What is winding deformation?
The definition of winding deformation in the power industry standard DL/T911-2004 "Frequency Response Analysis Method for Power Transformer Winding Deformation" is: the axial or radial dimensional changes that occur in the winding of a power transformer under mechanical or electric force, usually manifested as local twisting, bulging, or displacement of the winding. Transformers may experience winding deformation when subjected to short-circuit current impact or during transportation, which will directly affect the safe operation of the transformer.
The main reasons for winding deformation are:
1. Short circuit fault current surge
During the operation of power transformers, they inevitably suffer from various short-circuit currents, especially short-circuit faults at the transformer outlet or near area. The huge short-circuit surge current will cause the transformer windings to experience significant electrical forces (tens to hundreds of times that of normal operation), and cause the windings to rapidly heat up. At higher temperatures, the mechanical strength of the wire decreases, and the electric force is more likely to damage or deform the winding.
2. During transportation, installation, or lifting of the cover, there may be unexpected impacts, bumps, and vibrations that can cause deformation of the winding.
3. The protection system has a dead zone and malfunctions
The existence of dead zones or malfunction of the protection system can cause transformers to withstand stable short-circuit currents for a long time, which is also one of the reasons for transformer winding deformation faults. Roughly speaking, transformers that fail to trip in a timely manner during external short circuits account for approximately 30% of short-circuit damage accidents
4. The ability of the winding to withstand short circuits decreases
When a transformer winding experiences a short circuit, it will deform due to its inability to withstand the impact force of the short-circuit current. In recent years, statistical analysis of 110KV power transformers nationwide has shown that insufficient short-circuit capacity of windings has become the primary internal cause of power transformer accidents, seriously affecting the safe and reliable operation of power transformers.
The ZC-206A transformer winding deformation tester detects the amplitude frequency response characteristics of each winding of the transformer, and compares the detection results longitudinally or transversely. Based on the degree of change in the amplitude frequency response characteristics, it determines the possible deformation of the transformer winding.
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