Voltage Selection and Personal Safety in Low Voltage Direct Current Networks at Customer End

Low voltage direct current (LVDC) technology is becoming an attractive solution for the integration of renewable energies and the power supply of electronic loads. Since LVDC systems at the customer end are exposed to the daily contact of untrained users, they should be properly configured to guarantee the personal safety even under fault conditions. This paper derives guidelines for the selection of suitable voltage levels and the minimum requirements for protective devices from the perspective of personal safety in LVDC customer-end networks. For this purpose, a comprehensive analysis of the underlying influencing factors is presented, followed by a thorough discussion of the state-of-the-art in LVDC fault protection.

I. Introduction

In modern distribution systems, both the electricity generation and consumption increasingly involve dc technology. On the one hand, decentralized power generation and energy storage systems, such as photovoltaic (PV) plants and battery storages, are undergoing an unprecedented growth. On the other hand, a growing number of dc loads is finding its way into residential and commercial buildings, e.g., LED lighting, computers and laptops. Facing these new trends, distribution networks and smart grids based on low-voltage direct current (LVDC) energy transfer represent promising solutions to facilitate local energy balancing with enhanced controllability and higher power efficiency [1].