Research On On-line Condition Monitoring System For Transformer

With the development of national economy and power system, the demand on the reliability and safe of power system have been improved. On-line condition monitoring for power system can monitor the health status of the electric equipment in real time under the real state. It provides safeguard for the safe and steady running of power system. As the supplement and development of the integrative power system automation, substation with nobody on duty in the real meaning will be realized. At the same time, it is the precondition and an important part for the electric equipment condition maintenance and offers the basis for the condition maintenance. Under the background of developing the more high-level automation technology in substation, this paper describes the research and development work in on-line condition monitoring for electric equipment, specially transformer. According to the demand and target of on-line condition monitoring for electric equipment, a centralized on-line condition monitoring system for medium-small scale substation has been put forward in this paper based on the actuality and development trend in this field. It is expounded that the configuration of the system can monitor transformer, breaker, arrester and capacitative equipments in substation synthetically. As an important equipment in substation, the running state of transformer influences the stability of power system directly. The key job of this paper is to design and develop a kind of centralized on-line monitoring device for transformer. The device has the characteristic below : In the respect of the monitoring function, synthetical means are adopted to monitor transformer with combining non-electricity signals and electricity signals which can improve the accuracy of the state assessing effectively. It includes dissolved gas analysis, partial discharge detection, water content monitoring in transformer oil, monitoring of the electric parameter etc. . In terms of dissolved gas analysis, the system diagnoses the trouble by using the improved three-ratio method and the no-ratio method when the gas content or the produce speed of the gas exceeds the notice value. The differential balance method is used in partial discharge detection and the content of little water in transformer oil is monitored thought the capacitance sensor made of membrane. PT/CT will be used for monitoring the electric parameter in order to gain the running state of transformer. In the respect of the trouble diagnosing, a kind of three-dimension mode is proposed, i.e. making a comparison between the monitoring data and criterion, one's own data and the data with another same-type equipment. The result will be more general and accurate under this mode. In the respect of designing and developing for the device, the configuration of the hardware adopts the multi CPU structure and the key templates adopt the DSP+CPLD mode. Furthermore, the unified interface mode is adopted to deal with the front signals. Modular programming is used for the software design. It can be easier to expanding the distributed system while improving the device capability and make the device have better generality, suitability and expansibility.