Circuit Interrupter Grounded Neutral Detection
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Solution Overview
Problem
Existing circuit interrupters face difficulties in detecting grounded neutral conditions without applying a load current, as the small ground fault current makes detection challenging and often requires costly components like capacitors and transformers to achieve stability, increasing the overall cost.
Innovation Solution
A circuit interrupter design that utilizes a single ground fault current sensor and a processor to analyze the power supply's direct current output, determining the presence of specific characteristics indicative of a grounded neutral condition, allowing for accurate tripping of separable contacts without the need for additional costly components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitor and grounded neutral transformer are added to create an unstable feedback condition for amplifying ground fault current, then the detection capability for grounded neutral conditions without load current is improved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the capacitor and grounded neutral transformer from the detection circuit. Instead of using these additional components to create instability and amplification, the invention uses a simplified circuit that achieves grounded neutral detection through alternative means, thereby reducing device complexity while maintaining detection capability.
Solution Approach 2:
The patent creates an artificial ground fault current that copies or simulates the characteristics of a actual ground fault condition. By injecting a test current through the neutral conductor and measuring the voltage drop, the system can detect grounded neutral conditions without needing the complex amplification circuitry of capacitor and transformer combinations.
2Measurement precision
If a capacitor and grounded neutral transformer are used to amplify ground fault current for detection, then the detection sensitivity is improved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces expensive, complex components (capacitor and grounded neutral transformer) with simpler, cheaper alternatives. The new design uses basic circuit elements that are less costly to manufacture and assemble, reducing the overall manufacturing cost while achieving the same detection sensitivity through a different technical approach.
Solution Approach 2:
The patent changes the detection parameters by measuring voltage drop across the neutral conductor instead of directly measuring and amplifying ground fault current. This parameter change allows for simpler circuitry with lower manufacturing costs while maintaining the ability to detect grounded neutral conditions with the required sensitivity.
3Object-affected harmful factors
If the ground fault current is small without load current, then the safety risk is reduced, but the detection difficulty increases
Solution Approach 1:
The patent performs preliminary action by injecting a test current through the neutral conductor before an actual fault condition occurs. This artificial current creates a measurable voltage drop that allows the system to detect grounded neutral conditions proactively, even when no load current is present and when actual ground fault currents would be small and difficult to detect.
Solution Approach 2:
The patent introduces an intermediary measurement approach by measuring the voltage drop across the neutral conductor as an intermediate parameter. This voltage measurement serves as a mediator that indirectly indicates the presence of a grounded neutral condition, making detection easier without requiring direct measurement of small ground fault currents.
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 reliable detection of grounded neutral conditions with reduced costs by eliminating the need for unstable feedback circuits, ensuring accurate tripping of circuit interrupters even without load current, thereby improving the efficiency and cost-effectiveness of the detection process.
Implementation Method 1
a power supply electrically connected between the first and second electrical conductors, the power supply being configured to convert alternating current power from the first and second electrical conductors to a direct current power
Implementation Method 2
a ground fault detection circuit configured to sense a difference between a current through the first electrical conductor and a current through the second electrical conductor
Data Source
AI summary
A circuit interrupter includes a first electrical conductor, a second electrical conductor, separable contacts, an operating mechanism configured to open and close the separable contacts, and a trip circuit including a trip actuator configured to cooperate with the operating mechanism to trip open the separable contacts. The circuit interrupter also includes a ground fault detection circuit configured to sense a difference between currents through the first and second electrical conductors and to output an output signal based on the sensed difference, a power supply configured to convert alternating current power from the first and second electrical conductors to a direct current power, and a processor configured to receive the direct current power and the output signal. The processor is also configured to determine whether a characteristic of the power supply is present in the output signal and to control the trip circuit based on the determination.