The Research On Untying Method And Technical For Shenyang 500kV/220kV Electromagnetic Network

During the initial stage of 500 kV electric power network formations in Liaoning province, the electromagnetic loop network appears. The electromagnetic loop network is formed by lower and higher voltage network parallel operation, which is through the link of transformer's electromagnetic circuit. When local district loses high-voltage power, it is capable to transmit and accommodate power through low-voltage network. The electromagnetic loop network structure improves reliability and flexibility of power supply, but it brings about some adverse effects on the operation and management of power grid. In recent years, electromagnetic loop network becomes important cause leading to large-scale blackout of power grids. The research of the opening electromagnetic loop network could solve these accidents by academic field and engineering field. It's inevitable that the building of the power grid brings into effect power network structure with voltage-grading and district-dividing.Nowadays, Shenyang power grid has formed 500kV loop network's main network frame with the continuous construction, which is conjoined with the existing 220kV loop network, forming an electromagnetic loop with the two voltage levels. In such circumstance, the short circuit current in some substations will exceed the rated value of the 220kV circuit breakers. To limit the short circuit current, the 220kV loop structure has to be opened.This thesis studies on the electromagnetic loop network fundamental theory first, analyzes the benefit and weakness of the opening loop network, discusses the key technology, concludes the fundamental principle and the general process, etc. To combine with the features of Shenyang 500kV/220kV electromagnetic loop network, this thesis not only proposes the feasible scheme of the opening loop network, but also verifies the scheme's generality and feasibility. This thesis presents the calculation and analysis results of Shenyang power network in various operating states by using BPA software, including power flow distribution, short circuit calculation, N-1 analysis, etc. before and after the opening of the 220kV loop, in order to find out the benefit and weakness of the system, and put forward some suggestions to the programming of Shenyang power grid.