LA PROTECTION ELECTRIQUE DES RESEAUX HTB

Abstract

The protection devices constantly monitor the electrical state of the elements of a network and cause them to be de-energized (for example the opening of a circuit breaker), when these elements are the site of an undesirable disturbance: short-circuit, insulation fault… Choosing a protective device is not the result of insulation reflection, but one of the most important steps in the design of an electrical network. From operation analysis of electrical equipment (motors, transformers, etc.) on faults and the resulting phenomena, the choice of the most suitable protection devices aims to: • Participate in the protection of people against electrical hazards; • avoid equipment damage (a three-phase short-circuit on a medium voltage bus bar can melt up to 50 kg of copper in 1 second; the temperature of the arc can reach 10,000 ° C in its core); • Limit the thermal, dielectric and mechanical stresses to which these materials are subjected; • Preserve the stability and continuity of the network service; • Protect neighboring installations (for example, reduce the voltages induced in nearby circuits). To acquire these goals, a protection system should have specifications of quickness, selectivity and reliability. However, one must be aware of the limits of protection: flaws must occur in the beginning for it to work. Consequently; Protection is not capable of preventing disruption; it can only minimise its effects and time span. In addition, the choice of protection is often a technical and economical compromise between security and the availability of the electrical power supply.