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Power supply environment and safety hazard of wall socket

Dongyang Exploit Trade Co.,Ltd | Updated: Mar 08, 2018

At the age of electricity, people usually pay attention to the quality and performance with electric equipment itself, but ignored: if the power supply does not meet the requirements, any electrical appliances can exert its optimal performance, even cause fire, equipment damage and personal injury.

Most civilian and commercial electrical equipment comes from ac wall sockets, but if used improperly, the wall socket is not only a power source, but also a source of "electric shock" and fire.


Looking at the history and current situation of wall socket, it will be found that although the socket itself does not involve complex and sophisticated technology, it is not always as easy to use it correctly.


1. Plug/seat detector.


Edison invented the incandescent lamp to bring the world into the electric age, but the wall socket did not coincide with the bulb.

Considering the cost factor, when the electric fan, the toaster, the vacuum cleaner, and the hair dryer appear, they still follow the power supply of the bulb -- the lamp holder.

Although Harvey Hubbell invented the more convenient two-core plug/seat in 1904, the use of a lamp to get electricity has been in use until the 1920s.


Philip f. Labre is said to have been sensitive to an electrical accident at the landlady, and in 1928 he invented a three-core plug with a protective earth line.

It is of great significance to introduce the protection ground line to the safe electricity and electric equipment.


2. Various types of plugs/seats.


History in 80, however, this end of the ac wall socket with the increase of electricity consumption, electricity experience and accident lesson, due to technical, safety, economy and other factors, combined with the geographical, historical and political reasons, such as around the world in the development of civil electrical power supply device, does not use the original socket design and form the different standards, a variety of the wall socket.

The U.S. department of commerce (mofcom) has compiled a list of the world's common power plugs/sockets, and classified them by letter.


Most of these plugs are not compatible with each other, and if you take into account the difference in voltage and power in the same type, there are more.

This is obviously the case: even if the electrical equipment supply voltage is the same, it cannot be used in different areas.

The international electrotechnical commission has issued an international standard for power plugs/seats: IEC 60906-1 for the 250V voltage rating and IEC 60906-2 for 125V voltage levels.


It can be predicted that for a long time, the ac plug/seat will maintain the status quo.

In the absence of uniform standards and the need to address interchangeability, switching adapters becomes an effective approach.

Implement a style that converts a socket to a variety of plugs.

After the adaptor plug is improved, the scope can be wider.


But the problem has not been solved.

Because plug/block interconnection not only solves mechanical connections, but also requires electrical connections to be correct and more important.

Looking at the adapter adaptor, especially with two core access modes, they have solved the mechanical connection problem of different plugs well, but have lost the protection function provided by the protection ground line.

In the 3-core connection mode, the polarity of power supply after switching is also likely to be changed, which will be a hidden trouble for the safety of electricity.


3. Socket connection polarity.


Most electrical appliances do not distinguish between ac and fire lines.

The polarity of two or three-core sockets is considered for safety reasons.

For example, electrical switches are required to be installed on the phase line of the device, and the device will no longer be charged when the switch is disconnected.

If the power plug or socket polarity is reversed, this protection function is lost.


3.1 Chinese standard socket.


China standard wall socket connection mode, for example, in "GB50303-2002 construction quality acceptance of building electrical engineering is mandatory clause, in the specified in the standard 22.1.2: single phase two hole socket, on the right in the face of the socket hole or holes with the phase line connection, or left hole hole connected to the zero line, single phase three hole socket hole connected to the line, right left hole and the zero line connection;

Grounding (PE) wire is connected to the upper hole.

Such wiring is called "left zero right fire".


3.2 compatible socket with Chinese standards.


Belong to the "I" type of Oceania standard socket, socket with China similar appearance, basic compatible with both, but the installation in a different way -- rotated 180 degrees, the protection of ground wire position in lower part, became "left right zero" fire, with the Chinese standard plug connection, the electrical connection in the relationship has not changed, but using different standards of right Angle line plug, may is limited by the space a little trouble.


3.3 switch the reverse polarity of the socket.


The installation direction of the north American ANSI/NEMA standard socket is not limited, and the zero/fire line of the socket is identified by the size of the socket - the line is wider than the wire.

Correspondingly, the plug is also wider than the zero line.

Thus, even if the plug is two cores, it can prevent the plug.

The relevant standards also specify that the zero-line direction of the 20A plug is perpendicular to the direction of the fire line, and the matching socket is a t-shaped socket, which can be compatible with two different plugs.


Because the installation direction is not fixed, the zero line is not fixed in the observer.

When checking the wiring, follow the following: start from the protection ground, turn clockwise, then "zero line" and "fire line".


When you compare the Chinese (Australian) socket and the north American socket, you will find that the protection of the ground is the opposite.

When connecting different types of plugs through adapter adapters, the "zero/fire" position will be switched, and the electrical switch will be disconnected from the fire line, which may lead to safety hazards.

In other words, the conversion adapter solves the mechanical connection problem of different standard plugs/sockets, but does not solve the polarity problem of electrical connection.

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