2006 Muttrah Incident Report - authority for electricity regulation, oman

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FIGURE 10 Contact Damage The damage found on the isolating contacts (‘tulips’) is probably due to improper assembling and design and thus could not withstand the short circuit current from the feeder and busbar. 6.4 Technical Conclusions In an investigation of this type it is not possible to be definitive about the exact cause of failure. However both the KEMA and ABB Italy <strong>Report</strong>s identify the most probable cause as a flashover between the conductor arms on the truck and the rear feeder shutter on the cubicle. Both reports are coincident in attributing this failure to shortcomings in the design by ABB Arab of the interface between the truck and the cubicle. Furthermore as indicated in the report by MEDC engineers, the truck assembly was never tested in a Brush cubicle which could have identified the design shortcomings prior to installation. Additional shortcomings in the design and manufacturing of the truck assembly were also identified in both reports. These shortcomings include: • Contact support pillars and their machining on-site; • Low transversal stiffness of the truck which could have affected operation of the shutter mechanism; • Inadequate design of the truck position interlocking mechanism. On the basis of the above findings the inquiry concludes that the prime cause of the failure at <strong>Muttrah</strong> was poor design by ABB Arab of the interface between the truck and cubicle. Furthermore there were a number of other design and manufacturing 28
shortcomings in the trucks supplied which calls into question the quality control procedures of ABB Arab. 29
Page 1 and 2: REPORT INTO THE INCIDENT AT MUTTRAH
Page 3 and 4: GLOSSARY OF TERMS The terms defined
Page 5 and 6: 1 INTRODUCTION AND SUMMARY OF FINDI
Page 7 and 8: 2 SCOPE OF INVESTIGATION AND METHOD
Page 9 and 10: 2.3 Methodology In preparing its re
Page 11 and 12: outages on the distribution system
Page 13 and 14: FIGURE 2 Brush OCB Truck removed Mu
Page 15 and 16: contracts were subsequently awarded
Page 17 and 18: 5 SEQUENCE OF EVENTS The sequence i
Page 19 and 20: The protection relay indications fo
Page 21 and 22: BUSHING SHUTTER FIGURE 4 Reconstruc
Page 23 and 24: FIGURE 7 Truck - Cubicle Interface
Page 25 and 26: the shutter mechanism is mounted is
Page 27: 6.3 Cause of the Incident Based on
Page 31 and 32: Subsequent to the incident it emerg
Page 33 and 34: • That the design defects identif
Page 35: 10 RECOMMENDATIONS The inquiry make

2006 Muttrah Incident Report - authority for electricity regulation, oman

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