Redundancy method used in PLC related applications

Abstract

PLC related applications are more complex as far as more components are involved. If some error occurs, diagnosis can take some time, but a logical procedure will shorten the time needed to locate the fault. The probability of failure of different parts of typical PLC systems shows [1] that 95% of PLC systems are external faults and occur on plant items such as: sensors, actuators, transducers, limit switchers, and others. The possibility of determining the validity of the data gathered from all transducers of the control system assures a way of short time fault detection. Consequently, a fault-tolerant control system must be implemented using redundant structures, representing an alternative for malfunctioning element detection. This paper presents a method used to design and implement a control system based on redundant structures. A case study for the geothermal power plant at the University of Oradea was developed. The redundant structure considered was simulated using MathLab/Simulink and analyzed using different scenarios. Finally, a possible implementation of resulting control system structure is done using a programmable logical controller (PLC).

A review of redundancy in PLC-based systems

“…Each paradigm has different advantages and disadvantages. Since around 95% of the faults occur in sensors or external data providers [17], some designers only offer dual redundancy for those components, special algorithm for recovery, running on a single PLC. Reliability analysis with general causes for performance deterioration may be found in [18].…”

A Study of Programmable Logic Controllers (PLC) in Control Systems for Effective Learning

“…In the plant, CO2 is the primary working fluid for conversion of geothermal water to electrical energy [6]. Hence, the PLC control system must maintain a constant CO2 pressure and temperature during all the phases of its thermodynamic cycle [6]. Thus, a constant temperature needs to be maintained after vaporizing the CO2 which is done using redundant temperature transducers and monitored on a remote computer [6].…”

“…Hence, the PLC control system must maintain a constant CO2 pressure and temperature during all the phases of its thermodynamic cycle [6]. Thus, a constant temperature needs to be maintained after vaporizing the CO2 which is done using redundant temperature transducers and monitored on a remote computer [6]. Any deviations in the values of one of the transducers causes the PLC to switch the system to use the other transducer and continue normal operation, a method commonly known as Interlocking where two outputs are not active at the same time.…”

A Study of Programmable Logic Controllers (PLC) in Control Systems for Effective Learning

“…In the plant, CO2 is the primary working fluid for conversion of geothermal water to electrical energy [6]. Hence, the PLC control system must maintain a constant CO2 pressure and temperature during all the phases of its thermodynamic cycle [6].…”