Eliminating Transformer Inrush Current

VARCO Ensco 8500 Drilling RigThe two powerful drill drivers of the ENSCO 8500 series drill rig are each fed by a 6.5MVA transformer with taps at +7.5° and -7.5°. Every transformer, when connected to the grid / generator has a high inrush current (20-30 In), especially this phase shift transformer. Such inrush current will trip the mains /generator protection system. To eliminate this high inrush current, VARCO decided to integrate into its four most advanced drill-rigs eight HRVS-TX Transofters.

The Transofter is a new generation of soft-starting solutions, designed to eliminate high inrush current by switching “in” the soft-starter, at exactly the right time. The integrated TSR-6, transformer soft-starter protection relay, tests the phase angle and activates the soft-starter to eliminate the peak inrush current.

General information:
Drill Rig Manufacturing shipyard – Keppel FELS
Integrator – National Oilwell Varco
End User – Ensco
Drill Rig name – Ensco 8500, 8501, 8502, 8503
Planned depth – 8,500 ft depth
Oil Company – Nexen Petroleum U.S.A.
Application – 6.5 MVA drill driver transformer 4160V/ 833A Secondary with ±7.5° shifts.