On the evening of December 9, 2019, pre-holiday shopping at the Eaton Center in Toronto was interrupted by an unexpected . Shopping galleries plunged into darkness, and the only source of light was the Christmas tree - many hastened to post its photo on social networks as a completely mystical phenomenon. However, among the tweets there were those where the mysticism was explained easily and simply: the Christmas tree was connected to an uninterruptible power supply. Today we will talk about which UPSs tenants can use to organize uninterrupted power supply for their premises in shopping centers. After all, shopping must go on, right?
Guaranteed and uninterrupted power supply
But first, let's say why the blackout case at the Eaton Center shopping center in Toronto was included in the headline of the article. We are talking about namesakes, this shopping center has no connection with the manufacturing company Eaton. Simply 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 XNUMXth and XNUMXth centuries. One of the Etons founded a trading company, and the other an engineering company. And now back to the main topic.
A shopping center is a rather complex facility in terms of ensuring guaranteed and uninterrupted power supply. As you know, the administration of any shopping center is ready to rent free space to almost any tenant, as long as their business is in the legal field. It can get to the point that a bakery with powerful electric ovens or a fish shop with industrial refrigerators suddenly appears in the place of a closed clothing store. In other words, the load on the power grid can change frequently and in almost unpredictable ways.
In such conditions, it is important to distinguish between guaranteed and uninterrupted power supply.
Guaranteed the type of power supply is called, in which, in addition to the centralized power supply, a backup source of autonomous power supply is involved (usually a DGU, a diesel generator set). Large shopping centers can be served by several DGUs. With a guaranteed power supply, a break in the power supply of consumers from the centralized power grid is allowed only for the time of automatic switching on of the backup power source (DGU, gas power generator).
uninterrupted power supply assumes the presence of a third independent power source in the form of a UPS that supplies consumers for the time required to start an autonomous generator and reach the design load. It usually takes up to 3 minutes to start powerful DGUs; in winter, the coolant is constantly heated in them for a confident start.
Simplified scheme of power supply 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 different categories of consumers.
- Consumers II category, which include the majority of ordinary tenants of the shopping center, do not have a connection to a guaranteed power supply from a DGU and can rely only on the city power grid and their own (local) uninterruptible power supplies (UPS).
- Consumers I category automatically switch to the DGU in the event of an accident on the city power grids, but will be de-energized until the start of the DGU. For these tenants, power outages are critical to business or public safety. In the shopping center, such tenants usually include pharmacies with refrigerators for medicines, medical and dental offices, and leisure facilities for children.
- Consumers I special category receive uninterrupted power supply and cannot be switched off even for a short time. For such consumers, three sources of power supply are involved - the city substation and the DGU, and during the start-up of the DGU they are powered by industrial UPSs. Such consumers include fire alarm and automatic fire extinguishing systems, civil defense and emergency warning, emergency lighting, premises and equipment of the dispatch service of the shopping center. If IT companies rent space in the shopping center, they also order uninterrupted power supply for themselves.
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 one source to all consumers of this category inside the shopping center.
For ordinary shopping center tenants - 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 scheme, which will be discussed below.
Decentralized UPS Scheme - Advantages and Disadvantages
Decentralized and centralized UPS schemes are not mutually exclusive. These two strategies can and should be combined. For example, critical consumers (plus those who specifically paid) inside the shopping center are protected by large industrial UPSs, but in a particular store that does not have guaranteed power, primary and medium class UPSs can be locally used to provide protection for cash registers, server, printer and other technology.
Let's analyze the pros and cons of a decentralized power supply scheme and, first, about the advantages of using local UPSs:
- no new wiring required, existing wall outlets are used; local UPSs are easy to put into operation and connect to cash desks, computers, and other important equipment; when changing the leased premises, such UPSs are taken with them and deployed at a new location;
- local UPSs of the initial and middle class have a low cost - the budget of almost any small business will pull the purchase of such UPSs - and the power up to 3000 VA allows you to connect several cash desks or PCs to one UPS;
- the tenant is not tied to the level of allocated load, a change in the number of cash desks or other equipment due to the expansion of the business will not require a new agreement on the electricity supply contract;
- if the tenant already has a set of their own UPS, then it is logical to use them in a decentralized uninterruptible power supply scheme.
Sometimes the administration of the shopping center - especially if there is free capacity after the key tenant left - begins to persistently offer tenants to connect to the guaranteed or uninterrupted power supply network in case of a power outage from the city substation.
When is the best time to take advantage of a centralized uninterruptible power supply:
- business continuity is critical for the tenant (example - pharmacies with refrigerated medicine cabinets, medical and dental offices, beauty clinics with continuous cycle procedures, tenants providing online services such as IT companies): centralized uninterrupted power supply is designed for an unlimited supply time to consumers (subject to the supply of fuel for diesel generator sets), and local UPSs can only support the operation of the equipment for a short time - usually no more than 15-20 minutes, and if the electricity supply is not restored during this time, the equipment will still have to be turned off;
- if the number of local UPSs exceeds a dozen, and they are of different models and bought at different times, then monitoring the condition of the batteries and replacing them becomes a noticeable inconvenience, it becomes easy not to notice an already faulty battery, and as a result, the UPS will not be able to protect equipment in case of a power failure;
- during a power outage, numerous audible alarms from local UPSs can cause irritation and anxiety to visitors (for example, clients in beauty clinics).
Next - about the types and models of UPS that are best suited for shopping center tenants from among small businesses.
Recommendations on the type and power of the UPS for tenants of the shopping center
A story about the three types of UPS - offline UPS, line-interactive type and online UPS - can be found in almost every article on this topic, but it is indispensable 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 UPS (offline, back-UPS, stand-by) are not recommended in many cases due to the fact that the voltage supplied from the network directly relies on the load. Although the voltage in the standby UPS is filtered, it is not regulated in any way - if there is a low or high voltage in the network, then this is exactly what will go to the load.
Battery power in backup UPSs is turned on only when the input voltage is completely lost, and an approximate (approximate) voltage sine wave is supplied to the output, which adversely affects the performance of equipment with transformer power supplies, electric motors, chokes, Hi-Fi class audio and video equipment , heating boilers with circulation pumps, refrigerators and air conditioners, water pumps. It is strongly not recommended to use standby UPS to protect laboratory equipment and medical equipment, which can only be powered by a voltage with a perfect sine wave.
Line Interactive UPS (line-interactive) - the most practical in terms of the ratio "price / quality of power supply". An important difference between line-interactive UPSs and offline UPSs is the presence of a voltage regulator (also called an autotransformer, AVR, Automatic Voltage Regulator). Therefore, a line-interactive UPS is most useful when used in environments 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 line-interactive UPSs, such as the Eaton 5P and 5PX series, have microprocessor control and provide an ideal sine wave output voltage.
Online UPS (online, double conversion) - the exact opposite of an offline UPS in terms of power quality: no matter what the voltage or interference in the mains, an ideal sine wave will go to the load. Inside the UPS, a double conversion is performed - the AC input voltage is converted to DC, and then back to AC, already with ideal parameters. The only disadvantage of an online UPS is the high cost.
Eaton recommends the following line-interactive UPS models for shopping center tenants:
- if the protected equipment is equipped with a cable for connecting to a standard round Euro socket (DIN Socket Type-F type), then you can choose line-interactive UPS models Eaton Ellipse ECO (power from 500 VA to 1600 VA) or Eaton Ellipse PRO (power from 650 VA to 1600 VA) - each UPS has from four to eight outlets, the input voltage can be in the range of 161-284 V;
Source: Eaton - if you want to connect devices with "computer" cables (type IEC320-C13), then we can recommend line-interactive UPS of the 5th series - models Eaton 5E, 5S, 5SC - models with an approximated sine wave, 5P, 5PX - models with a pure sine wave voltage at the output (power from 500 VA to 3000 VA). Models differ in service functions, the presence of a display, the type of case, the possibility of hot battery replacement; for consumers with euro plugs when using the Eaton 5 series UPS, you can purchase IE-320 C14 / Socket Type-F adapter cables;
Eaton 5P line interactive UPS with pure sine wave output. Source: Eaton
In addition to the mentioned UPS models of the initial (Ellipse) and middle class (Series 5), there is a 9th series of UPSs made using double conversion technology, with a wide range of models for protecting corporate servers, as well as for working as part of data centers and at production facilities.
Eventually
The more sensitive your business is to downtime and losses, the more important UPS is to it. Therefore, study the question yourself and ask questions in the comments to the post or on our website if something is not clear.
Source: habr.com