Review Incident Shin.. - authority for electricity regulation, oman

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with the actual situation that arose here. The fault in this line, which led to an outage of a load of up to 65MW, was far from being a non-credible event. The objective of this plan should be to limit the customer outage until the circuit can be repaired and restored. The plan for such a fault should concentrate on minimizing the duration of restoration or repair. This includes several issues described below. 2.2.1. Locating the Fault We understood that the operation engineer did not have a very detailed indication 6 about the distance of the fault from the Wadi Jizzi grid station. Appropriate fault locators could have been installed in the Wadi Jizzi grid station to assist the operation engineer to locate the fault more precisely and provide the patrolling crew with a smaller area to search for the fault. This would have shortened the time for finding the fault location (in this case 2.5 hours) significantly. 2.2.2. Availability of Spare Parts Repair time of a line can be considerably reduced if all relevant spare parts are available in good quality, quantity and close to the line. Moreover, transportation would be available as well. We understood that spare conductors and sleeves were available at OETC, but that it took a) time to find them and b) time to transport them because a border station had to be passed. Spare insulators were not available at OETC at all. However, they were provided by Civil Co 7 . Having all spare parts available within a limited distance of the event would have reduced the time for getting spare parts to the fault location (in this case about 14 hours) significantly. 2.2.3. Repair Tools available We understood that maintenance contractor Civil Co has no crimping tools locally available for repairing the faulted 175 mm 2 conductors. Although not on a critical time path in this incident, the same requirements for these tools apply as for spare parts. They should be available in good quality, quantity and close to the line. According to the expired maintenance 6 The site-engineer assumed that the distance relay tripped in zone 1, which means that the fault should be somewhere between 0-80% of the line length from Wadi Al Jizzi. 7 It has to be noted that in this incident there was no need to replace the poles, since they were all intact. Since this review is about this incident only, we have not gone into detail about the availability of or repair of poles. We note however that in the event of a broken pole, the repair would be far more complicated and lengthy than in the current incident. Review Incident Shinas August 2007 8 09.10.2007 vs. 2 (final)
contract with Civil Co (we have only seen a version valid until 26/05/2007), necessary equipment, tools and instruments are to be provided by the contractor (see section 2.2.5). 2.2.4. People available For both patrolling and repair of the line, the same applies as for spare parts and repair tools. They should be available in good quality, quantity and close to the line. We understood that the line crew of OETC started patrolling half an hour after the fault, which means that they were readily available. Moreover, another patrolling crew was offered by MJEC and assisted OETC with patrolling. However, this was on an ad-hoc basis and not as a result of any plan by OETC. Repair of the line should be organized in such a way that the work order can be issued without delay. Preferably this should be done either by own personnel or under a (maintenance) contract (see section 2.2.5). The operation engineer of OETC on site had to coordinate patrolling, fault investigation, looking for spare parts, repair, safety switching and communication with police and MJEC,. He was the only person that was authorised to close and open earthing switches in grid stations as well. In our opinion the operation engineer is in the case of a fault overloaded with activities, which could negatively influence the duration of the supply interruption. 2.2.5. Maintenance Contract We have not seen the actual maintenance contract with contractor Civil Co and are unable to confirm that a maintenance contract was in place at the time of the incident. However, we received a copy of the contract that was valid until 26/5/2007. This maintenance contract covered emergency maintenance of 132 kV lines, including the provision of adequate qualified and experience staff for this purpose with all necessary equipment, tools etc. in order to carry out the maintenance and attending the emergencies in an effective manner. The contract specifies emergency maintenance for woodenpole structures specifically. The specification includes the replacements of broken insulators and making of mid span joints and restringing of broken and damaged conductors. However, the responsibility for the provision of spare parts is with the OETC, although collection of the materials is at Civil Co again. 2.2.6. Conclusion It can be concluded that due to the fact that spare parts and repair tools were not readily available, the interruption had a longer duration than necessary. If we consider that the fault location was known at 01.10h on 28 August and that the latest spare parts arrived on-site at Review Incident Shinas August 2007 9 09.10.2007 vs. 2 (final)
Page 1 and 2: Review Incident Shinas area 27-29 A
Page 3 and 4: necessary safety measures such as l
Page 5 and 6: 1. INTRODUCTION On 27 August 2007,
Page 7: We were told that the investment in
Page 11 and 12: One set of procedures is about trai
Page 13 and 14: crucial for the LDC staff to be bac
Page 15 and 16: 4.3. Spare parts Since spares were
Page 17 and 18: 4.6. Incident center As discussed i
Page 19 and 20: 5. CONCLUSIONS Based on the review

Review Incident Shin.. - authority for electricity regulation, oman

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