Prevention of risks associated with electrical installations:
Electrical risks are present at all stages of a project: construction, operation and maintenance. They are easier to master if they are taken into account from the design of the network. Risks affect people as well as property. The risks of electric shock and fire are always present but others can be added such as explosion, falls, untimely starting of machines…
The elimination of electrical risks must be approached from the design of networks. The choice of network architecture, equipment, etc., supplemented by calculation notes and selectivity study are necessary before any implementation to define the protection settings and guarantee compliance with installation and safety standards. The personnel ensuring the maintenance of the electrical installations must be trained and authorized.
Risk of fire:
The risk of fire linked to overloads and short circuits is dealt with by devices such as circuit breakers, protection relays, fuses and thermal relays. The choice of devices and their settings must be made according to a selectivity study so that they can provide protection while allowing operation without tripping under all the conditions envisaged.
Risk of electric shock:
The risk of electric shock is treated differently during operation and during maintenance operations.
Operators must be protected against direct contacts representing access to bare live parts and against indirect contacts which are accidental energizing of the masses when a fault appears.
Protection against direct contact is ensured by constructive measures such as insulation, cowlings with possible interlocks and removal.
Protection against indirect contacts depends on the earth connection scheme formerly called “neutral system”. It is ensured by the earth network, the earth electrode, the homopolar and differential protections and in certain cases the existing protections against short circuits. A study of this protection system is essential to ensure that in the event of an earth fault on an equipment item, the voltages appearing on the masses accessible by the personnel remain at a value below the danger threshold.
During maintenance operation:
The personnel carrying out maintenance or work operations are required to temporarily remove protection against direct contact: opening of electrical cabinets, removal of covers, etc. This personnel must be trained and hold an electrical authorization title to know the collective or individual protective equipment to use and to master the procedures. In the course of work, the elimination of electrical risks must be favored by separating the installation concerned from its potential power sources. This separation, which is one of the stages of electrical lockout, can be achieved by different means: disconnecting the circuit breaker, opening the disconnector, plug and socket assembly, etc.