FLISR Switching Sequence for Selective Fault Isolation
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Solution Overview
Problem
Existing electrical power distribution networks face challenges in quickly and efficiently isolating faults to prevent damage and ensure continuous power supply.
Innovation Solution
The implementation of a fault location, isolation, and system restoration (FLISR) network that includes a fault interrupting device and a series of switching devices with current and voltage sensing capabilities, which perform reclosing operations and accumulate fault current detections to determine when to isolate the fault.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reclosers perform multiple opening and closing operations to detect persistent faults, then fault detection accuracy is improved, but fault current flows for longer times causing significant stress on network components
Solution Approach 1:
The recloser performs periodic opening and closing operations at predetermined time intervals to test for continued fault presence. This periodic testing allows accurate fault detection while controlling the duration of fault current flow, thereby reducing stress on network components compared to continuous operation.
Solution Approach 2:
The recloser opens immediately upon detecting fault current, performing the protective action before significant stress can be applied to network components. Subsequent reclosing operations are timed to minimize exposure, with the recloser remaining open for predetermined intervals between tests.
2Reliability
If the first fault interrupter upstream from the fault opens immediately, then equipment damage and power interruptions are prevented, but coordination with other protective devices becomes complex
Solution Approach 1:
The protective function is segmented between the fault interrupter (recloser) and downstream switching devices. The recloser handles immediate fault detection and opening, while switching devices accumulate fault current detections and perform coordinated opening after a predetermined number of detections, dividing the protection tasks to simplify coordination.
Solution Approach 2:
Switching devices monitor and accumulate the number of times they detect fault current during recloser reclosing operations. This feedback mechanism allows the system to make coordinated decisions based on accumulated information, enabling reliable fault isolation while maintaining manageable coordination complexity through clear operational criteria.
3Measurement precision
If switching devices accumulate fault current detections to determine when to open, then selective fault isolation is achieved, but response time increases
Solution Approach 1:
Switching devices are pre-configured with a predetermined number of fault current detections required before opening. This preliminary setup allows the system to quickly isolate faults once the threshold is reached, minimizing response time while maintaining selective isolation capability through the pre-established detection criterion.
Data Source
AI summary
An electrical power network employing fault location, isolation and system restoration. The system includes a plurality of switching devices electrically coupled along a power line downstream of a fault interrupting device. The switching devices each have current and voltage sensing capability and the capability to provide pulse tests for detecting fault presence. The fault interrupting device performs reclosing operations, and when the plurality of switching devices detect fault presence a predetermined number of times in coordination with reclosing operations performed by the fault interrupting device and detect loss of voltage, each switching device opens. The fault interrupting device closes when the switching devices open, and the switching devices sequentially pulse test and close from a furthest upstream switching device when detecting return of voltage and no fault presence until a switching device closest to the fault pulse tests and detects fault presence and locks open.