Justification of the role and reliability of systems of protective disconnection of voltage to determine the accepted risk of electric injury

Formulation of the problem. Protective blackout is used as a means of electrical safety in electrical installations. By disconnecting the voltage for a sufficiently short time, a person who accidentally comes under voltage is de-energized and, as experience shows, remains alive without receiving dangerous injuries [1]. Protective shutdown is carried out by current leakage protection equipment, which is regulated by the Coal Mine Safety Rules and the safety rules of other galleys that conduct underground work and use an electrical power supply system with isolated neutral. But the equipment may not operate as a result of failures of its structural elements, especially elements of the electrical circuit, i.e. insufficient reliability of the equipment. Practical experience suggests that all deaths from electric shocks that occur annually in mines arise with an inactive protective shutdown system, but in literature these issues and the role of reliability are not adequately addressed. The purpose of the article is to disclose the conditions for reducing the risk of electrical injuries by applying protective voltage isolation in the power supply system and to justify recommendations on the acceptable level of its reliability to reduce the risk of electrical injuries. Conclusion. It is advisable to consider the logical-mathematical diagram of the formation of electrical injury as a “tree” of failures of electrical protective equipment in the power supply system of consumers with an isolated neutral of the supply transformer. To substantiate the mathematical model of electric trauma and to establish a relationship between the probability of failure-free operation of the system of protective shutdown Reveal the value of the reliability of protective shutdown of voltage in reducing the likelihood of damage and substantiate the formula for determining the necessary level of reliability of protective shutdown equipment, depending on the permissible risk of electrical injury.