Connect with us


How it works: Generator synchronization

Generators need to be synchronized if they are removed from the service and connected back to the power system during certain situations.

How it Works: Generator Synchronization

Have you ever panicked after looking at the clock in your car to see that you’re a whole hour late to work? And after you think up what you’re going to say to your boss, you remember that it was daylight’s saving this weekend and you haven’t changed the time on your car clock yet?

We’ve all been there, and we rely on synchronization a lot more than we might think.

But as much as we rely on it to do things like keep track of time, we also rely on it for processes like generator synchronization. In fact, the synchronization of generators is the reason why we don’t have a power outage at work any time a generator is shut down for repair.

If you don’t know about generator synchronization or how it works, keep reading for the complete breakdown of everything you’ll ever need to know about this vital process that keeps our power running.

Generator Synchronization: How It Works

What is generator synchronization? Generator synchronization must occur to match elements such as voltage, frequency, phase angles or phase sequences, and the waveform of the generator in order to keep the power system running functionally.

When two or more synchronizers are supplying energy to a power source, it is necessary to synchronize the generators. Electrical loads are not always consistent, which means the use of more than one generator is often needed to supply bigger power loads.

Synchronizing, or paralleling, generators match the parameters of one generator to another, allowing them to work together.

Why It’s Important

Since a generator cannot bring energy to a power system unless all of the necessary parameters are matched with that of the network exactly, synchronizing generators is absolutely crucial to any power system.

Commercial power plants prefer using several smaller power supply units instead of a singular large unit. When smaller units are used, more units have to be installed to generate enough power.

This requires generator synchronization, and it must occur every time a new unit is added or turned on. The parallel operation of generators that are smaller in size proves to be much more beneficial for five main reasons.

It’s More Reliable

The likelihood of a generator failing should be accounted for, especially when electricity is depended on for work or everyday life.

Because of this, having several generators instead of just one large unit acts as a fail-safe for any mishaps that could otherwise cause big issues for a large number of people.

It Continues Service

If a generator does fail or needs other maintenance, the presence of other power units allows for the supply load to continue without interruption even when the one unit in need of repair is turned off or removed.

Different Load Requirements Call for Different Units

Energy usage is not consistent all of the time, and sometimes power units are not needed during periods of small load demands.

Since a generator cannot be partially shutdown to account for the light-load demand, it is much smarter and efficient to have one or two generators running at a time. This also allows for more units to be synchronized during heavy-load periods.

It Makes Efficiency Much Higher

In order to get the most use out of a single generator, multiple generators should be used at once at their recommended output capacity, instead of increasing the output capacity on just one unit and potentially damaging it.

This helps with the efficiency of the generators, especially with the changing demands in output during light or heavy load periods.

More Capacity Expansion

The use of many generators means there is room for expansion as the demand for power grows bigger. New generators can simply parallel generator synchronization once they are added to the power plant and allow for more energy output.

What Happens When Generators Are Synchronized?

Generator synchronization is necessary and vital to existing power usage, but there are certain requirements that must be met for it to work. Voltage, frequency, phase angle, and phase sequence are the four main components that must be considered when synchronizing units.

Voltage Magnitude

The Root-mean-square (RMS) of the new generator should be the same as the bus bar or electric grid its being connected to.

The incoming voltage is higher than that of the bus bar or electric grid, a high reactive power will flow from the generator into the grid.

If the incoming voltage is lower than the bus bar (or electric grid) voltage, the incoming generator will actually absorb the high reactive power from the grid.

It is better to have the reactive power be even so that the uniting sources work together instead of overpowering each other.


The incoming generator and bus bar must also have matching frequencies. If the frequencies are not synced, the attempted paralleling will result in high acceleration and deceleration in the prime move that is responsible for increasing its torque.

The inconsistent flow caused by unmatched frequencies will cause the generator to not work as efficiently, if at all.

Phase Angle

The phase angle is a crucial component in generator synchronization that provides a decent amount of the information about a given generator.

The phase angles of the incoming generator voltage and the bus bar voltage must be set at zero. The phase angles of both can be observed by comparing the crossing and peaks of the voltage waveforms.

Phase Sequence

In a three-phase sequence, like such in a generator system, there are three types of voltages that produce the same magnitude, but the frequency of each is differentiated by a 120 degree angle.

The phase sequence of the three phases of the incoming generator must match the phase sequence that belongs to the bus bar it is being connected to.

This is one of the more complicated steps of the synchronization process and problems appear mostly after the initial installation of the generator or after maintenance.

Techniques for Generator Synchronization

There are three main manual techniques for generator synchronization: The Dark Lamp Method, The Two Bright, One Dark Method, and The Three Bright Lamp Method. These methods use actual lamp filaments to show whether or not certain parameters have been synchronized.

Dark Lamp Method

The Three Dark Lamps Method uses the bus bar to synchronize the incoming generator. While this method seems easy, it cannot provide information on generator or bus bar frequency, meaning it’s missing a lot information – or leaving you in the dark – for an informed synchronization.

The Dark Lamp Method is often less expensive to conduct. It is also more easy to determine the correct sequence.

However, this method can be unreliable, because there is plenty of room for error. For instance, the lamp will become dark at half of the usual rate of voltage, which means the synchronizing switch could actually be turned off, even where a phase difference is present.

Since this method relies on the lamps appearing to be “off” or dark, a lamp filament that is burned out could falsely indicate synchronization.

The flicker of the three lamps does not indicate which frequency is higher, meaning there is uncertainty in the aspect of determining frequency.

Two Bright, One Dark Method

The Two Bright, One Dark Method measures frequency of the generator and bus bar, but cannot check the correctness of the phase sequence. So while the frequencies can confidently be matched, the multiple phases of the phase sequences cannot be matched and will likely need repair after installation.

Synchroscope Method

The Synchroscope Method indicates whether the generator frequency is higher or lower than that of the grid frequency. This method accounts for one of the parameters in determining a parallel, but not all of them.

These three methods require manual synchronization that is determined by the presence of lamps. Modern methods automate the process of synchronization and thus are far more reliable than the three methods listed above.

Synchronization Use In the Real World

Unless you work in a power plant, you probably won’t have to synchronize more than the clock in your car with the one on your phone.

But knowing how generator synchronization actually works can give you a better idea of how our electrical systems operate.

So now that you know how this works, go out and remember there is somebody synchronizing generators all over the world so that we can have power without thinking too much about it.

Have any thoughts on this? Let us know down below in the comments or carry the discussion over to our Twitter or Facebook.

Editors’ Recommendations:

Chris has been blogging since the early days of the internet. He primarily focuses on topics related to tech, business, marketing, and pretty much anything else that revolves around tech. When he's not writing, you can find him noodling around on a guitar or cooking up a mean storm for friends and family.

Click to comment

You must be logged in to post a comment Login

Leave a Reply

More in Tech