The Purpose And Cycle Of The Transformer Winding Deformation Test

The transformer winding deformation tester is the core equipment for diagnosing the health condition of the transformer's windings. It is of vital importance for preventing the transformer from being damaged due to short-circuit impacts or other factors. During the transportation, installation, or operation of the transformer, it may be subjected to various short-circuit currents. The huge electrodynamic force can cause irreversible mechanical deformation of the windings, including:
Axial deformation: The overall height of the winding decreases or bulges.
Radial deformation: The diameter of the winding becomes larger (expands) or smaller (contracts).
Inter-turn/inter-breadth short circuit: Local insulation of the winding is damaged, resulting in a short circuit between the wires or wire buns.
Displacement: The entire winding undergoes offset or distortion.
These deformations will directly lead to a decline in the insulation performance of the transformer, an increase in partial discharge, and eventually may cause a serious insulation breakdown accident.
The main test items of the transformer winding deformation tester are to measure the frequency response characteristics of each winding of the transformer. The common connection methods (in accordance with the DL/T 911 "Frequency Response Analysis Method for Transformer Winding Deformation" standard):
Transformer winding deformation tester
End-to-end terminal grounding method: This is the most standard and commonly used method.
Excitation end: Connected to the leading end of the winding (such as the A terminal).
Response terminal: Connected to the end of the winding (such as the Am terminal. For a delta connection, the connection needs to be temporarily disconnected).
Grounding: The ends of the windings are reliably grounded together with the core and the casing.
Measure the windings of the high-voltage side A, B, and C phases, the medium-voltage side Am, Bm, and Cm phases, and the low-voltage side a, b, and c phases respectively.
End-to-end mid-point grounding method: This is mainly used for windings with mid-point outlet taps.
Capacitance coupling wiring method: A non-invasive approach that is suitable for preliminary assessment in certain special cases.
Test period:
Routine test (pre-test): Conducted once every 1-3 years, or in conjunction with the major overhaul cycle.
Mandatory test: This test must be conducted after the transformer is subjected to a short-circuit current impact.
In special circumstances:
Transformer inspection before and after removal from housing.
After the transformer was relocated and installed.
When there is any doubt about the condition of the transformer.
Applicable scenarios:
Fault diagnosis: Determine whether the transformer has been damaged due to an external short circuit.
Acceptance inspection: After the new transformer is installed or after major repairs, establish a "fingerprint" file or verify the quality of the maintenance.
State assessment: As an important part of transformer condition-based maintenance.
Advantages of Transformer Winding Deformation Tester Application
High sensitivity: Capable of detecting early and minor winding deformations that cannot be identified using traditional methods such as DC resistance or ratio.
Judgment is intuitive: Through the comparison of curves, the results are clear and understandable.
Testing safety: The test voltage is low (typically < 10V), and it will not cause damage to the insulation of the transformer.
Portable on-site: Modern instruments are highly integrated and easy to carry to the site for use.
Preventing catastrophic accidents: This is the final and most effective line of defense for diagnosing the mechanical integrity of transformer windings, preventing them from operating with defects and ultimately avoiding burnout accidents.