Rogowski Coil Current Transducer Online Calibration
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Solution Overview
Problem
Rogowski coil current transducers face accuracy limitations due to unknown sensitivity changes from environmental factors like temperature, mechanical constraints, humidity, and aging, which current signal processing cannot compensate, leading to measurement errors and requiring additional calibration efforts.
Innovation Solution
Incorporating a third conductor winding to receive a calibration current signal, allowing the transducer electronics to amplify and process both the current and calibration signals, enabling compensation for coil sensitivity and amplifier gain drifts, thereby eliminating measurement errors and allowing for continuous online calibration without interrupting the rated current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Rogowski coil current transducer is used for measuring current, then the device benefits from excellent linearity and high dynamic range, but measurement accuracy deteriorates due to unknown sensitivity changes from environmental factors
Solution Approach 1:
The patent implements a feedback mechanism by introducing a third conductor winding that receives a calibration current signal. This calibration signal generates a voltage that is processed by the transducer electronics to determine sensitivity changes. The system continuously monitors and compensates for sensitivity drift caused by environmental factors, maintaining measurement accuracy through automatic feedback adjustment without requiring manual recalibration.
2Measurement precision
If traditional calibration methods are used for Rogowski coils, then sensitivity changes can be compensated, but additional calibration efforts and maintenance interruptions are required
Solution Approach 1:
The patent enables continuous calibration by integrating a third conductor winding that receives calibration current signals during normal operation. The transducer electronics processes both the measurement signal from the secondary winding and the calibration signal simultaneously, allowing sensitivity compensation to occur continuously without interrupting the rated current measurement. This eliminates the need for separate calibration procedures and maintains uninterrupted service.
3Adaptability or versatility
If environmental factors like temperature and humidity are present, then the Rogowski coil operates in real-world conditions, but coil sensitivity and amplifier gain drift causing measurement errors
Solution Approach 1:
The system uses feedback control by continuously monitoring sensitivity changes through the third conductor winding's calibration signal response. The transducer electronics calculates sensitivity drift caused by environmental factors and automatically adjusts the measurement signal accordingly, compensating for temperature, humidity, and aging effects in real-time without requiring the system to be removed from its operating environment.
Solution Approach 2:
The Rogowski coil system performs self-calibration by using its own third conductor winding to generate calibration signals and process the resulting voltage through the existing transducer electronics. The system automatically detects and compensates for its own sensitivity drift without requiring external calibration equipment or manual intervention, making the calibration process self-service and eliminating measurement errors from environmental factors.
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 provides accurate and direct calibration of Rogowski coil sensitivity, compensating for environmental and aging effects, ensuring high measurement accuracy and reducing maintenance needs by enabling continuous online calibration without interrupting the current measurement.
Implementation Method 1
When placed around a primary conductor carrying an electrical current, the Rogowski coil generates a voltage proportional to the derivative of the current according to Ampere's law
Implementation Method 2
a third conductor winding having a pair of third terminals with a third number of loops, wherein the third conductor winding is adapted to receive a calibration current signal
Data Source
AI summary
An arrangement for measuring a current with a Rogowski type current transducer and transducer electronics. The current transducer has a primary conductor winding for carrying the rated current to be measured, and a secondary conductor winding. The secondary conductor winding adapted to induce a voltage signal VS′ between a pair of second terminals. The current transducer having a third conductor winding adapted to receive a calibration current signal. The voltage signal VS′ contains a coil sensitivity S and is a superposition of a rated current voltage signal and an additional calibration signal. The transducer electronics being adapted to amplify both the current voltage signal and the calibration signal in the same amplifier and divide the amplified current voltage signal by that part of the amplified calibration signal that contains the coil sensitivity and the gain.