Diesel, steam and electricity in the desert

Jon Lawson

The Rabigh II refinery in Saudi Arabia produces oil, and the associated steam turbine power station generates electricity for the state power utility SEC Saudi Electricity Company. Smooth and uninterrupted processes are extremely important here. It is therefore equally important that the power station can start up quickly after a grid disturbance. A system from Hanseatic Power Solutions based on Eaton solutions provides reliable and secure drive control for the black start generators.

Hanseatic Power Solutions (HPS) is located in Norderstedt, a city near Hamburg in the far north of Germany, and has more than 80 employees. The company's core activity is building control systems for the power generation and distribution sector. HPS has also made a name for itself as a specialist in the series production of compressor controllers and as a supplier of low-voltage and medium-voltage systems, DC supply systems, earthing systems and automation systems, and they provide consulting services for improving and ensuring availability and efficiency. HPS is a market leader in Germany and active internationally, drawing on extensive experience in solutions for critical areas. That includes hospitals, airports, banks and computer centres, where reliable supply of power is essential.

These competences were also key factors for an international project in Saudi Arabia, which involved upgrading the Rabigh II refinery and the associated steam turbine power station. As part of that project, HPS was contracted to supply the control technology for black start generators. After a grid outage these generators start up the steam turbines, which generate electricity using process steam from the refinery.

When there is a power outage at a refinery the size of Rabigh II, the impact is more than just high costs for the plant operator. After a power failure it is therefore essential to get the power station back in service as quickly as possible. This task is handled by three black start diesel generators. When grid power fails, these emergency generators supply power to the auxiliary drives used to start up the steam turbines. The station needs two operational generators with 5 MW capacity each for start-up. The third generator provides backup. Once the entire station is completely started up, which takes about 12 hours, it switches from black-start operation to normal operation.

The challenge with this project was to implement a cost-effective and reliable solution with high availability and compatible with local conditions. The refinery, located in the desert on the edge of the Red Sea, is largely surrounded by sand. The client therefore specified IP55 ingress protection to guard against harmful sand deposits inside equipment and provide complete touch protection. For HPS it was additionally important to be able to build the necessary control cabinets for the emergency generators in-house in order to maximise their internal value-added chain.

The refinery upgrade was the first project in the Middle East for the Asian prime contractor. That put a lot of pressure on all other companies involved in the project with regard to quality and delivery times. Within its scope of delivery, HPS relied on internationally proven partners such as Eaton.

The three black start emergency generators are located in the power house, each connected to the medium-voltage system through its own control unit. Each generator needs a motor control centre (MCC) for the auxiliary drives, amounting to some 20 motors for various pumps and fans. For this HPS chose Eaton's xEnergy technology with IP55 ingress protection. As an xEnergy partner, HPS is licensed to build the switchboard system in-house, so it fulfils the company's requirements for maximising internal value creation. The versatile switchboard system is available in various versions: fixed installation, plug-in or withdrawable. HPS opted for the withdrawable version to meet the requirement for extremely high availability in the event of a grid outage.

The MCC solution is designed with a suitable spare module for each power stage in the system. If a module becomes defective, a service technician can withdraw it without any sort of special tool and replace it with the spare module. The key advantages of this are that replacement takes only a few seconds so the auxiliary drive is quickly available again, the defective auxiliary drive module can be repaired immediately, and only the drive concerned has to be switched off instead of the entire system. This also makes an important contribution to boosting cost-effectiveness.

To meet the requirements for availability and reliability, HPS also used proven Eaton power circuit breakers and motor protection circuit breakers inside the switchboard system: 400 A NZM circuit breakers, DIL contactors, and both PKZ and PKE motor protection circuit breakers with electronic overload protection. The wide trip range of the PKE devices gave HPS a high degree of flexibility, which they needed because the power ratings of the drives on site were not known in advance and the wide adjustment range allowed them to cover a broad spectrum.

HPS completed the project successfully and on time in roughly nine months.

Thanks to HPS and Eaton, the Rabigh II refinery has a reliable and high-availability drive control system for the emergency generators that is able to restart the steam turbines of the power station in the event of an emergency.