How A 3 Phase Power Plant Works


We know how important 3 phase power plants are in keeping electricity available in homes.

We notice them at times and never thought more about their real work besides holding all the wires that run miles to light up an entire country.

How does everything work? Let’s have a tour around the important system called the power distribution grid.


3-Phase Power for Business

Power Engineering.

An overview of the electricity delivery process

Electricity goes through different stages before it reaches its final destination. The entire process goes through the following:

  • 3 phase power plant
  • Transmission substation
  • Distribution grid
  • Distribution bus
  • Regulator bank
  • Taps
  • Homes and businesses

It’s not as complicated as how it looks like from this list. Read on to know more about what happens in each stage.


The 3 phase power plant

Electricity starts at the power plant. It produces three different phases of AC power simultaneously.

If you’re wondering why it needs exactly three phases, it helps to understand first what a single phase power is.



What is a single phase power?

A single phase power is what you’ll find in your house.

When you use an oscilloscope on a normal wall plate outlet at home, you’ll discover its power that looks like a sine wave. This oscillates between -170 volts and 170 volts with a rate of 60 cycles per second.

This oscillating power is more known as AC or alternating current. Power plants produce AC, but they do this in three phases.



Why do power plants use 3 phase power?

A 3 phase power is basically three single phases synchronized and offset by 120 degrees.

It has 3 coils and 3 wires from the generator that sends average power that never goes zero, unlike in a single phase that takes 120 moments per second when it reaches zero.

To understand better without going through technical terms, you can take a look at this graph to see how it looks like.



The fourth wire

Power plants use 3 phase power and you can see it on the first three wires. Where’s fourth one?

The fourth is a neutral or the ground, which is literally the ground you step on. The earth is a good conductor used as a return path for electrons.



How do power plants generate electricity?

Most power plants have a spinning electrical generator. To make this generator spin, it has to use the available energy coming from different sources such as hydroelectric dams, wind turbines, diesel engines, or gas turbines.

The commonly used to spin the generator is a steam turbine. Burning coal, oil or natural gas, and nuclear reactors create the steam.


Transmission substation

The generated three phase power enters the transmission substation. It uses large step-up transformers to increase the voltage for long-distance transmission, typically around 155,000 to 765,000 volts

It also decreases amperage that helps lessen heat loss during the transmission. You’ll often see transmission lines as those huge steel towers.


Distribution grid

From the high-voltage transmission lines, power steps down to the distribution grid. It is also called distribution substation or power substation.

The distribution grid is composed of the following:

  • Transformers to reduce transmission voltages to distribution voltages which are usually less than 10,000 volts.
  • A distribution bus to split the power in different multiple directions.
  • Circuit breakers and switches to disconnect substations from transmission or distribution lines when necessary.


Distribution bus

From the substation’s transformer, power goes in the distribution bus. The bus distributes the power to two separate sets of distribution lines, each with a different voltage.

The smaller transformers in the bus decrease the voltage, usually in 7200 volts, for the first set of lines.

Power leaves through the other set at the high voltage of the main transformer. The high voltages are decreased again through another substation located near towns and neighborhoods.


Regulator bank

Along the lines from substations, you’ll notice regulator banks installed either above or under the ground. These banks regulate the voltage on the line to avoid Undervoltage and overvoltage issues.

Switches are used in regulator banks to disconnect from the lines during maintenance.



From the 3 phase power generated from power plants, electricity is now converted to single phase power with the help of taps.

You’ll typically see three wires on the main road. Taps run one or two of the phases to the side streets.

And finally, your home or business

Before you can turn on the lights at home, the power passes through a set of poles with one phase of power at 7200 volts and a ground wire. Sometimes, it can also have two or three phases depending on the location.

The pole has a transformer drum attached. It reduces the 7200 volts down to 240 volts, the normal household electrical service.

Every pole has a grounding wire stapled in a coil to its base in direct contact with the earth. This wire runs 6 to 10 feet underground.

It also has two insulated wires running from the transformer carrying 120 volts with a 240-volt difference. This makes it possible for homes to use 120-volt and 240-volt appliances.

The power enters the house through a watt-hour meter. This measures your power consumption and tells how much the electrical company should charge you.



But wait, there’s more

The watt-hour meter is where the power starts from at your house. To deliver the power effectively to each power outlet, the house needs fuses and circuit breakers.


A fuse is a safety device designed to overheat and burn out rapidly in case of current overload. It has a thin piece of foil or wire that kills the power to the power right away to avoid overheating.

It is highly recommended to replace the fuse every time it burns out.

Circuit breaker

Another safety device, the circuit breaker lets the power flow through the wire and connects it to the power outlet.

In every circuit breaker panel, there are two primary wires entering the main circuit breaker. This main circuit breaker cuts the power of the whole panel when necessary.



3 phase power isn't only for power plants

Don't you know that machines can also use 3 phase power? Machines running on this kind of power are guaranteed to run more efficiently and longer just like those huge power plants.

If you want to convert your single phase machines to 3 phase power for better power distrubution try, Dyna-Phase rotary converter units provide you the best solution.

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