Safety Integrity Level Verification Model for IED Protection Schemes

The ever-increasing complexity of intelligent electronic devices (IED) for the protection of electrical equipment leads to significant research challenges in evaluating their safety integrity level (SIL). The development of new technologies, components, operation, and maintenance requirements are factors that increase uncertainties and risks associated with the safety, integrity, and reliability of the IEDs. Based on both “the U.K. guidance on assessing the safety integrity of electrical supply protection” and Markov processes, this research proposes a methodology to assess and verify the integrity of protection schemes in industrial and commercial power systems. The average probability of failure on demand (PFDavg) and SIL level, are used to quantify the reliability of protection arrangements for radial distribution systems in accordance with the safety integrity foundations of IEC 61508 and IEC 61511 standards. The methodology is implemented with the IEEE 242-2001 case study, with illustrative results.