Hey there! As a supplier of photovoltaic transformers, I've been getting a lot of questions lately about the requirements for parallel connection of these transformers. So, I thought I'd take a few minutes to share some insights on this topic.
First off, let's talk about why you might want to connect photovoltaic transformers in parallel. In a photovoltaic power generation system, parallel connection of transformers can increase the overall capacity of the system, improve power supply reliability, and optimize the distribution of power. But it's not as simple as just hooking them up together. There are several key requirements that need to be met to ensure a safe and efficient parallel operation.
Voltage Ratio
One of the most important requirements is that the voltage ratios of the transformers to be connected in parallel must be the same. The voltage ratio is the ratio of the primary voltage to the secondary voltage of a transformer. 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 ratio of 10.5kV/0.4kV, when they are connected in parallel, the difference in the secondary voltages will create a loop current. This current will flow continuously through the transformers, increasing the copper losses and reducing the efficiency of the system. So, before connecting transformers in parallel, make sure to check and match their voltage ratios accurately.
Percentage Impedance
The percentage impedance of the transformers also needs to be similar. The percentage impedance represents the internal impedance of a transformer and is expressed as a percentage of the rated voltage. When transformers are connected in parallel, they share the load according to their impedance values. If the impedance values are significantly different, the transformer with the lower impedance will carry a larger proportion of the load, which may lead to overloading of that transformer while the other one is under - utilized.
Ideally, the difference in the percentage impedance of the transformers should be within a certain range, usually not more than ±10%. For instance, if one transformer has a percentage impedance of 4% and another has 6%, the load sharing will be uneven. The transformer with 4% impedance will take on more load, and if the total load is close to the rated capacity of the transformers, the 4% impedance transformer may overheat and fail.
Phase Sequence
The phase sequence of the transformers must be the same. Phase sequence refers to the order in which the voltages of the three - phase system reach their maximum values. In a three - phase power system, there are two possible phase sequences: ABC and ACB. If two transformers with different phase sequences are connected in parallel, a large short - circuit current will flow between them, which can cause serious damage to the transformers and the entire power system.
To ensure the correct phase sequence, proper testing and verification should be carried out before connection. This can be done using phase sequence indicators or other testing equipment. Once the phase sequence is confirmed to be the same for all transformers, they can be safely connected in parallel.
Connection Group
The connection group of the transformers should be identical. The connection group indicates how the windings of the transformer are connected (e.g., star - star, delta - delta, star - delta). Different connection groups will result in different phase relationships between the primary and secondary voltages. If transformers with different connection groups are connected in parallel, there will be a phase difference between their secondary voltages, which will also lead to circulating currents and potential damage.
For example, a transformer with a Yd11 connection group and one with a Yyn0 connection group cannot be connected in parallel directly. The phase difference between their secondary voltages will cause a large current to flow between them. So, it's crucial to select transformers with the same connection group for parallel operation.
Other Considerations
In addition to the above - mentioned electrical requirements, there are also some practical aspects to consider. The physical location of the transformers is important. They should be installed in a well - ventilated area to ensure proper cooling. Overheating can significantly reduce the lifespan of the transformers and affect their performance.
Also, proper protection devices should be installed for each transformer and the parallel - connected system as a whole. These protection devices can include over - current protection, over - voltage protection, and differential protection. They can detect abnormal conditions such as short - circuits or overloads and quickly disconnect the faulty part of the system to prevent further damage.
Now, if you're in the market for high - quality photovoltaic transformers that meet all these requirements for parallel connection, we've got you covered. Our transformers are designed and manufactured with the latest technology and strict quality control measures. We offer a wide range of products to suit different system requirements.
We also provide Integral Unit Substation, Pre - assembled Substation, and Pre - fabricated Cabin Shore Power Supply System to complement your photovoltaic power generation projects.
If you're interested in learning more about our products or have any questions regarding the parallel connection of photovoltaic transformers, don't hesitate to reach out. We're always ready to have a chat and help you find the best solutions for your needs. Whether you're a small - scale solar farm operator or a large - scale power generation company, we can provide you with the right products and technical support.
References
- Electric Power Distribution Handbook by Thomas A. Short
- Transformer Engineering: Design, Technology, and Diagnostics by G. K. Dubey
So, if you're looking for reliable photovoltaic transformers and related substation solutions, give us a shout. Let's work together to build a more efficient and sustainable power generation system!