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All-fiber quantum current transformer based on nitrogen-vacancy centers

Qingtao Guo, Chenggang Guan, 龚姣丽, junchang huang, Chaoqiang Dong, 何泓洋 He Hongyang, ruichang zheng, Qingling Mei, Junzhu Ye, liangyu chen, Mingqing Cai

Published Oct 13, 2026• 0 citations
Publisher

Abstract

High-voltage substations impose stringent requirements on current measurement, demanding simultaneously high electrical insulation and stable, high-precision performance. Here we propose and experimentally validate an all-fiber quantum current transformer based on nitrogen-vacancy (NV) centers in diamond. The transformer employs four optical fibers to realize power delivery and signal transmission between the high-voltage and low-voltage sides, completely eliminating metallic electrical connections. The system achieves a magnetic sensitivity of 4.05 nT/Hz 1/2 , with highly linear current response ( R 2 = 0.998) and a measurement accuracy better than 1%. This all-fiber architecture satisfies the dual constraints of high-voltage insulation and low power consumption while preserving the metrological precision of quantum sensing, providing a viable pathway toward non-invasive precision current monitoring in next-generation smart substations.

DOI
10.1364/oe.611797

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High-voltage substations impose stringent requirements on current measurement, demanding simultaneously high electrical insulation and stable, high-precision performance. Here we propose and experimentally validate an all-fiber quantum current transformer based on nitrogen-vacancy (NV) centers in diamond. The transformer employs four optical fibers to realize power delivery and signal transmission between the high-voltage and low-voltage sides, completely eliminating metallic electrical connections. The system achieves a magnetic sensitivity of 4.05 nT/Hz 1/2 , with highly linear current response ( R 2 = 0.998) and a measurement accuracy better than 1%. This all-fiber architecture satisfies the dual constraints of high-voltage insulation and low power consumption while preserving the metrological precision of quantum sensing, providing a viable pathway toward non-invasive precision current monitoring in next-generation smart substations.
In this report, we propose a quantum sensing architecture for high-voltage (HV) grid current measurement based on an integrated diamond quantum sensor (DQS). The DQS is installed in the HV line for non-invasive busbar current measurement. An optical fiber composite insulator (OFCI) is employed to deliver 532 nm laser for diamond excitation, 860 nm laser to energize sensing system and 830 nm light for communication between equipment on high-voltage and low-voltage side. The OFCI ensures robust insulation performance while facilitating high-precision, long-distance current measurements. Dual-channel microwave (MW) configuration implemented in the board-level measurement system tracks two resonant frequencies along the nitrogen-vacancy (NV) axis, effectively suppressing temperature drift. This quantum sensing scheme achieves a measurement range of up to 5000 A with an accuracy of 0.15%. This configuration presents a novel approach and reliable system for the practical application of quantum sensors in HV grid monitoring.
Diamond nitrogen-vacancy (NV) centers have attracted extensive research interest for quantum sensing applications across various physical domains, owing to their prolonged coherence times and the capability of optical readout at room temperature, which offers a promising technical pathway for detecting fast-responding and transient signals in emerging power systems. This work presents a quantum sensing device based on the Zeeman and Stark effects of NV centers, designed for power system measurement applications, with a rated voltage of 10kV and a rated current of 1kA, enabling simultaneous voltage and current sensing. The device achieves a measurement accuracy of 0.69% under the rated voltage of 10 kV and +0.23% under the rated current of 1 kA, verifying the feasibility of employing quantum sensing based on NV centers for simultaneous voltage and power measurements in power systems.
This dissertation presents the development and characterization of fully integrated quantum sensors based on nitrogen vacancy (NV) centers in diamond. While existing NV-based sensors are typically large and complex, this work focuses on miniaturizing the technology and demonstrating its application as a current sensor. The primary research question addressed is whether fully integrated NVbased quantum sensors with LED excitation can be realized with performance comparable to conventional sensor technologies. To this end, two sensor prototypes were developed: one as the smallest fully integrated NV quantum sensor with a complete electrical interface to date, achieving a sensitivity of 32 nT/ √ Hz; and another as the first NV-based sensor implemented on a flexible PCB, which is even smaller and achieves a sensitivity of 96 nT/ √ Hz. Thereby both sensors utilize randomly oriented diamond microcrystals. Methodologically, a novel procedure for determining the orientation of the diamond crystals was developed, allowing for effective signal extraction despite the random crystal orientation. Further, magnetic fields were simulated using COMSOL Multiphysics to investigate the feasibility of applying these sensors for current measurements. In this context, a new measurement concept for determining currents in segmented multi-wire cables of three-phase power grids was developed, demonstrating the potential of NV-based sensors in smart grid applications. The results indicate that these quantum sensors can be more easily integrated, even when diamonds are placed arbitrarily, thus paving the way for new applications in smart grid monitoring and other fields requiring compact, high-precision magnetic field sensors.
Abstract In power network systems, there is an urgent demand for highly accurate and miniaturized sensors, owing to their high safety level and limited installation space. Current sensors in high‐voltage grids are required to accommodate harsh environments and provide accurate measurements of several kiloamperes. Thus, this study proposed an integrated quantum diamond sensor to facilitate high‐accuracy, large‐dynamic‐range current measurements. The design incorporated optical fiber and directional microwave (MW) antennas to drive the diamond sensor, which significantly reduced the size and power consumption on the high‐voltage side. Remote‐control and demodulation systems are installed more than 10 m away from the low‐voltage side. The proposed approach achieved zero power consumption on the high‐voltage side and ensured efficient signal transmission. A passive diamond probe manufactured using microfabrication processes facilitated miniaturization and practical deployment. Through parameter optimization, a magnetic detection sensitivity of 4.86 nT·Hz −1/2 is achieved at a safe distance of 11 m, which can be further optimized to 0.77 nT·Hz −1/2 with enhanced MW power. This sensor achieved a current measurement error of ±0.4% in the 1000 A measurement range. Thus, this study provides a new solution for the application of diamond quantum sensors in power systems.
Precision measurements of electric current flow in motors and power converters is indispensable for efficient digital control by monitoring their energy use. Nitrogen-vacancy (NV) centers in a crystalline diamond are promising candidates for sensitive magnetometry and electric current measurements. In a diamond quantum sensor with NV centers, the Zeeman splitting of the electron spin state of the NV center can be utilized to detect magnetic field. This is because the splitting of the spectral line is proportional to the external magnetic field strength, and the arbitrary constant of the gyromagnetic ratio is independent of both frequency and magnetic field. Then, the Zeeman splitting can be measured with optically detected magnetic resonance (ODMR) spectroscopy.
The research focuses on the solid-state spin system of diamond NV (Negatively Charged Nitrogen Vacancy, NV) color centers, which exhibit excellent optical readout, polarization properties, and millisecond-scale coherent time. This makes it an important means to achieve quantum information processing and quantum precision measurement. Additionally, its ultrahigh sensitivity to magnetic fields provides a potential path for diamond’s high-precision current measurement. This paper investigates a reliable method in the field of direct current measurement using quantum sensing technology based on diamond NV color centers. It involves measuring the change in the optically detected magnetic resonance spectrum based on a fixed microwave frequency to achieve magnetic field measurement. Simultaneously, by utilizing the spatial distribution of magnetic sensor heads, it achieves current inversion. Finally, an experimental platform was constructed for validation. Preliminary results indicate that the linear fit error for direct current amplitude is less than 10^-7, confirming the feasibility of this technological approach and providing a potential application for diamond in measuring currents in power systems.