Complex process of evaluating safety of touch voltages for transmission line towers using ALARP method

For power line towers, electrical safety is generally associated with the grounding system and touch voltages of installed towers that are publicly accessible. The paper describes and discusses the entire process of safety assessments of transmission overhead line towers from the point of view of touch and step voltages, including measurements, fault simulations, database tools, and ALARP (‘as low as reasonably practicable’) evaluation. Grounding parameters change over time, which is associated with equipment aging, resulting in significant changes in the safety assessment of individual towers. Measuring the grounding of towers causes a considerable amount of needed service intervention, especially in extensive power transmission and distribution networks. The ALARP method can provide the prioritization for maintenance assessment and service works. The ALARP methodology is applied for high-voltage overhead line towers and is based on calculating the probability of human exposure to hazardous touch voltage. All discussed aspects were introduced into the Czech transmission system operator (CEPS) internal technical standards. The paper deals with a practical view of the complex safety assessment of grounding systems of power line towers and aims at conclusions from the use of ALARP methodology in practice.