Hey there! As a supplier of oil filled distribution transformers, I often get asked about the parallel operation conditions for these transformers. So, I thought I'd share some insights on this topic in this blog post.
First off, let's understand why we might want to operate oil filled distribution transformers in parallel. Parallel operation can increase the total capacity of the power supply system, improve the reliability of the power supply, and make it easier to manage the load. But for this to work smoothly, there are several important conditions that need to be met.
Voltage Ratio
One of the most crucial conditions is that the voltage ratios of the transformers in parallel should be the same. The voltage ratio is the ratio of the primary voltage to the secondary voltage. If the voltage ratios of two transformers are different, there will be a circulating current between them even when there is no load. This circulating current can cause additional losses, overheating, and even damage to the transformers.
For example, if one transformer has a voltage ratio of 10kV/0.4kV and another has a slightly different ratio, say 10.1kV/0.4kV, there will be a potential difference between their secondary sides. This potential difference will drive a current to flow between the two transformers, which is not ideal. So, when we're setting up parallel operation, we need to make sure that the voltage ratios of all the transformers are as close as possible.
Percentage Impedance
The percentage impedance of the transformers also needs to be similar. The percentage impedance represents the voltage drop in the transformer when it is carrying full - load current. If the percentage impedances of the transformers are different, the transformers will not share the load in proportion to their ratings.
Let's say we have two transformers with different percentage impedances. The transformer with the lower percentage impedance will carry more load than the one with the higher percentage impedance. This can lead to overloading of the transformer with the lower impedance and under - utilization of the other one. To ensure that the load is shared evenly among the transformers, the percentage impedances should be within a certain tolerance range, usually within ± 10% of each other.
Connection Group
The connection group of the transformers must be the same. The connection group indicates how the windings of the transformer are connected (e.g., star - star, star - delta, etc.) and the phase relationship between the primary and secondary voltages. If the connection groups are different, there will be a large phase difference between the secondary voltages of the transformers.
This phase difference will result in a large circulating current, which can be extremely dangerous for the transformers. For instance, if one transformer is connected in a star - star configuration and another in a star - delta configuration, the secondary voltages will have a phase shift. This phase shift will cause a huge current to flow between the transformers, and it can quickly damage the insulation and other components.
Phase Sequence
The phase sequence of the transformers must be identical. Phase sequence refers to the order in which the three phases of the electrical supply reach their maximum values. If the phase sequences of two transformers are different, the voltages of the corresponding phases will be out of phase.
When the phase sequences are mismatched, there will be a large circulating current, similar to the situation when the connection groups are different. This circulating current can cause significant damage to the transformers and disrupt the power supply system. So, before connecting transformers in parallel, we need to carefully check and ensure that the phase sequences are the same.
Same Polarity
The polarity of the transformers must be correct. Polarity refers to the relative direction of the induced voltages in the primary and secondary windings. If the polarities of two transformers are opposite, when they are connected in parallel, a short - circuit will occur.
For example, if the positive terminal of one transformer's secondary winding is connected to the negative terminal of another transformer's secondary winding, a large current will flow through the connection, which can damage the transformers and the associated equipment. So, we need to make sure that the polarities of all the transformers are the same before parallel operation.
Now, let me tell you a bit about the products we offer as an oil filled distribution transformer supplier. We have a wide range of high - quality transformers that can meet different customer needs. For instance, our 30 - 2500kVA/10kV Class I Energy - Efficiency Oil - Immersed Transformer is designed to provide efficient and reliable power supply. It has excellent energy - saving features, which can help you reduce your electricity costs in the long run.
We also have the Single And Three Phase Power Pole Mounted Distribution Transformer. These transformers are suitable for outdoor applications and are easy to install on power poles. They are built to withstand various environmental conditions and provide stable power supply.
Another great product in our lineup is the 3150 - 20000kVA/35kV Oil Immersed Power Transformer. This transformer is designed for high - power applications and can handle large loads with ease.
If you're interested in any of our products or have questions about the parallel operation of oil filled distribution transformers, don't hesitate to get in touch with us. We're here to help you choose the right transformers for your needs and ensure that they are installed and operated correctly. Whether you're looking to expand your power supply capacity or improve the reliability of your system, our team of experts can provide you with professional advice and support.
References
- Electrical Power Systems, by Turan Gonen
- Power System Analysis and Design, by J. Duncan Glover, Mulukutla S. Sarma, and Thomas J. Overbye