The non-intrusive condition monitoring of overhead transmission lines is a key method to ensuring the safe and stable operation of transmission systems. Especially, their sag/wind deflection are important parameters that should be monitored along with its current. In this paper, an innovative approach for non-contact and cost-effective monitoring of High Voltage Overhead Transmission Lines (HVOTLs) is developed, utilizing three uni-axis magnetic sensors strategically positioned on the tower, below (or above) the transmission lines. Initially, a magnetic field decoupling method in the context of spatial state variations across multiple conductors is proposed. Subsequently, an algorithm is presented to perform sag estimation, wind deflection detection, as well as current reconstruction. The efficacy of the proposed approach is corroborated through numerical simulations and finite-element analysis (FEA). Further validation is achieved using a scaled-down model in laboratory, reinforcing the practical feasibility of the method.

Accurate spatial position measurement of overhead power lines is essential for ensuring the reliability of power systems, especially in smart grid scenarios that require real-time monitoring. However, existing methods face significant challenges: contact-based techniques, such as tension or differential GPS (DGPS) sensors, are costly and cumbersome, while image-based methods are vulnerable to weather conditions. Magnetic sensors, offering a non-contact measurement approach, present a promising alternative. However, current technology often suffers from non-linearity and high uncertainty in alternating current (AC) environments, limiting their accuracy. This paper introduces a Frequency-Aided Extended Kalman Filter (FA-EKF) algorithm that integrates frequency information into the prediction model, thereby enhancing stability and efficiency in AC signal measurements. The proposed algorithm significantly reduces convergence time and measurement uncertainty. Experimental validation in laboratory-scale models demonstrates the method’s effectiveness, with a relative error of less than 2%. Further simulations show that the method achieves 97.5% relative accuracy at a 2.5-meter distance in one-dimensional measurements and maintains over 90% relative accuracy in two-dimensional measurements within a 1.5-meter radius around the target line in realistic scenarios. This paper also explores the impact of factors such as sensor spacing, angular deviation, and interference from other current sources.

Monitoring the sag of overhead transmission lines under varying environmental and load conditions is essential for ensuring safe operation, adequate ground clearance, and preventing conductor damage. In this study, the application of magnetoresistive sensors to non-contact sag measurement is investigated, and a novel measurement approach is proposed. First, the spatial distribution of the magnetic field and its relationship to conductor sag are examined through numerical integration and finite element simulations, providing recommendations for sensor placement. Next, a new sag measurement method is introduced and validated in multi-conductor setting simulations based on the observed linear relationship between magnetic field intensity along the tower vertical line and conductor sag. Finally, single- and multi-conductor laboratory experiments are conducted, and the results align closely with numerical predictions, demonstrating the feasibility of this approach. A comprehensive signal-to-noise ratio (SNR) analysis confirms that the observed linearity is measurable in real-world conditions. This method offers a reliable and cost-effective solution for overhead transmission line monitoring.

Magnetic measurement methods, which serve as a critical means for perceiving the operational status of transmission lines, enable the synchronous acquisition of both electrical parameters and spatial conditions of transmission lines. However, the coupling issue induced by current fluctuations and conductor galloping (CG) in magnetic field (MF) signatures cannot be effectively resolved by existing methods, rendering synchronous monitoring of CG and current significantly challenging. To address this problem, a synchronous online monitoring method for current and galloping is proposed in this paper, which employs a TMR sensor array deployed at a specific location above the conductor. Firstly, a spatial MF distribution model is established based on the CG equation, providing a theoretical foundation for sensor installation. Subsequently, a galloping discrimination index that is immune to current fluctuations is proposed, thereby enabling galloping monitoring even when current fluctuations are present. Then, the measurement accuracy of current during CG is effectively enhanced via algorithmic correction. The feasibility of the proposed method is validated using a scaled model constructed in the laboratory, and both the feasibility and uncertainty of its application in real-world scenarios are discussed.