Open-Phase Fault Monitoring via Magnetoresistive Current Sensing
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Solution Overview
Problem
Conventional methods struggle to accurately detect open-phase faults in nuclear power plant auxiliary power systems due to the difficulty in monitoring phase loss using current-type and voltage-type protections, especially in no-load conditions where current changes are minimal.
Innovation Solution
An open-phase fault monitoring system utilizing a current monitoring unit with tunnel junction magneto-resistive magnetic field sensors, a relay communication unit, and a data processing unit to accurately identify open-phase events by measuring currents through transformer cables and ground wires, employing algorithms for real-time detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional voltage-type protection is used, then voltage monitoring is simple, but open-phase detection accuracy deteriorates because synthesized voltage amplitude and phase angle remain substantially unchanged
Solution Approach 1:
The patent replaces conventional voltage-type protection with current monitoring based on magneto-resistive magnetic field sensing chips. This substitution enables accurate detection of open-phase events by measuring current changes through the zero-sequence current algorithm, achieving both ease of implementation and high detection accuracy.
Solution Approach 2:
The patent changes the monitoring parameter from voltage to current. By monitoring current flowing through the transformer cable and ground wire, the system can detect open-phase events through significant current changes, overcoming the limitation of voltage-type protection where synthesized voltage parameters remain substantially unchanged.
2Ease of operation
If conventional current-type protection is used, then current monitoring is straightforward, but detection accuracy deteriorates because no-load current is at mA level and does not change obviously after phase losing
Solution Approach 1:
The patent replaces conventional current transformers (CT) with magneto-resistive magnetic field sensing chips. This substitution enables accurate measurement of small no-load currents at mA level by detecting magnetic field changes, achieving both ease of operation and high measurement precision that conventional CT cannot provide.
Solution Approach 2:
The patent employs magneto-resistive magnetic field sensing chips that utilize composite material properties to detect magnetic field changes. These chips can accurately measure small currents by detecting magnetic field variations, overcoming the limitation of conventional CT in detecting mA-level no-load current changes during open-phase events.
3Ease of manufacture
If traditional measuring means such as current transformer are used, then device installation is conventional, but detection capability deteriorates due to inability to accurately detect mA level current changes
Solution Approach 1:
The patent replaces traditional current transformers with magneto-resistive magnetic field sensing chips. This substitution maintains ease of installation while dramatically improving reliability by enabling accurate detection of mA-level current changes that conventional CT cannot detect, ensuring reliable open-phase event identification.
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 system provides real-time, accurate, and cost-effective open-phase fault detection with small volume and easy installation, enhancing nuclear power plant safety by enabling timely maintenance.
Implementation Method 1
both including two magnetic field sensing chips with tunnel junction magneto-resistive type
Implementation Method 2
enclosed by two ferrite rings, where a center hole passes through a conductor to be measured, and a magnetic ring air gap is machined on one of the ferrite rings
Data Source
AI summary
The present disclosure relates to the technical field of electrical device state monitoring, and particularly discloses an open-phase fault monitoring system, in which a relay communication unit is configured with an MCU as a central control processing unit, and an external ADC realizes high-speed A/D conversion for a plurality of signals; a timing function is realized by a GNSS&RTC of the relay communication unit, a data interaction function is realized by a LORA module, and data is sent to a background industrial personal computer based on a designed sampling frequency. The system of the present disclosure has the advantages of small volume, high precision, low cost, easy installation and the like, and realizes real-time monitoring and accurate identification of a line open-phase fault of an auxiliary power supply system in a nuclear power plant.