What is a protection class?

A protection class defines the safety measures taken to prevent an electric shock. Especially for equipment with a metallic housing, there is a risk that the housing will become live if a device malfunctions. Many equipment components are conductive – e.g. an iron, where the metallic surface is conductive if safety measures fail. Without suitable measures, which are specified in the relevant protection classes, life-threatening situations can occur. It is therefore particularly important to define safety measures using protection classes.

The protection classes for electrical equipment are defined in the standards DIN EN 61140 (or VDE 0140-1). The symbols to be used for marking electrical equipment are specified in IEC 60417 of the International Electrotechnical Commission.

What is the difference between protection class and protection rating?

A protectionclass comprises the measures that protect against dangerous voltages – whereas a protection rating defines the degree of protection against contact, foreign objects, water, and mechanical stress. The protection class must therefore be distinguished from the IP protection rating (Ingress Protection according to DIN EN 60529 or ISO 20653).
You can find further information on the subject of protection ratings.

The four protection classes

According to the definition of DIN EN 61140 (VDE 0140-1), a distinction is made between four protection classes. These contain requirements for electrical equipment, which are described in more detail below. The "highest-risk" electrical equipment can be found in protection class 1. The lower the risk of an electrical device, the higher the protection class (2 or 3).

Protection class 0: Basic insulation

Protection class 0 means that, in addition to the basic insulation, no other measures exist to protect against electric shocks. In addition, devices in this protection class cannot be connected to a protective conductor system. There is therefore no marking with a specified symbol. International standards will no longer take this protection class 0 into account in the future. In Germany and Austria, protection class 0 is not permitted.

Protection class 1: Protective earthing

Protection class 1 contains the most comprehensive safety measures compared to the other protection classes. Protection class 1 is characterised by double protection, which - in addition to the generally existing basic insulation - provides earthing to the electrically conductive parts of a device. This is called equipotential bonding. Depending on the type of electrical equipment, this equalisation can be done in two ways:

Via a permanently installed connection cable
Or via a device connector with earth contact (= Schuko plug)

Typical examples of equipment in this protection class include electric irons, water heaters, washing machines, and refrigerators.

Protection class 2: Protective insulation

Electrical devices assigned to this protection class feature reinforced or double protective insulation between the mains circuit and the output voltage, or between the mains circuit and the housing. Due to the insulation, it is not possible to touch the electrically conductive parts of a device. Special plug-in connectors are used not only in protection class 1, but also in protection class 2. Unlike the Schuko plug, the contour plug-in connectors do not require a protective conductor.

Power tools or hair care appliances, for example, can be assigned to protection class 2.

Protection class 3: Protective low voltage

Devices that carry this protection class are considered equipment with the lowest risk or with the highest safety. It operates at a relatively low voltage, specifically protective extra-low voltage, also known as Safety Extra Low Voltage (SELV). This voltage is a maximum of 50 volts AC or 120 volts DC. Batteries or generators serve as the power source here.

Devices with an alternating voltage of less than 25 volts AC or 50 volts DC can be described as particularly safe. They provide protection against electric shock in the event of indirect or direct contact. Since the voltage is relatively low, electrical equipment with protection class 3 poses no danger to humans.

Examples of this protection class include toy cars, slot car tracks, various medical devices, or electrical equipment that can be used in a bathtub or shower.