For novice 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 needed to avoid "phase imbalance". Specialists strive to achieve a uniform load in the power supply of consumers. To explain this phenomenon clearly, let's take as an example an apartment building where an equal number of apartments are connected 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 and night.
The principle of operation 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, three wires are connected at one "zero" point. The other end of the high-voltage wires is brought out to the terminals named A, B and C.
Connected together ends at the "zero" point are connected to the ground loop in the substation. There is also a division of the high-voltage wire of zero resistance into:
- protective PE conductor (dyed yellow-green);
- working zero (colored in blue).
The power supply system in new buildings works according to the scheme described above. It is referred to as the TN-S system. In the switchboard of the building, electricians supply 3 phases, a PE conductor, as well as a neutral wire.
Most old apartment buildings do not have a PE conductor. The power supply system consists of 4 wires, it is called TN-C. It is outdated and considered insecure. Grounding of the neutral wire in this case is carried out in the switchboard 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 later 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 spread wires along the porches and apartments. Electricity is supplied to consumers using wires connected to one of three phases with a mains voltage of 220 volts. Also, a PE protective wire (only when using the new TN-S system) and a neutral wire are carried into the living space.
When zero-resistance wires are connected to each consumer of electricity, the uneven load on the power grid practically disappears.
Why do I need a protective conductor PE?
Protective wire or PE is needed for additional protection at home. In the event of a short circuit, it diverts current away from the broken wiring, thereby protecting people from electric shock and property from fire.
In such a network, the load is distributed evenly, since each floor of an apartment building is wired in phases.
The electrical system connected to the living quarters is a "star", which repeats all the vector characteristics of the transformer substation.
Such a system is reliable and optimal, but it also has its drawbacks, as malfunctions occur periodically. Most often, power outages are associated with poor quality wires, as well as poor quality connections.
Causes of a break in zero and phases
In case of poor contact of wires and increased loads on the power supply system, the network breaks.
If any of the three conductors that feed the house break, consumers connected to it will not receive electricity. At the same time, other consumers that are connected to the remaining two phases receive electricity in full. The current in the neutral wire is summed up from the remaining phases in working condition, and will be equal to this value.
All breaks in the network are connected with the power outage of apartments from electricity. Such accidents are not capable of damaging electrical appliances. Dangerous situations that threaten a fire in the premises and damage to equipment arise if the connection between the voltage transformer in the substation and the switchboard breaks. This situation occurs due to many factors, but the most likely cause of power outages is the fault of the electric crew.
Causes of a short circuit
A short circuit becomes possible when the current does not pass through "zero" to the ground loop A0, B0 and C0. Instead, the currents move along the outer circuits AB, BC and CA, which are powered by a voltage of 360 volts. Thus, on one apartment shield there may be too little voltage, since the economical tenant turned off all electrical appliances, and on the other, a voltage close to linear - 360 volts is formed. This causes damage to the wires. Devices, in turn, overheat as a result of off-design currents entering them.
To avoid such a situation and protect yourself from a sudden power surge, there are protection 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 the house
To identify a malfunction in the electrical wiring at home, most often they use a budget screwdriver with a light indicator. Such a device works due to the passage of capacitive current inside its case. The inside of such a device is equipped with the following components:
- metal bare tip, which serves to connect it to the phase or neutral conductor;
- resistor that reduces the amplitude of the current passing through the screwdriver to a safe value;
- an indicator light that lights up when current flows throughmetal part of the device. A lit indicator indicates the presence of current in the phase;
- platform, thanks to which the current passes through the human body and reaches the ground potential.
Experienced electricians for troubleshooting purchase more functional devices, for example, a multifunctional 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 comes into contact with the PE and N conductors, the light indicator should not light. If not, then the electrical circuit is faulty.
Causes of zero damage in the circuit
Damage to the neutral conductor usually occurs in places where the connection is poor quality. If the resistance at the junctions is high enough, the wires heat up. From elevated temperatures, the junction is oxidized, as a result of which the resistance increases even more. The wiring is heated to a melting temperature, due to which the problematic junction is completely destroyed.
How to avoid a short circuit?
To ensure a reliable connection of metal wires, it is necessary to increase the contact area. Connections 1 cm long will burn out after a month, if you increase the length of the twist by 2 times, the wiring will last a year, but if you connectwires are twisted so that the contact length is 5 cm, then the conductor will work for many years. To make the house even more secure, wrap the junction with an uninsulated piece of wire.
Modern tools for connecting contacts
The twisting method as a connection between two conductive parts is long out of date, now electricians use splicing tools (PPE). The case of such a product is made in the form of a cap, which winds the wires on top of each other, making the connection very reliable.
Even more convenient to use WAGO terminals. It is enough to insert the ends of the two wires that need to be connected together into special grooves until they click. After that, the connection is quite difficult to disconnect.
