Time-Admittance Switch Cascades for Inverter-Limited Fault Isolation
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Solution Overview
Problem
Conventional fault detection and isolation systems are inadequate for inverter-limited faults in microgrids powered by distributed generation resources, as they fail to detect faults caused by electronic inverters, leading to undetected outages and prolonged restoration processes.
Innovation Solution
A time-admittance fault detection and isolation system using time-admittance switches with a cascade trip sequence and radio communication to autonomously isolate inverter-limited faults without external communication, allowing for quick fault detection and isolation on both upstream and downstream sides of the fault.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high-current fault detection and isolation systems are used, then high-current faults from large spinning generators can be detected and isolated, but inverter-limited faults from distributed generation resources cannot be detected
Solution Approach 1:
The patent changes the detection parameter from current magnitude to time-admittance characteristics. Instead of relying on high fault current levels, the system measures the admittance (inverse of impedance) of the power line over time, which exhibits distinctive patterns during inverter-limited faults that differ from normal operation and other fault types.
Solution Approach 2:
The patent replaces the mechanical/electrical inertia-based detection method with an electronic measurement approach. Conventional systems rely on the mechanical inertia of spinning generators to produce high fault currents, while this system uses electronic admittance measurement to detect faults regardless of the power source type.
2Measurement precision
If conventional fault detection systems wait for high fault currents, then they can reliably detect traditional line faults, but they fail to detect inverter-limited faults where fault currents are limited to about two times rated current
Solution Approach 1:
The system transitions from detecting fault current magnitude to measuring time-admittance characteristics. The admittance measurement captures the dynamic electrical behavior of the line during faults, providing a reliable detection method that works across different fault current levels including inverter-limited scenarios.
3Extent of automation
If time-admittance switches are spaced apart along the power line with cascade trip sequence, then autonomous fault isolation can be achieved without communication, but the system complexity increases
Solution Approach 1:
The patent divides the power line into multiple sections with time-admittance switches positioned at strategic locations. Each switch independently monitors its local section and can autonomously trip to isolate faults, eliminating the need for complex communication coordination while achieving effective fault segmentation and isolation.
Solution Approach 2:
Each time-admittance switch is equipped with the capability to independently detect faults and execute tripping decisions based on local measurements. The switches serve themselves by making autonomous decisions without requiring external control signals or communication with other switches, simplifying the overall system architecture.
4Reliability
If the closest upstream time-admittance switch trips to isolate the fault, then the fault is isolated on the upstream side, but downstream portions of the line remain de-energized and require back-feeding
Solution Approach 1:
The system segments the fault isolation into two independent actions: upstream switching to clear the fault and downstream back-feeding to restore power. This segmentation allows the upstream switch to isolate the fault reliably while the downstream tie switch independently restores power to unaffected portions, improving overall restoration productivity.
Solution Approach 2:
The tie switch acts as an intermediary element that enables back-feeding of downstream portions from alternative sources. This intermediary component facilitates power restoration without requiring the fault to be cleared first, allowing parallel restoration operations to improve productivity.
Data Source
AI summary
A time-admittance fault detection and isolation system includes a series of time-admittance switches spaced apart along the power line, each including a respective time-admittance function. Together, the time-admittance functions define a cascade trip sequence in a downstream-to-upstream direction, which autonomously causes a closest upstream time-admittance switch to a fault to trip to isolate the fault on an upstream side of the fault without communication with the time-admittance switches. The fault detection and isolation system may also include a radio communicating a trip signal from the closest upstream time-admittance switch to the fault to a closest downstream time-admittance switch to the fault. The trip signal causes the closest downstream time-admittance switch to the fault to trip to isolate the fault on a downstream side of the fault. A tie switch closes to back-feed a portion of the electric power line downstream from the closest downstream time-admittance switch to the fault.