During the setup of the low-voltage systems in 2015, a malfunction alarm was also included. Kübler describes the disadvantages of the old system thus: “Previously, the systems could only trigger a collective failure, which was then transmitted to the plant’s security office.” In the process, a ring circuit transmitted the alarm to all circuit breakers, so it was impossible to determine remotely which outflow was actually affected. In the first step, to ascertain precisely which circuit breaker triggered the fault, the message outputs from all circuit breakers were sent to an additional control cabinet close to the system. A controller processed the signals and forwarded corresponding messages to the control center. “The wiring expense for this solution was, however, extremely high,” explains Kübler, “so we looked into alternatives.”
The Schaeffler employees from the plant facilities department hit the jackpot with WAGO. Hardware such as the fieldbus couplers and I/O modules from the modular WAGO 750 I/O-SYSTEM allows a significantly more elegant solution for fault message processing. In addition, each control cabinet array in the system was retrofitted with a PROFINET coupler. This includes a digital input module with 16 channels, which thus has sufficient capacity to evaluate all messages from the circuit breaker in detail. A central controller functions as the master in PROFINET and reads the signals from the PROFINET coupler; additional processing and the control center linkage function just as before. The use of WAGO’s PROFINET coupler has one essential advantage for Kübler: “All we have to do is connect the couplers with patch cables from array to array. Since we use a ring topology, the system functions even if one patch cable is interrupted.” The cables are connected directly through internal channels in the control cabinet. Expensive wiring through the raised floor of the system is no longer necessary. Since both the control lines and power cables are routed from the circuit breakers to loads through the common cable connecting compartment, the respective outflows would have to be disconnected from the power in order for signal cables to be laid.