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In Europe, a double insulated appliance must be labelled Class II or double insulated or bear the double insulation symbol: ⧈ (a square inside another square). As such, the appliance should not be connected to an earth conductor because the high-impedance casing will cause only low-fault currents that are unable to trigger the fusible cut-out.
Double insulation requires that the devices have both basic and supplementary insulation, each of which is sufficient to prevent electric shock. All internal electrically energized components are totally enclosed within an insulated body that prevents any contact with "live" parts.
Double insulation is a design concept where failure of one insulation system will not expose the user to a shock hazard due to the presence of a second independent layer of insulation. Reinforced insulation is a supplemental insulation system that is strong enough to effectively perform as if a double insulation system was present.
For example, power semiconductors connected to the line voltage may be switched by opto-isolators driven from low-voltage circuits, which then need not be insulated from the higher line voltage. Transformers allow the output of a device to float relative to ground to avoid potential ground loops. Power isolation transformers increase the safety ...
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A pothead is a type of insulated electrical terminal used for transitioning between overhead line and underground high-voltage cable or for connecting overhead wiring to equipment like transformers. [1] Its name comes from the process of potting or encapsulation of the conductors inside the terminal's insulating bushing.
A distribution system insulated from earth ground may attain a high potential due to transient voltages caused by static electricity or accidental contact with higher potential circuits. An earth ground connection of the system dissipates such potentials and limits the rise in voltage of the grounded system.
The idea that most countries require all devices to be double-insulated or grounded is just patently ridiculous. "Most" countries have few electrical safety rules at all, and even in industrialized nations ungrounded plugs are common and rarely are double insulated except for high current draw devices.