Transcript 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).
What happened afterwards?
 The MCB over-current detection cut the supply of the entire
SR2-EMD4 electrical switchboard, dedicated to the cooling of
different systems (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.
What is the reason?
 Flash over on transformer high voltage windings
18 kV – Phase W
A few numbers…
 Current in the Dipole before the fault:  6000A
 Transformer manufacturing date:
2002 but used inoperation for
 Transformer type
 Transformer rating
< 1000 hours (to be confirmed
by ALICE experiment).
Cast-resin
4.8 MVA
Primary
Voltage:
Current:
18 kV
154 A
Voltage:
Current:
900 V
3080 A
Secondary
 Transformer weight:
12.5 Tons
First analysis…
 FGC post-mortem:
no fault on converter side.
 80ºC when the fault
occurred (pt100 probes inside each windings).
 Transformer temperature:
 This is not a thermal problem (hot spot). The
supplier uses Class F insulation (155ºC).
 Expertise will be needed with the supplier.
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. ENEL and Cryo team shall be ready to intervene in case of another
unlikely power cut
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 avoid
tripping the other systems in case of a power converter failure