Reliability And Security Study Of The Digital Substation System

The electronic transformer and the intelligent switchgear make the digital substation possbile. The comprehensive communication system standard is the ensurance to achieve the digital substation. The latest issued IEC 61850 standard provides a comprehensive construction specification for the digital substation. These new technologies make the digital substation become inevitable.Compared with the conventional substation system, the digital substation system possesses a series of significant advantages. However, there are still many issues existed in it, such as its reliability and security issues. Up to now, there are a lot of researches on the conventional substation system reliability, seldom on the digital substation system. So establishing the reliability model of the digital substation system and evaluating the reliability of the entire system have a great significance for the design and operation of the digital substation. And the existing digital substation system security analysis methods almost focus on the qualitative analysis of the security policies, seldom on quantitative analysis the contribution of those security policies to the system security level. Therefore, establishing the digital substation system security analysis model also has a great significance for the safety operation of the substation.This paper introduces the basic features of the digital substation. Then, it analyzes the architecture characteristics and the reliability model of intelligent electronic devices within the digital substation, and uses the Markov state method to analyze and calculate the reliability parameters of the device. This paper also describes the typical technical characteristics of IEC 62439-3 standard, and introduces the main technical principles that support the network bumpless recovery. And then it applies IEC 62439-3 to the process bus. Compared with the traditional protection system, it analyzes alternative all-digital protection systems which utilize different process buses. Afterwards, it uses the reliability block diagram to calculate the reliability indices of those protection systems. The existing reliability analysis methods are almost direct for a single device or a single bay unit, rarely for the entire substation system. Therefore this paper presents a method to calculate the reliability parameters of the entire substation. Then the reliability parameters of a typical digital substation are analyzed and calculated.Finally, the paper introduces the major threats of the network security, the needs of the network security and the corresponding policies of the network security. Then combined the reliability theory and the vulnerability theory of the distributed systems, it presents a comprehensive approach to quantitative analyze the digital substation system security. Afterwards, it uses the method to analyze the security model of the digital substation communication system.