Grounding Impedance Measurement Using Multi-Frequency Modeling
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Solution Overview
Problem
Existing methods for determining grounding impedance of power engineering installations, such as overhead line pylons, are cumbersome, risky, or require complex setups, often leading to inaccurate measurements due to capacitive and inductive couplings, especially when considering the entire system's safety and local grounding system integrity.
Innovation Solution
Determine at least two impedance values using test currents at different frequencies close to the mains frequency (e.g., 10 Hz to 100 Hz) while the grounding device remains connected to other installations, employing a model to approximate the grounding impedance based on these values, minimizing error sources and simplifying the measurement process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ground wire is removed to measure local grounding impedance, then measurement accuracy is improved, but operation complexity and safety risks increase significantly
Solution Approach 1:
The patent introduces an intermediary modeling approach where a mathematical model represents the grounding system with connected components. Instead of physically disconnecting the ground wire, the invention uses measurement data combined with a system model to calculate the local grounding impedance, thereby avoiding the operational complexity and safety risks of physical disconnection while maintaining measurement accuracy.
2Productivity
If high-frequency methods are used to measure grounding impedance, then measurement speed is improved, but measurement accuracy deteriorates due to coupling errors
Solution Approach 1:
The patent changes the measurement parameters by using low-frequency test currents (e.g., 50 Hz or 16.67 Hz) instead of high-frequency signals. This parameter change eliminates capacitive and inductive coupling errors that plague high-frequency methods, while the modeling approach compensates for any reduction in direct measurement speed, providing both accuracy and practical efficiency.
3Measurement precision
If current measuring devices are installed at each connection point, then measurement accuracy is improved, but device complexity and installation time increase
Solution Approach 1:
The patent merges multiple measurement functions into a single measurement setup. Instead of installing separate current measuring devices at each connection point, the invention combines impedance measurements taken at the grounding device with a mathematical model of the connected system to derive local grounding impedance, thereby reducing device complexity and installation requirements while maintaining the ability to obtain accurate results.
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
Provides accurate and efficient measurement of grounding impedance with reduced effort and cost, allowing for precise assessment of local grounding systems without disconnecting them from the network, thus ensuring safety and reliability.
Implementation Method 1
at least two impedance values are determined on the grounding device with at least two different test currents at a specified frequency respectively
Data Source
AI summary
The present invention relates to a method (400) for determining a grounding impedance (210) of a grounding device (120) of a power engineering installation (110). The method comprises determining (406, 412) at least two impedance values on the grounding device (120), while the grounding device (120) is electrically connected to at least one further grounding device of at least one further power engineering installation (170, 180). Each of the at least two impedance values is determined with a respective test current at a specified frequency. The frequencies of the respective test currents are different. The method further comprises determining (414) at least one parameter of a model (500), which represents the grounding device (120) and the at least one further grounding device, as a function of the at least two impedance values. The at least one parameter comprises an approximate value for the grounding impedance (210) of the grounding device (120).