Micro-grid Relay Protection Settings Transition

Solution Overview

Problem

The existing methods for managing protection settings groups in micro-grids struggle to seamlessly transition between grid-connected and islanded modes, often leaving the system unprotected for several seconds during transitions due to the time required to switch between different fault current detection settings, leading to potential damage from power system events.

Innovation Solution

A method that uses a timer to determine if the micro-grid is correctly set to its appropriate protection settings group, automatically switching the relay settings from grid-connected to islanded or vice versa when a mismatch is detected, ensuring the micro-grid is always protected by staggering the transition of relays between settings groups.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the relay switches between grid-connected and islanded settings groups during micro-grid transitions, then the protection settings can be adapted to the current operational mode, but the system remains unprotected for several seconds during the transition period

Engineering Contradiction:

Improveprotection settings adaptationVSAvoidsystem protection continuity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by implementing a timer mechanism that anticipates the transition completion. When a transition is initiated, the timer is set to a predetermined duration matching the expected switch-over time. If the transition completes within this time window, the settings group changes successfully. If the timer expires before transition completion, the relay automatically reverts to the previous settings group, ensuring continuous protection without leaving the system vulnerable during the transition period.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If the fault current detection settings are optimized for grid-connected mode with higher fault currents, then detection accuracy is improved for utility grid faults, but the settings fail to detect lower fault currents when the micro-grid is islanded

Engineering Contradiction:

Improvefault current detection accuracyVSAvoiddetection capability across operational modes

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamics by making the fault current detection settings changeable based on operational mode. Two distinct settings groups are configured: one optimized for grid-connected operation with higher fault current thresholds, and another for islanded operation with lower thresholds. The relay dynamically switches between these settings groups based on the micro-grid's operational state, ensuring optimal detection accuracy for each mode while maintaining adaptability across both operational conditions.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If the relay transitions settings groups immediately upon detecting mode change, then adaptability is improved, but both relays may be in an intermediate state simultaneously causing system vulnerability

Engineering Contradiction:

Improvesettings transition responsivenessVSAvoidsystem protection stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by implementing a timer mechanism that anticipates the transition completion. When a transition is initiated, the timer is set to a predetermined duration matching the expected switch-over time. If the transition completes within this time window, the settings group changes successfully. If the timer expires before transition completion, the relay automatically reverts to the previous settings group, ensuring continuous protection without leaving the system vulnerable during the transition period.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10535993B2Control system countermeasures

Publication Date: 2020.01.14 S&C ELECTRIC CO

AI summary

A method for correcting protection settings in a relay provided in a micro-grid between a grid-connected settings group when the micro-grid is electrically coupled to a utility grid and an islanded settings group when the micro-grid is disconnected from the utility grid. The method determines whether the micro-grid is connected to the utility grid and what settings group the relay is in. The method changes the settings group of the relay to the grid-connected settings group if a time that the micro-grid is connected to the utility grid and the relay is in the islanded settings group exceeds a predetermined time and changes the settings group of the relay to the islanded settings group if the time that the micro-grid is not connected to the utility grid and the relay is in the grid-connected settings group exceeds the predetermined time.