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In this study, a long‐distance non‐contact current measurement method is proposed based on the non‐contact sensor array measurement technology, combined with a new current algorithm. The sensor array is a vertical array composed of three three‐axis magnetic field (MF) sensors that is placed on the ground plane below the measured overhead line. The proposed current algorithm can optimize the geometry of the overhead line using the spatial MF values measured by the sensor array and then the three‐phase currents can be calculated. To improve the accuracy of current measurement, the spatial MF model in the algorithm considers the influence of cable sag. It enables a more accurate coupling matrix between the measured overhead line and the sensor array to be established. Additionally, the current algorithm architecture is designed using a composite algorithm to more optimally obtain the best three‐phase current values. A scale‐down overhead‐line measurement system is developed to test the proposed current measurement method. The results show whether a cable sag exists when the three‐phase currents are approximately balanced, with errors less than 2.0%. Moreover, it can be determined whether cable sag exists when the three‐phase currents are unbalanced, with less than 3.4% errors. [ABSTRACT FROM AUTHOR]

With the growing infrastructure for overhead lines, the demand for overhead‐line condition‐monitoring technologies has become increasingly urgent. Traditional current transformers used to measure three‐phase currents are bulky and difficult to install, which further increases the cost of monitoring. In order to meet the current state assessment needs of transmission and distribution networks, this study uses a novel magnetic‐field sensor array to realize nonintrusive overhead‐line current detection. Based on the magnetic fields measured by magnetic‐field sensors placed on the ground under the overhead line, the proposed algorithm can be used to calculate the three‐phase current values. The proposed method does not require on‐site calibration before the field measurements are conducted. With partially known overhead‐line geometry specifications from utilities, the algorithm can optimize the overhead‐line geometry and finally achieve accurate current detection. The simulation and experimental results verify that the proposed current‐detection technique can accurately calculate the three‐phase currents of the overhead line with only three three‐axis magnetic‐field sensors. [ABSTRACT FROM AUTHOR]

We propose a new contactless phase comparison method for high-voltage overhead lines. Combined with single-axis electric field (EF) sensing technologies, the new phase comparison method can perform a remote field measurement before the measured two overhead lines are interconnected. In the new phase comparison method, two single-axis EF sensor arrays are placed below the two measured overhead lines individually. A synchronous driver system wirelessly triggers the two EF sensor arrays synchronously to measure space electric fields. Then, two sets of measured electric fields are received by the synchronous driver system, and these data are used to carry out 1) positive/negative sequence evaluation and 2) phase evaluation. Finally, the proposed method can determine whether the three-phase voltage phases of the two overhead lines are identical. In addition, in order to ensure that the EF sensor arrays can synchronously measure electric fields, each EF sensor is designed with a built-in GPS device. Firstly, we simulated the electric field distribution of overhead lines using a finite element analysis (FEA) software, and then designed the placement of EF sensors on the ground. Finally, we validated the proposed method by experimental tests on a reduced scale model of overhead lines. [ABSTRACT FROM AUTHOR]

Magnetic sensors have been widely used for current measurements in diverse industries. In order to achieve a large current measurement without an iron core structure, magnetic sensors are often arranged to be a circular array for designing a new electronic current transformer (ECT). However, this ECT with a circular array of magnetic sensors usually suffers from tradeoffs between the number of sensors and the measurement accuracy. This paper visualizes this tradeoff and proposes a 3-D magnetic-field model to analyze the impact of the magnetic sensor circular array position on current measurements. We develop an analytical expression of the current measurement errors to estimate the minimum number of required magnetic sensors and point out the acceptable deviations of the ECT position under various accuracy classes. Based on the estimation results, we design a new circular array with eight magnetic sensors and build a three-phase current measurement system. The test results demonstrate the efficiency and the robustness of the designed class-1.0 ECT, which successfully maintains accuracy class 1.0 under various position deviations in balanced or unbalanced three-phase power delivery systems. [ABSTRACT FROM AUTHOR]

Measuring the current in high-voltage direct current (HVDC) systems is always regarded as a challenging task. For transmission systems, dc current transformers or sensors are only available in substations and converter stations. In order to provide more flexibility and convenience, this paper proposes a contactless dc current sensor, which can be easily placed on-site in the environment of HVDC overhead transmission lines. The proposed method significantly improves the convenience and safety of the HVDC current measurement. Using a magnetic-field sensor array, the proposed current algorithm can optimally calculate the overhead-line currents with partially known overhead-line geometry. The simulation results in this paper demonstrate that the proposed method can accurately calculate the HVDC current. Moreover, the proposed method is validated by a reduced-scale HVDC overhead transmission line. [ABSTRACT FROM PUBLISHER]

Most traditional voltage transformers in transmission and distribution networks are installed inside the substations. Nearly no accessible voltage information in the real‐time scale is available for field engineers to carry out the field measurement for the purposes of the power quality inspection and the equipment maintenance. In order to offer an on‐site and easy‐to‐use solution for the field measurement, the authors propose a novel electric‐field (EF) sensor array based technique for measuring the overhead‐line voltage. Based on the EFs measured by the EF sensor array and the partially known overhead‐line geometry information from utilities, the proposed voltage algorithm can accurately calculate each‐phase voltage without an on‐site calibration before conducting the field measurement. The simulation results demonstrate that the authors' proposed technique with only three EF sensors can accurately calculate the overhead‐line voltages and successfully reconstruct the real‐time three‐phase waveforms. The experiment results verify the feasibility of the proposed voltage sensor for the overhead‐line voltage measurement. [ABSTRACT FROM AUTHOR]

How to measure ac currents in a bundle of inaccessible, enclosed conductors has been a challenging problem but with many potential applications. This paper presents a method to solve the problem using an array of magnetic field sensors. The proposed method consists of two novel ideas. The first idea is to use an off-site calibration method to establish sensor parameters including sensing position and angle, which provides more accurate sensor parameter estimation than their nominal values. The second idea is to “measure” (i.e., calculate) conductor currents and positions based on the sensed magnetic fields and preestablished sensor parameters. This process is simplified since the sensor information is obtained by the first idea. Both calibration and measurement tasks are formulated as nonlinear least square problems and solved efficiently. The proposed method is demonstrated for the cases involving ideal three-conductor system and practical residential service cable enclosed in a plastic conduit. The method has the potential for contactless current measurement of Romex cables and overhead distribution lines. [ABSTRACT FROM PUBLISHER]