Rogowski Cable Sensor with Magnetic Coupling for High Current Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current sensors, particularly those with magnetic cores, are ineffective in measuring high currents characteristic of short circuits due to saturation and lack of proportional response, and Rogowski-type sensors face installation challenges with loop accuracy and variability, leading to measurement drifts over time.
Innovation Solution
A Rogowski-type current sensor with a cable loop design featuring a connection sleeve containing electronic memory for calibration parameters and a deformable circular ring for maintaining or opening the loop, ensuring accurate and durable installation, and a non-magnetic body to prevent measurement interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Rogowski-type sensors with cable loops are used, then measurement of high currents is improved, but installation accuracy and reproducibility deteriorate due to loop diameter and circumferential angle variations
Solution Approach 1:
The sensor is divided into a fixed portion and a mobile portion that can be assembled separately. The fixed portion contains the transformer winding with defined geometric parameters, while the mobile portion is positioned and fixed to complete the loop, allowing precise control of the loop geometry during assembly.
Solution Approach 2:
A positioning device with a conical portion acts as an intermediary between the mobile portion and the fixed portion. This conical interface ensures precise alignment and reproducible positioning of the mobile portion relative to the fixed portion, eliminating variations in loop diameter and circumferential angle.
2Ease of operation
If cable ends are connected with overlapping portions or sleeves, then the loop can be closed, but measurement accuracy deteriorates due to play between cable ends and assembly imprecision
Solution Approach 1:
The mechanical connection between cable ends is replaced by a magnetic coupling system. The mobile portion and fixed portion are attracted to each other through magnetic force, eliminating the need for mechanical play or overlapping portions while maintaining a secure closed loop configuration.
Solution Approach 2:
The connection method changes from mechanical (overlapping or sleeved ends with inherent play) to magnetic attraction, where the gap between ends is controlled by magnetic force rather than mechanical interference, achieving both ease of closure and high precision.
3Device complexity
If magnetic core transformers are used, then sensor structure is simplified, but measurement capability deteriorates due to saturation at high currents
Solution Approach 1:
The magnetic core is extracted from the transformer structure, leaving only the winding. This air-core transformer eliminates magnetic saturation while maintaining the essential transformer function of inducing voltage in the secondary winding proportional to the primary current.
Solution Approach 2:
The sensor uses a composite structure combining the cable insulation material with the transformer winding, where the cable itself serves as the magnetic path replacement. This integrated design achieves both structural simplicity and high current measurement capability without magnetic saturation.
4Reliability
If the sensor requires frequent adjustments and recalibration, then initial installation complexity increases, but long-term reliability improves
Solution Approach 1:
The transformer is pre-calibrated during manufacturing with defined geometric parameters and winding turns. This preliminary calibration eliminates the need for field recalibration, as the sensor maintains its calibration characteristics throughout its service life due to the rigid, reproducible assembly structure.
Solution Approach 2:
The sensor design incorporates self-aligning features through the conical positioning interface and magnetic attraction, which automatically maintain the correct geometric relationship between components without requiring external adjustment or calibration procedures during installation or operation.
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 provides a reliable, easy-to-install current sensor that maintains accurate measurements over time, preventing measurement drifts and ensuring precise monitoring of high currents without the need for frequent adjustments, suitable for permanent installations in electrical equipment.
Implementation Method 1
Current sensors are used on electricity transmission installations to measure certain faults and in particular short-circuits by means of currents induced in them by the current flowing in the element to be monitored
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a sensor including a cable (5) that is wound in a loop around a material to be monitored and including a Rogowski coil (10). The sensor is original in that it is open on the ends thereof (6, 7), that is, the coil (10) is flush with the end surfaces (25) of the cable (5), and in that an abutment between the two ends establishes perfect continuity between the coil and the measurement on a circumference. The cable can be provided with a temperature sensor and a memory in which the measurement characteristics of the sensor are recorded. The sensor is reliable, precise, and capable of being permanently left on electrical equipment or easily reinstalled.