Non-Network Frequency Monitoring for High-Impedance Fault Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-impedance faults in energy transmission lines with solidly grounded neutral points are difficult to detect due to low fault currents and lack of voltage shift, posing a risk to safety as they often go undetected in medium-voltage networks.
Innovation Solution
Introducing an electrical measurement signal with a non-network frequency into the energy transmission device to measure frequency-band-related characteristics, allowing for the detection of faults by comparing measured values to reference values, and generating a fault signal when deviations indicate a fault.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional monitoring methods are used at network frequency, then the monitoring system operates with standard equipment, but high-impedance faults cannot be reliably detected
Solution Approach 1:
The patent changes the frequency parameter of the measurement signal from the network frequency (50/60 Hz) to a non-network frequency (e.g., 1 kHz or higher). This parameter change allows the measurement signal to be distinguished from operating currents and enables reliable detection of high-impedance faults that are invisible at network frequency, directly resolving the contradiction between detection reliability and measurement difficulty
Solution Approach 2:
The patent introduces a non-network frequency measurement signal as an intermediary carrier to detect faults. This intermediary signal passes through the transmission line and reflects off faults, allowing indirect detection of high-impedance faults without directly measuring the difficult fault current at network frequency
2Device complexity
If solidly grounded neutral point configuration is used, then the network structure is simplified, but voltage shift detection becomes impossible
Solution Approach 1:
The patent changes the detection parameter from voltage shift (which requires asymmetric grounding) to impedance change at non-network frequency. By measuring the real and imaginary components of impedance at a frequency other than network frequency, the system can detect faults in solidly grounded networks where traditional voltage relay methods fail
3Ease of operation
If asymmetric loading is present during operation, then the network operates under realistic conditions, but residual current becomes unsuitable as a detection criterion
Solution Approach 1:
The patent extracts the detection measurement from the problematic residual current at network frequency and separates it into real and imaginary components at non-network frequency. By measuring impedance components (real part representing resistive losses, imaginary part representing reactive components) at a different frequency, the system eliminates the interference caused by asymmetric loading while maintaining realistic operating conditions
Data Source
AI summary
A method monitors an energy transmission device, in particular an energy transmission line or an energy distribution network, via which electric current is transmitted at a predefined network frequency. An electrical measurement signal having at least one non-network frequency, i.e. a frequency which differs from the network frequency, or a non-network frequency band, is fed into the energy transmission device at a predefined position thereon. An electrical measured quantity related to the non-network frequency or the non-network frequency band is measured at the predefined position or a different position on the energy transmission device with the formation of at least one measured value or frequency-band-related measured value characteristic. A fault signal is generated if the measured value, the frequency-band-related measured value characteristic, a comparative value or comparative value characteristic formed with the measured value or the measured value characteristic indicates a fault in the energy transmission device.