For beginning electricians, the question often arises: "What is the zero wire in the power supply system at home?" To answer this question, you should know that a neutral wire is necessary to avoid “phase imbalance”. Specialists strive to achieve a uniform load when supplying consumers with electricity. To clearly explain this phenomenon, let’s take an apartment building as an example, where an equal number of apartments connect to one of the three phases. However, uneven consumption in this case still remains. After all, people in each apartment use different electrical appliances at different times of the day or night.
The principle of the neutral wire
Electricity comes to consumers from a voltage transformer, which is able to convert the voltage of an industrial network to 380 volts. The secondary winding of the transformer is connected according to the "star" scheme, that is, the three wires are connected at one point "zero". The second end of the high voltage wires is output to the terminals under the names A, B and C.
The ends connected together at the point “zero” are connected to the ground loop in the substation. There is also a separation of the high-voltage wire of zero resistance into:
- protective PE conductor (painted in yellow-green color);
- working zero (painted in blue).
According to the scheme described above, the power supply system in new buildings works. It is referred to as the TN-S system. In the switchboard of the building, electricians fail 3 phases, a PE conductor, as well as a neutral wire.
Most older apartment buildings lack a PE conductor. The power supply system consists of 4 wires, it is called TN-C. It is outdated and considered unsafe. The grounding of the neutral wire in this case is carried out in the distribution panel of the house.
Phases and zero from the voltage transformer are carried out to residential premises by underground or above-ground high-voltage wires, connecting them in the future to the input shield of the house. Thus, a system of three phases with a voltage of 380/220 volts is formed. From the introductory shield, electricians lay wires along the entrances and apartments. Electricity is supplied to consumers through wires connected to one of the three phases with a network voltage of 220 volts. A PE protective wire (only when using the new TN-S system) and a neutral wire are also carried into the living room.
When wires of zero resistance are routed to each consumer of electricity, the uneven load on the power grid practically disappears.
Why do we need a PE protective conductor?
A protective conductor or PE is necessary for additional protection at home. In the event of a short circuit, it diverts current from the place of destruction of the wiring, thereby protecting people from electric shock, and property from fire.
In such a network, the load is distributed evenly, since on each floor of the apartment building phase wiring is carried out.
The electrical system, connected to the living quarters, is a “star” that repeats all the vector characteristics of a transformer substation.
Such a system is reliable and optimal, but it also has its drawbacks, since malfunctions periodically arise. Most often, interruptions in the supply of electricity are associated with poor quality of wires, as well as with poor-quality connection.
Causes of a break in zero and phases
With poor wire contact and increased loads on the power supply system, the network breaks.
If any of the three conductors supplying the house breaks, consumers connected to it will not receive electricity. At the same time, other consumers who are connected to the remaining two phases receive electricity in full. The neutral wire current is summed from the phases remaining in the working state, and will be equal to this value.
All breaks in the network are connected to disconnecting the power of the apartments from electricity. Such accidents are not able to damage electrical appliances. Dangerous situations that threaten a fire in the room and equipment breakdown occur if the connection between the voltage transformer at the substation and the distribution panel breaks. This situation arises due to many factors, but the most likely cause of power outages occurs due to the error of the electrician team.
Causes of Short Circuit
A short circuit becomes possible when the current does not pass through the "zero" to the ground loop A0, B0 and C0. Instead, currents move along the external circuits of AB, BC and CA, which are powered by a voltage of 360 volts. Thus, on one apartment panel there may be too little voltage, since the economical tenant turned off all electrical appliances, and on the other a voltage is formed, close to linear - 360 volts. This causes damage to the wires. Devices, in turn, overheat as a result of off-currents arriving at them.
To avoid such a situation and protect yourself from a sudden power surge, there are protective devices that are installed inside the apartment shields. They are also placed in the case of expensive electrical appliances to prevent breakdowns, for example, in refrigerators and freezers.
Method for determining zero and phase in a house
To identify a malfunction in the wiring of a house, a budget screwdriver with a light indicator is most often used. Such a device works due to the passage of capacitive current inside its housing. The inside of such a device is equipped with the following components:
- a metal bare tip, which serves to connect it to the phase or neutral conductor;
- a resistor that reduces the amplitude of the current passing through the screwdriver to a safe value;
- indicator light that lights up when current flows through the metal part of the device. A lit indicator indicates the presence of current in the phase;
- platform through which current passes through the human body and reaches the earth's potential.
Experienced electricians will find more functional devices for troubleshooting, for example, a multi-function electronic indicator in the form of a screwdriver, powered by two batteries, thanks to which the device is capable of creating a voltage of 3 volts. In addition to determining the phase, such devices perform other tasks.
If the lamp lights up when the device comes into contact with an electrical contact, then a phase has been detected. When the indicator is in contact with the PE and N conductors, the indicator light should not light. If this is not the case, then the circuitry is faulty.
Causes of Zero Damage in the Circuit
Damage to the neutral conductor usually occurs in those places where the connection is poor. If the resistance at the junction is high enough, the wires are heated. From elevated temperatures, the junction is oxidized, as a result of which the resistance increases even more. The wiring is heated to its melting point, due to which the problematic joint is completely destroyed.
How to avoid short circuit?
To ensure a reliable connection of metal wires, it is necessary to increase the contact area. Connections with a length of 1 cm will be fenced off after a month, if you increase the twist length by 2 times, the wiring will last a year, but if you connect the wires with twist so that the contact length is 5 cm, then the conductor will work for many years. To secure the house even more, it is necessary to wrap the junction with an uninsulated piece of wire.
Modern tools for connecting contacts
The method of twisting as a connection of two conductive parts is long outdated, now electricians use tools for connection (PPE). The case of such a product is made in the form of a cap, which winds the wires onto each other, making the connection very reliable.
WAGO terminals are even more convenient to use . Enough ends of the two wires that must be connected together, insert into special grooves until they click. After this, it is quite difficult to disengage the connection.