INSTRUMENTATION & CONTROL | MONITORING
How DVR improves plant performance
Data validation and reconciliation is a software modelling method that uses station process measurements, fundamental equations and statistical analysis to produce a set of corrected measurements. This analysis determines the most probable process values, which can be used to optimise performance. By Graig Pattison
Graig Pattison
Professional engineer, GSE TrueNorth (Division of GSE Solutions)
THE MAJORITY OF US NUCLEAR reactors have reached their original 40-year licensed lifetime and renewed their licences for an additional 20 years. Some stations are moving forward with more licence renewals to operate for 80 years. But age-induced failures in instrumentation and control systems can reduce the reliability of plant systems and increase the potential for station trips. Data validation and reconciliation (DVR) can provide insight when instrumentation errors are increasing — often observable precursors of failure. This can help the utility to develop better and more cost-effective mitigation strategies for ageing instrumentation. The goal of an instrument is to provide the actual
value for a measured parameter. Unfortunately, all instrumentation has some amount of associated error, so their measured values have a uncertainty or confidence
interval. The sources of instrumentation error can include: ● The intrinsic accuracy of the instrument itself. ● Improper installation of the instrument or inadequate
location chosen for installation (eg a flow meter installed immediately after an elbow in a pipe).
● The ‘drift’ error that may occur between instrument calibrations, or if the instrument is never calibrated.
● The compensation that may be necessary to determine a desired resultant parameter depending on the measurement system. Errors associated with the
compensation are then part of the final desired parameter value.
● Errors introduced due to the nature and accuracy of the acquisition system.
Many instrument locations do not have redundant measurements, so it is even more important that a measurement be as accurate as possible. Many secondary side instruments are neglected and not regularly maintained, whether it is due to parts, costs, manpower, low priority ranking compared to other work, etc. These issues can exacerbate the error and lead to instruments providing inaccurate results. There are numerous systems available that can be used
to help monitor a station during operation, but a weakness of most online monitoring systems is that they depend on plant instrumentation to provide continual accurate measurements. Most stations also use thermodynamic modelling systems but although these are good for certain scenarios, their weakness is that they often rely on very few input measurements to produce the output. Assuming that plant instrumentation is providing accurate ongoing measurements, or relying on a small number of measurements, can mean there are errors input to decisions, calculations, modifications, etc, with unintended consequences. DVR helps to resolve these issues.
Above: Data validation and reconciliation (DVR) can provide insight when instrumentation errors are increasing 28 | November 2021 |
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