Towards a formal model of protection functions for power distribution networks

The protection system is a crucial part of the power grid. It protects people, equipment, and property. Reliability of such mission critical systems is of an extreme importance. Protection systems have strict requirements to reliability including dependability, security and timeliness. Although it undertakes rigorous testing and commissioning, it fails in some circumstances causing faults in the network, resulting in loss of power. It is hard to catch these hidden and undetectable errors in the design and installation. Since protection function is essentially a piece of code, formal methods can be used for rigorous testing of the software and provide definitive proof of the system properties. This paper proposes a formal model (to use in formal verification techniques) for protection systems. The paper develops closed loop model of the electrical network with its protection system. The model is developed in IEC 61499 language for the further generation of its formal model in SMV language. The model is validated via simulation and comparison with a comprehensive model of the electrical network in Matlab Simulink. In future work, the generated SMV model will be used to formally verify reliability requirements of the protection system.