5 Rules to Consider When Buying a Phase-Shifting Transformer

Jun 24, 2021 | Transformers | 0 comments

In recent times, electric power grids in India have become bigger and complex due to the increasing demands in power supply which complicates the power flow within and between the grids. As a result, the control of power flow has become more important than ever. This is where a Phase-shifting transformer comes to the rescue. Though there are few other control measures, the installation of PST has proven to be more economical and efficient.

Scope of a Phase-shifting transformer


Have you ever thought about how the power generated from a source several miles away reaches your premise?  Well, the generated power from the power generating stations reaches a substation where it is stepped up for high voltage, transmitted through transmission lines, reaches another substation where the voltage is stepped down and is supplied to homes and businesses using low voltage distribution lines.

Say 100MW power is generated in a power station and it is transmitted through two parallel transmission lines carrying 50W each. Now say line 2 is in an overload situation, then the load in line 2 is reduced to 27MW, and the load in line 1 is increased to 73MW. This customized load sharing is done by the phase-shifting transformer or PST.  A phase-shifting transformer also mitigates unwanted power transfer and improves operating performance.

So what exactly is a PST?

A Phase-shifting transformer (PST) is a special type of transformer used to control the flow of power in the electric transmission networks.  PSTs control and perfectly regulate the load sharing in parallel lines independently of the generation.  They are cost-effective means for reliable and efficient power flow management and grid asset management in complex grids.

phase-shifting-transformer-in chennai

How phase-shifting works? 

The Power flow through a line is directly proportional to the sine of the phase angle difference of the voltage between the transmitting and receiving end of the line. So a shift in phase angle in the sending or receiving circuit will change the power flow in the line.

In a PST, there are two transformers – a shunt unit connected in parallel with the line and a series unit connected in series with the line. The shunt unit causes a 90° phase difference and is fed to the series unit, where it adds up the phase-shifted power to the line thus resulting in the desired power flow in the receiving end.

The phase-shifting transformers are extensively used in massive power grids to ensure reliability and stability and allow the increased utilization of renewable energy.    

5 rules to consider when buying a Phase-Shifting Transformer

Are you here because you have a plan of purchasing a phase-shifting transformer? Don’t worry if you have no clue regarding the technical terminologies mentioned above. Leave it to us. This blog post lists out 5 rules that you need to consider before buying a phase-shifting transformer.  Once you check box all these, then you are good to go.

1. Be clear on the objective

First and foremost, it is essential to consider the actual objective of your phase-shifting transformer. This is determined by how and where the transformer will be installed and what is required to serve its purpose.  Having a clear-cut objective will help you quickly sort out the right set of transformers out of which you can pick the best match. When you are not clear of your purpose, you will lose out huge money purchasing the wrong one.

Therefore, Rule 1: Yes, I know what I am looking for and why. (Say Yes or no).

2. Be specific on the type of configuration

There are many types of phase-shifting transformers available out there.

  • Based on no. of cores: Single core PST & Two core PST
  • Based on no. of Tanks: Single tank PST & Two tanks PST
  • Based on regulation/component winding: Direct & Indirect PSTs
  • Based on the output voltage amplitude: Asymmetrical & Symmetrical PSTs.

Each type of PSTs has its characteristics and suits different applications. The indirect configuration offers an easier modular design, but the overall cost is higher than the direct type. The asymmetrical type is relatively simple compared to the symmetrical PST but changes the voltage amplitude.  Therefore, it is crucial to match your requirements with the type of configuration needed.

Rule 2: I know my requirements, and what configuration is needed to fulfill them. (Say Yes or no).

3. Have your phase requirements ready

Do you need a single-phase or three-phase PST?

A single-phase transformer has 2 lines of AC (1 conducting wire and 1 neutral) and a three-phase transformer has 3 lines of AC (three conducting wires and 1 neutral if needed). Three-phase transformers better accommodate loads.  In general, a single-phase transformer is preferred for small operations. If there are more loads for operation, then a three-phase transformer may help to keep up. Again the decision depends on the equipment to which the transformer is connected.

Rule 3: Hope you know what phase you need! Don’t you? (Say Yes or no).

4. Have an idea of the input-output voltage & load phase angle

It is important to keep your voltage requirement in mind before making the purchase. You need to buy a transformer with a voltage rating that is not less than 80% of the voltage requirement of your application. In PSTs, the phase angle plays a significant role. Choosing the transformer with the required load phase angle will determine the extent to which the power flow can be controlled.

Rule 4: What is the input-output voltage you need? Can you answer it? (Say Yes or no).

5. Be aware of the space requirements and noise levels

PSTs are highly specialized pieces of equipment, with more windings and tap changers than traditional power transformers and a large number of connections between the three phases. This implies that they require a lot of space. If you are not sure if the transformer will fit, you can ask the manufacturer if any customization is possible.  Also, ensure if high-quality core materials and precise manufacturing processes are carried out to achieve lower noise levels.

Rule 5: Do you have a lot of space to accommodate PST? (Say Yes or no).


 As you can see, phase-shifting transformers can go a long way in sustaining the power grids by avoiding system overloads and instabilities and also help in the reduction of operating costs. We believe that the above rules will help you choose the right PST for your business. Did you answer ‘yes’ to most questions, then you are good to go. If not, you will have to know your requirements before making a purchase.

If you still feel doubtful, we in EVR power are here to help.  Our well-experienced sales team will assist you in picking the perfect PST that matches your requirements.

 EVR power’s phase-shifting transformers are manufactured exquisitely to avoid system overloads and instabilities, increase the transmission capacity, and protect high-voltage equipment from thermal overload. We do offer other different kinds of transformers such as distribution transformers, Small power transformers, Isolation/Ultra isolation transformers, converter/Inverter transformers, etc.

Do you think you have a point to add up to this list? Feel free to leave a comment below! Have an amazing day!


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