，提出了一种实时检测TA饱和区和线性区的新方法。在故障开始后对TA二次电流实时进行多尺度小波变换，由于TA二次电流波形在故障发生时刻／进入饱和时刻和出饱和时刻都有奇异性，分别对应小波模极大值，因此可以根据小波模极大值的不同特征判断对应时刻的是进饱和点还是出饱和点。实现了母差保护在TA饱和区内闭锁，线性区内开放，从而避免了区外故障TA饱和时保护的误动作。即使出现故障发展，由区外故障转区内故障，差动保护仍能可靠快速地动作，以满足系统稳定要求。 本文采用基于采样值的比率制动式电流差动保护算法作为保护的主判据，可以明显提高保护动作速度和减少计算量；具有较强的抗TA饱和能力，在区内故障时无制动，区外故障时有极强的制动特性。更多还原

【Abstract】 At present the special protective devices for busbars in middle and low voltage distribution networks are still not common. Only appended to original busbar protections, so the faults occurred in middle and low voltage busbars have to be cleared by back-up relaying with long time delay. Thus, some kind of faults may spread which originally could be cleared and tremendous economy loss may appear. The necessity of appending special protective device for middle and low voltage busbars in important consumers’ substation and that in electrical auxiliary system of power plant is disserted.Microprocessor based high voltage busbar protection has rapidly expanded. On the basis of analysis grouping-principle based middle and low voltage protection are put forward. The special busbar protection has adopted effective measures so that large improvement such as simpleness, reliability, economy, sensitivity and some appending additional functions has been obtaimed.The bus differential protection based on instantaneous values of currents is the most useful scheme nowadays. But it is easy to be influenced by current transformer saturation and to make misoperation. A new method is proposed to detect and distinguish current transformer saturation and linear sections, and the wavelet transform theory is used to detect the singular points of signals. Because the current waveforms got from current transformer have singularity at the points of fault occurrence, the start of saturation and the end of saturation, we can distinguish these points according to their characters on line. Thus, to open or block it in current transformer linear or saturation sections, the bus differential protection can be realized. Even if the fault spread from external fault zone to internal fault zone, the differential protection can avoid misoperation.Main criterion of protection is composite-percentage current differential algorithm according to every sampled value, which can accelerate the protection’s trip, reduce large amounts of calculation and have strong stability to TA saturation.更多还原