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Uninterrupted power supply of shopping centers or Shopping Must Go On



On the evening of December 9, 2019, the pre-holiday shopping of visitors to the Eaton Center shopping center in Toronto was interrupted by an unexpected blackout . Shopping galleries plunged into darkness, and the only source of light was the Christmas tree - many of them rushed to post their photos on social networks as a completely mystical phenomenon. However, among the tweets there were those where the mysticism was explained easily and simply: the tree was connected to an uninterruptible power supply. Today we will talk about which UPS tenants can organize uninterrupted power supply for their premises in shopping centers. After all, shopping must go on, isn't it?

Guaranteed and uninterrupted power supply


But first, let’s say why a blackout case was made in the splash screen at the Eaton Center in Toronto. We are talking about namesakes, this shopping center has no connection with the production company Eaton. Just Eaton (Eaton) is a fairly common surname among talented emigrants who arrived in the United States from the British Isles at the turn of the 19th and 20th centuries. One of Eatons founded a trading company, and the other an engineering company. Now back to the main topic.

A shopping center is a rather complex object in the sense of providing guaranteed and uninterrupted power supply. As you know, the administration of any shopping center is ready to lease free space to almost any tenant, if only their business is in a legal field. It may come to the point that a bakery with powerful electric ovens or a fish shop with industrial refrigerators suddenly appears in the place of the closed clothing store. In other words, the load on the power grid can change often and in an almost unpredictable way.

In such conditions, it is important to distinguish between guaranteed and uninterrupted power supply.

Guaranteedthe type of power supply is called, in which, in addition to centralized power supply, a standby source of autonomous power supply is used (usually it is a diesel generator set, diesel generator set). Large shopping centers can serve several diesel generator sets. With guaranteed power supply, a break in the power supply to consumers from a centralized power supply is allowed only for the time the backup power source (DGU, gas generator) is automatically turned on.

Uninterruptedpower supply assumes the presence of a third independent power source in the form of a UPS, which feeds consumers for the time necessary to start an autonomous generator and its output to the rated load. It usually takes up to 3 minutes to start powerful diesel generator sets; in winter, for a reliable start, the coolant is constantly heated in them.


Simplified power supply circuit of the shopping center. Source: Grandmotors

As a rule, the power supply of the shopping center is built according to the classical scheme of dividing the tenants and internal services of the shopping center into various categories of consumers.

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The use of industrial UPS in the shopping center for a special category of consumers is carried out according to a centralized scheme. In this scheme, electricity is supplied from a single source to all consumers of this category inside the shopping center.

For ordinary tenants of shopping centers - shops, cafes, gyms, beauty parlors, etc., providing a centralized guaranteed or uninterrupted power supply can be too expensive an option. In such cases, it is economically feasible to use the so-called decentralized uninterruptible power supply, which will be discussed below.

Decentralized UPS scheme - advantages and disadvantages


Decentralized and centralized uninterruptible power supplies are not mutually exclusive. These two strategies can and should be combined. For example, critical consumers (plus those who paid specifically) inside the shopping center are protected by large industrial UPSs, but in a particular store that does not have guaranteed power supply, primary and middle class UPSs can be locally used to protect cash registers, a server, a printer, etc. technicians.

We will analyze the pros and cons of a decentralized power supply scheme and, first, the advantages of using local UPSs:

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Sometimes the administration of the shopping center - especially if there is free capacity after the key tenant has left - begins to aggressively offer tenants to connect to the guaranteed or uninterrupted power supply network in case of power failure from the city substation.

Here's the best time to use centralized uninterruptible power:

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  • if the number of local UPSs exceeds ten, and they are of different models and purchased at different times - then monitoring the condition of the batteries and replacing them becomes a noticeable inconvenience, it becomes easy not to notice a faulty battery, and as a result, the UPS will not be able to protect the equipment in the event of a power outage;
  • during a power outage, numerous audible alarms from local UPSs can cause irritation and anxiety for visitors (for example, clients in beauty clinics).

Further, about the types and models of UPSs that are best suited for tenants of shopping centers from among small businesses.

Recommendations on the type and capacity of UPS for tenants of the shopping center


The story about the three types of UPSs - offline UPS, line-interactive type and online UPS - can be found in almost every article on this topic, but you can not do without it if you give advice on choosing uninterruptible power supplies.


Schemes of three types of UPS: a) offline, b) line-interactive, c) online. Source: Eaton

The simplest and cheapest redundant UPSs (offline, back-UPS, stand-by) are not recommended in many cases because the voltage supplied from the mains directly supplies the load. Although the voltage in the backup UPS is filtered, but it is not regulated in any way - if the network has low or high voltage, then this is what will go to the load.

The battery power in the backup UPS is turned on only when the input voltage completely disappears, and the approximated (approximate) form of the voltage sine wave is applied to the output, which affects the performance of equipment with transformer power supplies, electric motors, reactors, Hi-Fi audio and video equipment , heating boilers with circulation pumps, refrigerators and air conditioners, water pumps. It is strongly not recommended to use redundant UPSs to protect laboratory equipment and medical equipment that can only be powered with voltage with a perfect sinusoid.

Line Interactive UPS(line-interactive) - the most practical in terms of the ratio of “price / quality of power supply”. An important difference between linear-interactive UPS and offline-UPS is the presence of a voltage stabilizer (also called autotransformer, AVR, Automatic Voltage Regulator). Therefore, a line-interactive UPS is most useful when used in conditions where the input voltage can vary widely. The voltage stabilization capabilities of such UPSs are quite significant - from 150-160 V to 270-290 V at the input, depending on the model, while the output will be stable 230 V. Modern linear-interactive UPSs, such as the Eaton 5P and 5PX series, have microprocessor control and provide a perfect sine wave output voltage.

Online UPS(online, double conversion) is the exact opposite of an offline UPS in terms of power quality: whatever the voltage or interference in the mains, an ideal sine wave will come to the load. A double conversion is performed inside the UPS - the AC input voltage is converted to DC, and then again to AC, already with ideal parameters. The only drawback of online UPS is the high cost.

Eaton recommends the following line-interactive UPS models for tenants in the shopping center:

  • ( DIN Socket Type-F), - Eaton Ellipse ECO ( 500 · 1600 ·) Eaton Ellipse PRO ( 650 · 1600 ·) — , 161–284 ;


    : Eaton
  • «» ( IEC320-13), - 5- — Eaton 5E, 5S, 5SC – , 5P, 5PX – ( 500 · 3000 ·). , , , ; Eaton 5- - IE-320 C14 / Socket Type-F;


    - Eaton 5P . : Eaton

In addition to the mentioned models of primary (Ellipse) and middle class UPSs (Series 5), the Eaton product line includes the 9th series of UPSs made using double conversion technology, with a wide range of models for protecting corporate servers, as well as for working with data centers and production facilities.

Eventually


The more sensitive your business is to downtime and loss, the higher the importance of the UPS for it. Therefore, study the question yourself and ask questions in the comments to the post or on our website if something turns out to be incomprehensible.

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