Digital Protective Relay Inflection Point Noise Elimination
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Solution Overview
Problem
Digital protective relays face erroneous operations due to noise influences such as disturbances and harmonic waves, which existing technologies have not effectively addressed.
Innovation Solution
A digital protective relay system that samples analog signals, identifies inflection points, compares electrical variation quantities, and employs Discrete Time Fourier Transform and root mean square processing to distinguish and eliminate electrical disturbances and harmonic waves from electrical quantity detection signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a digital protective relay uses a microprocessor to implement protective algorithms, then the reliability and additional functions (self diagnostic, fault recording) are improved, but the device becomes susceptible to erroneous operations due to noise such as disturbances and harmonic waves
Solution Approach 1:
The patent segments the noise elimination process into two distinct parts: disturbance elimination through inflection point detection and harmonic wave elimination through DFT analysis. This segmentation allows each type of noise to be handled by a specialized algorithm, improving overall reliability without compromising the protective relay's core functions
Solution Approach 2:
The patent applies preliminary action by performing noise elimination processing before the protective relay makes fault detection decisions. The inflection point search and DFT analysis are conducted on the raw electrical quantity signals before they are used for protective algorithm calculations, preventing noise from causing erroneous operations
2Object-affected harmful factors
If an erroneous sample elimination algorithm is mounted on the program storage unit, then noise elimination capability is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the noise elimination functionality from the general protective algorithm and implements it as a separate preprocessing stage. The inflection point search and DFT analysis are performed on the raw signals before they enter the protective algorithms, separating noise handling from fault detection logic and reducing overall program complexity
Solution Approach 2:
The patent introduces an intermediary processing stage between signal acquisition and protective algorithm execution. This intermediary stage includes the inflection point detector and DFT analyzer, which prepare cleaned signals for the protective algorithms, reducing the complexity burden on the main protective relaying logic
Data Source
AI summary
The present disclosure relates to provide an active erroneous sample elimination device or erroneous sample elimination method for a relay capable of correctly implementing erroneous sample elimination processing even during a plurality of electrical disturbances mixed with an electrical quantity detection signal, and a digital protective relay according to the present disclosure may include a converter that samples an analog signal and converts the sampled signal to a digital signal; and a processor that searches an inflection point at which an electrical variation quantity varies from an increase to a decrease or from a decrease to an increase based on the digital signal, and compares an electrical variation quantity prior to and subsequent to the inflection point with a preset electrical quantity.