All appliances that use the supply voltage must provide at least Class 2 protection for the user. This is to ensure that if one of the layers fails, the second layer of backup still exists. This makes electrical equipment very safe to use. The appliance can be level 1 or level 2.
In the PAT test, it is important to first identify the category of the device, because the test of the Class 1 device is different from the test of the Class 2 device.
According to the specific degree of protection provided, the electrical appliances are divided into five types of equipment structures, namely, level 1, level 2, level 3, level 0, and level 01. The most important of these are Level 1 and Level 2. For completeness, all classes are described below.
Level 1
The protection here is provided by a combination of insulation and the use of a power earth. The fire that is disassembled by reference is best displayed.
In the open plug, three wires are connected to the LIVE, NEUTRAL and EARTH pins. In the fire, the brown LIVE line and the blue NEUTRAL line are connected to the plastic connector. The green/yellow ground wire is connected to the metal casing of the fire.
The user is protected from electric shock by the plastic insulation of the connector. This will hold the LIVE and NEUTRAL wires in place and prevent them from coming into contact with the metal casing of the electric stove. This plastic insulation of the connector is referred to as basic insulation.
If this basic insulation fails, such as due to excessive movement of the cable in contact with the metal casing, the fire user may be shocked if the EARTH wire is not present.
By connecting the metal casing of the electric stove, the EARTH wire keeps all of these metals at the EARTH potential. This means that an electric shock cannot occur even if the metal casing of the fire is directly connected to the LIVE voltage. In fact, the fuse will blow out in the plug or main fuse box to protect the user.
In summary, in Class 1 devices, the user is protected by a combination of basic insulation and EARTH connections, providing two levels of protection.
When the PAT Testing Class 1 equipment is tested for earth continuity and insulation resistance.
level 2
In a Class 2 device, the user is protected by at least two layers of insulation. Therefore, Class 2 devices are also referred to as double insulation. They do not require an Earth connection.
It can be best displayed by looking at the opened Level 2 drill. It can be seen internally that in addition to providing a substantially insulated plastic connector, there is additional insulation provided by the plastic housing of the drill bit.
The user is protected by two separate layers of insulation. When the PAT test Class 2 device, only the insulation resistance test is performed.
Level 2 equipment is always indicated by a double-frame symbol on the nameplate.
Level 3
Equipment manufactured to Class 3 standards is designed to be powered by a special safety isolating transformer whose output is referred to as Safe Extra Low Voltage or SELV. This must not exceed 50 V AC, usually less than 24V or 12V. All three types of equipment are marked with a special symbol. Earth is not used in Class III equipment
The electrical safety of Class 3 equipment is addressed in the design of safety isolating transformers where the spacing between the windings is equivalent to double insulation. The transformer is marked for use in Class III appliances.
Level 0 and level 01
Such equipment is not intended for normal use in commercial or residential environments. It is only proposed to be completed here.
Class 0 equipment relies only on basic insulation to prevent electric shock. For this reason, they do not have built-in level 2 protection and are not allowed to be sold. The brass lamp shown here is an example of a two-wire metal enclosure appliance with only basic insulation. There is no regulation to connect the ground to the lamp holder.
In Class 01 equipment, a ground connection is provided, but it uses a twin-core cable or a 2-pin plug connection, so it cannot be connected to the earth. In class 0 devices, one relies only on basic insulation to prevent electric shock. Class 01 devices are not allowed because they have only level 1 protection.
If a Class 0 or Class 01 device is encountered during a PAT test, it may fail.
Identify Class I and Class II appliances
Since the PAT tests performed on Class 1 and Class 2 devices are different, it is very important to identify one from the other. No other field of PAT testing can lead to more confusion than this, and there are many myths surrounding this. Some of the content listed will provide information.
If there is a fuse in the plug, it must be level 1.
It is made of metal and must therefore be level 1
The case is plastic, so it must be level 2
It has a three-core cable, so it must be level 1
The plug has a metal ground pin, so it must be level 1
None of the above statements are simple ways to identify Class I and Class II devices, and some are very misleading.
The simplest application rule is the following rule.
If the nameplate has a double box, then the device is level 2. If not, then it is level 1.
Example - Kettle
The nameplate on this kettle obviously does not have a "double box" symbol, so according to our rules, it must be level 1. The ground connection of the plug terminates in the outer metal casing of the heating element. When performing a PAT test on this kettle, earth continuity and insulation resistance tests must be performed.
Example - Plug-in power supply
The nameplate of this plug-in transformer clearly shows the "double box" symbol, so this is a level 2 device. Note that it has a plastic ground pin because Class II is not required. [Not all Class 2 appliances have plastic ground pins]. Only the insulation resistance test must be performed during the PAT test.
Example - main extension
The nameplate on the extension is molded in plastic. It obviously does not have a "double box" symbol, so it must be level 1. When PAT tests this extension, Earth continuity and insulation resistance tests must be performed.
Example - Table Lamp
The nameplate on this lamp clearly shows the "double box", so it is a level 2 device. [Note that this is a large class 2 device in a metal case]. The bulb holder is made of plastic and provides the required double insulation. Only the insulation resistance test must be performed during the PAT test.
Example - Desktop Fan
The nameplate of the fan not only does not have a "double box" symbol, but also indicates that the device must be grounded. So this is obviously a level 1 device. Please note that it does not have any metal accessible to the user.
Example - Metal Light
If the metal lamp has a nameplate, it is a primary device because it has a grounding point on the base. However, due to the lack of a nameplate, it must fail.
Are the Level 1 and Level 2 devices safe?
Since both have built-in level 2 protection, they are safe for general use.
However, for Class 1 devices, one of the security layers is provided by a ground connection. In order to be effective, the wiring in the building must be checked regularly to check that the ground in the power outlet is properly grounded. This usually depends on the cable entering the promised floor jacket or by driving the local pile to the ground. Therefore, Class 1 equipment relies on external wiring in the building to provide full level 2 protection.
However, Class 2 devices always provide Class 2 protection regardless of the state of the cabling installation. Two layers of protection are built into the design to make Class 2 devices safer than Class 1 devices.
Orignal From: Electrical protection level
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