A large oil and gas company experienced a major blackout in its northern part of the grid. The blackout caused the tripping of the high voltage feeder line and tripped generators connected to the network. Major oil and gas production stations ran into a forced shut down for a considerable amount of time. DNV conducted a Power Failure Investigation (PFI) to investigate the possible root cause of the failure and was asked to make recommendations to prevent such occurrences in future.
Another industrial system was designed to operate with its own electric power generation, exporting the excess power to the 400 kV transmission grid. In normal operation the industrial plant operates in parallel with the power grid, monitored by a supervisory system, a control system and an interlocking system. In case of a disturbance in the transmission grid, the system has to switch to island operation to avoid the interruption of electric power supply to consumers connected to the industrial plant. Two events in the 400 kV transmission grid, requiring island operation of the industrial plant, led to a blackout in both cases. DNV performed a qualitative assessment to assess the current situation, identify main issues regarding the system design, operation and maintenance regime. DNV analysed the system and the failure documentation. Based on its findings DNV recommended improvements of the system and suggested additional analysis.
In the power supply of refineries or critical infrastructures, switchgears are installed with high speed transfer systems to automatically switch to a different feeder in the event of a failure of one feeder. In a third industrial project, a refinery experienced two faults in the feeding network, leading to the impairment of process plants. DNV made a model of the power supply of the refinery, including the electricity distribution systems of adjacent infeeding network to perform dynamic simulation calculations of all conceivable relevant error scenarios. Based on the outcomes of the simulation results, it is advised to:
- Activate unused operating modes of the high speed transfer system
- Reduce the response time of the circuit breakers in the switchgears which have high speed transfer systems
- Adaption of individual network protection parameters in the analysed electrical network
Results
These three cases show engineering errors in the design, insufficient system operation (knowledge) and malfunction of hardware in the system. The blackouts caused the shutdown of industrial plants leading to multimillion losses in revenues. The losses in revenue of these three cases have been estimated over EUR 100 million.