Voltage Regulation of Transformer

What is Voltage Regulation in a Transformer?

Define Voltage Regulation of Transformer

Let's now understand what the voltage regulation means for an Electrical Transformer. The electrical voltage regulation of a transformer is the percentage change of the electrical voltage, specifically the secondary voltage of the Electrical Transformer when the transformer is from no load condition to a full load condition while that Electrical Transformer is getting a consistent and constant input voltage.

Let’s explain what this percentage change of electrical voltage means, when the Electrical Transformer is in no load condition then there is no voltage being drawn from the Electrical Transformer but as soon as the transformer is connected to a load then the Transformers start to provides a specific voltage to the load attached and that is called full load condition. 

Now Based on the factors mentioned above this voltage that is being drawn from the Transformer can fluctuate and thus needs proper regulation to deliver a safe and reliable supply of electricity to the electrical load. This is where the Transformer voltage regulation came into play.

For a transformer to be categorised or considered as a good Transformer in terms of voltage regulation it should offer minimum drop in its voltage supply under all types of load condition and it should ensure a stable and reliable output for  all types of electrical loads.

However an electrical transformer can be labelled as a poor voltage regulating transformer, if there is a significant drop in the output voltage of the electrical transformer under extreme load conditions or during extreme environment conditions surrounding the transformer and if the transformer delivers an unstable supply of electricity and offers inefficient performance. 

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Key Factors Affecting Voltage Fluctuations in Transformers

There are four different factors that can influence the voltage requirement for a transformer thus producing a voltage fluctuation even during a normal operating condition. 

• Load variation is the first factor in voltage fluctuation because the entire working of the transformer is to provide the sufficient voltage to the attached electrical load.  so if the load requirement changes frequently then it can easily cause voltage fluctuation.
• Second factor is the quality of the transformer winding. If the transformer winding is not of good quality then it can cause high resistance depending on the operating conditions thus can easily cause voltage fluctuation due to fluctuating resistance of Transformer winding.
• There is a proper part in an Electrical Transformer called tap changer that is used to control the output voltage of the electrical transformer and if that tap changer is not working properly or has improper setting then it can very easily cause voltage fluctuation in the electrical transformer.
• The final factors that influence the voltage fluctuation is the quality distribution system.  The distribution system can produce fluctuating load due to the number of reasons like line losses or damage in the wires or the poor quality materials used in the wires of the distribution system.

Voltage Regulation of Transformer Formula

Why is Voltage Regulation Necessary?

There are a number of reasons why it is important to control the voltage fluctuation through voltage regulation of the transformer.

• The voltage regulation of the transformer ensures that the electrical loads attached with the electrical transformer gets a stable voltage supply. This is highly important for sensitive electrical appliances and machinery that are easily affected by fluctuating load.
• The voltage regulation of Transformer also shows that the overall efficiency of the Electrical Transformer and the electricity distribution system remains high enough to ensure the Transformer compliance with international standards and be cost effective.
• The voltage fluctuation can also damage the electrical equipment and industrial machines attached to the Electrical Transformer. If the fluctuating voltage exceeds the voltage limit of the machinery or even if it is too much for the Transformer itself it can damage any machinery for the transformer itself.
• Voltage regulation of transformers is also highly important as it is a compulsory part of all types of national and international standards that regulate the electrical devices, the electricity distribution system and all types of  electricity generating plants.

Keep reading: What Is An OLTC Transformer and How Does It Work?

Types of Voltage Regulation in Transformers

As voltage can fluctuate in either direction it can fluctuate above the average voltage requirement and it can  fluctuate below the average voltage requirement. Based on that there are three types of voltage regulation in electrical Transformers.

Zero Voltage Regulation of Transformer

The zero voltage regulation of a transformer is the most common and the most basic type of voltage regulation that occurs during the normal operations of electrical. In zero voltage regulation there is basically no voltage fluctuation observed on the Transformer output. This means that the on load voltage of the Electrical Transformer is the same as the off load condition. 

In more simple words  we can say that when there was an electrical load attached to the Electrical Transformer and the Transformer was switched on Load condition there was no significant  increase or decrease in the voltage of the transformer as compared to its load condition. 

This is a perfect condition for the Electrical Transformer because this means that the transformer is working perfectly and maintaining and delivering a stable voltage output. This type of transformer working is very important for sensitive applications where very sensitive electrical equipment is attached to the Electrical Transformer. 

Positive Voltage Regulation

Just like this zero voltage regulation of Transformer the positive voltage regulation of a transformer is also a normal condition but it is not a common condition.  In positive voltage regulation the output voltage of the Electrical Transformer drops slightly when any electrical load is attached to the Transformer as compared to its off Load voltage.

This slight decrease in the Transformer voltage is mostly due to the resistance and power losses of the transformer itself. All types of Electrical Transformer losses are responsible for this light  drop in the voltage of the Electrical Transformer.

Negative Voltage Regulation 

The negative voltage regulation is an unusual event and it does not occur normally but there are certain conditions and scenarios where the Transformer can experience negative voltage regulation. In negative voltage regulation is a case or scenario in which the output voltage of the transformer increases slightly when any external load is applied or attached to the Transformer as compared to the  voltage off Load condition. In simple words, this means that the Electrical Transformer is providing more voltage than the equipment needs.

Get it free: Guide to Tap Changer in Pad Mounted Transformer

Working Mechanism of Voltage Regulation in a Transformer

How Transformer Tap Changers Adjust Voltage Levels

Voltage regulation of transformers is done through a transformer part called tap changer. Tap changer is not just a part, it's a complete mechanism that works to enable the transformer to deliver variable output voltage depending on the load or operating conditions.

The tap changer changes the number of turns of the transformer winding enabling it to deliver variable output voltage from a single winding and single input voltage. The tap changer ensures that the Transformer  delivers variable voltage without compromising its operation.

There are two types of tap changer.

• The on load tap changer
• The off load tap changer

The on load tap changer is a type of tap changer that regulates the voltage output of an Electrical Transformer during its operations. The on load tap changer does not need the electrical transformer to be switched off or cut off from the power distribution system and then change the or regulate the voltage output rather it does it during the transformer operation and as needed by the current loading condition.

However the off load tap changer is a tap changer that can only regulate the Transformer output voltage before it is de-energized. Means that you need to cut off the input supply of the Electrical Transformer and wait till it is completely de-energized and then you can do the adjustment on the tap changer to change the output voltage or to regulate the output voltage of the electrical transformer.

Important here to know that the tap changer does not regulate the Transformer voltage on its own. It works to control or adjust the Transformer winding that in return then regulates or controls the output voltage of the Electrical Transformer. So tap changer working quality depends on the transformer turn ratio and transformer winding quality and reliability.

Learn more: Differences Between NLTC and OLTC Transformers

The Automatic voltage regulators (AVRs)

The automatic Voltage regulator is a part of Transformer voltage regulation systems that in most cases work in combination with the tap changer to enable Transformer automatically and frequently change the Transformer voltage as per the various and fluctuating load requirements. 

One of the main features of the automatic voltage regulator is that it maintains the Transformer output voltage at a given point. It's an electronic device that continuously monitors and calculates the voltage that is delivered by the Transformer and that is needed at the electrical load. Then by comparing both voltages, the device calculates the difference between the provided voltage and the minimum voltage required by the electrical load or by these the device decides whether to send a signal to the tap changer of the Electrical Transformer or not. 

As this device is called automatic voltage regulator means this device work continuously with the Electrical Transformer and continuously monitor the load requirement of the electrical load attached with the transformer and it continuously send signals to the tap changer specially the on load tap changer that can easily change the Transformer output voltage without interrupting or requirement of the energizing of the Electrical Transformer.

The automatic voltage regulator can also work with the off load tap changer because there are certain conditions or scenarios where the voltage is either too much or the requirement of the project needs you to de-energize the Electrical Transformer before changing the voltage output or do the voltage regulation activity on the Transformer. So this way automatic voltage regulators  can work with both on load and off load tap changer.

How to Improve Voltage Regulation in Transformers

There are Several things that you can do to improve the voltage regulation of the transformer.

• First thing is to have quality Transformer parts specially automatic voltage regulating devices, tap charger, transformer winding and other associated sensors. Having quality parts in an electrical transformer ensures that the transformer operations their quality efficiency and reliability remains as per the standards. The quality voltage regulating parts will make sure that the transformer never Fails to respond to fluctuating voltage requirements.
• The proper tap changer setting is highly important for the Electrical Transformer to deliver safe and reliable electrical voltage that meets the demand of ever fluctuating load. Need to make sure that the tap changer is in perfect condition and has the optimal setting to minimise the stress on the electrical transformer.
• Another important thing that you can do to improve the electrical transformer voltage regulation ability is to have a Transformer design that is specifically developed to tackle the voltage fluctuation. There are certain standards that guide the Transformer designer to design the Transformer and its parts in a manner that they offer maximum reliability and offer resistance against fluctuation of load.

Conclusion

Voltage regulation of transformers is a very important feature as it is a vital process for delivery of safe, reliable, stable and efficient electricity to the attached load.  A proper voltage regulation of the Transformer ensures that the electrical equipment attached with the Electrical Transformer will receive stable electricity. The proper voltage regulation of Transformer also ensures that there will be minimum power losses and also ensures power quality, that is why the international standards. Different Transformer parts  like tap changer, automatic voltage regulators and other design features are very important in performing voltage regulation in electrical transformers.

Follow Up

Transformer voltage regulation is a crucial  aspect of  any Electrical Transformer without which any standard Transformer cannot offer normal stable and efficient electricity. We at Daelim Transformer,  offer Transformers  of all types sizes and Power capacity  that can ensure proper and perfect voltage regulation in transformers to their excellent design and build quality.

All our electrical transformers are designed and developed within compliance of international standards including but not limited to ANSI, IEEE, ISO, ASTM. If you have any questions regarding the electrical Transformers or the voltage regulation of electrical Transformers then you can contact us and our team of experts will lead you through the process.