Protective Measures for the Safety of Individuals and Property in Electrical Engineering
When using electrical systems, it is of utmost importance to prevent harm to both individuals and animals and to protect property from hazards. For this reason, specific protective measures are necessary to avoid and prevent electrical accidents.
In the event of faults in electrical systems or devices, it is crucial to prevent the maintenance of dangerously high touch voltages. One way to achieve this is through the automatic shutdown of the system.
Basic Protective Measures for the Safe Operation of Electrical Systems
Basic protection ensures protection against electric shocks during normal operation when no faults exist in the electrical system.
Basic protection can be achieved through basic insulation or enclosures. It is essential that hazardous live parts are not accessible and that touchable conductive parts never become hazardous live conductors.
Basic insulation of live parts
Live parts must be completely covered with electrically and mechanically resistant insulation. This insulation should only be removable by means of destruction. Oxide layers, fibrous coverings, varnishes, and enamel coatings do not meet these requirements.
Enclosures or casings
Enclosures or casings, such as those for switches or outlets, provide protection against direct contact. They must at least comply with the IP 2X or IP XXB protection rating. For easily accessible surfaces of enclosures, a minimum protection rating of IP 4X or IP XXD is required. Enclosures or casings must be securely fastened and removable only with tools.
Basic protection is necessary when the operating voltage exceeds 25V AC or 60V DC and is categorized into protection classes.
Protection Classes in Electrical Engineering
In electrical engineering, there are different protection classes that define protection against electrical hazards.
Protection Class 0:
In this protection class, there is no additional protection against electric shock apart from basic insulation. Connection to the protective earthing system is not possible. Protection is solely provided by the environment of the equipment.
Protection Class I:
In this protection class, electrical equipment is connected to the protective earthing system, providing additional protection against electric shocks.
Protection Class II:
In this protection class, electrical equipment is protected by double or reinforced insulation. This achieves protection against electrical hazards without a connection to the protective earthing system.
Protection Class III:
In this protection class, electrical equipment is protected by safety extra low voltage. The voltage is reduced to a safe, low level to ensure protection against electrical hazards.
It is important to select the appropriate protection class according to the requirements and operating conditions of the electrical systems and devices to ensure adequate protection for individuals and property.
Fault Protection in Electrical Engineering
The aim of fault protection is to ensure protection against electric shock in the event of a fault. Once a fault occurs in the electrical system, fault protection must become active and initiate a shutdown.
In modern electrical installations, efforts are made to reduce the shutdown times . This is achieved through the use of automatic shutdown devices in the event of a fault.
Automatic shutdown is performed by overcurrent protection devices such as circuit breakers or residual current devices (RCDs).
There are specific shutdown times that must be adhered to:
- For final circuits without sockets and a rated current of ≤ 32A, the shutdown time should be ≤ 0.4 seconds.
- For final circuits without sockets and a rated current > 32A, the shutdown time should be ≤ 5 seconds.
- For final circuits with sockets and a rated current of ≤ 32A, the shutdown time should be ≤ 0.4 seconds.
- For final circuits with sockets and a rated current ≤ 63A, the shutdown time should be ≤ 0.4 seconds.
- For final circuits without sockets and a rated current > 63A, the shutdown time should be ≤ 5 seconds.
- For distribution circuits (feeders), the shutdown time should be ≤ 5 seconds.
These shutdown times ensure effective protection against hazardous situations in the event of a fault. It is important to correctly select and use the appropriate overcurrent protection devices according to the specified shutdown times to ensure the safety of individuals and property.
Additional Protection in Electrical Engineering
Additional protection represents an extra safety measure used when basic protection or fault protection is not sufficient.
A common additional protection mechanism is the installation of a residual current device (RCD), also known as a ground fault circuit interrupter. This device detects deviations in current flow and immediately shuts off in the event of a fault. A residual current device monitors the electric current in a circuit and detects the smallest deviations that could indicate a fault current, such as insulation failure or direct contact with live parts. Once such a fault current is detected, the RCD immediately shuts off the circuit to minimize the risk of electric shock.
The use of a residual current device as additional protection is particularly important in areas where individuals are exposed to an increased risk, such as bathrooms, outdoor areas, or construction sites. Adding protection with a residual current device enhances safety and reduces the risk of electrical accidents.
It is advisable to consider additional protection in electrical installations to ensure a comprehensive safety strategy and minimize potential hazards in the event of failures in basic protection or fault protection.