Calculating magnetic shielding effectiveness for high-power dc comparator by magnetic circuit method

Magnetic shielding is very important in the design of a high-power dc comparator. This paper addressed the application of magnetic circuit method to calculate the magnetic shielding effectiveness of high-power dc comparators when an external radial magnetic field is added. The mathematical relationship between the magnetic shielding effectiveness and the parameters of the magnetic shielding body were obtained. To verify the validity of the calculation method, we developped a procedure to measure the magnetic shielding effectiveness of the magnetic body by measuring the induction voltage of the detection winding instead of the magnetic intensity at a point in the magnetic shielding body, making the manipulation much easier. The result calculated with the magnetic circuit method turns out to be closer to the measured one compared with that calculated with a conventional algorithm proposed by Ren, suggesting that the magnetic circuit method is an applicable tool for estimating the toroidal cavity magnetic shielding effectiveness of a heavy current comparator when a radial magnetic field is added.

220kV无人值守变电所改造

针对无人值守变电所已从 3 5、1 1 0 k V扩大到 2 2 0 k V,无锡供电设计研究院以“因陋就简、因地制宜 ,因势利导 ,节约投资”为设计标准 ,进行 2 2 0 k V无人值守变电所改造设计。介绍了 3种典型的改造设计方案 ,包括改造二次接线 ,增加 RTU的方案 ;采用综合自动化系统的方案和更换部分二次设备、增加 RTU的方案 ,分别介绍了各方案对二次设备。