Ground Fault Detecting Circuit Using Resistance Elements
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Solution Overview
Problem
Conventional ground fault detecting circuits are large in size, expensive, and have poor detection accuracy due to the use of three-phase transformers and complex voltage division systems.
Innovation Solution
A compact ground fault detecting circuit using resistance elements connected to AC lines and a ground voltage, with a determination circuit that calculates the absolute value of voltage across a specific resistance element to detect ground faults, eliminating the need for a three-phase transformer and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a three-phase transformer is used in the ground fault detecting circuit, then the detection function is achieved, but the device size becomes large and the cost increases
Solution Approach 1:
The patent extracts the ground fault detection function from the complex three-phase transformer system and implements it using a simple resistance element connected to the neutral point. This removes the bulky transformer while retaining the essential detection capability through voltage monitoring across the resistance element.
Solution Approach 2:
Instead of using a three-phase transformer to detect ground faults, the patent creates a simplified equivalent detection system using a resistance element that replicates the detection function. The resistance element serves as a substitute that provides the same ground fault detection capability without the size and cost of a transformer.
2Measurement precision
If a three-phase transformer is used in the ground fault detecting circuit, then the detection function is achieved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces the expensive three-phase transformer with a inexpensive resistance element for ground fault detection. The resistance element is a low-cost component that can be easily manufactured and replaced if needed, significantly reducing the overall manufacturing cost while maintaining detection functionality.
Solution Approach 2:
The patent extracts the essential detection function from the expensive transformer system and implements it using a simple, low-cost resistance element. This removal of the transformer eliminates the primary cost driver while preserving the ground fault detection capability.
3Measurement precision
If a complex voltage division system is used, then the detection function is achieved, but the circuit complexity increases
Solution Approach 1:
The patent extracts the ground fault detection function from the complex voltage division system and implements it using a single resistance element connected to the neutral point. This simplifies the circuit topology while maintaining the ability to detect ground faults through voltage monitoring.
Solution Approach 2:
The patent creates a simplified detection system that copies the essential function of the complex voltage division system. The resistance element provides a direct voltage signal that indicates ground fault conditions, replicating the detection capability without the complexity of multiple voltage division components.
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
The solution allows for high-accuracy detection of ground faults without a three-phase transformer, making the device compact and cost-effective, with significant voltage amplitude changes indicating fault occurrence.
Implementation Method 1
the voltage across the terminals of the fourth resistance element increasing in amplitude when the ground fault occurs
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In the ground fault detecting circuit (6), one terminals of first to third resistance elements (31 to 33) are connected to first to third AC lines (RL, SL, TL), respectively, the other terminals of the first to third resistance elements (31 to 33) are commonly connected to one terminal of a fourth resistance element (34), and the other terminal of the fourth resistance element (34) is connected to a line of a ground voltage (GND). On the basis of a voltage across the terminals of the fourth resistance element (34), the ground fault detecting circuit (6) detects whether a ground fault has occurred or not. Since a current does not flow through the fourth resistance element (34) in the normal state and flows through the fourth resistance element (34) after the occurrence of a ground fault, it is possible to detect the occurrence of the ground fault at a high accuracy.