Zeeman Effect Current Sensor for DC Cable Shields
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Solution Overview
Problem
Existing devices are unable to accurately measure currents in direct current electrical energy transmission cables due to interference from external magnetic fields.
Innovation Solution
A device utilizing the Zeeman effect, featuring measurement cells with gas sensitive to the Zeeman effect, a polarized light source, and a polarimetry system to measure the rotation of polarization angle, which cancels out external magnetic field contributions and measures the current-induced magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inductive transformers are used to measure current, then electromagnetic induction principle enables measurement, but they do not allow measurements on direct current electrical energy transmission cables
Solution Approach 1:
The patent replaces the electromagnetic induction-based inductive transformer with an optical measurement system utilizing the Zeeman effect. This substitution enables direct current measurement capability while eliminating the fundamental limitation of inductive transformers, achieving both adaptability to DC cables and reliable measurement accuracy through optical detection methods.
Solution Approach 2:
The invention changes the measurement parameter from electromagnetic induction to optical polarization rotation caused by the Zeeman effect. By measuring the rotation of polarized light passing through a gas under magnetic field influence, the system achieves accurate DC current measurement where traditional inductive methods fail.
2Device complexity
If conventional measurement devices are used, then device simplicity is maintained, but surrounding magnetic fields such as Earth's magnetic field affect the measurement result
Solution Approach 1:
The patent extracts and eliminates the influence of external magnetic fields by using a differential measurement approach. The system measures the rotation of polarized light in two opposite directions and subtracts the readings, thereby removing the contribution of Earth's magnetic field and other environmental magnetic interference while preserving the measurement of the current-induced magnetic field.
Solution Approach 2:
The invention implements a feedback mechanism where the measurement system continuously monitors and compensates for external magnetic field influences. By measuring in both directions and processing the differential signal, the system actively eliminates environmental interference, ensuring precise current measurement despite the presence of surrounding magnetic fields.
3Ease of operation
If measurement is performed in the presence of environmental magnetic fields, then measurement can be conducted, but the contributions of environmental magnetic fields cannot be distinguished from current-induced magnetic fields
Solution Approach 1:
The patent employs asymmetric measurement directions to differentiate between environmental and current-induced magnetic fields. By measuring the polarization rotation in two opposite directions and observing that environmental fields produce symmetric effects while current-induced fields produce asymmetric effects, the system can isolate and measure the current component accurately.
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 device effectively measures cable shield currents by eliminating external magnetic field interference, allowing for accurate monitoring and control of insulation state in high-voltage DC or AC transmission grids.
Implementation Method 1
A device for measuring a current in at least one cable shield of an electrical transmission grid by the Zeeman effect in the presence of a magnetic field from the environment
Implementation Method 2
at least one polarimetry system configured so as to measure a first parameter corresponding to the rotation of a polarization angle due to the beam passing through the assembly of one or more measurement cells
Data Source
AI summary
The invention relates to a measurement device (1) for measuring a current in at least one cable shield of an electrical transmission grid using the Zeeman effect in the presence of a magnetic field (BT) from the environment, in particular the Earth's magnetic field or magnetic noise, comprising:at least one assembly of one or more measurement cells (3, 3′),at least one source of polarized light (7),at least one polarimetry system (11),in whichthe assembly of one or more measurement cells (3, 3′) is configured so as to define at least one pair of first and second measurement sections (I1, I2), the measurement sections (I1, I2) of a pair being parallel and arranged perpendicular to a conductor (31) that is connected to the cable shield and on the opposite sides of the conductor (31), the polarized beam of light (9) flowing through the second measurement section (I2) in the opposite direction with respect to through the first section (I1) so that the contributions of the magnetic field from the environment to the first parameter in the first and second measurement sections (I1, I2) cancel each other out.