Availability analysis of 4-20mA pressure trasmitters under harsh environmental conditions using the discriminant classifier

Abstract

Instrumentation and control (I&C) systems act as the central nervous system of the Nuclear Power Plant as the erroneous functioning of them can become a reason for an inevitable casualty. The information from these instruments is crucial for plant operators to assess and continuously monitor the plant status. This fact highlights the significance of instrument availability during all possible environmental conditions in a Nuclear Power Plant (NPP). Along with several instruments used in an NPP, transmitters have gained momentous significance in the instrumentation loop as they provide critical information about the plant status. Therefore, the CN0289 pressure transmitter, which has been used extensively in industrial applications, is taken as an object of study for this paper. The instrumentation availability analysis depends on its evaluation under the faulted environment that may be caused by severe accidents. So, the aberrations in the output of the transmitter circuit under harsh environmental conditions have been observed in a well privileged simulating environment MULTISIM. The effect of accidental conditions like elevated temperature, humidity and high pressure have been analyzed on electronic components of the circuit and components most critical for the instrument availability have been identified. Later, a discriminant classifier has been implemented to analyze the instrument condition under different environmental scenarios for its availability. For this purpose, faulty signals are generated in MATLAB by using the statistical formulas of the faults observed in the output of the transmitter circuit. A set of timedomain distinguishing features have been selected to evaluate the instrument usability by the discriminant classifier. Based on these distinguishing features, a quadratic curve separates the faulty signals from the healthy ones indicating the availability of the instrument in a particular scenario. So, this analysis aids in assessing the instrument performance and later a guideline to ameliorate its design for operation under harsh environmental conditions.