Generator Protection Using Historical Phase Reference
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Solution Overview
Problem
Existing methods for synchronizing electric generators with power grids are inadequate in detecting asynchronous conditions, particularly in remote generation facilities, leading to potential damage during reconnection after transient faults, as they are either too sensitive or require costly and impractical installations of synchronizing relays.
Innovation Solution
A method that involves providing a synchronizing signal from the generator, establishing a reference signal based on historical system information, and determining the phase angle difference between the two signals to isolate the generator from the grid if the difference exceeds a predetermined value, using a protective relay system that includes a CPU and GPS for accurate timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional synchronizing relays are used to detect asynchronous conditions, then generator protection is improved, but device complexity and installation cost increase significantly
Solution Approach 1:
The generator protection system uses its own existing synchronizing signal and historical system information to detect asynchronous conditions, eliminating the need for separate protective relays. The method leverages resources already present in the system (synchronizing signal, historical data storage, CPU processing) to provide protection functionality without additional dedicated devices.
Solution Approach 2:
The existing synchronizing signal generation system is made multi-functional by using it not only for synchronization control but also for asynchronous condition detection. The historical system information is utilized for both normal operation reference and protection detection, allowing one system to serve multiple purposes including protection without requiring separate specialized equipment.
2Measurement precision
If vector shift relays are used to detect islanding conditions, then sensitivity is improved, but false trips increase due to excessive sensitivity
Solution Approach 1:
The system continuously maintains historical system information as a reference before asynchronous conditions occur. This pre-established reference enables the detection algorithm to distinguish between normal phase variations and actual asynchronous conditions, allowing sensitive detection without triggering false trips during normal operations or transient disturbances.
Solution Approach 2:
The detection method uses feedback comparison between the current synchronizing signal and the historical reference signal to determine asynchronous conditions. This feedback mechanism allows the system to adapt to normal variations while maintaining sensitivity to actual faults, reducing false trips by continuously comparing against the established reference rather than using fixed thresholds.
3Reliability
If synchronizing relays are installed at each remote circuit breaker, then detection coverage is improved, but installation cost and complexity become prohibitive
Solution Approach 1:
The generator at the remote facility uses its own synchronizing signal and local historical system information to detect asynchronous conditions caused by remote circuit breaker operations. This self-service approach eliminates the need for synchronizing relays at remote circuit breakers, as the generator itself performs the detection function using resources already available at its location.
Solution Approach 2:
The detection functionality is extracted from the remote circuit breaker location and concentrated at the generator control system. Instead of distributing synchronizing relays throughout the system, the method extracts the essential detection capability and implements it centrally at the generator using its synchronizing signal and historical data, reducing the number of installations required.
Data Source
AI summary
A method for protecting an electrical generator which includes providing an electrical generator which is normally synchronously operated with an electrical power grid; providing a synchronizing signal from the electrical generator; establishing a reference signal; and electrically isolating the electrical generator from the electrical power grid if the synchronizing signal is not in phase with the reference signal.