Ground Fault Detection in Isolated Two-Wire Power Lines
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Solution Overview
Problem
Existing two-wire power line systems in ECP-equipped trains face challenges in detecting ground faults or leakage current due to their isolation from ground, which limits the effectiveness of fault detection methods.
Innovation Solution
The implementation of high impedance voltage dividers connected between each wire of the power line and ground, combined with analog to digital conversion and logic circuits, allows for the detection of faults by comparing output voltages and generating a fault signal when they are not approximately equal or within a predetermined range, with additional features like impedance calculation and fault location identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the two-wire power line is isolated from ground to provide floating operation, then system reliability and safety are improved, but fault detection capability deteriorates
Solution Approach 1:
The patent introduces ground reference circuits as intermediary components that provide a reference path to ground without creating a direct ground fault. These circuits include resistors and voltage dividers that allow measurement of voltage potentials relative to ground while maintaining the isolated floating operation of the power line, thus enabling fault detection without compromising system reliability
Solution Approach 2:
The patent replaces traditional ground-based fault detection methods with voltage comparison electronics. By using operational amplifiers and voltage dividers to create virtual ground references, the system can detect faults through electrical voltage comparisons rather than direct ground connections, maintaining isolation while enabling detection
2Difficulty of detecting and measuring
If voltage dividers are added to enable fault detection, then fault detection capability is improved, but device complexity increases
Solution Approach 1:
The ground reference circuits serve multiple functions simultaneously: they provide voltage division for signal conditioning, establish reference potentials for comparison, and enable fault detection without requiring separate dedicated components for each function. This multi-functionality reduces overall system complexity despite adding detection capability
Solution Approach 2:
The patent combines the voltage division, reference generation, and fault detection functions into integrated circuits where operational amplifiers and resistors serve dual purposes. The same components that condition signals also provide reference voltages for fault detection, merging multiple functions into unified circuit blocks
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 solution enables accurate and reliable detection of faults in two-wire electric power lines isolated from ground, ensuring the safety and efficiency of ECP brake systems by identifying faults and calculating their impedance, thereby facilitating timely and precise brake activation along the train length.
Implementation Method 1
substantially identical high impedance voltage dividers connected between each of the two wires of the power line and ground
Data Source
AI summary
An apparatus and method for detecting faults in a two-wire electric power line isolated from ground includes substantially identical high impedance voltage dividers connected between each of the two wires of the power line and ground, circuits for carrying the output voltages from each voltage divider, a circuit for comparing the output voltages, and outputting a fault signal indicative of a ground fault.