Plant Protection Trip Setpoints Adapted to Process Noise
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Solution Overview
Problem
Nuclear power plants face unnecessary reactor trips due to process noise from fluctuating process variables, which can be attributed to fixed analysis setpoints that do not account for instrumentation and control system uncertainties, leading to potential safety and economic inefficiencies.
Innovation Solution
A method to derive variable trip setpoints from fixed analysis setpoints by selecting a first fixed analysis setpoint, reducing the response time margin, converting units, and determining a variable analysis setpoint that includes floor, step, and rate analysis setpoints, while reflecting uncertainties of the instrumentation and control system to determine floor, step, and rate trip setpoints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed analysis setpoints are used for plant protection system, then safety analysis can be performed with simplified assumptions, but unnecessary reactor trips occur due to process noise and instrumentation uncertainties
Solution Approach 1:
The patent transforms fixed analysis setpoints into variable trip setpoints that dynamically adapt to actual process conditions. The system continuously monitors process variables and adjusts trip setpoints in real-time based on measured values and uncertainty margins, rather than relying on static predetermined values. This dynamic adjustment prevents unnecessary trips while maintaining safety requirements.
Solution Approach 2:
The patent changes the parameter representation from fixed numerical values to variable setpoints that incorporate uncertainty margins. The trip setpoint is calculated as a function of the analysis setpoint plus or minus an uncertainty margin, allowing the system to account for instrumentation and control uncertainties. This parameter transformation enables the system to distinguish between normal process variations and genuine safety threats.
2Device complexity
If fixed analysis setpoints are used, then the system design is simpler, but the system cannot account for instrumentation and control uncertainties
Solution Approach 1:
The patent introduces an uncertainty margin as an intermediary element between the analysis setpoint and the trip setpoint. This uncertainty margin acts as a buffer that absorbs measurement uncertainties and instrumentation errors. By adding this intermediary layer, the system maintains the simplicity of fixed analysis setpoints while compensating for measurement imprecision through the calculated uncertainty buffer.
3Reliability
If variable trip setpoints are implemented, then unnecessary trips are reduced, but the setpoint determination process becomes more complex
Solution Approach 1:
The patent performs preliminary calculation of uncertainty margins during the safety analysis phase, before actual operation. The uncertainty margin is pre-determined based on instrumentation specifications and control system characteristics. During operation, the system simply applies this pre-calculated margin to the analysis setpoint to generate the trip setpoint, avoiding complex real-time calculations while maintaining reliability.
Data Source
AI summary
A method of determining variable trip setpoints at the time of performing a safety analysis on a plant protection system includes: selecting a fixed analysis setpoint including a first analysis setpoint at which safety functions are initiated according to process variables of a power plant, and a first reaching time representing a time required to reach the first analysis setpoint; deriving a variable analysis setpoint satisfying conditions of the first fixed analysis setpoint; and determining a variable trip setpoint by reflecting uncertainty of an instrumentation and control system in relation to the variable analysis setpoint.