Faults in outlets: what causes the appearance and how to eliminate

The way to connect electrical appliances to the power supply using a plug and socket exists for a very long time and works reliably. In most cases, such compounds have been functioning properly for decades, without requiring special repairs and maintenance.

However, each landlord can cite facts from his life when malfunctions occurred in these simple-looking devices. But often the causes of their occurrence were not analyzed and ... repeated, oddly enough.

How does an electrical outlet work?

A very simple at first glance question, many people, even with the education of electricians, do not pay enough attention.

Failures of sockets by types of destruction arise due to:

• mechanical breakdowns;

• excess electrical loads.

In the first case, due to the application of excessive force, the threads of the connecting parts are torn off or the insulating bodies and covers are broken. Insufficient fastening force of the parts leads to the subsequent tearing out of the socket under voltage from the junction box or burning or disconnecting the wires.

Electrical failures usually occur gradually, but manifest quickly and seriously.

The main purpose of the plug and socket is to reliably transfer the rated load current to the connected electrical appliance. This determines not a simple mechanical imposition of one live part on another, but the creation of a tight clamp, eliminating the voltage loss in the contact connection by creating a minimum electrical resistance in all places of connection.

The Joule-Lenz law, which explains the process of the release of thermal energy Q inside the conductor during the flow of electric current through it, allows us to analyze the operation of the contact connection between the plug and the outlet.

Q = I²∙ R ∙ t.

The above formula shows that to reduce the heating of the contacts, it is necessary to limit one of the components:

• flowing load current I;

• electrical resistance of contacts R;

• operating time t.

Let's say we need to turn on the vacuum cleaner for 10 minutes to clean the room. Faster to complete this work simply does not work. At the same time, it makes no sense to delay the cleaning due to excessive energy consumption. It turns out that it is possible to operate with the current flowing through the contacts, but not always.

It is not always possible to limit the load current. The power of the vacuum cleaner, for example, 1000 watts during the cleaning process remains virtually unchanged.

It remains to consider the effect of electrical resistance on heating. And here, as a rule, everything is left to chance or the experience of an electrician invited for installation.

Two electrical standard

Existing household appliances are created by various manufacturers to connect voltage to a network in a strictly defined way. Moreover, in our apartments there are always devices released a couple of decades ago and more recently.

The photo shows two types of the most common forks. Compare them visually and with a measuring tool.

The left design is made with the thickness of the electrodes under the old standard with a diameter of 4 mm, and the right - 4.8. The micrometer shows that these dimensions have a little manufacturing error.

In both cases, brass is selected as the metal for the contact pins. This means that the specific resistance of the electrodes is the same, and different conditions for the passage of current are created only due to different diameters of the metal.

Thickened 4.8 mm electrodes are designed for reliable passage of loads up to 16 amperes, which are characteristic of modern household appliances with a power of up to 16x220 = 3.5 kW.On the plugs and sockets of the old model, you can find the inscriptions of the permissible values ​​of currents and voltage of 6 A, 250 V.

The comparison photo shows two types of parallel-connected sockets with covers removed for clarity: the old and the new standards.

It is difficult to visually notice that the nests are designed for plugs with different diameters of the electrodes. Quite simply, you can plug the plug of an old or new design into the sockets of any outlet. The distance between the centers of all contacts, maintained at 19 mm, allows this to be done, and the deviation of the diameters at first glance does not affect much. A slight difference will show only the applied mechanical force.

However, each pair of contacts was created by the manufacturer for a specific connection. For this, the efforts of the springs of the contact pads and their hole diameters were selected.

What happens when someone else's plug is plugged in

1. Thicker electrodes push apart the brass petals of the socket receptacle more and stretch the spring more powerfully. For their installation, often the diameter of the hole in the socket of the dielectric casing is not enough and its “home craftsmen” are additionally expanded with a drill or a knife blade.

If the load of the appliance is small and the plug is installed for long-term operation, then this is not critical. When the devices are connected to the outlet quite often, and current loads cause significant contact heating, then it is better to avoid such situations: spring contacts quickly lose their elasticity.

To connect electrical appliances of small power, equipped with euro plugs, special plug-adapters with a diameter of contact leads of 4 mm are produced to old sockets. On the reverse side they have enlarged sockets with contact springs.

The disadvantage of this design is the weak contact fastening made by unstable riveting at the junction of the plates to the electrode. Such an adapter works reasonably well when you connect a computer or laptop. But if a perforator or vacuum cleaner with a power of 1 kW is fed through it, then excessive heating of the structure begins.

2. Thin electrodes of the old standard in the expanded sockets will also work. On this principle, plugs of electric razors, low-power battery chargers, mobile phones and similar devices are made. Their low load does not cause contact heating.

But, it is only necessary to increase the power consumption, as the reduced surface of the contact joint and the insufficient compression of the parts create increased resistance to electrical transition and, as a result, unacceptable heating of the structure.

A similar case of an unclenched terminal socket and the consequences of a bad clamp is shown in the photo.

High temperature burned the insulation layer, and this violation can lead to fire or short circuit.

Thus, a combination of plugs and sockets of different standards with a flow of loads of several tens of watts is quite acceptable. But, with an increase in electricity consumption even up to currents recommended by the manufacturer, such combinations should be avoided due to the design features of the parts.

Features of the operation of sockets and plugs of the Euro standard

The most widespread in the Russian market are Schuko contact joints, equipped with a pair of grounding brackets on a socket and contact pads on a plug.

When they are installed without connecting to a PE conductor, the protection of non-conductive parts from an emergency occurrence of potential on the device’s body and the accumulation of static electricity are not performed.

Installing the plug and removing it requires some effort. This can be a prerequisite for the violation of the mechanical strength of the structure and requires careful handling.

If a socket is used that is not deepened, as on the standard model, then the plug does not fully fit into it.This creates the possibility of touching bare parts of live parts or causing a short circuit.

Typical mistakes by unskilled electricians

Incorrect wiring or wire selection

In old houses still working out its resource aluminum wiring, called "noodles" on the slang of electricians. It has a fairly low mechanical strength and requires careful handling. The soft core is easily cut by the blade of the knife and is deformed from a slight compression by pliers, and with several bends in one place it can break off.

Such places are not always noticeable during installation and after commissioning do not create malfunctions. But, when loads of even nominal values ​​flow through them due to a small decrease in the cross-sectional area of ​​the conductor, local heating begins to appear, which eventually increases microcracks and destroys the metal.

Excessive wire temperature is transmitted to the plug and socket. Their contacts begin to oxidize and darken, it is worse to conduct current, which further worsens the operating conditions of the entire structure.

When connecting multicore copper wires to the socket contacts, it is necessary to twist them so that the entire bundle is fully involved in the current transfer. Cutting of individual veins, and, therefore, a decrease in their number is unacceptable.

Individual electricians cut wires to connect outlets without creating a margin in length. This makes it very difficult in the future to repair and replace defective parts.

Violations of the rules for tightening screws

One of the common mistakes is the installation of parts with contaminated or oxidized surfaces. A similar layer already has a high electrical resistance and will cause heating under heavy loads. To clean the contact surface of the wire, the platforms of the plug and the socket is quite simple even with a screwdriver.

When tightening the screws, the tightening force should be taken into account and the wires should not be pinched excessively. Otherwise, their metal is easily compressed, loses its shape and reduces its cross section. Separate “masters” tighten the screws with screwdrivers with wide handles in all their heroic power.

At the same time, a weakened force also disrupts electrical contact.

Sometimes the clamping screw can be long and rest against the back of any stopper that prevents the normal clamping of the wire in the terminal. One possible similar case is shown in the picture.

When tightening the screw, make sure that the force that pushes the metal core with the upper washer to the contact pad does not squeeze the wire out of the connection, and when using the ring, it does not push it apart, but compresses it.

Checking the quality of connecting the wire by pulling it by hand is never superfluous and helps to detect weak fastening.

For individual designs of sockets and plugs, the threaded connection of the mounting screw and nut is created as an additional current path. In this case, their working surfaces must be kept clean, without any signs of corrosion.

If a worn thread or signs of oxidation are found on a nut or screw, then do not try to repair it. It is much easier to replace both connected parts with new and serviceable ones.

Recommendations for safe outlet repair

According to the current rules for the operation of electrical installations, any work with electrical wiring, even when the voltage is off, must be performed by trained electrical personnel.

However, on the Internet there are many "tips" to violate these laws and independently, on the basis of the recommendations of an article pursuing primarily commercial goals, at your own risk and risk, try to eliminate the malfunction.

Decide what to do in this case yourself, but keep in mind that the consequences of errors when turned on under load can be very serious, and site owners usually do not bear responsibility for their advice.

When replacing faulty sockets with new ones, try to install those models that use springs not in the form of common ordinary staples, but in the form of cylinders, as shown in the photo.

Such designs create the most dense squeeze of contact joints and have proven themselves during long-term operation.