Power System Disturbance Detection Using Frequency and Power Flow
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Solution Overview
Problem
Existing electric power delivery systems lack the ability to determine whether disconnecting from a utility during a frequency disturbance would benefit or harm a distributed generation site, as previous solutions did not consider the direction of power flow, leading to potential system collapse if the disturbance is internal.
Innovation Solution
The implementation of intelligent electronic devices (IEDs) that monitor frequency, rate-of-change of frequency, and power flow to determine if a disturbance is internal or external, and accordingly decide on appropriate control actions such as disconnecting from the utility, using software modules and machine-readable media to execute protective actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system disconnects from the utility during a frequency disturbance, then system stability is improved, but system collapse may occur if the disturbance is internal
Solution Approach 1:
Instead of automatically disconnecting during frequency disturbances, the system inverts the approach by first determining the disturbance origin through power flow direction analysis. The IED evaluates whether power is flowing into or out of the distributed site to distinguish internal from external disturbances, thereby avoiding premature disconnection that could cause system collapse.
Solution Approach 2:
The system implements feedback by continuously monitoring power flow direction and using this information to adjust the protection strategy. The IED uses real-time power flow data to determine disturbance origin and accordingly decides whether to disconnect or remain connected, creating a closed-loop control system that adapts to actual system conditions.
2Stability of the object's composition
If the system remains connected during a frequency disturbance, then the distributed site can ride through the disturbance, but system stability may be compromised if the disturbance is external
Solution Approach 1:
The system inverts the traditional protection approach by not automatically remaining connected during disturbances. Instead, it uses power flow direction analysis to determine disturbance origin, and only remains connected when the disturbance is confirmed to be external and safe to do so. This inversion prevents both unnecessary disconnection and dangerous connection.
Solution Approach 2:
The IED implements feedback control by continuously monitoring power flow direction and using this information to dynamically adjust the connection state. The system evaluates real-time conditions and makes informed decisions about whether to maintain or break connection, ensuring both continuity and stability.
3Device complexity
If the system uses only frequency monitoring for disturbance detection, then the detection mechanism is simple, but the system cannot distinguish between internal and external disturbances
Solution Approach 1:
The system merges frequency monitoring with power flow direction analysis in a unified protection scheme. The IED combines multiple measurement inputs (frequency and power flow) to comprehensively determine disturbance origin, thereby gaining complete information without proportionally increasing complexity.
Solution Approach 2:
The IED performs multiple functions using a single integrated device: it monitors frequency, analyzes power flow direction, determines disturbance origin, and executes appropriate protection actions. This multi-functionality eliminates the need for separate specialized devices for each function.
Data Source
AI summary
A system for determining a disturbance in an electrical power delivery system external to a distributed site based on rate of change of frequency and power flow at the distributed site. The system may open a breaker to isolate the distributed site from the electric power delivery system upon detection of a disturbance external to the distributed site.