Introduction to Electrical Engineering

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Pro: ČEKO IMPORT a.s.
Vydal: České vysoké učení technické Praha Autor: Vladimír Kůla, Michal Kříž

Strana 28 z 112

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This protection usually provided means insulation live parts (e. The other possibility how provide protection against direct contact situate live parts out reach.e. For that reason the first task prevent anybody (persons livestock) from touching dangerous live parts. In the course many year utilization electricity, system protection against electric shock has been developed. under single fault condition. The other potential, i. During the normal service may come such case that the insulation may disrupted or that the metal enclosure may come contact with live parts. live parts electrical household appliances are covered enclosures) means barriers obstacles around the live parts larger equipment electrical substations. FUNDAMENTAL RULES FOR PROTECTION AGAINST ELECTRIC SHOCK As mentioned the previous text, case touching live part, that means part with a potential different from the potential earth, current flows through the body from the live part to the earth. This has provided during the whole life electrical equipment (household appliances etc.g. This the usual way of protection against direct contact overhead transmission lines. the potential the live parts, usually potential compared with the zero potential the earth. The current can pass through the human body either case touching live parts of different potential case standing the place with some potential and touching live part with different potential.FUNDAMENTAL RULES FOR PROTECTION AGAINST ELECTRIC SHOCK 29 5.e. called the voltage live parts. when basic insulation fails), are called exposed conductive parts.) electrical installation. That called single fault condition and, such case, the called protection against indirect contact has be provided. The conductive parts electric equipment that can touched and that are not normally live, but may become live case of fault (e. The main objective this protection ensure that persons and livestock shall protected against dangers that may arise from the contact with live parts the electrical equipment installation. This first step protection, which has be provided during the normal service electrical equipment and/or electrical installation, called protection against direct contact basic protection protection under normal conditions.g. One these different potentials usually potential earth, which we consider equal zero. conductors are insulated) means enclosures which live parts are situated (e. That means contact with parts that are not live during the normal service and may become live case fault, i. The protection can achieved one the following methods: - preventing current from passing through the body any person any livestock; - limiting the current which may pass through body value lower than the current. .g