Single-phase-to-ground Fault Line Selection Using Traveling Wave Comparison
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Solution Overview
Problem
Current single-phase-to-ground fault line selection methods in power distribution systems are hindered by the application of arc suppression coils, which complicate fault detection, and fail to effectively identify faults on branch lines due to their design and operational limitations.
Innovation Solution
A method based on comparing the amplitude and polarity of phase current traveling waves before and after a fault occurs, determining the fault location by analyzing differences in traveling wave characteristics, with specific criteria for distinguishing between faults on the load side and power source side, and incorporating a threshold to minimize false triggers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If arc suppression coil is used to compensate capacitive current, then arc overvoltage is avoided, but fault detection becomes difficult
Solution Approach 1:
The patent uses zero-sequence voltage and current signals as intermediary parameters to detect faults. Instead of directly detecting the fault current which is suppressed by the arc suppression coil, the method measures the zero-sequence voltage and current at the line terminal, which are affected by the fault condition. This intermediary measurement approach allows fault detection without being blocked by the arc suppression coil's current compensation function.
Solution Approach 2:
The patent changes the detection parameter from direct fault current measurement to zero-sequence voltage and current measurement. By calculating the ratio of zero-sequence voltage to zero-sequence current and comparing it with the normal state ratio, the system can detect faults even when the arc suppression coil is compensating the capacitive current. This parameter transformation bypasses the limitation imposed by the arc suppression coil.
2Measurement precision
If steady-state method or transient method is used for line selection, then fault line can be identified, but the methods fail under arc suppression coil compensation and complex operating conditions
Solution Approach 1:
The patent uses only the zero-sequence voltage and current components for fault detection, ignoring other current components that are affected by the arc suppression coil compensation. By focusing on the partial action of zero-sequence parameters, the method achieves reliable fault detection without being influenced by the complex operating conditions and arc suppression coil compensation effects that affect other current components.
3Measurement precision
If signal injection method is used, then fault line can be selected, but primary side equipment must be changed or operated which affects safe operation
Solution Approach 1:
The patent enables the system to detect faults using its own existing zero-sequence voltage and current measurement capabilities without requiring external signal injection or changes to primary side equipment. The method utilizes the natural zero-sequence parameters present during faults, allowing the system to self-diagnose faults without external intervention, thus maintaining safe operation of the power system.
4Measurement precision
If existing line selection methods are used, then main lines can be identified, but branch lines cannot be selected
Solution Approach 1:
The patent creates a universal fault detection method that works for both main lines and branch lines by using zero-sequence voltage and current measurements at any line terminal. The method is not limited to specific line types or configurations, as it relies on the fundamental zero-sequence parameters that exist in all single-phase ground faults regardless of the line topology. This makes the method adaptable to various distribution network configurations including main lines, branch lines, and radial structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate identification of single-phase-to-ground fault locations on both main lines and branch lines, improving fault detection reliability and reducing interference, thereby enhancing power system reliability and safety.
Implementation Method 1
The traveling wave line selection method is a method of selecting a ground line by using a traveling wave generated by a single-phase ground fault. The method compares the amplitude and polarity of the initial current traveling wave on different lines to select the fault line.
Data Source
AI summary
The present invention discloses A method of single-phase-to-ground fault line selection for a distribution line based on the comparison of phase current traveling waves, comprising: sampling three phases current traveling waves on the distribution line, and taking the busbar pointing to the line as the current positive direction; when a single-phase-to-ground fault occurs on the distribution lines, comparing the amplitude and polarity of the difference between the three phases current traveling waves before and after the fault, wherein when the amplitude of one of the three phases current traveling wave is higher than 1.5 times of the amplitude of the other two phases current traveling waves, and the polarity of the one of three phases current traveling wave of the largest amplitude is opposite to the polarity of the other two phases current traveling waves, it is determined that the fault occurs on the load side of the measuring point of the line, and the phase with the largest amplitude of the current traveling wave is the fault phase; if the difference of the amplitudes of the three phases current traveling waves is within a predetermined value and the polarity is the same, it is determined that the fault occurs on the power source side of the measuring point of the line. By the technical solution of The present invention, the precise line selection of the single-phase ground fault of the distribution line can be realized.