To be able to use a product containing electrical components, certain standard requirements must be fulfilled.
DIN 49440:1989-12 and DIN 49441:1972-06
In order to ensure that all plugs fit to an associated socket, certain design and measurement requirements must be fulfilled. Standard DIN 49440:1989-12 contains a technical drawing with required measurements of a type F socket [14]. An extraction from this standard can be seen in appendix A. Standard DIN 49441:1972-06 contains technical drawings with required measurements valid for type F plugs as well as required additions if said plug is supposed to be operable with a socket of type E as well [15]. An extraction of this standard can be seen in appendix B. In order to operate a plug of type C in a socket of type F, no alterations to the design is required [15].
SS-IEC 60884-1 and IEC 60884-2-5
Standard IEC 60884-2-5 and SS-IEC 608874-1 comprises requirements regarding plugs and socket for general use, for example when plugs and socket are used within a household.
Standard IEC 60884-2-5 is an updated version of standard SS-IEC 608874-1 and this master thesis will therefore have its base on the original standard but use the updated version when possible [16], [17].
Section 10 regarding protection against electric shock states in paragraph 1 that a design must guarantee that live parts are not accessible when the product is mounted. This also applies after removal of parts which can be removed without the use of a tool. When a plug is partially or completely inserted in a socket, live parts are required to not be accessible [16], [17].
External parts of plugs must be of insulating material according to paragraph 10.4. This however is with exception of assembly screws, current-carrying and earthing pins, earthing straps and metal rings around pins that fulfills requirements in paragraph 10.2.1 or 10.2.2 [17].
A shutter can be a person or an object that covers or closes an opening, e.g. a person who opens and closes doors at hotels, or a mechanism on the lens of a camera that opens and closes so the quantity of the light entering the camera can be regulated [18].
According to standard IEC 608874-1, a shutter must be integrated in a socket due to personal safety since it offers increased contact protection for children as well as adults against electric shocks. A shutter must be designed in such way that they can’t without difficult be operated by anything other than a plug according to paragraph 10.5, and the shutter should not be able to be accidentally removed. A commonly used shutter design opens when both opening is pressed simultaneously by the pins of a plug [19]. An example of this type of shutter system is presented in figure 2.5 which displays a shutter system designed in 1928 for a socket of type G.
Figure 2.5. Shutter system designed by MK Electric. [19]
The shutter system presented in figure 2.5 is still in use for certain G type sockets. By inserting the plug, the earthing pin which also is the longest pin, pushes the shutter away and the entire plug can be inserted in the socket. Upon removal of the plug, a spring which is not visible in figure 2.5, pushes the shutter back to its original position [19].
To ensure that the grounded contacts is in contact at all times, paragraph 11.1 requires that the design must be made so the grounded connection is made before current-carrying contact when inserting a pin into a socket. The paragraph further requires that the grounded connection is broken after the current-carrying pins has separated [16].
In paragraph 14.3 the standard also includes the requirements that the pins must be locked against rotation and not be removable without destroying the plug [17].
IEC 62368-1:2018
Standard IEC 62368-1:2018 comprises safety requirements regarding audio and video, information and communication technology equipment [20].
According to standard IEC 62368-1:2018 paragraph 0, there are three kinds of persons that can come in contact with a product; a skilled person, an instructed person and an ordinary person.
A skilled person is a person with training or expertise in the equipment technology, an instructed person is a person who have been instructed and trained by a skilled person, or who is
supervised by a skilled person and an ordinary person represents everyone else. Depending on what type of persons that will handle a product with energy sources, different safeguards must be met to decrease the risk of pain, injury and, in case of fire, property damage. The most commonly used basic safeguard against an electrical energy source capable of causing pain is electrical insulation. A supplementary safeguard may be additional insulation or a protective earthed conductive barrier. Another factor that will determine the level of safeguard required is the grade of energy source. According to paragraph 0.3, energy sources can be divided into three groups; class 1, class 2 and class 3. The classes are defined according to table 2 [20].
Table 2.2. Division of energy classes [20]
Energy source Effect on the body Effect on combustible materials Class 1 Not painful, but may be detectable Ignition not likely
Class 2 Painful, but not an injury Ignition possible, but limited growth and spread of fire
Class 3 Injury Ignition likely, rapid growth and
spread of fire
An energy source that origins from a wall socket is considered a class 3 energy source. In the event of a proper shock, the rate of the heartbeat can become out of balance and lead to dangerous consequences. If combustible material is used, ignition will probably be inevitable and a rapid growth and spread of fire will occur, especially if other furniture such as curtains etc. is close by [20].
When an ordinary person is intended to operate an electrical product with energy source of class 3, following safeguards must be met according to paragraph 4.3.2.4; there must be an equipment basic safeguard and equipment supplementary safeguard, or a reinforced safeguard [20].
According to paragraph 0.5.8, equipment safeguards is defined as following [20]:
- Basic safeguard: Valid under normal operating conditions
- Supplementary safeguard: Valid in the event of failure of the basic safeguard
- Reinforced safeguard: Valid under normal operating conditions and in the event of a single fault condition elsewhere in the equipment
In part Annex V paragraph U.1, an accessible part of an equipment is a part that can be touched by a body part. All parts that can be touched is regarded as an accessible part if the part of the equipment can be opened without the use of a tool. However, accessible parts do not include parts that have become accessible when floor standing equipment with a mass over 40 kg is tilted. According to part Annex K paragraph K.3 and K.4, safety interlock is not a sufficient safety measure for an ordinary person when handling a product with energy source 2 or 3. The usage of a tool is thereby required to hinder the energy source of being located in an accessible area [20].
IP-classification
Ingress protection classification (IP-classification) is an international standard (EN 60529) which specifies different levels of safety requirements for electrical products. The European standard EN 60529:1991 applies in Sweden where the official version, written in Swedish, includes standards EN 60529:1991, EN 60529/A1:2000 and EN 60529/A2:2013. Depending on the level of effective sealing, a product’s classification can be high or low. IP-classification normally consists of the letters IP, followed by 2 digits where the first digit indicates the product’s capability to withstand penetration from foreign objects. The second digit indicates the product’s capability of withstanding penetration from liquids. Depending on if an electrical product is intended to be used indoors or outdoors, the level of IP-classification varies [21].
Figure 2.6 below illustrates and describes the different levels of IP classifications an electrical product can have. The figure can be seen in a larger format in appendix C.
Figure 2.6. IP ratings. [22]
When there are no specified requirements of either solid- or water penetration, the respective digit is then denoted by the number zero (0), i.e. IP10 has no water penetration safety requirements while IP01 has no solid penetration safety requirements. The digit is replaced with the letter X if there is a lack of sufficient data to assign a protection level [21].
An indoor Smart Plug should, at minimum, have an IP20 classification.