Design of a Low-Cost Residual Current Sensor for LVDC Power Distribution Application

Low-voltage DC power distribution is a promising alternative to supply future commercial buildings, datacenters and all-electric ships. Since those new power distribution networks will need to employ higher voltage levels to cope with increasing electricity consumption, safety becomes an issue to be addressed. Electric shock protection in conventional AC networks is mainly provided through the use of residual current protection devices (RCD), which are able to measure small leakage currents and interrupt the electric circuit when a dangerous level is reached. In DC systems, the same approach can be used, however, the lack of commercial available DC-RCD demands the development of DC based devices and the high cost of current sensors able to be employed in residual current sensing encourages the development of low-cost DC transducers. This paper focuses on a crucial stage of a DC-RCD, the residual DC current sensor, proposing a low-amplitude current sensor based on a closed-loop self-oscillating fluxgate technology. A detailed design procedure is described and an experimental prototype is used to validate it. A sensor with high linearity and 1% accuracy was achieved with a total material cost below USD 5.00.