Generating high availability with POWERLINK
In areas such as the chemical, petrochemical and power generation industries, high availability is a critical requirement of control systems and their associated hardware. A good way to ensure this is through network redundancy – and with an open source protocol like POWERLINK, high availability comes at minimal added cost. That's why Czech control system specialist ZAT uses a ring-configured POWERLINK bus as the foundation for its highly reliable redundant control systems.
With more than 50 years of automation experience both in the Czech Republic and globally, ZAT is a well-known supplier of control systems for industries where equipment safety and reliability are crucial. From engineering, assembly and implementation to commissioning and servicing – the company provides a full range of services for the complex automation underlying continuous processes such as conventional and nuclear power generation.
The products manufactured by the company are based on a combination of proprietary ZAT systems as well as technology from other vendors. A example of this is the company's flagship ZAT-Plant Suite DCS system, based on SandRA (Safe and Reliable Automation) – a series of powerful next-generation control stations developed and produced at ZAT. When developing the new control system in 2009, rather than drawing on its own proprietary I/O modules, ZAT elected to integrate B&R X20 distributed I/O stations to benefit from the solution's openness.
Complete success thanks to B&R's X20 I/O system
The X20 I/O system from B&R was initially connected via PROFIBUS DP and fully integrated into the ZAT-Plant Suite. Supported by the ZAT Pertinax development environment, it has completely replaced the ZAT I/O modules that were used previously. This new arrangement was first put into practice in the Náchod heating plant, where a control system for one of the boilers was refurbished in 2009.
The success experienced with B&R's X20 system inspired ZAT to include POWERLINK support in its SandRA control stations. The decision was thus made to develop a special communication board for the SandRA Z200 control station that included the managing node (MN) features of POWERLINK. Through direct cooperation with IXXAT Automation, a specialist in industrial protocols, the BB0012E1 board was quickly brought to life. It features two Ethernet 10/100 Base-T ports and the POWERLINK MN software implemented on an FPGA.
Communication between SandRA Z200 and the distributed X20 I/O modules over POWERLINK first took place at the Opatovice power station, where the system prevents deposits from forming in the fuel line to the tanks of the air cooling system.
"Our new solution ensures the high availability of the control technology, which has a direct positive impact on the operational reliability of the entire plant. The cost-effective redundant control systems developed for this application – featuring B&R components – have gone on to become an integral part of ZAT's current product line." Pavel Kulík, Technology Processes Manager, ZAT
Redundant ring on the POWERLINK bus
In the power generation industry, high availability means that control systems must eliminate all potential points of failure. ZAT therefore decided to partner with IXXAT to integrate redundant ring-topology network software with a redundant POWERLINK MN into the SandRA Z200 control stations.
"The arrangement features a pair of redundant control stations, each containing a control board, communication board, power supply and the POWERLINK bus in a ring topology," explains Pavel Kulík, manager of the Technology Processes department at ZAT, "which not only ensures the operability of the entire control network should any of the elements fail, but also allows hot-swapping – all implemented with just a minimal increase in cost."
The solution with a pair of redundant ZAT SandRA Z200 control stations and nineteen remote X20 I/O stations from B&R transferring 1,670 I/O signals over the redundant-ring POWERLINK bus was introduced in late 2012 to control the dry fly ash collection system in the Opatovice power station. After all, were this system to fail, the entire plant would have to be shut down.
In May 2013, the control system for air cooling was also reconfigured to use the ring topology. In this case, a single SandRA Z200 control station includes internal redundancy of the control and communication boards, with four X20 stations rounding out the system.
High-availability through technological partnership
"The close cooperation between ZAT, IXXAT and B&R, together with the friendly attitude of the technology operator, opened up a pathway to an exceptional modernization of the control systems employed in the Opatovice power station," reports Kulík. "This new solution ensures the high availability of the control technology, which has a direct positive impact on the operational reliability of the entire plant. The cost-effective redundant control systems developed for this application – featuring B&R components – have gone on to become an integral part of ZAT's current product line."