Protecting power

01 Oct 11

Voice over Internet Protocol (VoIP) streamlines business network infrastructures, because one network does the work of two. The Ethernet LAN supports both voice and data. Another advantage is that VoIP phones can be powered right over the Ethernet communication line. There is no need for a separate wall outlet and wiring to power users’ phones.
The perceived and real advantages of deploying unified communications, in small business applications in particular, can sometimes be negated by the fact that the requirement for power protection is often overlooked. Whilst the telecom lines have battery backup power from the telephone exchange, and traditional PABX systems feature built-in battery systems, servers used to run VoIP systems require separate AC powered back-up systems, in the form of an Uninterruptible Power System (UPS).
Power over Ethernet (PoE) has also redefined the way organisations think about powering network components, but it requires data centre managers and facilities managers to reconsider the way power protection is extended to VoIP devices.
The right UPS for a VoIP infrastructure will be governed by many factors that determine the right topology, power rating, battery runtime, form factor and remote UPS management.
These factors change dramatically with the adoption of PoE. For example, a communication closet with PoE capabilities consumes approximately four times as much power as one without PoE. This difference affects UPS sizing and battery runtime, which in turn, influence UPS footprint and installation options.
The good news is that centralised PoE power sourcing enables you to effectively provide centralised power protection – plus multi-layered power protection for added confidence. Power protection and distribution technologies are readily available today to ensure that VoIP networks are not vulnerable to the anomalies found in commercial utility power.
Selecting the optimum UPS
The right UPS for a VoIP infrastructure will be governed by many factors that determine the selection of:


  • Topology – standby, line-interactive or online.

  • Power rating – from 500W and up.

  • Battery runtime – from 30 minutes to eight hours of runtime during power outages.

  • Form factor – desktop, rack-mount or tower.

  • Remote UPS management – Simple Network Management Protocol (SNMP), Web and/or integrated with existing management systems.


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Key considerations
Which UPS topology should you use? The two most common UPS topologies are line-interactive and online. Line-interactive UPSs protect equipment and sensitive applications against the most common power quality problems at an attractive cost and high energy efficiency, but mission critical VoIP applications typically need an even higher level of protection.
To provide availability comparable to the traditional, circuit-switched phone system, a large VoIP infrastructure should have the protection an online UPS offers, including:
Complete isolation from utility power aberrations.
Online UPSs use a rectifier and inverter to completely isolate equipment from utility power and deliver clean sine wave power. All transfers to and from battery backup mode are completely seamless. In the rare event of a problem with the UPS, an automatic bypass redirects the power path around internal UPS circuitry to continue to power loads.
Precise voltage regulation.
With line-interactive UPSs, output voltage fluctuates within a fairly large window. In contrast, online UPSs deliver steady and precise voltage even in extreme low-line conditions, without draining batteries.
Generator compatibility.
More and more organisations combine the power quality provided by a UPS with the unlimited backup time of a generator. When starting up, generators may generate frequency fluctuations that some UPSs will not tolerate. Online UPSs are designed for full generator compatibility.
Monitor and manage
The economical standby topology is suitable for only the smallest UPSs, those that would be deployed at users’ desks if their PC, IP phone and other desktop electronics were not protected by a centralised UPS. Distributed protection using standby UPS, or a combination of centralised and distributed using Line Interactive and Standby UPS may also be the most economical solution for small system applications.
Finally, monitoring and managing the UPS to ensure power quality and uptime is essential.  A common oversight in the installation of UPS in IT and unified communications applications is the failure to monitor the UPS, resulting in ‘surprise’ failures during power outages due to UPS batteries that have passed their use by date.
Keeping an eye on the status of power devices across the network, and intervening before a blip cascades into a catastrophe, is a top priority. The UPS can communicate with the protected server directly (via USB) or through the network (via Web/SNMP card), so UPS monitoring and management software can be fully integrated into the network management system. 

 

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