Transformer installation, in parallel and standalone use.
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The company currently has a 500Kva transformer; it previously had a 250Kva transformer. Now, both transformers need to be installed and used in parallel. All other parameters of the transformers are compatible with each other, but is it acceptable for there to be such a large difference in capacity? The power supply department does not allow it; when connecting to the cabinet, a circuit breaker should be used for interlocking. Is it acceptable to use them without connecting them in parallel?
Why must devices with such small capacity be operated in parallel? The prerequisite for parallel operation is that the capacity, connection method, and connection group number must be identical! Otherwise, the transformer will burn out! You can look up the relevant standards for transformer installation; interlocking can be achieved through appropriate relay protection units.
Conditions for parallel operation of transformers: 1. The transformer connections have the same grouping； 2. The voltage transformation ratios of the transformers should be equal, with the maximum allowable error not exceeding ±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. Once these conditions are met, they can run in parallel.
What I mean is that if there are no two-way single-pole isolators for power distribution, the power supply department does not allow the cabinets to be connected and operated independently at the same time.
Meeting a few necessary conditions for the 3rd floor is sufficient.
The short-circuit percentages for 6# hgchgc 250KVA and 500KVA are different, so they cannot operate in parallel. Is it necessary to run them in parallel?
It’s completely impossible; there’s no need even to think about it. The capacity difference between 500 and 250 is half; using them in parallel will burn out the 250 transformer.
It is best not to use these two transformers in parallel. You can compare the various requirements for parallel operation of transformers by referring to the specifications on the nameplates of the two transformers. Simply in terms of capacity, they are not suitable for parallel operation; if connected in parallel, it will result in a situation where a larger transformer is used to drive a smaller one, causing the smaller transformer to become overloaded.