Summary
This paper describes the design and manufacture of a 250 MVA, 735 kV three-phase transformer equipped with reinforced side turrets capable of withstanding a 20 MJ internal arcing fault, as required by one utility’s power transformer specifications. The aim of the design is to prevent turret failures which may result in violent ejection of components, major oil leakage, nearby equipment damage, and significant personnel hazards. The use of side turrets is typically prohibited due to these risks; however, transportation constraints made 735 kV sideturrets the only feasible solution for the transformer described in this paper. Consequently, the side-turrets were structurally reinforced using an arc-resistant approach previously validated by full-scale experimentation.
Read more Read lessNumerical analyses demonstrate that only a structurally reinforced‑turret concept can safely withstand high‑energy internal arcs, whereas venting‑based solutions are not viable, since they are fundamentally incapable of limiting the rapid pressure rise driven by arcing power. In the event of an arc inside the turret, the reinforced structure contains the initial high‑pressure rise locally and then allows the pressure to diffuse into the main tank. To meet electrical air clearances for 735 kV bushings, two reinforced turrets were installed at 45° to the vertical plane, increasing both design and manufacturing complexity.
Both experimental observations and explicit dynamic simulation results show that the pressure rise from an arc inside a bushing turret is significantly higher than for an arc inside the main tank, due to the turret’s smaller oil volume and lower flexibility. The mechanical integrity of the reinforced turret and the main tank was evaluated using nonlinear finite‑element analyses.
Bolted joints were specifically optimized to remain leak‑tight, and all side components— including bushings and valves—were selected to withstand the specified design pressure.
This paper summarizes the key features of the reinforced turret design and the associated manufacturing challenges. The proposed reinforced‑turret methodology significantly reduces fire risks, enhances substation safety, and offers a scalable foundation for future turret designs at various voltage classes and arc‑energy levels.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | A2_11718_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Canada |
| Study committees | |
| File size | 1 MB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
BRODEUR Samuel - Hitachi Energy Canada; LAMOTHE Patrice - Hitachi Energy Canada; DASTOUS Jean-Bernard - Hydro-Québec, Canada
Keywords
Power Transformer, high-energy arcing fault, bushing turret, rupture prevention
