0093-9994 (c) 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2937863, IEEE Transactions on Industry Applications Topology of Continuous Availability for LED Lighting Systems G. Parise (L.Fellow IEEE) M. Allegri L. Parise (S.M. IEEE) R. Pennacchia F. Regoli G. Vasselli Abstract. Lighting systems with a big number of luminaires in large halls are a case of distributed loads that need topologies with modularity, whenever possible to ensure a uniform distribution of the supplying circuits, an easier installation, management and maintenance. The LED luminaires give a great impact on the system operation due to their auxiliary series devices and to the high inrush currents of the ac/dc switching power supplies. This paper proposes a topology to design LED lighting systems, configured in a modular scheme of a main AC distribution and a branch DC distribution supplying luminaires clusters. Each cluster is provided as a “double-dual corded” equipment with double power supply and double control type, digital and analogic. The suggested topology aims to make available a system that allows overcoming fault situations by design and permits maintenance activities limiting and recovering degradation conditions. In this way, the lighting system of special locations, for which there is the willingness-to-accept greater financial costs against loss service risks, can satisfy the requirement of continuous availability system. To provide more details on the proposed design criteria this paper describes, as case study, the lighting system of a parliamentary hall with one thousands of luminaires. Index terms: distributed loads, modular system, service continuity, In-Op approach, dual corded equipment. SYMBOLS A/D switching power device AC/DC CAS system with continuous availability DD dimmer device i(pIL) inrush current in p.u. of A/Ds Im magnetic tripping current of PD In current nominal value of PD k=Im/In magnetic tripping factor of PD LL LED luminaires MC manual control rate (%) nsd number of the A/Ds PD protective device pIL current of A/D PSB partition switchboard S sector lines serving related lighting sectors SB local switchboard in field I. INTRODUCTION Lighting systems in large halls are a case of distributed loads that need a modular configuration for a uniform distribution of the supplying circuits and to expedite the installation, maintenance and control procedures, besides exigencies of energy saving and visual comfort. A lighting system suitable for lower energy consumption, easy control and advanced technology is currently available with luminaires with LED lamps. The electronic LED luminaires require series devices such as switching power devices and dimmer devices, so systems with several hundred luminaires (the case study has one thousands of luminaires) are less reliable than the obsolete classic luminaires. Many control zones (CZ) compose the luminaires system that require independent regulations for various exigencies and scenic effects in a same scenario (Figure 1). For institutional environments, national and international assembly halls, congress centers, theaters, stadiums, sports centers and entertainment locations, a reduced availability of the lighting system is not admissible. Therefore, this paper suggests to adopt a topology for the lighting system usually adopted for systems that need continuous availability (CASs), adopting “double- dual corded” equipment supplied by two sources and dimmed by two control types. Availability differs from reliability, as it admits that the system components may suffer failure, but that the system is still available at the time or in the period in which its use is required. A CAS topology must allow operational performance by design for the service continuity such as fault selectivity, immunity from interference between different areas of the system, the easy maintenance of the system on its parts, the flexibility and the expandability (In-Op approach) [1]. The topology to be fault tolerant requires a backbone appropriate to the type of loads area with system sections that have active partitions supplied by different sources (Figure 2 UPS A-B). Each partition switchboard (PSB) has redundant distribution paths (S lines) simultaneously serving assigned load groups by modules of local switchboard (SB) in the S lighting sectors. Each distribution element (UPS, PSB, SB) with its serial components is operated independently, but via tie-switches, at each panel level, can restore local fault avoiding that a single faulted element affects downside the following subsystem (Figure 2, 3, 4, 5). The natural deterioration of the components need monitoring the residual time of their good operation. Considering that the system is constituted by a large number of electronic components subject to childhood failures and successively for the ordinary operation, the design of a CAS requires adopting Figure 1. Lighting system with three control zones CZ1, CZ2 and CZ3.