Human element factors affecting reliability and safety

Many system reliability prediction methods are based solely on equipment failures, neglecting the human component of man-machine systems (MMS). These methods do not consider the identification of the root causes of human errors. The reliability and safety of industrial and commercial power systems and processes (i.e., MMS) are dependent upon human characteristics and many dependent and dynamic interactive factors. The consequences of human errors are very diverse and can range from damage to equipment and property, injury to personnel or fatalities, to disruption of scheduled system operation, all of which represent a significant cost to society. This paper focuses on accidents-injuries and the disruption of scheduled system operation caused by human element factors and shows that the human element is a very significant factor affecting the reliability and safety of electrical systems. The paper initially presents several case studies to reveal the frequency of human errors which disrupted scheduled computer and utility system operation. This paper also presents statistics on the injury accident rate in electric utilities and the number of days lost to injury accidents. It presents some of the factors that direct human behavior and discusses how these factors help identify the possible root causes of electrical accidents, using an accident-injury sequence model to determine the cause of human errors. Knowledge of human factors can be used to mitigate their impact on power system interruptions and injury accidents (e.g., increased productivity, increased reliability, decreased errors, increased safety, etc.).