A High-Precision Noninvasive DC Voltage Measurement Method Based on a Near-Field Differential Array

Abstract

Noninvasive voltage measurement is crucial for the condition monitoring and fault diagnosis of ultrahigh-voltage direct current (UHVDC) systems. Existing electric-field inversion methods often suffer from sensitivity to sensor placement and vulnerability to common-mode interference, limiting their practical accuracy. To address these issues, this article proposes a noninvasive direct current (DC) voltage-inversion method based on a near-field differential array and the charge simulation method (CSM). Multiple electric field sensors are arranged radially near the conductor to form a differential configuration, which suppresses common-mode interference caused by ground-potential fluctuations and remote disturbance sources, and converts the conventional vector-field inversion into scalar operations, significantly reducing the dependence on precise sensor positioning. Furthermore, the optimal sensor deployment angle is derived through simulation analysis, further enhancing system robustness. Experimental validation is conducted on a 20-kV platform, achieving an inversion error better than 0.20 % of full scale (FS) and confirming that a 100-V source-voltage fluctuation can be reliably resolved. The experimental results demonstrate that the differential near-field configuration possesses strong adaptability to complex electric-field environments and maintains high measurement accuracy even under severe field distortion in enclosed spaces. With its advantages of high precision, strong anti-interference capability, and flexible installation, the proposed method provides a practical engineering solution for voltage monitoring in UHVDC transmission systems.