Transmission Line Fault Detection Using Setting-Point Voltage Change
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Solution Overview
Problem
Existing fault detection methods in power transmission systems face challenges with high sampling rates in distance protection and inaccuracies in vector calculations, leading to inefficiencies and delays in fault detection.
Innovation Solution
A method and apparatus utilizing a time domain lumped parameter model to determine voltage changes at a setting point on an electrical line by obtaining voltage and current at a measurement point, employing differential equations to calculate differential values of current, and comparing these changes against a fault threshold for rapid fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high sampling rate is used to achieve accurate voltage calculation for fast fault detection, then the fault detection speed is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent changes the mathematical approach from time-domain differential equations requiring high sampling rates to frequency-domain vector calculations using Fourier algorithms. This parameter transformation allows accurate fault detection with standard sampling rates by exploiting the frequency characteristics of fault signals rather than relying on high-time-resolution measurements.
Solution Approach 2:
The patent replaces the mechanical measurement approach (direct high-rate voltage sampling) with a computational approach (Fourier-based vector calculation). Instead of mechanically capturing rapid voltage changes through high sampling, the system uses signal processing to extract fault information from lower-rate measurements, substituting physical measurement constraints with mathematical transformation.
2Ease of operation
If vector calculations are used to determine voltage at the setting point, then the fault detection method becomes simpler to implement, but the measurement precision deteriorates in very short data windows
Solution Approach 1:
The patent applies preliminary filtering and signal conditioning before vector calculation by using the Fourier algorithm to decompose the signal into fundamental frequency components. This preliminary action of extracting the fundamental frequency content from the measured signal ensures that subsequent vector calculations are based on clean, filtered data, maintaining precision even with short data windows.
Solution Approach 2:
The patent introduces the Fourier algorithm as an intermediary processing step between raw measurement and final vector calculation. This intermediary transforms the raw signal into frequency-domain components, serving as a bridge that preserves measurement precision while enabling simplified vector-based fault detection logic.
3Measurement precision
If the waiting time for data collection is extended to improve vector calculation accuracy, then the measurement precision is improved, but the fault detection speed deteriorates
Solution Approach 1:
The patent changes the domain of analysis from time-domain transient behavior to frequency-domain steady-state characteristics. By transforming the problem into the frequency domain using Fourier algorithms, the system can extract accurate voltage and current vectors from short-duration measurements without requiring extended waiting periods, thus maintaining both precision and speed.
Data Source
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AI summary
A method, system and apparatus of fault detection in line protection for a power transmission system. A voltage (u) at a measurement point on an electrical line is obtained. The measurement point is a point at which a protection device for the line protection is installed. A current (i) at the measurement point is further obtained and a differential value of the current is determined. Then, a voltage (u q) at a setting point on the electrical line is determined from the voltage (u) at the measurement point, the current (i) at the measurement point and the differential value of the current (i) according to a time domain lumped parameter model for the electrical line. The voltage change between the determined voltage at the setting point during the fault period and a voltage at the setting point determined during a pre-fault period can be further determined. The fault detection can be performed based on the determined voltage change and a fault threshold. It can ensure voltage determination accuracy and detection reliability with a low sampling rate. Moreover, the solution can work right after the fault inception, almost no waiting time is required, and thus it may achieve a super-fast line protection.