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14 July 2015:

Authority for Electricity Regulation, Oman published the
Investigation Report - Loss of Power and water Production at Sohar Power Company

The Authority for Electricity Regulation, Oman is today publishing a formal investigation report into the loss of power and water production at Sohar 1 Power and Desalination Plant (owned by Sohar Power Company ("SPC") on the 5th and 19th of May 2015. The incident resulted in serious interruptions of water supply to customers in the North Batinah Governorate.

Qais Saud Al Zakwani- Executive Director & Member of the Authority, said:

the Sohar incident caused extensive water shortages in the North Batinah Governorate and caused much distress to public. The Authority conducted a formal investigation of the incident and is today making the incident report available for public inspection.".

"The principal findings of the investigation are as follows:

  1. The main cause of the incident was due to a rupture of the sea water supply pipe to the Oman Oil Refineries and Petroleum Industries Company (ORPIC) facilities on 3rd of May 2015. This caused flooding of the sea water intake area and the local switchgear and control room for the Sohar Power Company (SPC) seawater supply pumps with water level reaching 1-1.5 m above ground.
  2. Although the plant remained operational while dewatering works were in progress, the complete power plant tripped on 5th May 2015 resulting in loss of production of power and water.
  3. The sea water stood for about 3 days and in all probability this led to the loss/compromise of cable insulation integrity. Loss of communication was because the communication interface modules were going into a faulted state due to swarm of fault alarms coming from the field instrumentation cables.
  4. Field cables to pumps and other signals in the sea water intake area were initiating numerous sporadic fault signals that appeared to be the reason for the communication interface modules going into faultaed state. The numerous sporadic fault signals were likely being generated due to signal short circuits in the field cables caused by loss of cable insulation integrity."

"The delay in initiating the dewatering process certainly would have contributed to the degradation of any instrumentation cables with damaged outer sheaths. SPC were dependent on ORPIC and Majis Industrial Supply Company (MISC) to expedite dewatering of intake area."

"Loss of the sea water supply has a direct impact on shutting down the Sohar Power and Desalination Plant. As the Sohar Power and Desalination Plant is the only major source of desalination water in the North Batinah governorate, any disruption has serious consequences for the wellbeing of the people that rely on this as the only source of potable water."

"Although SPC have resources to operate and maintain the plant under normal conditions, they did not have personnel on site with the right skills to trouble shoot the problems being encountered. There were insufficient personnel at site familiar with dealing with such emergency situations; hence SPC had to mobilize O&M personnel from other plants to support the efforts."

"There was a failure to consider other options, including following the procedure set out in the Operation Manual. The Operation Manual stated if the distribution piping needed to be filled; the procedure was to use a temporary water pump. Once filled, the plant could be restarted using any of the seawater supply pumps. This was not considered. If the procedure stated in the Operation manual was considered, the quickest way to restore the plant, without knowing the cause of the communication failures, would have been to isolate the I/O rack causing the communication failures"

"The Authority will act to ensure that all of the recommendations/actions are implemented by SPC in order to avoid a reoccurrence of similar incidents in the future. Furthermore, the Authority will issue recommendations to other existing generation and desalination plants to avoid similar incidents and direct the Oman Power and Water Procurement Company to include specific requirements to be considered during the design of future projects."

Background - The Incident

The Sohar 1 Power and Desalination Plant owned by Sohar Power Company SAOC (SPC) supplies power to the Main Interconnected System (MIS) and water to the public networks in the North Batinah region of the Sultanate of Oman.
The water supply for the region is heavily and solely dependent on this desalination plant and operation of the desalination plant is very critical.

On May 3rd 2015 at 20.50 hours, there was flooding of the sea water intake area and the local switchgear and control room for the power plant seawater supply pumps due to rupture of the sea water supply pipe to the Oman Oil Refineries and Petroleum Industries Company (ORPIC) facilities. Although the plant remained operational while dewatering works were in progress, the complete power plant tripped on 5th and 19th of May 2015 resulting in loss of production of power and water. The outage of the plant resulted in extensive water shortages in North Batinah region and caused inconvenience to the public.

The Authority for Electricity regulation, Oman engaged the services of WorleyParsons Oman Engineering LLC for an independent assessment of the plant outage to understand the causes of the outages and provide recommendations to mitigate against a future reoccurrence.

The incident report recommended:

  1. Immediately install barriers to divert surface runoff water away from the seawater supply pumps;
  2. Install permanent redundant dewatering pumps to remove any water that floods the underground galleries.
  3. the MISC signals should be connected and configured in the DCS to provide operators with status of the sea water differential level across the intake screens.
  4. Review the DCS code and all I/O modules for the presence of forced logic. If forced logic is fouond the DCS programming code should be revised to remove the force logic.
  5. Based on risk analysis, the sparing philosophy and the level of spare parts held in inventory need to be ascertained.
  6. Install permanent pumps to fill the sea water distribution header.

 

Sohar IWPP Investigation Report