by August 4, 2004 0 comments



It’s not just about buying a UPS for your IT infrastructure. Uptime required, sensitivity to power problems, climatic conditions, cooling are just a few other factors to keep in mind. 

Power conditioning equipment is a key element of any network infrastructure. Given the power problems in this country, IT decision makers need to choose the right power conditioning equipment to keep their networks running. Today, it’s not just about choosing a large UPS to backup all your systems, even though it’s the main one. The objective here is to determine the uptime you want for your network equipment, which is not going to be 100 percent for everything. Power conditioning equipment would also vary depending upon the type of business you’re in, because the sensitivity levels for some equipment is higher than others towards power problems. 

Before arriving at the solutions, you need to first analyze the power situation in your area, for which you should take the help of a power consultant. Try to understand the major power disturbances in your area. The basic ones include spikes and surges, brownouts, and harmonic distortions. If you are in an industrial area with heavy machinery, then you may encounter power surges or sags. Surges occur when heavy machinery is switched off or the generator is switched on, and sags occur when the machine is switched on again or additional load is put on the generator. Both cases can be disastrous for your IT equipment. If you’re not in such an area, and have setup operations in a business park, you would still need power conditioning equipment because basic power cuts are common across the country.

Key deciding factors
The first step to choosing a large UPS system is to understand the nature of your electrical load and its dynamic response. Electro-mechanical load such as motors used in industrial applications need significantly more power to turn on initially. When they’re switched on or off, they generate significant EMI on the line, and could also draw current twice their rated value. This has to be accounted for during your UPS capacity planning. 

Analyze the power situations in the area:
Try to understand the major power disturbances in your area. The basic ones include spikes and surges, brownouts, and harmonic distortions
Determine power requirements of your equipment:
The type of power conditioning should be chosen depending upon your equipment. This will not only determine the technology that you want to use but would help you in taking a decision regarding centralized or distributed power conditioning
Choose the UPS technology:
There are three basic technologies that most UPSs follow: Offline, Line Interactive and Online. You may want to implement any of these, depending upon the equipment that you want to service

Non-Linear load such as computers, hubs and switches used in an IT infrastructure on the other hand, can draw up to five times the current during the first half cycle. How sensitive is the load to power problems is another issue. If you have sensitive telecom equipment that would take days to reconfigure if it reboots due to a power glitch, you need a UPS that will not let this glitch pass through. Similarly, if you need backup for medical equipment, then the UPS must conform to stringent emission norms. There are various international EMI (Electro-Magnetic Interference) standards, which UPS manufacturers must follow.

These have been laid out by the IEC (International Electrotechnical Commission). 

Another critical decision is whether to go for centralized or distributed power distribution. In a very large network, you would require one or more large UPS to back up all systems. Here again, depending upon the criticality of the load, you may need to go for redundant power backup. The most feasible option is a genset, which would take over from the UPS for most of the load. You may need an additional UPS or longer backup servers in your data center. 

Cooling is very critical in a data center, because a large amount of heat is generated due to the sheer number of servers installed. Similarly, life of UPS batteries gets reduced with an increase in temperature. Batteries are a high recurring cost in a UPS, so you’d want to get the maximum life from them as possible. You would therefore need to keep these factors in mind as well and ensure that you’ve got an efficient cooling system in place. You might need to provide additional power backup to your air-conditioning system so that it can continue to keep the data center’s temperature under control.

Types of UPS

Offline UPS
Low cost
Basic operations
No surge protection

For: 
Standalone 
workstations

Line Interactive
Moderate cost
Basic surge protection
Load not isolated from power source

For: 
Applicable everywhere except 
for mission-critical applications

Online UPS
High cost
Total surge protection
Load isolated from 
power source

For: 
Mission-critical
applications

In addition to these, you also need to factor in other power conditioning equipment, such as surge suppressors, voltage regulators or isolation transformers for conditioning the power that is being fed into your systems. While surge suppressors reduce the level of incoming spikes, voltage regulators provide constant voltage and protection from surges and spikes.

Finally, isolation transformers are used to isolate sensitive equipment from noise in the mains voltage. 

Manageability and scalability are two other critical factors to be kept in mind. You’ll need a system that can keep a watch of your power conditioning equipment, temperature and battery failure. Most large UPS systems support SNMP, so they can be easily managed remotely. They must also be able to monitor the batteries’ performance, and be able to predict whether any of them is about to fail. 

The Technologies
On the technology front, there hasn’t been too much action happening in power conditioning equipment. There are still three basic technologies that most UPSs follow: Offline, Line Interactive and Online. Offline UPS systems provide the most basic form of protection and are thus used on standalone workstations only. In technical terms, their basic job is to switch to battery, the moment there’s a power cut so that the load doesn’t get affected. 

Line Interactive UPS systems are the most used of the lot and enjoy the biggest market share in India. These are a step ahead of Offline UPS systems and offer limited power conditioning mechanisms. These UPS systems include a power conditioning device between the primary power source and the converter that is used to convert the power source from AC to DC and vice versa. This device is like Constant Voltage Transformer that saves the device from voltage surges and dips. But, it does not have the capability to isolate the load from the direct power supply. Thus, some of the disturbances in power supply can leak to the load, compromising on its efficiency. 

Though, Line Interactive UPS systems can be used with the generators easily as compared to Offline systems that can create problems and discharge batteries rapidly. But even in the case of Line Interactive systems one needs to take care of some things before generator power is poured into the system. It has to be made sure that the frequency window of the UPS that depicts power failure be widened enough so that it does not shift to battery supply when there is a change in the generator’s output frequency.

Finally, the best form of UPS systems is Online, and also the most expensive. In this system, the load is isolated from the main power supply. It is always supplied power from the batteries. When there is any kind of surge the battery compensates for that and the load does not get affected. When the power fails totally, the batteries take over seamlessly without any lag time. These are helpful while using generators, since all the surges are isolated from the load and it is always safe from any kind of power surge.

There’s another type of UPS technology, which is batteryless. It is based on the flywheel concept, where the backup energy is stored into rotational energy. Whenever there’s a power cut, this rotational energy is converted to power. This system is also connected to a genset, which comes on soon after the power cut. 

Another critical factor that determines which UPS to go for, is the geographical location. The UPSs for different vendors have varying sensitivity to climatic conditions. For this, you may need to enquire whether the vendor has deployed UPSs in another area with similar climatic conditions as yours, and what has been the success rate. 

By Anil Chopra, Geetaj Channana

IN BRIEF




Given the number of power problems in this country, having efficient power conditioning equipment is a must. Before deciding what to buy, analyze the power situation in your area, the amount of load you want to backup, and for how long you need to backup. Also determine how sensitive is your load to power problems and then choose the necessary power conditioning equipment for it

COMING UP




What was earlier known as the humble server room in an organization is today known as the data center, and not without good reason. Data centers are increasing in complexity with new types of products introduced such as blade servers, high-density racks, enterprise storage and disaster recovery solutions. Data centers today pack much more equipment in the same room than before. Therefore planning the power requirements becomes a critical part of designing a data center. Given this situation, power-conditioning vendors are gearing up their equipment to handle the new situation. APC for instance, introduced its InfraStruxure equipment to handle everything from power to cooling to racks in a data center. Power conditioning equipment vendors are also designing their equipment to be more modular, so that it can be scaled up to handle any increases in the load

 

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