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Sivacon S8 low-voltage switchboard in withdrawable-unit design.

Power distribution

Highly available Withdrawable-unit design for GEA separator systems

Separator solutions of GEA operate in power plants and other critical infrastructures. Thus, maximum availability is a key requirement. In a current project in Iraq power supply is ensured by a particularly powerful Sivacon S8 switchboard from Siemens.

As technological leader for separator solutions, GEA concentrates at its main production location in Oelde/Westphalia/Germany the know-how for more than 3,000 processes and procedures related to separators and decanters. The separators, decanters and process lines are used worldwide in many industries and applications. Plants for the oil industry play an important role in this. On the one hand, they place particularly high demands on availability. On the other hand, the associated infrastructures are frequently situated in regions with extreme climates – in Siberia as well as in the Arab deserts, or on the high seas. GEA installations have proven their high reliability and precision at those locations for decades.

Current power plant project in Iraq

Due to this expertise, in spring 2015, the separator experts from Oelde were awarded a challenging order for the mega-deal Power Plant Shat al Basra, tendered by the Iraqi Ministry of Energy. "From the technical point of view, rather everyday work," – that is the way Norbert Klein from the sales team characterizes the task – "but with a high power plant output of 1,250 MW and, above all, a very short preparation time of just six months, this is a great challenge for us."

In concrete terms, the project was about the separator systems for the new power plant construction in Iraq. Among others, crude oil is used there for power generation, which is available in the Near and Middle East in large amounts and at accordingly low cost. In the installations planned and built by GEA, the unrefined oil is washed and treated so that it can be burnt in gas turbines. To ensure round-the-clock power generation, the installation must be highly available and fail-safe. In addition, maintenance and on-site service on this market requires longer preliminary work, not least for geographical reasons. 

 

GEA Separator OSE120

Decision in favor of the Siemens low-voltage switchboard 

"In this context, the technology must be the right one, especially in terms of availability, in order to prevail against international market players," Dirk Oppel knows, the Product Manager Automation at GEA in Oelde. And he does not only refer to the procedural hardware: "Also the electrical power distribution inside the plant is a very important issue for us." The associated specifications are normally made by the customer. Of course, the GEA engineers can also make recommendations, based on their long experience. As Oppel says, "We want to offer our customers a trouble-free technology and the high standards we are used to."

On this background, the decision in the current project was in favor of a Sivacon S8 low-voltage switchboard from Siemens. Already before, GEA had gained a lot of positive experience with the quality and reliability of the switchboards manufactured in Leipzig, Germany. As estimated by Dirk Oppel and Norbert Klein, the good cooperation, especially in engineering and design, also spoke in favor of Siemens. 

In detail, the switchboard supplies the separators of the treatment lines, transfer pumps, valves, pipe trace heaters, as well as the associated generator sets. The process control connection of the switching technology to the overall plant automation – also implemented by Siemens – takes place via two Simatic S7-400H controllers; the system is operated via the SCADA software WinCC on a panel PC. Network safety is ensured by Scalance S modules – another argument in favor of Siemens, as Dirk Oppel states: "A real solution out of one hand."

GEA product manager Dirk Oppel (l.) and Siemens promotor Guido Neumann

Low-voltage switchboard conforming to IEC

In functional and industrial buildings, as well as in the process industry, the Sivacon S8 switchboard generation enables consistent and simple power distribution up to 7010 A. The rated current of the switchboard now ordered by GEA is 4780 A, a typical value for separators. The rated operational voltage is 400 V. 

As a design verified low-voltage power switchgear and controlgear assembly, Sivacon S8 fulfills the design verification according to the latest standard IEC 61439-2. The European IEC certification is not only accepted in the Arab countries, but also very much demanded there. Exceeding the specifications of IEC 61439-2, the standard design already includes the verification of testing under arcing conditions in accordance with IEC 61641 or VDE 0660 Part 500, Supplement 2. This separate test is voluntary, but was stipulated by the customer in this case. It proves that the switchgear verifiably fulfills the stipulated safety criteria when an internal arc occurs. The so-called rated short-time withstand current, i.e. the mechanical strength in case of short circuit, is 85 kA for one second.

Design and scope

The switchboard for the power plant project in Iraq is designed as a double-fronted switchboard, making optimum use of the restricted standing surface. Each of the two fronts comprises 13 cubicles. Every two opposite cubicles are set up symmetrically, using a common busbar section. This is enabled by the high flexibility of the withdrawable units, which can be equipped with multiple types of switching devices, motor contactors, or also drive technology.

The infeed from the transformer takes place via a separate circuit-breaker for each busbar section. An additional coupling circuit-breaker provides operational reliability also in case of failure: If one incoming feeder cubicle fails, one side just supplies the other side additionally. Automatic changeover is done by a Simatic S7 controller. At all three points, there are Sentron 3WL air circuit breakers. This circuit-breaker type is particularly flexible in use, and consistently communication-capable. In the upper range of ratings, the 3WL air circuit-breaker is the smallest circuit-breaker of its class worldwide. 

32 withdrawable units are designed as cable feeders with molded-case circuit breakers type Sentron 3VL. With optimized communication capability and a particularly compact design, they also fulfill the requirements on space-saving electrical distribution boards. Another 86 small withdrawable units are used for switched voltage supply. Sinamics frequency converters with two redundantly running fans for heat dissipation are directly mounted on eleven withdrawable units. Five withdrawable units are equipped with Sirius soft starters. This complete solution saves space in the switchboard, and reduces the installation and commissioning costs.

Details increase availability

The planners from Siemens and GEA paid special attention to the motor feeders. To maximize availability also at this point, now 85 motor management devices of the type Simocode pro V Profinet are used. As the first motor management system, Simocode pro V Profinet only recently supports the Profinet system redundancy function. This means: The devices can be connected to highly available systems with two control units. Both CPUs thus have access to the Simocode pro field device. In case of a cable rupture, or if one CPU fails, the other one takes over smoothly. This ensures uninterrupted communication at any time. Moreover, commissioning is also simplified in this way.

The Profinet bus is also set up redundantly, so that the maximum volume of failure only comprises the drives of one withdrawable unit. The design with degree of protection IP42 makes the switchboard insensitive to water falling in inclined position, as could escape from defective pipes of the air-conditioning system. The copper busbars are completely silver-plated, in order to protect them against corrosion in salty maritime climate. Not the least, all switching devices are designed with higher ratings than required for normal conditions, in order to ensure reliable operation even at temperatures up to 50°C.

Conclusion

Maximum availability was the central requirement GEA placed on the low-voltage switchboard for the separator system in the Iraqi power plant. Siemens meets this requirement with an IEC design verified double-fronted switchboard of the Sivacon S8 generation. Numerous technical details increase the availability even beyond the usual high standard: For example, 85 advanced motor management devices are used, which as the first management system support the Profinet system redundancy.

Picture credits: Siemens AG