Recloser Control Frequency ROCOF Islanding Detection

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Solution Overview

Problem

Electric power delivery systems face challenges in detecting open circuit conditions between microgrids and macrogrids, leading to potential energization of power lines during maintenance, which can disrupt operations and safety.

Innovation Solution

A recloser control system that uses frequency (F) and rate of change of frequency (ROCOF) measurements to detect open circuit conditions, sending signals to trip the recloser and disconnect the microgrid from the macrogrid, preventing energization beyond the point of common coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional open circuit detection methods are used, then the system structure remains simple, but the detection reliability is insufficient leading to potential energization during maintenance

Engineering Contradiction:

Improveopen circuit detection reliabilityVSAvoiddetection system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the detection parameter from traditional voltage-based methods to frequency and rate of change of frequency (ROCOF) measurements. By monitoring frequency deviations and their rate of change, the system can reliably detect open circuit conditions without requiring complex additional hardware, thus improving detection reliability while maintaining reasonable system complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional mechanical or simple electrical detection mechanisms with a computational approach using frequency analysis. The recloser control uses processor-based frequency and ROCOF calculations to detect open circuits, substituting physical detection methods with signal processing techniques that leverage existing measurement capabilities

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If frequency and ROCOF measurements are used for detection, then detection precision is improved, but the complexity of measurement and control increases

Engineering Contradiction:

Improveopen circuit detection precisionVSAvoidfrequency measurement complexity

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent makes the frequency measurement system multi-functional by using the same frequency and ROCOF measurements for multiple purposes: normal operation monitoring, open circuit detection, and anti-islanding protection. This universal approach improves detection precision without proportionally increasing measurement complexity, as the same measurements serve multiple detection needs

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system implements feedback by continuously monitoring frequency and ROCOF measurements and comparing them against predefined thresholds. When frequency deviations or ROCOF values exceed these thresholds, the system triggers protective actions. This feedback mechanism enables precise detection while maintaining manageable control complexity through automated threshold-based decision making

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If the recloser trips to isolate the microgrid, then safety during maintenance is improved, but the loss of power supply increases

Engineering Contradiction:

Improvesafety during maintenanceVSAvoidpower supply interruption time

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The patent applies preliminary action by detecting open circuit conditions and tripping the recloser before maintenance personnel are exposed to potential energization hazards. By proactively isolating the microgrid upon detecting frequency/ROCOF anomalies indicative of open circuits, the system prevents harmful energization events before they can affect maintenance safety, thereby addressing safety concerns at their source

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements preliminary anti-action by preparing and executing the recloser trip command as soon as open circuit conditions are detected through frequency and ROCOF analysis. This preemptive protective action counteracts the potential harmful effect of unexpected energization during maintenance, eliminating the safety hazard before it can manifest, thus prioritizing personnel safety over continuous power supply

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS11218023B2Recloser control fast open circuit detection

Publication Date: 2022.01.04 SCHWEITZER ENGINEERING LABORATORIES INC

AI summary

The present disclosure relates to a recloser control that detects islanding based on a continuous analysis of frequency and rate of change of frequency. For example, a recloser control may include protection circuitry that is communicatively coupled to a recloser. The recloser control may receive measurements of an electrical characteristic in an electric power delivery system. The recloser control may determine frequency (F) and a rate of change of frequency (ROCOF) based on the received measurements. The recloser control may detect islanding of a microgrid in the electric power delivery system based at least in part on F and ROCOF. The recloser control may send a signal to the recloser to trip the recloser based on the islanding of the microgrid.