Abstract
Some industrial incidents are attributed to insulation degradation of electrical assets. The leakage current can be a crucial indicator for online insulation monitoring of asset. To realize per-phase monitoring, the measurement accuracy of milliampere-level leakage current is limited by the strong load current noises. This article proposes an advanced current sensor with a dual-core topology based on differential-mode (DM) measurement. An analytical model of magnetic field of the dual-core sensor is originally presented. It helps clarify the significances of the inner core in filtering noises and reducing the influence of system operation and cable positioning. Then, a comprehensive design procedure is fully investigated by selecting the optimal position and approach for magnetic field detection, and a high-speed and low-noise signal conditioning circuit is presented. The proposed current sensor is tested in the laboratory. Experimental results indicate that measurement errors can remain within 0.1mA in the testing scope, where the load current is up to 100A and the DM current varies from 0-7mA. The proposed sensor is further validated with superior performance compared with two commercial industrial sensors. The contribution of this article lies in providing the analytical analysis and design of a novel DM current sensor for leakage current measurement, which achieves online per-phase insulation monitoring for industrial electrical assets.
Highlights
Industrial power system faces the risk of low-automatized and low-secure operation
To realize online per-phase insulation monitoring for industrial electrical assets based on leakage current measurement, a novel current sensor with a dual-core topology is proposed [17]
The main contribution of this paper lies in proposing an advanced DM current sensor that is capable of per-phase online insulation monitoring for industrial electrical assets
Summary
Industrial power system faces the risk of low-automatized and low-secure operation. New technical difficulties are brought in the system reliability with the large-scale integration of renewable energy resources and varied industrial loads [1]. There are many products for small current measurement on a single wire, which are well qualified in measuring the leakage current of the insulators and the transformer core [18]-[20] They may fail in online insulation monitoring in this application of Fig. 1, due to a lack of focus on several crucial effects. To realize online per-phase insulation monitoring for industrial electrical assets based on leakage current measurement, a novel current sensor with a dual-core topology is proposed [17]. The main contribution of this paper lies in proposing an advanced DM current sensor that is capable of per-phase online insulation monitoring for industrial electrical assets. The analytical analysis provides the guide of geometric configuration and benefits the procedure of designed sensor
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