# Random Violation Risk Degree Based Service Channel Routing Mechanism in Smart Grid
## 1 Introduction  
Smart gird, integrated power network with communication network, incorporates the latest innovative technologies to bring a revolutionary change and innovation of traditional power for future green energy [1; 2; 3; 4; 5]. Although smart grid has lots of promising features, such as intelligent de-centralized control, resilience, flexibility, sustainability, digitalization, intelligence, consumer empowerment, renewable energy, smart infrastructure and so on, a number of critical challenges and open issues like need to be further discussed [6; 7; 8; 9]. One of these critical challenges is risk of smart grid communication which is always the critical constraint in ultra high voltage (UHV) Grid [7], Smart Home [8], Microgrids [9] and other smart grid applications. Due to the complexity of smart grid communication environment, different communication technologies are used for the realization of smart grid, such as Optical fiber technology, power line communication (PLC), 4G/5G, wireless mesh network and so on [10; 11; 12]. Among these communication technologies, optical fiber technology and the corresponding synchronous digital hierarchy (SDH) technology is widely used in the smart grid communication transmission network for the high bandwidth, high anti-interference, small signal attenuation and long transmission distance. However, there still exists communication violation risk. With SDH technology, one optical fiber can carry multiple service channels. Each single service channel may have a great transmission capacity, such as STM-16 (10 Gbit/s). In this case, even a short interruption of the fiber can still cause a large amount of data loss. Therefore, the occurrence ofinterrupted service channel must be limited. To achieve this purpose, the statistical path availability \(A_{SPA}\) model is normally adopted to model the service channel and the basic rules to guarantee the availability of service channels are also specified [12]. According to the rules, in the process of service channel planning, different levels of electric power communication services should be allocated to the different channels. For example, to guarantee the service quality, a service with statistical availability greater than 99.9% should be allocated to a channel with the predetermined statistical availability higher than 99.9%. In addition, to ensure the requirements of high availability and high real-time, services are planned with the primary channel and backup channel. Thus, when some electric power communication failure events occur and some channels are interrupted, the services can be safeguarded. However, in practice, the faults of transmission equipment and optical cables carrying the service channels occur randomly. Therefore, during a period of time, the actual path availability \(A_{APA}(t)\) of service channels may be significantly higher than 99.9%, or may be less than 99.9% due to a sudden failure. The backup channel strategy cannot ensure that the actual channel availability will not violate the rules. Thus, in practice, there exists a risk that service channel may violate the availability requirements, namely there exists a service channel violation risk (_SCVR_). In this case, the challenge that electric power communication network channel planning faces is how to effectively control the availability decline because of the channel random failures, thus to reduce the probability of _SCVR_. To solve this problem, the availability-aware routing mechanism should be considered. Through scientific and rational route planning, when a channel fails, the service carried by the channel can be conveyed by another channel and will not be affected, thus the violation risk caused by channel random failure can be avoided. To achieve the above goal, firstly, a probability distribution model of _SCVR_ should be studied and designed. Then, a _SCVR_ based routing mechanism should be proposed to reduce the failure number (_FN_) and failure duration of the electric power communication service.