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ALICE DIPOLE Transformer break down

ALICE DIPOLE Transformer break down. G. Le Godec / V. Montabonnet 25/03/2010. ALICE DIPOLE CONVERTER. RPTI.SR2.RBAWV.R2 950V / 6500 A. What happened first?. 25/03/2010 – 13h33 [ Iout =6000A, Vout =630V]: 18 kV MCB: Over current detection Fire detection in SR2 (converter location).

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ALICE DIPOLE Transformer break down

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  1. ALICE DIPOLETransformer break down G. Le Godec / V. Montabonnet 25/03/2010

  2. ALICE DIPOLE CONVERTER • RPTI.SR2.RBAWV.R2 • 950V / 6500 A

  3. What happened first? • 25/03/2010 – 13h33 [Iout=6000A, Vout=630V]: 18 kV MCB: Over current detection • Fire detection in SR2 (converter location).

  4. What happened afterwards? • The MCB over-currentdetectioncut the supply of the entire SR2-EMD4 electrical switchboard, dedicated to the cooling of differentsystems (TCR, cryo plant, SR2 and Point 2 underground LHC converters and DC cables) • As consequences: • stop of the cryo plant • stop of the TCR • stop of converters (surface and underground) in Point2 due to the stop of the water cooling NB: The TCR has been put back in operation on Thursday afternoon.

  5. What is the reason? • Flash over on transformer high voltage windings

  6. 18 kV – Phase W

  7. A few numbers… • Current in the Dipole before the fault:  6000A • Transformer manufacturing date: 2002 but used in operation for • < 1000 hours (to be confirmed by ALICE experiment). • Transformer type Cast-resin • Transformer rating 4.8 MVA • Primary • Voltage: 18 kV • Current: 154 A • Secondary • Voltage: 900 V • Current: 3080 A • Transformer weight: 12.5 Tons

  8. First analysis… • FGC post-mortem: no fault on converter side. • Transformer temperature:  80ºC when the fault occurred (pt100 probes inside each windings). •  This is not a thermal problem (hot spot). The supplier uses Class F insulation (155ºC). • Expertise will be needed with the supplier.

  9. TE/EPC Action • Transformer replacement Thursday afternoon 25/03 until Friday afternoon 26/03 • TE-EPC will need a 2-3 hours slot to test the transformer and the converter (Friday afternoon? Evening?) without LHC beam. EN-EL and Cryo team shall be ready to intervene in case of another unlikely power cut

  10. The future… • Spare situation: no spare transformer for ALICE Dipole / LHCb for the next weeks. • Return of the faulty transformer to the supplier (Analysis and repair). TE-EPC will closely follow the manufacturer analyze to evaluate the risk and to take proper action if required. • Improve the electrical distribution selectivity if possible to avoidtripping the othersystems in case of a power converterfailure

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