Fault Protection Device for Two-Wire Network Spur Isolation
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Solution Overview
Problem
Current two wire combined power and data network systems, such as IEC61158 Fieldbus, face issues with intermittent or continuous faults leading to unnecessary isolation of spurs, which disrupt data communications, as existing fault protection devices cannot differentiate between faults that affect data transmission and those that do not.
Innovation Solution
A fault protection device with a failure status determination algorithm that monitors current on spurs, initiating isolation only if a pre-determined number of intermittent faults occur within a specific time frame or if a fault persists for a certain duration, allowing non-disruptive faults to be ignored and enabling continued data communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fault protection devices isolate spurs upon detecting faults, then system reliability is improved by preventing fault propagation, but data communication continuity deteriorates due to unnecessary isolation during non-disruptive faults
Solution Approach 1:
The system changes the parameter of fault evaluation from binary (fault present/absent) to multi-dimensional (fault count, time duration, communication impact assessment). By monitoring multiple parameters and changing the decision criteria based on their combination, the system distinguishes between disruptive and non-disruptive faults, isolating spurs only when necessary to maintain both reliability and communication continuity
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring communication status and fault characteristics, then adjusting isolation decisions based on this feedback. The evaluation algorithm uses real-time feedback about whether faults actually impact data transmission to dynamically adjust protection actions, preventing unnecessary isolations while maintaining system reliability
2Device complexity
If fault protection devices use simple fault detection, then device complexity is reduced, but measurement precision deteriorates in distinguishing disruptive from non-disruptive faults
Solution Approach 1:
The fault detection function is segmented into multiple independent monitoring components: fault occurrence detection, communication status monitoring, time duration measurement, and evaluation algorithm. This segmentation allows each component to remain relatively simple while the collective system achieves high measurement precision in distinguishing fault types through the coordinated operation of these modular functions
3Object-affected harmful factors
If fault protection devices isolate spurs for any fault condition, then harmful factors are reduced by preventing fault propagation, but productivity deteriorates due to loss of operational devices
Solution Approach 1:
The system applies partial isolation action by evaluating each fault condition individually and isolating only those spurs with truly disruptive faults. Instead of excessive isolation of all spurs with any fault, the system uses selective partial action based on communication impact assessment, maintaining productivity by keeping non-disruptive devices operational while still preventing harmful fault propagation through targeted isolation when necessary
Data Source
AI summary
A segment of a two wire combined power and data network for automation has a trunk, a spur mounted thereon and a fault protection device. The fault protection device includes a controller adapted to monitor the spur current, and isolation means to fully or partially isolate the spur from the trunk upon receiving of an activation signal from controller. The controller comprises a failure status determination algorithm comprising an intermittent fault count over time step and a fault duration step. The intermittent fault count step is satisfied if a pre-determined number of separate faults are detected over a first time period. The fault duration step is satisfied if a fault is detected which persists for longer than a second time period. The controller issues the activation signal upon determination of a failure status on the spur which satisfies the intermittent fault count and/or the fault duration step of the algorithm.