2006 Muttrah Incident Report - authority for electricity regulation, oman

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SF6 Circuit Breaker A Circuit Breaker using Sulphur Hexaflouride as the insulating medium Spouts Name commonly used to describe the combination of Bushing and Contacts in the Cubicle. Switchboard A Switchboard is formed by a collection of Cubicles and their associated Trucks. Truck or Carriage The moveable portion of a switchboard. Contains the Circuit Breaker and the Busbar and Feeder moving Contacts. Vacuum Circuit Breaker A Circuit Breaker using a vacuum as the insulting medium. 4
1 INTRODUCTION AND SUMMARY OF FINDINGS This report presents the findings of a technical investigation undertaken by the Authority for Electricity Regulation, Oman into the incident that occurred at Muttrah Old Stores Primary Substation on Tuesday 28 March 2006 and which resulted in fatal injuries to two persons. In the course of the investigation the inquiry met with key personnel of Muscat Electricity Distribution Company SAOC (MEDC), Al-Wadi Contracting Company (Al-Wadi) and ABB Arab, the contractors and suppliers involved, the Royal Omani Police and the Public Prosecutor’s Office. The inquiry team also visited the site of the incident and reviewed photographic evidence taken by Authority staff and other parties. The analysis and conclusions presented in this report have been produced in response to the information made available to the inquiry by all the persons and companies involved in the incident. Throughout the investigation all persons and companies involved co-operated fully with the investigation and the inquiry team wishes to express its appreciation of the professional manner in which the recipients handled its inquiries, which were sometimes of a sensitive and difficult nature. 1.1 Summary of Findings The inquiry concludes that the most probable cause of the incident was a flashover between the conductor arms on the circuit breaker truck manufactured by ABB Arab and the rear feeder shutter on the original Brush cubicle. The evidence presented to the inquiry attributes this flashover to shortcomings in the design by ABB Arab of the interface between the truck and the cubicle. With respect to contractual issues, the inquiry finds that Al-Wadi Contracting Company was not qualified to bid for the Muttrah retrofitting contract, and that therefore Al-Wadi Contracting Company should not have been awarded the contract. Furthermore, having been awarded the contract Al-Wadi Contracting Company failed to ensure that the 5
Page 1 and 2: REPORT INTO THE INCIDENT AT MUTTRAH
Page 3: GLOSSARY OF TERMS The terms defined
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 and 28: 6.3 Cause of the Incident Based on
Page 29 and 30: shortcomings in the trucks supplied
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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