Study On Reliability Probability Model Of Wide Area Measurement System

Wide area measurement system plays an important part in wide area protection system, an essential part in electric power system as well as a vital role in guaranteeing secure operation of power system and power supply quality and preventing faults expansion from accidents. With the capacity of interconnected system increasing and electric voltage rank heightening, the regional range and user numbers which are affected by faults of electric power system are becoming larger and larger. How to monitor and control the operation process of electric power system in real-time to ensure steady and safe and reliable operation of electric power system is an important issue which electric power professionals have to face. Meanwhile, with the development of reform of electric power system and the request for higher power supply's quality, reliability assessment for electric power system has broadly aroused people's attention and research.The final purpose of reliability assessment for electric power system is an efficient way to guarantee the normal operation of WAMS. Wide area measurement system consists of three parts: data acquisition system, communication backbone network and monitoring center. The state of each part could affect that of wide area measurement system. So the reliability assessment for WAMS should begin from each subsystem.An evaluation method for WAMS network component reliability is presented.An reliability index of syschronized phasor measurement unit is proposed and then a suitable reliability model based on the hardware and software modules. Especially, a markov state space is built for the GPS module which is in stand-by mode. Based on the availability of a PMU, the reliability model of data acquisition system is built according to the principle of the location of PMU in electric power system.Communication backbone network of WAMS is the way to transport the phasor data in time accurately and completely. Communication backbone network is important part of WAMS whose reliability request is highly strict. According to the specification and function characteristics, a reliability model of communication backbone network is built through node searching algorithm and minimal path set method based on the connectivity reliability theory. The reliability indexes such as the connectivity reliability and average time between failures and etc.are calculated.The monitoring center is the most important part of WAMS and repairable. The subsystem of the monitoring center seem to be a complicated software system as whole. There are two states: operational and repairable state. The failure distribution model seems to be constant and thus the monitoring center station meet the Markov process.An example of wide area measurement system of IEEE 14 has been evaluated and so does each subsystem. Especially the important index of communication backbone network is calculated. Whether considering the reliability of communication backbone network or not will cause different influence on the whole wide area measurement system. The results show the validity of the reliability model.