# Information Extraction from Industrial Sensor Data Using Time Series Meta-Features  
[PERSON]  
1 Institute for Automation/Computer Science, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany; [EMAIL_ADDRESS]  
[PERSON]  
2 WSW Wuppertaler Stadtwerke GmbH, Bromberger Str. 39-41, 42281 Wuppertal, Germany; [EMAIL_ADDRESS]  
[PERSON]  
3 TRIMET Aluminium SE, Aluminiumallee 1, 45356 Essen, Germany; [EMAIL_ADDRESS]  
[PERSON]  
4 Alcoa Nederland Holding B.V., Weena 796, 3014 DA Rotterdam, The Netherlands; [EMAIL_ADDRESS]  
[PERSON]  
1 Institute for Automation/Computer Science, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany; [EMAIL_ADDRESS]  
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component in the corresponding time series. A strength value close to 0 indicates a weak trend or seasonal component in the corresponding time series. Beside the trend and seasonal strength, more time series meta-features, e.g., the spectral entropy, seasonal period or autocorrelation coefficients, can be computed. Time series meta-features should be selected according to the type of the time series and the problem in question [9; 10]. Expert knowledge about a specific domain, in our case the aluminum electrolysis, can help to find suitable meta-features that describe the different characteristics of time series. The core business of TRIMET Aluminium SE is the development and production of aluminum products. Figure 2 shows one of the three pot rooms containing 120 reductions in an end-to-end configuration at the Essen site in Germany. In total, TRIMET Aluminium SE Essen (TAE) operates 360 reduction cells that produce liquid aluminum. The industrial production of aluminum is based on the Hall-Heroult process, in which alumina (Al\({}_{2}\)O\({}_{3}\)) is dissolved in liquid cryolite (Na\({}_{3}\)AlF\({}_{6}\)) with an excess of aluminum fluoride (AlF\({}_{3}\)) [11; 12]. The Hall-Heroult process is performed with an almost constant energy supply to ensure stable aluminum production [12; 13]. Due to the energy transition, the energy supply in Germany is increasingly reliant on renewable energy sources, which means that the energy supply for the industrial aluminum production is no longer constant but variable [12]. In order to ensure a stable operation of the reduction cells with a variable energy supply, TAE has started to equip the reduction cells with magnetic field compensation and shell heat exchangers [14]. The magnetic field compensation is used to prevent bulging of the liquid aluminum at high current levels, while the shell heat exchangers are designed to control the heat loss from the side walls of the cells, maintaining a protective side ledge. Additional thermocouples are mounted on some cells to monitor the heat balance. Due to the corrosive environment, loose or faulty thermocouples are unavoidable and can result in incorrect heat balance calculations.