What is a split winding? What are its requirements?

A split winding refers to the division of the low-voltage winding of a transformer into multiple parts that are electrically independent. These divided low-voltage winding sections are each connected to two generators, allowing each generator to operate independently or simultaneously. In the event of a failure in one generator, the other generator can continue to operate normally. Such a winding is known as a dual split winding, where each split winding section has a capacity equal to half of the transformer's total capacity. The split winding can also be arranged in a radial split configuration (low-high-low arrangement).

If the low-voltage winding is split into three parts, with no electrical connections between them, and each part can be connected to a separate generator, it is referred to as a three-split winding. The capacity of each split winding section in this case is one-third of the transformer's total capacity.

The requirements for a split winding are as follows:

a. The various branches of the split winding in an up-transformer must have a sufficiently large total impedance to ensure that a generator failure does not cause another generator to shut down. This high impedance helps limit the short-circuit current from flowing into the other generator.

b. The total impedance between the branches of the split winding and other non-split windings must be balanced.

c.  In a three-phase axial split transformer, each column of the high-voltage winding must be connected in parallel vertically, while a single-phase transformer can have two columns of high-voltage winding connected in parallel. This arrangement ensures that each branch of the split winding can continue to operate if one or two branches are disconnected. Surge arresters are used to protect the operating branches.

d. Branches of split windings with the same rated voltage should be able to operate in parallel.

e. The insulation structure between the various parts of the split winding and other windings must have sufficient electrical strength. This is necessary because a significant induced voltage can occur between adjacent terminals when an impulse voltage acts on the high-voltage winding.

f. Split impedance voltage: For a single-phase dual split winding, the split impedance voltage is four times that of the impedance voltage for a non-split dual winding. In the case of a three-phase axial dual split, the split impedance voltage is approximately 3.5 times that of the impedance voltage for a non-split dual winding. The impedance voltage of a split transformer can be calculated using the impedance voltage calculation method for non-split windings, with the final impedance voltage multiplied by the specified factors.

g.  A split transformer must be able to withstand the mechanical forces generated by short-circuit currents.

LuShan, est. 1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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