Reliability level versus load-carrying capacity of the uninterruptible power systems (UPS)


The paper addresses the electric energy power supply, with particular emphasis on the functioning of the uninterruptible power supply systems (UPS). There were conducted considerations associated with the possibilities of covering the increasing demand for energy (as a result of the load infrastructure development) by parallel combining of the UPS power supplies. There were also analysed the possibilities of providing the expected reliability of the power supply of the priority loads as the effect of the redundancy introduction in the system. There are described the functional properties of the basic redundant UPS structures. The obtained results of studies performed in the UPS EVER POWERLINE GREEN 33 systems have been presented and commented on.

KEYWORDS: uninterruptible power systems, equipment reliability, load of the power supply systems, redundancy


1. Introduction

In the human economic activity – due to the prevalence of using the increasingly advanced devices and systems in all areas of his functioning – the meaning of issues of the reliability of energy supplies and the quality and reliability of power supply is constantly growing [1-3, 5, 7, 10].

The quality of the supplied power is mainly connected with performance parameters of voltage (energy) and with the reliability (continuity) of power supply. Research shows that even the best electrical power distribution systems may be unreliable (can crash), and therefore they do not meet the critical requirements, connected with the powering of the priority loads.

Most entrepreneurs, in order to maximally limit the risk of data processing errors or costly downtime of the devices or systems caused by failures or abnormal voltage quality in the electricity network, decide to install the uninterruptable power supply systems (UPS) between the energy distribution system and the strategic loads [1-5, 7-12].

Depending on the required reliability level of the power of the secured energy loads, it is possible to further increase the operational reliability of the power supply systems by applying the redundant systems, that is by introducing additional units, which could be used in case of damaging of the basic units. This is inextricably connected with the evident increase of the investment costs of the system [2, 3, 7, 8, 10]. 

In many cases, during the development of the economic units’ infrastructure, there appears the need to adjust (increase) the delivered power, what is realized by replacing the existing solution with the power supply system with a higher rated power or by the parallel connection of further units in order to obtain the increased system load.

The paper addresses the issue of increasing the capacity and reliability (operational reliability) of the uninterruptable power supply systems. It refers to the functioning of priority loads. There are presented the functional properties of basic redundant UPS systems. The results of studies conducted in the physical systems, on the example of UPS EVER POWERLINE GREEN 33, have been posted and commented.

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dr inż. Karol Bednarek - EVER Sp. z o.o

Published:  Computer Applications in Electrical Engineering, edited by R. Nawrowski, Publishing House of Poznan University of Technology, vol. 12, Poznan 2014, p. 364-375.