工程实用励磁变压器保护方案探讨

大容量发电机变压器组采用自并励励磁系统后 ,由于机端短路电流很大 ,以致很难选择供励磁变压器保护用的高压侧电流互感器。提出利用发电机变压器组的不完全接线差动保护和励磁变压器专用保护共同分担整个励磁变压器保护 ,以便降低对其高压侧电流互感器准确限值系数要求 ,并对励磁变压器高压侧电流互感器额定电流比选择给出参考意见。同时比较了励磁变压器差动保护和过流保护方案的优劣 ,建议励磁变压器采用电流速断作为主保护以简化接线

An algorithm for eliminating the influence of harmonic waves to the rate-of-rise protection

The thesis details the influence of harmonic waves in the short circuit current to the rate of rise protection. On the base of it, an algorithm is presented to handle the sample date for eliminating the influence of harmonic waves, at the same time considering the characteristics that DC component in transient short circuit current of subway can be shown with exponential form and the principle that the integral result of AC component for a cycle is zero. By simulation with Labwindows/CVI, it is proved that the algorithm can smooth the transient electric current wave and the error is very small.