Stone Europa Carton produces folding box board and corrugated base papers at various sites in Germany. A new energy management system was installed at the Hoya plant as part of an extensive modernization project for the in-house power generating facilities comprising two steam turbines and a gas turbine with a total installed power of 11.3 MW. The system was designed, planned and installed by Cohrs + Partner Automatisierungs GmbH of Harpstedt. It uses INTERBUS for transmitting all relevant data relating to the power system.
An important criterion in the decision to use INTERBUS was the fact that optic fiber cables were already in situ for networking the individual buildings. It was possible to use these for INTERBUS, meaning that the considerable cost of installing new cables could be saved. In addition to the INTERBUS information, the glass fiber cables which run for about 1100 meters also transmit data via Ethernet and RGB.
Protecting the data to be
transmitted in an environment
contaminated with electromagnetic fields
The central station for the energy management system is an A500 PLC supplied by AEG Schneider. From here, the INTERBUS network runs through the six buildings, each of which contains a data distribution cabinet with a patch field and an INTERBUS coupler. All measured values as well as the meter pulses for the energy consumption and the energy generated by the in-house power station are transmitted to the PLC via the optic fiber cables.
Resistant to Interference thanks to Optic Fiber
The large number of powerful drives mean that the buildings are heavily contaminated with electromagnetic fields. Consequently, networking using conventional methods would have involved significantly greater expense in cabling and for protective measures against surge voltages and potential differences.
The FIX32 process control system operates as the energy management system on a superordinate level to the installed PLC. Communication with the PLC has been implemented using Modbus. From here, all the information is sent to four screens which have been installed in the individual buildings and are connected to the process control system via Ethernet. These four screens inform the local operating personnel fully about the energy states of the entire plant, making it possible to optimize consumption levels.
Powerful and, as a result,
cost-intensive drives are required
for moving the paper reels
which weigh several tonnes
The objective is to avoid exceeding the 15 minute peak value fixed in a contract with the power supply company, otherwise considerable premium costs are charged. These would exceed the costs for the newly installed system even if the maximum value were only to be exceeded once.
Dipl.-Ing. Reimund Richter