A dynamic relative displacement evaluation method for extra‐high voltage transformer withstanding short‐circuit impact

Abstract

The extra-high voltage (EHV) transformer winding disks are subjected to dynamic electromagnetic forces caused by short-circuit currents. These periodically decaying impact forces may endanger the safety of the transformer. The winding constraint conditions around the circumference are different due to the influence of axial pressure structures and magnetic boundaries. Moreover, this difference becomes more evident as the voltage and capacity increase. To investigate the spatial differences and time effects of EHV transformer shortcircuit faults, this paper proposes a reliability evaluation method based on dynamic relative displacement (DRDEM) for the first time. Firstly, the suitable and efficient analysis method is summarized by comparing the deviation among different calculated impedances and the measured value. Then, the space-time effect of windings is obtained by the static magnetic field and dynamic structural field based on equivalent compression supports. Furthermore, a 50 MVA/110 kV transformer is designed for the destructive short-circuit test to simulate the short-circuit ability feature of the EHV transformer. The disassembly phenomena after all the tests indicate that the DRDEM is more adaptable in characterizing the winding ability to withstand short circuit when investigating the spatial differences and time effects.

Strongly Coupled Circuit‐Magnetic‐Structural Effect on Winding Vibration Process of Power Transformer

“…Each disk suffers two reaction forces and two damping forces, which are from upper spacer and lower spacer respectively. During vibration, the forces suffered by one disk are balanced, which means that the sum of them is zero, as shown in (10).…”

“…By solving (10), the compression of spacers and the displacements of disks can be calculated, which means that the spatial distributions of disks can be obtained.…”

“…During vibration, when the characteristic parameters, such as electromagnetic forces of conductors, mechanical stress of pressboard and displacements of the disks, are greater than the design strength, the winding collapses [7,8]. Therefore, the accurate calculation of the vibration process and the characteristic parameters is crucial to assessing the short-circuit strength of power transformers [9,10].…”

Study on the dynamic mechanical properties of winding‐block axial structure considering short circuit strain rate effect

“…Transformer short-circuit faults pose a huge threat to the reliable operation of power systems. Relying on relay protection measures, short-circuit faults can generally be removed within a few hundred to several thousand milliseconds, so the impact of short-circuit faults is first and foremost on the transformer structure [1][2][3][4].…”

Comparative analysis of the characteristics of outlet short circuit and winding insulation fault of distribution transformer and its preventive measures

“…Transformer is a key equipment of power grid, and its operation state is closely related to the safe and stable operation and reliable power supply of power system [1][2][3][4][5]. In fact, the faults often occur during the operation of transformer.…”