Can transformers of different models be connected in parallel on high-voltage lines?

Transformers of different models can be used in parallel on high-voltage lines.

They can be used in parallel, as long as the primary side input voltage remains stable

They can be used in parallel, but several points need to be taken into consideration: First, whether the high-voltage power supply cable can meet the power requirements. II. Each transformer used in parallel should be equipped with its own protective devices; otherwise, a failure in one of them can easily lead to a complete interruption of power supply. III. When operating in this parallel mode, it is essential to ensure that it is not possible to operate the transformers in a closed-loop configuration on the low-voltage side.

Your 16 kVA unit is likely intended for use as a power supply for transformers and temporary office facilities (it seems too small for normal purposes). If your 200 kVA transformer is connected in parallel to supply the same user, it’s essential to pay attention to the phase sequence – this is the most important factor. Additionally, there should be a sufficient margin in your high-voltage power supply, and this is also something you need to keep in mind.

To meet the conditions for parallel operation of transformers

1. If the high-voltage cable permits it, transformers of the same model with capacities of 160 Kva, 200 Kva, or 250 Kva can be connected in parallel, but care must be taken to ensure that the output voltage levels are identical, meaning the voltage difference on the low-voltage side should not exceed 5%. 2. A 16Kva transformer cannot be connected in parallel with a 200Kva transformer (on the low-voltage side).

When two or more transformers have their primary sides connected to the same power source and their corresponding secondary sides connected together to supply power to the same load, this mode of operation is called parallel operation. Transformers are operated in parallel, which enhances the reliability of power supply. If a transformer fails, it can be disconnected, allowing the remaining transformers to continue supplying power to the load. In cases of excessive load, some secondary loads can also be disconnected, thereby ensuring uninterrupted power supply to the important loads. Transformers are operated in parallel, which can improve their operational efficiency under certain conditions. The efficiency of a transformer varies within a certain range. The transformer achieves its highest efficiency when its fixed losses are equal to its variable losses; at this point, the load on the transformer is approximately 50% of its rated capacity. Both too high and too low loads result in reduced efficiency. Controlling the number of input units can enable the transformer to operate at high efficiency under certain conditions. The transformers are operated in parallel; by supplying power to the load together, this eliminates the drawback associated with individual operation of multiple transformers, where uneven load distribution leads to inconsistent load rates for each transformer. Although parallel operation of transformers has its advantages, not any two transformers can be operated in parallel. Transformers operating in parallel must meet certain conditions, and these conditions are: 1. The connection groups of the transformers must be identical ； 2. The voltage transformation ratios of the transformers should be equal, with the maximum allowable error not exceeding ±0.5% ； 3. The percentage of short-circuit impedance of the transformers should be as equal as possible, with the maximum allowable error not exceeding ±10% ； 4. The capacity ratio of the transformers shall not exceed 3:1. The two transformers mentioned by the poster can supply power to loads independently; they cannot be operated in parallel as the conditions for parallel operation are not met. This post was last edited by duke9894109 on 2009-2-21 12:48.]

1. The wiring groups of the transformers must be identical； 2. The voltage transformation ratios of the transformers should be equal, with the maximum allowable error not exceeding ±0.5% ； 3. The percentage of short-circuit impedance of the transformers should be as equal as possible, with the maximum allowable error not exceeding ±10% ； 4. The capacity ratio of the transformers shall not exceed 3:1.

You are referring to parallel operation, where the high-voltage side is connected to a section of busbar or circuit; this approach is feasible. The issue you mentioned occurs frequently in many rural areas. In that case, it truly is parallel operation, as both the high-voltage and low-voltage sides are connected together, but several conditions must be met. ① Same wiring group ； ② The transformation ratio difference must not exceed ±0.5% ； ③ The short-circuit voltage value must not exceed ±10% ； ④ The capacity ratio of the two transformers should not exceed 3:1. Different wiring configurations result in voltage differences in the secondary windings of parallel transformers. Coupled with the internal resistance of the transformers, this leads to large circulating currents within the secondary side of the transformers, which can cause them to burn out. If the turns ratio of transformers differs, the secondary voltages will vary, and circulating currents will be generated in the secondary windings. These circulating currents not only consume part of the transformer’s capacity but also increase its losses, resulting in a reduced output of energy by the transformer. A large difference in turns ratio can disrupt the normal operation of the transformer. The short-circuit voltage of the transformer is inversely proportional to the load distribution of the tap changer. If the short-circuit voltages differ, the transformer capacity cannot be fully utilized; transformers with lower short-circuit voltages become overloaded, while those with higher short-circuit voltages operate underload. The capacity ratio of transformers should not exceed 3:1, as transformers with different capacities have different short-circuit voltages, resulting in uneven load distribution and inefficient operation ； At the same time, when the mode of operation changes during maintenance or in the event of an accident, transformers with a small capacity will not be able to serve as a backup. Requirements also exist for the fuses on the high-voltage side. The fuse on the primary side of the transformer serves as a backup protection in case of faults in the transformer itself or at the secondary side outlet. According to operational guidelines, for transformers with a capacity of 100 KVA or less, the primary-side fuse can be selected to have a current rating of 2–3 times the rated current; meanwhile, considering the mechanical strength of the fuse, it should generally not be less than 10 A. For transformers with a capacity of 100 KVA or more, the primary-side fuse can be chosen to have a current rating of 1.5–2 times the rated current. Let’s talk about these first; they might not be useful to you

The high-voltage sides can be connected in parallel to the same high-voltage line, but the low-voltage sides cannot be used in parallel; there are specific regulations governing the parallel operation of the high-voltage and low-voltage sides of a transformer.

What the original poster is referring to must be parallel operation! I believe that as long as the voltage levels on the primary side are equal, it is possible to operate in parallel on the high-voltage lines of the same power supply! As for the discussion upstairs on the parallel operation of transformers, moral support is given. But that’s another matter!