Research On State Evaluation Of Protection Device In The New Generation Smart Substation

Relay protection being the first line of defense to ensure the safety of power grid operation, its reliability is of great significance. Developing more scientific and advanced condition-based maintenance of relay protection to ensure its reliable operation is the inevitable choice of power grid development. Condition assessment is the key part of condition-based maintenance, the practical evaluation method of relay protection still remains to be perfect. With the rapid development of power system technology, the structure and technology of substation secondary system is also in constant innovation. The smart substation has been digital and network, which makes great changes to how relay protection equipment work. And the new generation smart substation has achieved the online monitoring function of secondary equipment, which makes a part of state variables became observable indicators and makes the practical state assessment work possible.At first, the paper analyzes the characteristics of secondary system's network architecture and relay protection's secondary loop in various stages of substation, and analyzes the architecture, monitoring method and the main monitoring indicator of online monitoring system in new generation smart substation. The paper starts with the failure mode of protection device, then analyzes the important modules of protection devices, and put forward feasible monitoring indicators.Then, the paper does research on time-varying failure rate of protection devices, establishes the time-varying aging failure rate under considering the operating temperature of the modules, and integrates the aging failure rate with the occasional failure rate of each module with the series model.At last, the paper set up a relatively well-developed evaluation index system based on the online monitoring data and operation and maintenance information, and put forward classified processing method. The paper optimizes the existing state assessment method by the work as follows: the paper combines the unascertained rational number method and entropy weight method, and establish the combination weighting method by linear weight; the paper put forward a dynamic correction coefficient which can modify the evaluation result indirectly to make up the insufficient of the existing method that is unable to characterize the variation trend; the paper analyzes the deficiency of the existing evaluation principle and put forward a modifying method.The condition assessment method of relay protection equipment established in this paper is more perfect in all aspects. The research advances the practical condition based maintenance further, and gives some reference to the following development of secondary system's on-line monitoring function in new generation smart substation.