In complex industrial systems, human error has been cited as a cause or a contributing factor in accidents and disasters. The need for improved Human Reliability Assessment (HRA) methodologies that should be applied in Probabilistic Safety Assessments, ever since the early 1990s, has motivated a number of major activities in research and development worldwide. Therefore, the main purpose of this paper is to show the practical application of Human Error Assessment and Reduction Technique (HEART) for HRA in Electric Power Company of Serbia (EPCS). The usefulness of this technique for HRA has been approved in a case study of an accident which occurred during a repair on a 10/0.4 kV steel lattice tower “Maričiće“, Kuršumlija (jurisdiction of EPCS, ED “Jugoistok”, Nis, Serbia). For the purpose of this study, a database on work-related injuries, accidents, and critical interventions that occurred over a 10-year period was created. The research comprised an analysis of 1074 workplaces, with a total of 3997 employees. The case study performed at the EPCS confirmed that the HEART is based on knowledge of human activities and relies on expert opinion to determine the Error Producing Condition (EPCs) that affected the situation. The HEART can be used in different industrial systems, as a risk assessment, accident investigation and design tool. In addition, it is a relatively fast tool for assessment of human error probability that is easily applied and understood.