Three phase = line voltage 380 Volts, Single phase = phase voltage 220 Volts
The article is addressed to novice electricians. I, too, was once a beginner, and I am always happy to share knowledge and raise the professional level of my readers.
So, why do some electrical panels receive a voltage of 380 V, and some - 220? Why do some consumers have three-phase voltage, while others have single-phase? There was a time when I asked myself these questions and looked for answers to them. Now I’ll tell you in a popular way, without the formulas and diagrams that textbooks abound.
Very briefly, for those who will not read further: the voltage of 380 V is called linear and operates in a three-phase network between any of the three phases. The 220 V voltage is called phase and operates between any of the three phases and neutral (zero).
In other words. If one phase approaches the consumer, then the consumer is called single-phase, and its supply voltage will be 220 V (phase). If they talk about three-phase voltage, then we are always talking about a voltage of 380 V (linear). Who cares? More details below.
How are three phases different from one?
In both types of power there is a working neutral conductor (ZERO). I talked in detail about protective grounding here; it is a broad topic. In relation to zero in all three phases - the voltage is 220 Volts. But in relation to these three phases to each other, they have 380 Volts.
Voltages in a three-phase system
This happens because the voltages (with active load, and current) on the three phase wires differ by a third of the cycle, i.e. at 120°.
You can read more in the electrical engineering textbook - about voltage and current in a three-phase network, and also see vector diagrams.
It turns out that if we have three-phase voltage, then we have three phase voltages of 220 V each. And single-phase consumers (and there are almost 100% of them in our homes) can be connected to any phase and zero. You just need to do this in such a way that the consumption in each phase is approximately the same, otherwise phase imbalance is possible.
Read more about phase imbalance and what causes it - here.
And it is best to protect yourself from phase imbalance using a voltage relay, for example Barrier or FiF EuroAutomatika.
In addition, it will be difficult for the overly loaded phase and it will be offensive that others are “resting”)
Re-grounding the neutral wire
Re-grounding of the neutral conductor is protection installed at the intervals specified by the rules of the Electrical Installation Code along the entire length of the neutral. The task of re-grounding includes reducing the voltage in the neutral wire and electrical appliances that have been grounded relative to the ground. This property is useful as protection against a break in the neutral wire and in the event of a breakdown of electrical voltage on the housing of electrical devices.
When creating protection in the electrical network, try to select the neutral and protective conductors in such a way that in the event of a short circuit to the metal body of the equipment, a short circuit in the network or melting of the fuses occurs. Usually, when a circuit breaker is installed, this factor causes it to trip.
Important! If a short circuit occurs in a neutralized electrical circuit, the resulting voltage must be three times higher than the rated current.
The neutral must be continuous from each electrical installation housing to the neutral conductors of the electricity sources.
Advantages and disadvantages
Both power systems have their pros and cons, which change places or become insignificant when the power passes the 10 kW threshold. I'll try to list.
Single-phase network 220 V, advantages
- Simplicity
- Cheapness
- Below dangerous voltage
Single-phase network 220 V, cons
- Limited consumer power
Three-phase network 380 V, advantages
- Power is limited only by wire cross-section
- Savings with three-phase consumption
- Power supply for industrial equipment
- Possibility of switching a single-phase load to a “good” phase in case of deterioration in quality or power failure
Three-phase network 380 V, cons
- More expensive equipment
- More dangerous voltage
- Limits the maximum power of single-phase loads
What is the danger of damaging the neutral wire?
Overheating of the neutral wires due to poor contact.
Zero is damaged due to mechanical stress, short circuits, poor-quality connections or as a result of old wiring. Neutral break:
- PEN conductor in the power cable - there is only one ground loop left, which is not visually noticeable;
- combustion of a conductor in the switchboard - phase conductors become distorted, the voltage increases to 380 V;
- there is a break in the apartment panel - the second phase remains in the sockets, household appliances are not powered from them.
When is it 380 and when is it 220?
So why do we have a voltage of 220 V in our apartments and not 380? The fact is that, as a rule, consumers with a power of less than 10 kW are connected to one phase. This means that one phase and a neutral (zero) conductor are introduced into the house. This is exactly what happens in 99% of apartments and houses.
Single-phase electrical panel in the house. The right machine is introductory, then through the rooms. Who can find mistakes in the photo? Although, this shield is one big mistake...
However, if you plan to consume power more than 10 kW, then a three-phase input is better. And if you have equipment with three-phase power supply (containing three-phase motors), then I strongly recommend introducing a three-phase input into the house with a linear voltage of 380 V. This will save on wire cross-section, on safety, and on electricity.
Three-phase input. Input machine for 100 A, then - to a three-phase direct connection meter Mercury 230.
Despite the fact that there are ways to connect a three-phase load to a single-phase network, such modifications sharply reduce the efficiency of motors, and sometimes, all other things being equal, you can pay 2 times more for 220 V than for 380.
Single-phase voltage is used in the private sector, where power consumption, as a rule, does not exceed 10 kW. In this case, a cable with wires with a cross section of 4-6 mm² is used at the input. The current consumption is limited by the input circuit breaker, the rated protection current of which is no more than 40 A.
I already wrote about choosing a circuit breaker here. And about the choice of wire cross-section - here. There are also heated discussions of issues.
But if the consumer’s power is 15 kW or higher, then three-phase power must be used. Even if there are no three-phase consumers in this building, for example, electric motors. In this case, the power is divided into phases, and the electrical equipment (input cable, switching) does not bear the same load as if the same power was taken from one phase.
An example of a three-phase electrical panel. Consumers are both three-phase and single-phase.
For example, 15 kW is about 70A for one phase; you need a copper wire with a cross-section of at least 10 mm². The cost of a cable with such cores will be significant. But I have never seen single-phase (single-pole) circuit breakers with a current greater than 63 A on a DIN rail.
Electrician's recommendations
For hidden wiring, built-in electrical panels are chosen, and exposed wires are connected in overhead distribution panels. The shield body is placed so that it can be easily reached.
Electricians advise observing the following conditions:
- horizontal sections of wires from the panel to the sockets are made at a height of 2.5 m from the floor;
- wiring in the walls is placed vertically or horizontally; it is prohibited to install it along an oblique line;
- connect the wires with adapters in installation boxes;
- the underground connection to the power pole is made with a single piece of wire without connections;
- Do not connect the switch to the neutral wire;
- When laying on wooden walls, insulating hoses with asbestos linings are used.
The distribution housing is selected according to the type of room, taking into account the characteristics of the microclimate - in aggressive environments, boxes with maximum protection from direct water jets and dust are used.
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And at the input (in front of the counter) there are approximately the following “boxes”:
Three-phase input. Introductory machine in front of the counter.
A significant disadvantage of a three-phase input (noted above) is the limitation on the power of single-phase loads. For example, the allocated power of three-phase voltage is 15 kW. This means that for each phase - a maximum of 5 kW. This means that the maximum current in each phase is no more than 22 A (practically 25). And you have to spin, distributing the load.
I hope it is now clear what three-phase voltage 380 V and single-phase voltage 220 V are?
Star and Delta circuits in a three-phase network
There are various variations for connecting a load with an operating voltage of 220 and 380 Volts to a three-phase network. These patterns are called “Star” and “Triangle”.
When the load is designed for a voltage of 220V, it is connected to a three-phase network according to the “Star” circuit , that is, to phase voltage. In this case, all load groups are distributed so that the powers in the phases are approximately equal. The zeros of all groups are connected together and connected to the neutral wire of the three-phase input.
All our apartments and houses with single-phase input are connected to Zvezda; another example is the connection of heating elements in powerful heaters and convection ovens.
When the load has a voltage of 380V, it is switched on according to the “Triangle” circuit, that is, to linear voltage. This phase distribution is most typical for electric motors and other loads where all three parts of the load belong to a single device.
Where does the voltage come from?
To supply electricity to an outlet, it must be generated somehow. To generate electricity, technologies from the late 19th century are still mostly used - electromagnetic induction, which converts mechanical energy into electrical energy. In other words, generators. The difference between generators is only in how mechanical energy is supplied. Previously, these were bulky steam engines. Over time, hydraulic turbines for running water (hydroelectric power stations), internal combustion engines, and nuclear reactors were added.
The operating principle of the generator is based on magnetic induction. The rotational movement of the generator is converted into electric current. That is, we can say that a generator is the same electric motor, but of reverse action. If voltage is applied to the electric motor, it will begin to rotate. The generator works in reverse. The rotational movement of the generator shaft is converted into electric current. Therefore, in order to rotate the generator shaft, we will need some kind of external energy. It could be steam that spins the turbine, which in turn spins the generator shaft
Operating principle of thermal power plants
or it can be the force of the water flow, which, with the help of a hydraulic turbine, spins the generator shaft, and it, in turn, also generates electric current
Operating principle of hydroelectric power station
Well, or it could even be a windmill
Wind power plant
In short, the principle is the same everywhere.
By the way, a nuclear reactor is not capable of generating energy on its own. In fact, a nuclear power plant is the same primitive steam boiler, where the working fluid is ordinary steam. Yes, today there are other ways to generate electricity, such as the same solar cells, beta-galvanic and isotope nuclear batteries, “mythical” tokomaks. However, the above-mentioned “high-tech” has significant limitations - the prohibitive cost of materials, installation and setup, dimensions and low efficiency. Therefore, it is not worth seriously considering all this as a full-fledged high-power power plant (at least in the next couple of decades).
Power distribution system
Initially, the voltage is always three-phase. By “initially” I mean a generator at a power plant (thermal, gas, nuclear), from which a voltage of many thousands of volts is supplied to step-down transformers, which form several voltage stages. The last transformer lowers the voltage to a level of 0.4 kV and supplies it to end consumers - you and me, apartment buildings and the private residential sector.
Large enterprises with power consumption of more than 100 kW usually have their own 10/0.4 kV substations.
Three-phase power supply – stages from generator to consumer
The figure shows in a simplified way how from generator G a voltage (everywhere we are talking about three-phase) 110 kV (can be 220 kV, 330 kV or another) is supplied to the first transformer substation TP1, which lowers the voltage for the first time to 10 kV. One such transformer substation is installed to power a city or region and can have a capacity of the order of a few to hundreds of megawatts (MW).
Next, the voltage is supplied to the second stage transformer TP2, at the output of which the end-user voltage is 0.4 kV (380V). The power of transformers TP2 is from hundreds to thousands of kW. From TP2, voltage is supplied to us - to several apartment buildings, to the private sector, etc.
Such voltage level conversion stages are necessary in order to reduce losses during the transportation of electricity. Read more about losses in cable lines in my other article.
The circuit is simplified, there may be several steps, the voltage and power may be different, but the essence does not change. There is only one final voltage of consumers - 380 V.
Finally, a few more photos with comments.
Electrical panel with three-phase input, but all consumers are single-phase.
Three-phase input. Switch to a smaller cross-section of wires to connect them to the meter.
Three phase = line voltage 380 Volts, Single phase = phase voltage 220 Volts
The article is addressed to novice electricians. I, too, was once a beginner, and I am always happy to share knowledge and raise the professional level of my readers.
So, why do some electrical panels receive a voltage of 380 V, and some - 220? Why do some consumers have three-phase voltage, while others have single-phase? There was a time when I asked myself these questions and looked for answers to them. Now I’ll tell you in a popular way, without the formulas and diagrams that textbooks abound.
Very briefly, for those who will not read further: the voltage of 380 V is called linear and operates in a three-phase network between any of the three phases. The 220 V voltage is called phase and operates between any of the three phases and neutral (zero).
In other words. If one phase approaches the consumer, then the consumer is called single-phase, and its supply voltage will be 220 V (phase). If they talk about three-phase voltage, then we are always talking about a voltage of 380 V (linear). Who cares? More details below.
Registration of permission
At the first stages, the following will need to be agreed upon with power engineers:
- permissible power;
- number of phases;
- type of input line and energy meter;
- metering tariff (depending on the meter);
- Based on the quality of the insulation of the house electrical network, a connection diagram is agreed upon (if the wiring is old, then permission will not be given);
- How reliable is the grounding of the electrical wiring in the house?
Important! Independent connection to power lines is prohibited by law. The electrical connection must be made by highly qualified specialists.
Next, measurements are made from a private house to 380V networks; if this distance exceeds 300 meters in the city or 500 meters outside the city, then you will have to pay for the installation of an additional support pole.
The next step will be to discuss the required power:
- no more than 16 kW;
- from 16 to 50 kW;
- from 50 to 160 kW.
Typically, up to 50 kW is allowed; if a larger figure is needed, an additional transformer will be required, which is very expensive and difficult.
Further list of required documents:
- a copy of your passport (required to draw up an agreement for connecting electricity);
- application for connection to electrical lines;
- identification code;
- site plan;
- a plan for the placement of the power line pole closest to the site;
- title document for a residential (non-residential) property;
- approved complete residential plan;
- information about the required power and a list of all electrical appliances used in the house (or the estimated number of devices if the house has not yet been put into operation).
The application for electrical wiring to the house should be written in two copies, in order to keep one (with the visa of the specialist accepting the document).
How are three phases different from one?
In both types of power there is a working neutral conductor (ZERO). I talked in detail about protective grounding here; it is a broad topic. In relation to zero in all three phases - the voltage is 220 Volts. But in relation to these three phases to each other, they have 380 Volts.
Voltages in a three-phase system
This happens because the voltages (with active load, and current) on the three phase wires differ by a third of the cycle, i.e. at 120°.
You can read more in the electrical engineering textbook - about voltage and current in a three-phase network, and also see vector diagrams.
It turns out that if we have three-phase voltage, then we have three phase voltages of 220 V each. And single-phase consumers (and there are almost 100% of them in our homes) can be connected to any phase and zero. You just need to do this in such a way that the consumption in each phase is approximately the same, otherwise phase imbalance is possible.
Read more about phase imbalance and what causes it - here.
And it is best to protect yourself from phase imbalance using a voltage relay, for example Barrier or FiF EuroAutomatika.
In addition, it will be difficult for the overly loaded phase and it will be offensive that others are “resting”)
Electrical panel assembly
The input switch and meter are sealed by power grid workers, so they are located at the beginning of the switchboard so as to provide this opportunity.
Step by step assembly:
- fastening of automatic devices and RCDs on the rail according to the drawn up diagram;
- connecting elements to the input switch using a comb;
- connecting phase wires with wires with lugs;
- installation and connection of the zero bus;
- checking (tightening) joints with a screwdriver;
- turning on the power, checking the operation of the machines;
- determining network parameters using a multimeter.
Before starting to operate the 380V network, make sure that all elements of the internal system (sockets, sockets, switches) are installed and connected.
When is it 380 and when is it 220?
So why do we have a voltage of 220 V in our apartments and not 380? The fact is that, as a rule, consumers with a power of less than 10 kW are connected to one phase. This means that one phase and a neutral (zero) conductor are introduced into the house. This is exactly what happens in 99% of apartments and houses.
Single-phase electrical panel in the house. The right machine is introductory, then through the rooms. Who can find mistakes in the photo? Although, this shield is one big mistake...
However, if you plan to consume power more than 10 kW, then a three-phase input is better. And if you have equipment with three-phase power supply (containing three-phase motors), then I strongly recommend introducing a three-phase input into the house with a linear voltage of 380 V. This will save on wire cross-section, on safety, and on electricity.
Three-phase input. Input machine for 100 A, then - to a three-phase direct connection meter Mercury 230.
Despite the fact that there are ways to connect a three-phase load to a single-phase network, such modifications sharply reduce the efficiency of motors, and sometimes, all other things being equal, you can pay 2 times more for 220 V than for 380.
Single-phase voltage is used in the private sector, where power consumption, as a rule, does not exceed 10 kW. In this case, a cable with wires with a cross section of 4-6 mm² is used at the input. The current consumption is limited by the input circuit breaker, the rated protection current of which is no more than 40 A.
I already wrote about choosing a circuit breaker here. And about the choice of wire cross-section - here. There are also heated discussions of issues.
But if the consumer’s power is 15 kW or higher, then three-phase power must be used. Even if there are no three-phase consumers in this building, for example, electric motors. In this case, the power is divided into phases, and the electrical equipment (input cable, switching) does not bear the same load as if the same power was taken from one phase.
An example of a three-phase electrical panel. Consumers are both three-phase and single-phase.
For example, 15 kW is about 70A for one phase; you need a copper wire with a cross-section of at least 10 mm². The cost of a cable with such cores will be significant. But I have never seen single-phase (single-pole) circuit breakers with a current greater than 63 A on a DIN rail.
Therefore, in offices, stores, and especially in enterprises, only three-phase power is used. And, accordingly, three-phase meters, which come in direct connection and transformer connection (with current transformers).
Installation cost
Installing electrical wiring is an important issue. A correctly drawn up house wiring plan is a guarantee of safety. If a person has never encountered such a problem in his practice, then it is better to seek help from trusted specialists.
To do this, you should familiarize yourself with the approximate prices for this type class=”aligncenter” width=”607″ height=”477″[/img]
Initially, you should be prepared for the fact that installing electrical wiring in a house will cost much more than in an apartment.
What's new in the VK SamElectric.ru group?
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And at the input (in front of the counter) there are approximately the following “boxes”:
Three-phase input. Introductory machine in front of the counter.
A significant disadvantage of a three-phase input (noted above) is the limitation on the power of single-phase loads. For example, the allocated power of three-phase voltage is 15 kW. This means that for each phase - a maximum of 5 kW. This means that the maximum current in each phase is no more than 22 A (practically 25). And you have to spin, distributing the load.
I hope it is now clear what three-phase voltage 380 V and single-phase voltage 220 V are?
Star and Delta circuits in a three-phase network
There are various variations for connecting a load with an operating voltage of 220 and 380 Volts to a three-phase network. These patterns are called “Star” and “Triangle”.
When the load is designed for a voltage of 220V, it is connected to a three-phase network according to the “Star” circuit , that is, to phase voltage. In this case, all load groups are distributed so that the powers in the phases are approximately equal. The zeros of all groups are connected together and connected to the neutral wire of the three-phase input.
All our apartments and houses with single-phase input are connected to Zvezda; another example is the connection of heating elements in powerful heaters and convection ovens.
When the load has a voltage of 380V, it is switched on according to the “Triangle” circuit, that is, to linear voltage. This phase distribution is most typical for electric motors and other loads where all three parts of the load belong to a single device.
Power distribution system
Initially, the voltage is always three-phase. By “initially” I mean a generator at a power plant (thermal, gas, nuclear), from which a voltage of many thousands of volts is supplied to step-down transformers, which form several voltage stages. The last transformer lowers the voltage to a level of 0.4 kV and supplies it to end consumers - you and me, apartment buildings and the private residential sector.
Large enterprises with power consumption of more than 100 kW usually have their own 10/0.4 kV substations.
Three-phase power supply – stages from generator to consumer
The figure shows in a simplified way how from generator G a voltage (everywhere we are talking about three-phase) 110 kV (can be 220 kV, 330 kV or another) is supplied to the first transformer substation TP1, which lowers the voltage for the first time to 10 kV. One such transformer substation is installed to power a city or region and can have a capacity of the order of a few to hundreds of megawatts (MW).
Next, the voltage is supplied to the second stage transformer TP2, at the output of which the end-user voltage is 0.4 kV (380V). The power of transformers TP2 is from hundreds to thousands of kW. From TP2, voltage is supplied to us - to several apartment buildings, to the private sector, etc.
Such voltage level conversion stages are necessary in order to reduce losses during the transportation of electricity. Read more about losses in cable lines in my other article.
The circuit is simplified, there may be several steps, the voltage and power may be different, but the essence does not change. There is only one final voltage of consumers - 380 V.
Finally, a few more photos with comments.
Electrical panel with three-phase input, but all consumers are single-phase.
Three-phase input. Switch to a smaller cross-section of wires to connect them to the meter.
In the electrical equipment of residential apartment buildings, as well as in the private sector, three-phase and single-phase networks are used. Initially, the electrical network comes from a power plant with three phases, and most often a three-phase power network is connected to residential buildings. Further it has branches into separate phases. This method is used to create the most efficient transmission of electric current from a power plant to its destination, as well as to reduce losses during transportation.
Photo
Finally, a few more photos with comments.
Electrical panel with three-phase input, but all consumers are single-phase.
Three-phase input. Switch to a smaller cross-section of wires to connect them to the meter.
Friends, that’s all for today, good luck to everyone!
I look forward to your feedback and questions in the comments!
