How to adjust the sensitivity of a residual current transformer?
Apr 17, 2026| 1. Sensitivity optimization during the design and selection phase. Sensitivity is determined during product design by the core material, winding structure, and shielding measures:
High permeability materials: Using iron-nickel soft magnetic alloys (such as permalloy), microcrystalline or amorphous materials can significantly improve the initial permeability, enhancing the response to small leakage currents.
Uniform winding distribution: By optimizing the distribution of the secondary windings, phase difference and ratio difference are reduced, improving the accuracy of the transmission characteristics.
Adding a magnetic shielding layer: Effectively suppresses external electromagnetic interference, reducing the risk of malfunction. Experiments show that the error can be optimized from 10% to about 2%.
Core cross-sectional area design: Appropriately increasing the cross-sectional area can improve output power and sensitivity, especially suitable for electromagnetic residual current protection devices.
2. Parameter Calibration During Installation and Use
In practical applications, sensitivity matching calibration can be performed using the corresponding equipment:
Some protection devices allow setting the current transformer sensitivity via a menu to calibrate the displayed current to match the measured value (e.g., ABB CPX-C series). This operation must be performed under professional guidance to ensure that the set current matches the load.
3. Testing and Verification Methods
According to national standards (e.g., GB 16916.1-2014), its non-operating performance can be tested by applying 6 times the rated current (6In) to verify whether the balance characteristics meet the standards.
Use a high-precision current transformer calibration device (e.g., HESE equipment) for error detection to ensure that the accuracy class reaches 0.5 or even higher.
