Uninterruptible Power Supply Communications

However well uninterruptible power supplies perform their role, their protection is ultimately incomplete unless they can communicate their power status in real time. Otherwise, during a protracted power blackout, their battery autonomy would merely delay rather than prevent an unexpected loss of power to the load and ensuing damage. Similarly, UPSs must inform their users of their own status and battery condition to allow preventative action before a failure occurs.

In this article, Tan Yu Ming, General Manager at Kohler Uninterruptible Power, explains how UPS communications can be implemented to avoid these undesirable scenarios.

Nearly all data centres and computer networks have some form of Uninterruptible Power Supply (UPS) protection in place. If the mains supply fails, the UPS battery takes over until incoming power is restored or a diesel powered generator is brought online to replace the mains. In either scenario, loss of data and damage to equipment is prevented.

However, what if there isn’t a generator in place and power blackout time exceeds the battery autonomy? If this happens, the battery merely delays rather than prevents a system crash, unless the UPS provides a warning of the mains failure condition. Accordingly, modern UPS systems have built-in abilities to communicate with the critical load and remote monitoring stations as appropriate to installation requirements.

The simplest solution is a set of volt-free contacts on the UPS; these can signal an alarm condition detected by the UPS to any designated equipment around the site. An orderly shutdown of the critical load can be initiated if the mains power blackout exceeds a preset time, for instance. Most installations, however, have more complex requirements and accordingly require more sophisticated solutions. For example, problems could arise within the UPS itself as well as with the incoming power; there may be multiple UPSs on site, or the site may be unattended for some or all of its operating cycle.

Network-based communications

These situations and others can be managed if the UPS has SNMP capability, allowing it to interface with major network management systems.  SNMP, a standard protocol, is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) suite. An SNMP UPS becomes an intelligent, network-connected device capable of transmitting management variables across enterprise-wide networks and the Internet. The UPS can log events, continuously monitor power quality, report on battery status, load and temperature, perform self-diagnostics and store the collected information into a management information base (MIB). Users’ operating systems can then use SNMP management software to collect and display MIB information in an easily-understood format.

Once available, the information can be used for a variety of control and management functions, which all improve the UPS system’s ability to provide uninterrupted, protected power. Auto shutdown of supported computers locally or across a network during a power failure is particularly important. This is most commonly achieved using Remote Control Command (RCCMD), a software solution available for many different operating systems. After a preset battery time following a power failure, monitoring software – which can be resident in either a PC or an SNMP adapter card – transmits an RCCMD shutdown signal. Remote RCCMD clients respond by initiating their own shutdown procedure.

Intelligence in the design can be used for phased shutdown of equipment across a site. Less-essential devices can be shut down first, decreasing the UPS battery load and maximising the critical equipment’s backup time. Sections of a system can also be isolated for security reasons. The UPS and network system can thus be tuned for optimum responses to power outages, but provision must also be made for issues within the UPS itself – especially on remote sites or outside of office hours without local manning.

Remote monitoring and battery priority

Under these circumstances a remote monitoring solution offers the expertise and resources necessary to keep the UPS running. A remote monitoring installation on a user’s site communicates constantly with the UPS, automatically detecting any alarm or error messages. If an incident is detected, the service automatically emails a status message and any fault details to the provider’s service centre. Trained specialists can then interrogate and manage the UPS, perform all necessary remote diagnostics and if appropriate send a repair technician to the site.

Battery integrity is core to secure UPS power, so a UPS communications system should include provision for battery monitoring and status reporting. For example, a solution like this can check the internal resistance, temperature and voltage of every battery sequentially. Through an Equalisation process, the system corrects the charging voltage operating range, preventing gassing, dry-out and thermal runaway. Warnings are provided when attention is required.

In this brief article we have seen why communication is essential to secure UPS operation, and how modern networking and Internet technology is used to provide solutions to meet today’s system complexities. These can include remote monitoring setups for sites that are sometimes or always without manning. Special provision should also be made for monitoring and maintaining the UPS batteries on which the system depends.


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