Fault Current Component Determination in AC Generators
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Solution Overview
Problem
Existing methods struggle to accurately separate fault current components from differential currents in AC current generators, especially with increasing leakage currents due to larger photovoltaic units, leading to reduced sensitivity in fault current detection.
Innovation Solution
A method and device that generate an electric signal dependent on generator voltages with respect to earth potential, scale it by a dynamically updated scaling factor, and subtract it from the differential current to isolate the fault current component, ensuring the effective value reaches a minimum, thus accurately separating leakage and fault currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If photovoltaic units are increased in power and dimension without a transformer, then the power output is improved, but the leakage current increases due to increased capacitances with respect to earth potential
Solution Approach 1:
The patent segments the differential current into two distinct components: leakage current and fault current. By measuring both the differential current and the voltage between input lines and earth potential, the system separately identifies and evaluates each current component, allowing the harmful leakage current to coexist with high power output while maintaining fault detection capability.
2Power
If high leakage currents are present, then the power output can be maintained, but the sensitivity of the differential current transformer is reduced for fault current detection
Solution Approach 1:
The patent segments the differential current into two distinct components: leakage current and fault current. By measuring both the differential current and the voltage between input lines and earth potential, the system separately identifies and evaluates each current component, allowing the harmful leakage current to coexist with high power output while maintaining fault detection capability.
Solution Approach 2:
The patent introduces voltage measurement between the input lines and earth potential as an intermediary parameter. This voltage measurement serves as a mediator that enables the system to distinguish between leakage current and fault current components, thereby maintaining detection sensitivity even in the presence of high leakage currents.
3Measurement precision
If frequency filtering is applied to remove leakage current components, then the leakage current separation is improved, but the method proves insufficient to effectively remove the essential leakage current component
Solution Approach 1:
The patent introduces voltage measurement between the input lines and earth potential as an intermediary parameter. This voltage measurement serves as a mediator that enables the system to distinguish between leakage current and fault current components, thereby maintaining detection sensitivity even in the presence of high leakage currents.
Solution Approach 2:
The patent changes the measurement parameters from solely current-based to a combination of current and voltage measurements. By measuring both the differential current and the voltage between input lines and earth potential, the system gains additional information that enables effective separation of leakage and fault current components without relying on insufficient frequency filtering.
Data Source
AI summary
For the purpose of determining a fault current component of a differential current which is measured as a current sum over a plurality of lines carrying a current of an AC current generator, an electric signal which depends on generator voltages present at the AC current generator with respect to earth potential and which is in phase with a leakage current component of the differential current is generated. The electric signal is scaled by multiplying it by a scaling factor; and the scaled electric signal is subtracted from the differential current to obtain a remainder. The scaling factor is repeatedly updated such that the effective value of the remainder reaches a minimum at the present value of the scaling factor.