In a recent CIGRE publication the loss of a single phase GSU transformer due to an HV bushing turret rupture was discussed. In this case an OIL/SF6 RIP bushing failed catastrophically inside its turret which led to the rupture of the turret and the loss of a multi-million-dollar transformer from the resultant fire.
Transformer manufacturers have been working on ways to improve the mechanical resilience of transformer tanks to better withstand the overpressure generated by an internal arcing fault. IEEE also offers a guide (C57.156-2016) describing measures that transformer manufacturers can take to help mitigate tank rupture. However, the article in the CIGRE publication was quick to highlight that more work is required to improve the mechanical resilience of bushing turrets as oil-filled turrets may not be able to withstand a catastrophic failure of the oil end part of the bushing. The article goes on to describe a retrofit solution for HV bushing turrets using PRD protection. We would like to suggest an alternate solution to mitigate this risk by installing bushings that can maintain their oil end structural integrity in the event of an arcing fault. This would have protected the transformer from a catastrophic turret rupture and the subsequent fire that destroyed the transformer. In an earlier blog article, we described an internal arc fault test that was conducted on an RHM International 230 kV dry type RIF® bushing which passed the stated test criteria of “no ignition of the arc or destruction of the oil side of the bushing under the supporting plate”.
Air End
Oil End
