Study On Retrofit Scheme Of Improving Relaying Protection Reliability Of Hulunbuir

The massive breakdowns of power system caused by the miss-trip of relay protection devices have occurred from time to time, which do great harm to the national economy and people's lives. With the rapid development of national economy, the power grids are constructed with each passing day and the performance of the equipments are gradually increasing. The relay protection system must be able to respond to the faults and abnormal operating conditions, and act on the breakers to trip or give signals. With the constant expansion of power systems, the requirements of the security and stability of system are more and more rigid. Therefore, the relay protection devices play an increasingly important role. For this reason, application of microcomputer-based relay protection devices, which is used to overcome the shortcomings of the conventional-type protection devices in order to prevent the malfunction of relay protection and improve the reliability of the operation, is of great significance.In this paper, the relay protection system of Hulunbuir grid is as a research subject. On the basis of comprehensive analysis of performances of relay protection devices in the grid, aiming at the features of weakness in Hulunbuir grid and the practical problems of protection devices, advanced protection principles and technologies are used to reform conventional protection devices, so as to improve the reliability of protection devices and the safety and stability of the grid. From the principles, configurations, setting value adjustment to realizations in protection, transformer protection, bus protection and line protection are updated and upgraded in devices. The new microcomputer-based protection device adapted in this paper fundamentally resolves the contradiction between the sensitivity and reliability which conventional protection devices have. For transformer protection, it is effective to suppress the influences caused by all kinds of factors, such as inrush current, TA saturation, and improve the sensitivity of transformer protection. And for bus protection, the dead zone protection of bus tie established solves the defect that conventional protections exist a dead zone. For line reclosing, the time setting of single-phase reclosing, which is in line with practical situations in engineering, is given. The new microcomputer-based protection device not only optimizes protection principles, but also simplifies the tests in operation fields and improves the reliability of protection devices.Finally, specific examples are given to show the accuracy and reliability of the new microcomputer-based protection devices using in the transformation and infrastructure, and this new device effectively ensures the safety, reliability and stability of Hulunbuir grid.